githubmirror/libmicrohttpd

src/include/microhttpd.h
4 055 строк141 KB
Christian Grothoff
releasing 0.9.69
15 дек 2019, 16:17
15 дек 2019, 16:173a661f8
/*
     This file is part of libmicrohttpd
     Copyright (C) 2006--2019 Christian Grothoff (and other contributing authors)

     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Lesser General Public
     License as published by the Free Software Foundation; either
     version 2.1 of the License, or (at your option) any later version.

     This library is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Lesser General Public License for more details.

     You should have received a copy of the GNU Lesser General Public
     License along with this library; if not, write to the Free Software
     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

/**
 * @file microhttpd.h
 * @brief public interface to libmicrohttpd
 * @author Christian Grothoff
 * @author Karlson2k (Evgeny Grin)
 * @author Chris GauthierDickey
 *
 * All symbols defined in this header start with MHD.  MHD is a small
 * HTTP daemon library.  As such, it does not have any API for logging
 * errors (you can only enable or disable logging to stderr).  Also,
 * it may not support all of the HTTP features directly, where
 * applicable, portions of HTTP may have to be handled by clients of
 * the library.
 *
 * The library is supposed to handle everything that it must handle
 * (because the API would not allow clients to do this), such as basic
 * connection management; however, detailed interpretations of headers
 * -- such as range requests -- and HTTP methods are left to clients.
 * The library does understand HEAD and will only send the headers of
 * the response and not the body, even if the client supplied a body.
 * The library also understands headers that control connection
 * management (specifically, "Connection: close" and "Expect: 100
 * continue" are understood and handled automatically).
 *
 * MHD understands POST data and is able to decode certain formats
 * (at the moment only "application/x-www-form-urlencoded" and
 * "mulitpart/formdata"). Unsupported encodings and large POST
 * submissions may require the application to manually process
 * the stream, which is provided to the main application (and thus can be
 * processed, just not conveniently by MHD).
 *
 * The header file defines various constants used by the HTTP protocol.
 * This does not mean that MHD actually interprets all of these
 * values.  The provided constants are exported as a convenience
 * for users of the library.  MHD does not verify that transmitted
 * HTTP headers are part of the standard specification; users of the
 * library are free to define their own extensions of the HTTP
 * standard and use those with MHD.
 *
 * All functions are guaranteed to be completely reentrant and
 * thread-safe (with the exception of #MHD_set_connection_value,
 * which must only be used in a particular context).
 *
 *
 * @defgroup event event-loop control
 * MHD API to start and stop the HTTP server and manage the event loop.
 * @defgroup response generation of responses
 * MHD API used to generate responses.
 * @defgroup request handling of requests
 * MHD API used to access information about requests.
 * @defgroup authentication HTTP authentication
 * MHD API related to basic and digest HTTP authentication.
 * @defgroup logging logging
 * MHD API to mange logging and error handling
 * @defgroup specialized misc. specialized functions
 * This group includes functions that do not fit into any particular
 * category and that are rarely used.
 */

#ifndef MHD_MICROHTTPD_H
#define MHD_MICROHTTPD_H

#ifdef __cplusplus
extern "C"
{
#if 0                           /* keep Emacsens' auto-indent happy */
}
#endif
#endif

/* While we generally would like users to use a configure-driven
   build process which detects which headers are present and
   hence works on any platform, we use "standard" includes here
   to build out-of-the-box for beginning users on common systems.

   If generic headers don't work on your platform, include headers
   which define 'va_list', 'size_t', 'ssize_t', 'intptr_t',
   'uint16_t', 'uint32_t', 'uint64_t', 'off_t', 'struct sockaddr',
   'socklen_t', 'fd_set' and "#define MHD_PLATFORM_H" before
   including "microhttpd.h". Then the following "standard"
   includes won't be used (which might be a good idea, especially
   on platforms where they do not exist).
   */
#ifndef MHD_PLATFORM_H
#if defined(_WIN32) && ! defined(__CYGWIN__) && \
  ! defined(_CRT_DECLARE_NONSTDC_NAMES)
#define _CRT_DECLARE_NONSTDC_NAMES 1
#endif /* _WIN32 && ! __CYGWIN__ && ! _CRT_DECLARE_NONSTDC_NAMES */
#include <stdarg.h>
#include <stdint.h>
#include <sys/types.h>
#if ! defined(_WIN32) || defined(__CYGWIN__)
#include <unistd.h>
#include <sys/time.h>
#include <sys/socket.h>
#else  /* _WIN32 && ! __CYGWIN__ */
/* Declare POSIX-compatible names */
#define _CRT_DECLARE_NONSTDC_NAMES 1
#include <ws2tcpip.h>
#if defined(_MSC_FULL_VER) && ! defined (_SSIZE_T_DEFINED)
#define _SSIZE_T_DEFINED
typedef intptr_t ssize_t;
#endif /* !_SSIZE_T_DEFINED */
#endif /* _WIN32 && ! __CYGWIN__ */
#endif

#if defined(__CYGWIN__) && ! defined(_SYS_TYPES_FD_SET)
/* Do not define __USE_W32_SOCKETS under Cygwin! */
#error Cygwin with winsock fd_set is not supported
#endif

/**
 * Current version of the library.
 * 0x01093001 = 1.9.30-1.
 */
#define MHD_VERSION 0x00096900

/**
 * MHD-internal return code for "YES".
 */
#define MHD_YES 1

/**
 * MHD-internal return code for "NO".
 */
#define MHD_NO 0

/**
 * MHD digest auth internal code for an invalid nonce.
 */
#define MHD_INVALID_NONCE -1

/**
 * Constant used to indicate unknown size (use when
 * creating a response).
 */
#ifdef UINT64_MAX
#define MHD_SIZE_UNKNOWN UINT64_MAX
#else
#define MHD_SIZE_UNKNOWN  ((uint64_t) -1LL)
#endif

#ifdef SIZE_MAX
#define MHD_CONTENT_READER_END_OF_STREAM SIZE_MAX
#define MHD_CONTENT_READER_END_WITH_ERROR (SIZE_MAX - 1)
#else
#define MHD_CONTENT_READER_END_OF_STREAM ((size_t) -1LL)
#define MHD_CONTENT_READER_END_WITH_ERROR (((size_t) -1LL) - 1)
#endif

#ifndef _MHD_EXTERN
#if defined(_WIN32) && defined(MHD_W32LIB)
#define _MHD_EXTERN extern
#elif defined (_WIN32) && defined(MHD_W32DLL)
/* Define MHD_W32DLL when using MHD as W32 .DLL to speed up linker a little */
#define _MHD_EXTERN __declspec(dllimport)
#else
#define _MHD_EXTERN extern
#endif
#endif

#ifndef MHD_SOCKET_DEFINED
/**
 * MHD_socket is type for socket FDs
 */
#if ! defined(_WIN32) || defined(_SYS_TYPES_FD_SET)
#define MHD_POSIX_SOCKETS 1
typedef int MHD_socket;
#define MHD_INVALID_SOCKET (-1)
#else /* !defined(_WIN32) || defined(_SYS_TYPES_FD_SET) */
#define MHD_WINSOCK_SOCKETS 1
#include <winsock2.h>
typedef SOCKET MHD_socket;
#define MHD_INVALID_SOCKET (INVALID_SOCKET)
#endif /* !defined(_WIN32) || defined(_SYS_TYPES_FD_SET) */
#define MHD_SOCKET_DEFINED 1
#endif /* MHD_SOCKET_DEFINED */

/**
 * Define MHD_NO_DEPRECATION before including "microhttpd.h" to disable deprecation messages
 */
#ifdef MHD_NO_DEPRECATION
#define _MHD_DEPR_MACRO(msg)
#define _MHD_NO_DEPR_IN_MACRO 1
#define _MHD_DEPR_IN_MACRO(msg)
#define _MHD_NO_DEPR_FUNC 1
#define _MHD_DEPR_FUNC(msg)
#endif /* MHD_NO_DEPRECATION */

#ifndef _MHD_DEPR_MACRO
#if defined(_MSC_FULL_VER) && _MSC_VER + 0 >= 1500
/* VS 2008 or later */
/* Stringify macros */
#define _MHD_INSTRMACRO(a) #a
#define _MHD_STRMACRO(a) _MHD_INSTRMACRO (a)
/* deprecation message */
#define _MHD_DEPR_MACRO(msg) __pragma (message (__FILE__ "(" _MHD_STRMACRO ( \
                                                  __LINE__) "): warning: " msg))
#define _MHD_DEPR_IN_MACRO(msg) _MHD_DEPR_MACRO (msg)
#elif defined(__clang__) || defined (__GNUC_PATCHLEVEL__)
/* clang or GCC since 3.0 */
#define _MHD_GCC_PRAG(x) _Pragma (#x)
#if (defined(__clang__) && (__clang_major__ + 0 >= 5 ||     \
                            (! defined(__apple_build_version__) && \
  (__clang_major__ + 0  > 3 || (__clang_major__ + 0 == 3 && __clang_minor__ >= \
                                3))))) || \
  __GNUC__ + 0 > 4 || (__GNUC__ + 0 == 4 && __GNUC_MINOR__ + 0 >= 8)
/* clang >= 3.3 (or XCode's clang >= 5.0) or
   GCC >= 4.8 */
#define _MHD_DEPR_MACRO(msg) _MHD_GCC_PRAG (GCC warning msg)
#define _MHD_DEPR_IN_MACRO(msg) _MHD_DEPR_MACRO (msg)
#else /* older clang or GCC */
/* clang < 3.3, XCode's clang < 5.0, 3.0 <= GCC < 4.8 */
#define _MHD_DEPR_MACRO(msg) _MHD_GCC_PRAG (message msg)
#if (defined(__clang__) && (__clang_major__ + 0  > 2 || (__clang_major__ + 0 == \
                                                         2 && __clang_minor__ >= \
                                                         9)))                                            /* FIXME: clang >= 2.9, earlier versions not tested */
/* clang handles inline pragmas better than GCC */
#define _MHD_DEPR_IN_MACRO(msg) _MHD_DEPR_MACRO (msg)
#endif /* clang >= 2.9 */
#endif  /* older clang or GCC */
/* #elif defined(SOMEMACRO) */ /* add compiler-specific macros here if required */
#endif /* clang || GCC >= 3.0 */
#endif /* !_MHD_DEPR_MACRO */

#ifndef _MHD_DEPR_MACRO
#define _MHD_DEPR_MACRO(msg)
#endif /* !_MHD_DEPR_MACRO */

#ifndef _MHD_DEPR_IN_MACRO
#define _MHD_NO_DEPR_IN_MACRO 1
#define _MHD_DEPR_IN_MACRO(msg)
#endif /* !_MHD_DEPR_IN_MACRO */

#ifndef _MHD_DEPR_FUNC
#if defined(_MSC_FULL_VER) && _MSC_VER + 0 >= 1400
/* VS 2005 or later */
#define _MHD_DEPR_FUNC(msg) __declspec(deprecated (msg))
#elif defined(_MSC_FULL_VER) && _MSC_VER + 0 >= 1310
/* VS .NET 2003 deprecation do not support custom messages */
#define _MHD_DEPR_FUNC(msg) __declspec(deprecated)
#elif (__GNUC__ + 0 >= 5) || (defined (__clang__) && \
  (__clang_major__ + 0 > 2 || (__clang_major__ + 0 == 2 && __clang_minor__ >= \
                               9)))                                             /* FIXME: earlier versions not tested */
/* GCC >= 5.0 or clang >= 2.9 */
#define _MHD_DEPR_FUNC(msg) __attribute__((deprecated (msg)))
#elif defined (__clang__) || __GNUC__ + 0 > 3 || (__GNUC__ + 0 == 3 && \
                                                  __GNUC_MINOR__ + 0 >= 1)
/* 3.1 <= GCC < 5.0 or clang < 2.9 */
/* old GCC-style deprecation do not support custom messages */
#define _MHD_DEPR_FUNC(msg) __attribute__((__deprecated__))
/* #elif defined(SOMEMACRO) */ /* add compiler-specific macros here if required */
#endif /* clang < 2.9 || GCC >= 3.1 */
#endif /* !_MHD_DEPR_FUNC */

#ifndef _MHD_DEPR_FUNC
#define _MHD_NO_DEPR_FUNC 1
#define _MHD_DEPR_FUNC(msg)
#endif /* !_MHD_DEPR_FUNC */

/**
 * Not all architectures and `printf()`'s support the `long long` type.
 * This gives the ability to replace `long long` with just a `long`,
 * standard `int` or a `short`.
 */
#ifndef MHD_LONG_LONG
/**
 * @deprecated use #MHD_UNSIGNED_LONG_LONG instead!
 */
#define MHD_LONG_LONG long long
#define MHD_UNSIGNED_LONG_LONG unsigned long long
#else /* MHD_LONG_LONG */
_MHD_DEPR_MACRO (
  "Macro MHD_LONG_LONG is deprecated, use MHD_UNSIGNED_LONG_LONG")
#endif
/**
 * Format string for printing a variable of type #MHD_LONG_LONG.
 * You should only redefine this if you also define #MHD_LONG_LONG.
 */
#ifndef MHD_LONG_LONG_PRINTF
/**
 * @deprecated use #MHD_UNSIGNED_LONG_LONG_PRINTF instead!
 */
#define MHD_LONG_LONG_PRINTF "ll"
#define MHD_UNSIGNED_LONG_LONG_PRINTF "%llu"
#else /* MHD_LONG_LONG_PRINTF */
_MHD_DEPR_MACRO (
  "Macro MHD_LONG_LONG_PRINTF is deprecated, use MHD_UNSIGNED_LONG_LONG_PRINTF")
#endif


/**
 * Length of the binary output of the MD5 hash function.
 */
#define  MHD_MD5_DIGEST_SIZE 16


/**
 * @defgroup httpcode HTTP response codes.
 * These are the status codes defined for HTTP responses.
 * See: https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml
 * Registry export date: 2019-06-09
 * @{
 */

/* 100 "Continue".            RFC7231, Section 6.2.1. */
#define MHD_HTTP_CONTINUE 100
/* 101 "Switching Protocols". RFC7231, Section 6.2.2. */
#define MHD_HTTP_SWITCHING_PROTOCOLS 101
/* 102 "Processing".          RFC2518. */
#define MHD_HTTP_PROCESSING 102
/* 103 "Early Hints".         RFC8297. */
#define MHD_HTTP_EARLY_HINTS 103

/* 200 "OK".                  RFC7231, Section 6.3.1. */
#define MHD_HTTP_OK 200
/* 201 "Created".             RFC7231, Section 6.3.2. */
#define MHD_HTTP_CREATED 201
/* 202 "Accepted".            RFC7231, Section 6.3.3. */
#define MHD_HTTP_ACCEPTED 202
/* 203 "Non-Authoritative Information". RFC7231, Section 6.3.4. */
#define MHD_HTTP_NON_AUTHORITATIVE_INFORMATION 203
/* 204 "No Content".          RFC7231, Section 6.3.5. */
#define MHD_HTTP_NO_CONTENT 204
/* 205 "Reset Content".       RFC7231, Section 6.3.6. */
#define MHD_HTTP_RESET_CONTENT 205
/* 206 "Partial Content".     RFC7233, Section 4.1. */
#define MHD_HTTP_PARTIAL_CONTENT 206
/* 207 "Multi-Status".        RFC4918. */
#define MHD_HTTP_MULTI_STATUS 207
/* 208 "Already Reported".    RFC5842. */
#define MHD_HTTP_ALREADY_REPORTED 208

/* 226 "IM Used".             RFC3229. */
#define MHD_HTTP_IM_USED 226

/* 300 "Multiple Choices".    RFC7231, Section 6.4.1. */
#define MHD_HTTP_MULTIPLE_CHOICES 300
/* 301 "Moved Permanently".   RFC7231, Section 6.4.2. */
#define MHD_HTTP_MOVED_PERMANENTLY 301
/* 302 "Found".               RFC7231, Section 6.4.3. */
#define MHD_HTTP_FOUND 302
/* 303 "See Other".           RFC7231, Section 6.4.4. */
#define MHD_HTTP_SEE_OTHER 303
/* 304 "Not Modified".        RFC7232, Section 4.1. */
#define MHD_HTTP_NOT_MODIFIED 304
/* 305 "Use Proxy".           RFC7231, Section 6.4.5. */
#define MHD_HTTP_USE_PROXY 305
/* 306 "Switch Proxy".        Not used! RFC7231, Section 6.4.6. */
#define MHD_HTTP_SWITCH_PROXY 306
/* 307 "Temporary Redirect".  RFC7231, Section 6.4.7. */
#define MHD_HTTP_TEMPORARY_REDIRECT 307
/* 308 "Permanent Redirect".  RFC7538. */
#define MHD_HTTP_PERMANENT_REDIRECT 308

/* 400 "Bad Request".         RFC7231, Section 6.5.1. */
#define MHD_HTTP_BAD_REQUEST 400
/* 401 "Unauthorized".        RFC7235, Section 3.1. */
#define MHD_HTTP_UNAUTHORIZED 401
/* 402 "Payment Required".    RFC7231, Section 6.5.2. */
#define MHD_HTTP_PAYMENT_REQUIRED 402
/* 403 "Forbidden".           RFC7231, Section 6.5.3. */
#define MHD_HTTP_FORBIDDEN 403
/* 404 "Not Found".           RFC7231, Section 6.5.4. */
#define MHD_HTTP_NOT_FOUND 404
/* 405 "Method Not Allowed".  RFC7231, Section 6.5.5. */
#define MHD_HTTP_METHOD_NOT_ALLOWED 405
/* 406 "Not Acceptable".      RFC7231, Section 6.5.6. */
#define MHD_HTTP_NOT_ACCEPTABLE 406
/* 407 "Proxy Authentication Required". RFC7235, Section 3.2. */
#define MHD_HTTP_PROXY_AUTHENTICATION_REQUIRED 407
/* 408 "Request Timeout".     RFC7231, Section 6.5.7. */
#define MHD_HTTP_REQUEST_TIMEOUT 408
/* 409 "Conflict".            RFC7231, Section 6.5.8. */
#define MHD_HTTP_CONFLICT 409
/* 410 "Gone".                RFC7231, Section 6.5.9. */
#define MHD_HTTP_GONE 410
/* 411 "Length Required".     RFC7231, Section 6.5.10. */
#define MHD_HTTP_LENGTH_REQUIRED 411
/* 412 "Precondition Failed". RFC7232, Section 4.2; RFC8144, Section 3.2. */
#define MHD_HTTP_PRECONDITION_FAILED 412
/* 413 "Payload Too Large".   RFC7231, Section 6.5.11. */
#define MHD_HTTP_PAYLOAD_TOO_LARGE 413
/* 414 "URI Too Long".        RFC7231, Section 6.5.12. */
#define MHD_HTTP_URI_TOO_LONG 414
/* 415 "Unsupported Media Type". RFC7231, Section 6.5.13; RFC7694, Section 3. */
#define MHD_HTTP_UNSUPPORTED_MEDIA_TYPE 415
/* 416 "Range Not Satisfiable". RFC7233, Section 4.4. */
#define MHD_HTTP_RANGE_NOT_SATISFIABLE 416
/* 417 "Expectation Failed".  RFC7231, Section 6.5.14. */
#define MHD_HTTP_EXPECTATION_FAILED 417

/* 421 "Misdirected Request". RFC7540, Section 9.1.2. */
#define MHD_HTTP_MISDIRECTED_REQUEST 421
/* 422 "Unprocessable Entity". RFC4918. */
#define MHD_HTTP_UNPROCESSABLE_ENTITY 422
/* 423 "Locked".              RFC4918. */
#define MHD_HTTP_LOCKED 423
/* 424 "Failed Dependency".   RFC4918. */
#define MHD_HTTP_FAILED_DEPENDENCY 424
/* 425 "Too Early".           RFC8470. */
#define MHD_HTTP_TOO_EARLY 425
/* 426 "Upgrade Required".    RFC7231, Section 6.5.15. */
#define MHD_HTTP_UPGRADE_REQUIRED 426

/* 428 "Precondition Required". RFC6585. */
#define MHD_HTTP_PRECONDITION_REQUIRED 428
/* 429 "Too Many Requests".   RFC6585. */
#define MHD_HTTP_TOO_MANY_REQUESTS 429

/* 431 "Request Header Fields Too Large". RFC6585. */
#define MHD_HTTP_REQUEST_HEADER_FIELDS_TOO_LARGE 431

/* 451 "Unavailable For Legal Reasons". RFC7725. */
#define MHD_HTTP_UNAVAILABLE_FOR_LEGAL_REASONS 451

/* 500 "Internal Server Error". RFC7231, Section 6.6.1. */
#define MHD_HTTP_INTERNAL_SERVER_ERROR 500
/* 501 "Not Implemented".     RFC7231, Section 6.6.2. */
#define MHD_HTTP_NOT_IMPLEMENTED 501
/* 502 "Bad Gateway".         RFC7231, Section 6.6.3. */
#define MHD_HTTP_BAD_GATEWAY 502
/* 503 "Service Unavailable". RFC7231, Section 6.6.4. */
#define MHD_HTTP_SERVICE_UNAVAILABLE 503
/* 504 "Gateway Timeout".     RFC7231, Section 6.6.5. */
#define MHD_HTTP_GATEWAY_TIMEOUT 504
/* 505 "HTTP Version Not Supported". RFC7231, Section 6.6.6. */
#define MHD_HTTP_HTTP_VERSION_NOT_SUPPORTED 505
/* 506 "Variant Also Negotiates". RFC2295. */
#define MHD_HTTP_VARIANT_ALSO_NEGOTIATES 506
/* 507 "Insufficient Storage". RFC4918. */
#define MHD_HTTP_INSUFFICIENT_STORAGE 507
/* 508 "Loop Detected".       RFC5842. */
#define MHD_HTTP_LOOP_DETECTED 508

/* 510 "Not Extended".        RFC2774. */
#define MHD_HTTP_NOT_EXTENDED 510
/* 511 "Network Authentication Required". RFC6585. */
#define MHD_HTTP_NETWORK_AUTHENTICATION_REQUIRED 511


/* Not registered non-standard codes */
/* 449 "Reply With".          MS IIS extension. */
#define MHD_HTTP_RETRY_WITH 449

/* 450 "Blocked by Windows Parental Controls". MS extension. */
#define MHD_HTTP_BLOCKED_BY_WINDOWS_PARENTAL_CONTROLS 450

/* 509 "Bandwidth Limit Exceeded". Apache extension. */
#define MHD_HTTP_BANDWIDTH_LIMIT_EXCEEDED 509


/* Deprecated codes */
/** @deprecated */
#define MHD_HTTP_METHOD_NOT_ACCEPTABLE \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_HTTP_METHOD_NOT_ACCEPTABLE is deprecated, use MHD_HTTP_NOT_ACCEPTABLE") \
  406

/** @deprecated */
#define MHD_HTTP_REQUEST_ENTITY_TOO_LARGE \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_HTTP_REQUEST_ENTITY_TOO_LARGE is deprecated, use MHD_HTTP_PAYLOAD_TOO_LARGE") \
  413

/** @deprecated */
#define MHD_HTTP_REQUEST_URI_TOO_LONG \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_HTTP_REQUEST_URI_TOO_LONG is deprecated, use MHD_HTTP_URI_TOO_LONG") \
  414

/** @deprecated */
#define MHD_HTTP_REQUESTED_RANGE_NOT_SATISFIABLE \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_HTTP_REQUESTED_RANGE_NOT_SATISFIABLE is deprecated, use MHD_HTTP_RANGE_NOT_SATISFIABLE") \
  416

/** @deprecated */
#define MHD_HTTP_UNORDERED_COLLECTION \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_HTTP_UNORDERED_COLLECTION is deprecated as it was removed from RFC") \
  425

/** @deprecated */
#define MHD_HTTP_NO_RESPONSE \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_HTTP_NO_RESPONSE is deprecated as it is nginx internal code for logs only") \
  444


/** @} */ /* end of group httpcode */

/**
 * Returns the string reason phrase for a response code.
 *
 * If message string is not available for a status code,
 * "Unknown" string will be returned.
 */
_MHD_EXTERN const char *
MHD_get_reason_phrase_for (unsigned int code);


/**
 * Flag to be or-ed with MHD_HTTP status code for
 * SHOUTcast.  This will cause the response to begin
 * with the SHOUTcast "ICY" line instad of "HTTP".
 * @ingroup specialized
 */
#define MHD_ICY_FLAG ((uint32_t) (((uint32_t) 1) << 31))

/**
 * @defgroup headers HTTP headers
 * These are the standard headers found in HTTP requests and responses.
 * See: http://www.iana.org/assignments/message-headers/message-headers.xml
 * Registry export date: 2019-06-09
 * @{
 */

/* Main HTTP headers. */
/* Standard.      RFC7231, Section 5.3.2 */
#define MHD_HTTP_HEADER_ACCEPT "Accept"
/* Standard.      RFC7231, Section 5.3.3 */
#define MHD_HTTP_HEADER_ACCEPT_CHARSET "Accept-Charset"
/* Standard.      RFC7231, Section 5.3.4; RFC7694, Section 3 */
#define MHD_HTTP_HEADER_ACCEPT_ENCODING "Accept-Encoding"
/* Standard.      RFC7231, Section 5.3.5 */
#define MHD_HTTP_HEADER_ACCEPT_LANGUAGE "Accept-Language"
/* Standard.      RFC7233, Section 2.3 */
#define MHD_HTTP_HEADER_ACCEPT_RANGES "Accept-Ranges"
/* Standard.      RFC7234, Section 5.1 */
#define MHD_HTTP_HEADER_AGE "Age"
/* Standard.      RFC7231, Section 7.4.1 */
#define MHD_HTTP_HEADER_ALLOW "Allow"
/* Standard.      RFC7235, Section 4.2 */
#define MHD_HTTP_HEADER_AUTHORIZATION "Authorization"
/* Standard.      RFC7234, Section 5.2 */
#define MHD_HTTP_HEADER_CACHE_CONTROL "Cache-Control"
/* Reserved.      RFC7230, Section 8.1 */
#define MHD_HTTP_HEADER_CLOSE "Close"
/* Standard.      RFC7230, Section 6.1 */
#define MHD_HTTP_HEADER_CONNECTION "Connection"
/* Standard.      RFC7231, Section 3.1.2.2 */
#define MHD_HTTP_HEADER_CONTENT_ENCODING "Content-Encoding"
/* Standard.      RFC7231, Section 3.1.3.2 */
#define MHD_HTTP_HEADER_CONTENT_LANGUAGE "Content-Language"
/* Standard.      RFC7230, Section 3.3.2 */
#define MHD_HTTP_HEADER_CONTENT_LENGTH "Content-Length"
/* Standard.      RFC7231, Section 3.1.4.2 */
#define MHD_HTTP_HEADER_CONTENT_LOCATION "Content-Location"
/* Standard.      RFC7233, Section 4.2 */
#define MHD_HTTP_HEADER_CONTENT_RANGE "Content-Range"
/* Standard.      RFC7231, Section 3.1.1.5 */
#define MHD_HTTP_HEADER_CONTENT_TYPE "Content-Type"
/* Standard.      RFC7231, Section 7.1.1.2 */
#define MHD_HTTP_HEADER_DATE "Date"
/* Standard.      RFC7232, Section 2.3 */
#define MHD_HTTP_HEADER_ETAG "ETag"
/* Standard.      RFC7231, Section 5.1.1 */
#define MHD_HTTP_HEADER_EXPECT "Expect"
/* Standard.      RFC7234, Section 5.3 */
#define MHD_HTTP_HEADER_EXPIRES "Expires"
/* Standard.      RFC7231, Section 5.5.1 */
#define MHD_HTTP_HEADER_FROM "From"
/* Standard.      RFC7230, Section 5.4 */
#define MHD_HTTP_HEADER_HOST "Host"
/* Standard.      RFC7232, Section 3.1 */
#define MHD_HTTP_HEADER_IF_MATCH "If-Match"
/* Standard.      RFC7232, Section 3.3 */
#define MHD_HTTP_HEADER_IF_MODIFIED_SINCE "If-Modified-Since"
/* Standard.      RFC7232, Section 3.2 */
#define MHD_HTTP_HEADER_IF_NONE_MATCH "If-None-Match"
/* Standard.      RFC7233, Section 3.2 */
#define MHD_HTTP_HEADER_IF_RANGE "If-Range"
/* Standard.      RFC7232, Section 3.4 */
#define MHD_HTTP_HEADER_IF_UNMODIFIED_SINCE "If-Unmodified-Since"
/* Standard.      RFC7232, Section 2.2 */
#define MHD_HTTP_HEADER_LAST_MODIFIED "Last-Modified"
/* Standard.      RFC7231, Section 7.1.2 */
#define MHD_HTTP_HEADER_LOCATION "Location"
/* Standard.      RFC7231, Section 5.1.2 */
#define MHD_HTTP_HEADER_MAX_FORWARDS "Max-Forwards"
/* Standard.      RFC7231, Appendix A.1 */
#define MHD_HTTP_HEADER_MIME_VERSION "MIME-Version"
/* Standard.      RFC7234, Section 5.4 */
#define MHD_HTTP_HEADER_PRAGMA "Pragma"
/* Standard.      RFC7235, Section 4.3 */
#define MHD_HTTP_HEADER_PROXY_AUTHENTICATE "Proxy-Authenticate"
/* Standard.      RFC7235, Section 4.4 */
#define MHD_HTTP_HEADER_PROXY_AUTHORIZATION "Proxy-Authorization"
/* Standard.      RFC7233, Section 3.1 */
#define MHD_HTTP_HEADER_RANGE "Range"
/* Standard.      RFC7231, Section 5.5.2 */
#define MHD_HTTP_HEADER_REFERER "Referer"
/* Standard.      RFC7231, Section 7.1.3 */
#define MHD_HTTP_HEADER_RETRY_AFTER "Retry-After"
/* Standard.      RFC7231, Section 7.4.2 */
#define MHD_HTTP_HEADER_SERVER "Server"
/* Standard.      RFC7230, Section 4.3 */
#define MHD_HTTP_HEADER_TE "TE"
/* Standard.      RFC7230, Section 4.4 */
#define MHD_HTTP_HEADER_TRAILER "Trailer"
/* Standard.      RFC7230, Section 3.3.1 */
#define MHD_HTTP_HEADER_TRANSFER_ENCODING "Transfer-Encoding"
/* Standard.      RFC7230, Section 6.7 */
#define MHD_HTTP_HEADER_UPGRADE "Upgrade"
/* Standard.      RFC7231, Section 5.5.3 */
#define MHD_HTTP_HEADER_USER_AGENT "User-Agent"
/* Standard.      RFC7231, Section 7.1.4 */
#define MHD_HTTP_HEADER_VARY "Vary"
/* Standard.      RFC7230, Section 5.7.1 */
#define MHD_HTTP_HEADER_VIA "Via"
/* Standard.      RFC7235, Section 4.1 */
#define MHD_HTTP_HEADER_WWW_AUTHENTICATE "WWW-Authenticate"
/* Standard.      RFC7234, Section 5.5 */
#define MHD_HTTP_HEADER_WARNING "Warning"

/* Additional HTTP headers. */
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_A_IM "A-IM"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_ACCEPT_ADDITIONS "Accept-Additions"
/* Informational. RFC7089 */
#define MHD_HTTP_HEADER_ACCEPT_DATETIME "Accept-Datetime"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_ACCEPT_FEATURES "Accept-Features"
/* No category.   RFC5789 */
#define MHD_HTTP_HEADER_ACCEPT_PATCH "Accept-Patch"
/* Standard.      https://www.w3.org/TR/ldp/ */
#define MHD_HTTP_HEADER_ACCEPT_POST "Accept-Post"
/* Standard.      RFC7639, Section 2 */
#define MHD_HTTP_HEADER_ALPN "ALPN"
/* Standard.      RFC7838 */
#define MHD_HTTP_HEADER_ALT_SVC "Alt-Svc"
/* Standard.      RFC7838 */
#define MHD_HTTP_HEADER_ALT_USED "Alt-Used"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_ALTERNATES "Alternates"
/* No category.   RFC4437 */
#define MHD_HTTP_HEADER_APPLY_TO_REDIRECT_REF "Apply-To-Redirect-Ref"
/* Experimental.  RFC8053, Section 4 */
#define MHD_HTTP_HEADER_AUTHENTICATION_CONTROL "Authentication-Control"
/* Standard.      RFC7615, Section 3 */
#define MHD_HTTP_HEADER_AUTHENTICATION_INFO "Authentication-Info"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_C_EXT "C-Ext"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_C_MAN "C-Man"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_C_OPT "C-Opt"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_C_PEP "C-PEP"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_C_PEP_INFO "C-PEP-Info"
/* Standard.      RFC8607, Section 5.1 */
#define MHD_HTTP_HEADER_CAL_MANAGED_ID "Cal-Managed-ID"
/* Standard.      RFC7809, Section 7.1 */
#define MHD_HTTP_HEADER_CALDAV_TIMEZONES "CalDAV-Timezones"
/* Standard.      RFC8586 */
#define MHD_HTTP_HEADER_CDN_LOOP "CDN-Loop"
/* Obsoleted.     RFC2068; RFC2616 */
#define MHD_HTTP_HEADER_CONTENT_BASE "Content-Base"
/* Standard.      RFC6266 */
#define MHD_HTTP_HEADER_CONTENT_DISPOSITION "Content-Disposition"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_CONTENT_ID "Content-ID"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_CONTENT_MD5 "Content-MD5"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_CONTENT_SCRIPT_TYPE "Content-Script-Type"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_CONTENT_STYLE_TYPE "Content-Style-Type"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_CONTENT_VERSION "Content-Version"
/* Standard.      RFC6265 */
#define MHD_HTTP_HEADER_COOKIE "Cookie"
/* Obsoleted.     RFC2965; RFC6265 */
#define MHD_HTTP_HEADER_COOKIE2 "Cookie2"
/* Standard.      RFC5323 */
#define MHD_HTTP_HEADER_DASL "DASL"
/* Standard.      RFC4918 */
#define MHD_HTTP_HEADER_DAV "DAV"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_DEFAULT_STYLE "Default-Style"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_DELTA_BASE "Delta-Base"
/* Standard.      RFC4918 */
#define MHD_HTTP_HEADER_DEPTH "Depth"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_DERIVED_FROM "Derived-From"
/* Standard.      RFC4918 */
#define MHD_HTTP_HEADER_DESTINATION "Destination"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_DIFFERENTIAL_ID "Differential-ID"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_DIGEST "Digest"
/* Standard.      RFC8470 */
#define MHD_HTTP_HEADER_EARLY_DATA "Early-Data"
/* Experimental.  RFC-ietf-httpbis-expect-ct-08 */
#define MHD_HTTP_HEADER_EXPECT_CT "Expect-CT"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_EXT "Ext"
/* Standard.      RFC7239 */
#define MHD_HTTP_HEADER_FORWARDED "Forwarded"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_GETPROFILE "GetProfile"
/* Experimental.  RFC7486, Section 6.1.1 */
#define MHD_HTTP_HEADER_HOBAREG "Hobareg"
/* Standard.      RFC7540, Section 3.2.1 */
#define MHD_HTTP_HEADER_HTTP2_SETTINGS "HTTP2-Settings"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_IM "IM"
/* Standard.      RFC4918 */
#define MHD_HTTP_HEADER_IF "If"
/* Standard.      RFC6638 */
#define MHD_HTTP_HEADER_IF_SCHEDULE_TAG_MATCH "If-Schedule-Tag-Match"
/* Standard.      RFC8473 */
#define MHD_HTTP_HEADER_INCLUDE_REFERRED_TOKEN_BINDING_ID \
  "Include-Referred-Token-Binding-ID"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_KEEP_ALIVE "Keep-Alive"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_LABEL "Label"
/* Standard.      RFC8288 */
#define MHD_HTTP_HEADER_LINK "Link"
/* Standard.      RFC4918 */
#define MHD_HTTP_HEADER_LOCK_TOKEN "Lock-Token"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_MAN "Man"
/* Informational. RFC7089 */
#define MHD_HTTP_HEADER_MEMENTO_DATETIME "Memento-Datetime"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_METER "Meter"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_NEGOTIATE "Negotiate"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_OPT "Opt"
/* Experimental.  RFC8053, Section 3 */
#define MHD_HTTP_HEADER_OPTIONAL_WWW_AUTHENTICATE "Optional-WWW-Authenticate"
/* Standard.      RFC4229 */
#define MHD_HTTP_HEADER_ORDERING_TYPE "Ordering-Type"
/* Standard.      RFC6454 */
#define MHD_HTTP_HEADER_ORIGIN "Origin"
/* Standard.      RFC-ietf-core-object-security-16, Section 11.1 */
#define MHD_HTTP_HEADER_OSCORE "OSCORE"
/* Standard.      RFC4918 */
#define MHD_HTTP_HEADER_OVERWRITE "Overwrite"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_P3P "P3P"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_PEP "PEP"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_PICS_LABEL "PICS-Label"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_PEP_INFO "Pep-Info"
/* Standard.      RFC4229 */
#define MHD_HTTP_HEADER_POSITION "Position"
/* Standard.      RFC7240 */
#define MHD_HTTP_HEADER_PREFER "Prefer"
/* Standard.      RFC7240 */
#define MHD_HTTP_HEADER_PREFERENCE_APPLIED "Preference-Applied"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_PROFILEOBJECT "ProfileObject"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_PROTOCOL "Protocol"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_PROTOCOL_INFO "Protocol-Info"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_PROTOCOL_QUERY "Protocol-Query"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_PROTOCOL_REQUEST "Protocol-Request"
/* Standard.      RFC7615, Section 4 */
#define MHD_HTTP_HEADER_PROXY_AUTHENTICATION_INFO "Proxy-Authentication-Info"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_PROXY_FEATURES "Proxy-Features"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_PROXY_INSTRUCTION "Proxy-Instruction"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_PUBLIC "Public"
/* Standard.      RFC7469 */
#define MHD_HTTP_HEADER_PUBLIC_KEY_PINS "Public-Key-Pins"
/* Standard.      RFC7469 */
#define MHD_HTTP_HEADER_PUBLIC_KEY_PINS_REPORT_ONLY \
  "Public-Key-Pins-Report-Only"
/* No category.   RFC4437 */
#define MHD_HTTP_HEADER_REDIRECT_REF "Redirect-Ref"
/* Standard.      RFC8555, Section 6.5.1 */
#define MHD_HTTP_HEADER_REPLAY_NONCE "Replay-Nonce"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_SAFE "Safe"
/* Standard.      RFC6638 */
#define MHD_HTTP_HEADER_SCHEDULE_REPLY "Schedule-Reply"
/* Standard.      RFC6638 */
#define MHD_HTTP_HEADER_SCHEDULE_TAG "Schedule-Tag"
/* Standard.      RFC8473 */
#define MHD_HTTP_HEADER_SEC_TOKEN_BINDING "Sec-Token-Binding"
/* Standard.      RFC6455 */
#define MHD_HTTP_HEADER_SEC_WEBSOCKET_ACCEPT "Sec-WebSocket-Accept"
/* Standard.      RFC6455 */
#define MHD_HTTP_HEADER_SEC_WEBSOCKET_EXTENSIONS "Sec-WebSocket-Extensions"
/* Standard.      RFC6455 */
#define MHD_HTTP_HEADER_SEC_WEBSOCKET_KEY "Sec-WebSocket-Key"
/* Standard.      RFC6455 */
#define MHD_HTTP_HEADER_SEC_WEBSOCKET_PROTOCOL "Sec-WebSocket-Protocol"
/* Standard.      RFC6455 */
#define MHD_HTTP_HEADER_SEC_WEBSOCKET_VERSION "Sec-WebSocket-Version"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_SECURITY_SCHEME "Security-Scheme"
/* Standard.      RFC6265 */
#define MHD_HTTP_HEADER_SET_COOKIE "Set-Cookie"
/* Obsoleted.     RFC2965; RFC6265 */
#define MHD_HTTP_HEADER_SET_COOKIE2 "Set-Cookie2"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_SETPROFILE "SetProfile"
/* Standard.      RFC5023 */
#define MHD_HTTP_HEADER_SLUG "SLUG"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_SOAPACTION "SoapAction"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_STATUS_URI "Status-URI"
/* Standard.      RFC6797 */
#define MHD_HTTP_HEADER_STRICT_TRANSPORT_SECURITY "Strict-Transport-Security"
/* Informational. RFC8594 */
#define MHD_HTTP_HEADER_SUNSET "Sunset"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_SURROGATE_CAPABILITY "Surrogate-Capability"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_SURROGATE_CONTROL "Surrogate-Control"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_TCN "TCN"
/* Standard.      RFC4918 */
#define MHD_HTTP_HEADER_TIMEOUT "Timeout"
/* Standard.      RFC8030, Section 5.4 */
#define MHD_HTTP_HEADER_TOPIC "Topic"
/* Standard.      RFC8030, Section 5.2 */
#define MHD_HTTP_HEADER_TTL "TTL"
/* Standard.      RFC8030, Section 5.3 */
#define MHD_HTTP_HEADER_URGENCY "Urgency"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_URI "URI"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_VARIANT_VARY "Variant-Vary"
/* No category.   RFC4229 */
#define MHD_HTTP_HEADER_WANT_DIGEST "Want-Digest"
/* Standard.      https://fetch.spec.whatwg.org/#x-content-type-options-header */
#define MHD_HTTP_HEADER_X_CONTENT_TYPE_OPTIONS "X-Content-Type-Options"
/* Informational. RFC7034 */
#define MHD_HTTP_HEADER_X_FRAME_OPTIONS "X-Frame-Options"

/* Some provisional headers. */
#define MHD_HTTP_HEADER_ACCESS_CONTROL_ALLOW_ORIGIN \
  "Access-Control-Allow-Origin"
/** @} */ /* end of group headers */

/**
 * @defgroup versions HTTP versions
 * These strings should be used to match against the first line of the
 * HTTP header.
 * @{
 */
#define MHD_HTTP_VERSION_1_0 "HTTP/1.0"
#define MHD_HTTP_VERSION_1_1 "HTTP/1.1"

/** @} */ /* end of group versions */

/**
 * @defgroup methods HTTP methods
 * HTTP methods (as strings).
 * See: http://www.iana.org/assignments/http-methods/http-methods.xml
 * Registry export date: 2019-06-09
 * @{
 */

/* Main HTTP methods. */
/* Not safe. Not idempotent. RFC7231, Section 4.3.6. */
#define MHD_HTTP_METHOD_CONNECT "CONNECT"
/* Not safe. Idempotent.     RFC7231, Section 4.3.5. */
#define MHD_HTTP_METHOD_DELETE "DELETE"
/* Safe.     Idempotent.     RFC7231, Section 4.3.1. */
#define MHD_HTTP_METHOD_GET "GET"
/* Safe.     Idempotent.     RFC7231, Section 4.3.2. */
#define MHD_HTTP_METHOD_HEAD "HEAD"
/* Safe.     Idempotent.     RFC7231, Section 4.3.7. */
#define MHD_HTTP_METHOD_OPTIONS "OPTIONS"
/* Not safe. Not idempotent. RFC7231, Section 4.3.3. */
#define MHD_HTTP_METHOD_POST "POST"
/* Not safe. Idempotent.     RFC7231, Section 4.3.4. */
#define MHD_HTTP_METHOD_PUT "PUT"
/* Safe.     Idempotent.     RFC7231, Section 4.3.8. */
#define MHD_HTTP_METHOD_TRACE "TRACE"

/* Additional HTTP methods. */
/* Not safe. Idempotent.     RFC3744, Section 8.1. */
#define MHD_HTTP_METHOD_ACL "ACL"
/* Not safe. Idempotent.     RFC3253, Section 12.6. */
#define MHD_HTTP_METHOD_BASELINE_CONTROL "BASELINE-CONTROL"
/* Not safe. Idempotent.     RFC5842, Section 4. */
#define MHD_HTTP_METHOD_BIND "BIND"
/* Not safe. Idempotent.     RFC3253, Section 4.4, Section 9.4. */
#define MHD_HTTP_METHOD_CHECKIN "CHECKIN"
/* Not safe. Idempotent.     RFC3253, Section 4.3, Section 8.8. */
#define MHD_HTTP_METHOD_CHECKOUT "CHECKOUT"
/* Not safe. Idempotent.     RFC4918, Section 9.8. */
#define MHD_HTTP_METHOD_COPY "COPY"
/* Not safe. Idempotent.     RFC3253, Section 8.2. */
#define MHD_HTTP_METHOD_LABEL "LABEL"
/* Not safe. Idempotent.     RFC2068, Section 19.6.1.2. */
#define MHD_HTTP_METHOD_LINK "LINK"
/* Not safe. Not idempotent. RFC4918, Section 9.10. */
#define MHD_HTTP_METHOD_LOCK "LOCK"
/* Not safe. Idempotent.     RFC3253, Section 11.2. */
#define MHD_HTTP_METHOD_MERGE "MERGE"
/* Not safe. Idempotent.     RFC3253, Section 13.5. */
#define MHD_HTTP_METHOD_MKACTIVITY "MKACTIVITY"
/* Not safe. Idempotent.     RFC4791, Section 5.3.1; RFC8144, Section 2.3. */
#define MHD_HTTP_METHOD_MKCALENDAR "MKCALENDAR"
/* Not safe. Idempotent.     RFC4918, Section 9.3; RFC5689, Section 3; RFC8144, Section 2.3. */
#define MHD_HTTP_METHOD_MKCOL "MKCOL"
/* Not safe. Idempotent.     RFC4437, Section 6. */
#define MHD_HTTP_METHOD_MKREDIRECTREF "MKREDIRECTREF"
/* Not safe. Idempotent.     RFC3253, Section 6.3. */
#define MHD_HTTP_METHOD_MKWORKSPACE "MKWORKSPACE"
/* Not safe. Idempotent.     RFC4918, Section 9.9. */
#define MHD_HTTP_METHOD_MOVE "MOVE"
/* Not safe. Idempotent.     RFC3648, Section 7. */
#define MHD_HTTP_METHOD_ORDERPATCH "ORDERPATCH"
/* Not safe. Not idempotent. RFC5789, Section 2. */
#define MHD_HTTP_METHOD_PATCH "PATCH"
/* Safe.     Idempotent.     RFC7540, Section 3.5. */
#define MHD_HTTP_METHOD_PRI "PRI"
/* Safe.     Idempotent.     RFC4918, Section 9.1; RFC8144, Section 2.1. */
#define MHD_HTTP_METHOD_PROPFIND "PROPFIND"
/* Not safe. Idempotent.     RFC4918, Section 9.2; RFC8144, Section 2.2. */
#define MHD_HTTP_METHOD_PROPPATCH "PROPPATCH"
/* Not safe. Idempotent.     RFC5842, Section 6. */
#define MHD_HTTP_METHOD_REBIND "REBIND"
/* Safe.     Idempotent.     RFC3253, Section 3.6; RFC8144, Section 2.1. */
#define MHD_HTTP_METHOD_REPORT "REPORT"
/* Safe.     Idempotent.     RFC5323, Section 2. */
#define MHD_HTTP_METHOD_SEARCH "SEARCH"
/* Not safe. Idempotent.     RFC5842, Section 5. */
#define MHD_HTTP_METHOD_UNBIND "UNBIND"
/* Not safe. Idempotent.     RFC3253, Section 4.5. */
#define MHD_HTTP_METHOD_UNCHECKOUT "UNCHECKOUT"
/* Not safe. Idempotent.     RFC2068, Section 19.6.1.3. */
#define MHD_HTTP_METHOD_UNLINK "UNLINK"
/* Not safe. Idempotent.     RFC4918, Section 9.11. */
#define MHD_HTTP_METHOD_UNLOCK "UNLOCK"
/* Not safe. Idempotent.     RFC3253, Section 7.1. */
#define MHD_HTTP_METHOD_UPDATE "UPDATE"
/* Not safe. Idempotent.     RFC4437, Section 7. */
#define MHD_HTTP_METHOD_UPDATEREDIRECTREF "UPDATEREDIRECTREF"
/* Not safe. Idempotent.     RFC3253, Section 3.5. */
#define MHD_HTTP_METHOD_VERSION_CONTROL "VERSION-CONTROL"

/** @} */ /* end of group methods */

/**
 * @defgroup postenc HTTP POST encodings
 * See also: http://www.w3.org/TR/html4/interact/forms.html#h-17.13.4
 * @{
 */
#define MHD_HTTP_POST_ENCODING_FORM_URLENCODED \
  "application/x-www-form-urlencoded"
#define MHD_HTTP_POST_ENCODING_MULTIPART_FORMDATA "multipart/form-data"

/** @} */ /* end of group postenc */


/**
 * @brief Handle for the daemon (listening on a socket for HTTP traffic).
 * @ingroup event
 */
struct MHD_Daemon;

/**
 * @brief Handle for a connection / HTTP request.
 *
 * With HTTP/1.1, multiple requests can be run over the same
 * connection.  However, MHD will only show one request per TCP
 * connection to the client at any given time.
 * @ingroup request
 */
struct MHD_Connection;

/**
 * @brief Handle for a response.
 * @ingroup response
 */
struct MHD_Response;

/**
 * @brief Handle for POST processing.
 * @ingroup response
 */
struct MHD_PostProcessor;


/**
 * @brief Flags for the `struct MHD_Daemon`.
 *
 * Note that MHD will run automatically in background thread(s) only
 * if #MHD_USE_INTERNAL_POLLING_THREAD is used. Otherwise caller (application)
 * must use #MHD_run() or #MHD_run_from_select() to have MHD processed
 * network connections and data.
 *
 * Starting the daemon may also fail if a particular option is not
 * implemented or not supported on the target platform (i.e. no
 * support for TLS, epoll or IPv6).
 */
enum MHD_FLAG
{
  /**
   * No options selected.
   */
  MHD_NO_FLAG = 0,

  /**
   * Print errors messages to custom error logger or to `stderr` if
   * custom error logger is not set.
   * @sa ::MHD_OPTION_EXTERNAL_LOGGER
   */
  MHD_USE_ERROR_LOG = 1,

  /**
   * Run in debug mode.  If this flag is used, the library should
   * print error messages and warnings to `stderr`.
   */
  MHD_USE_DEBUG = 1,

  /**
   * Run in HTTPS mode.  The modern protocol is called TLS.
   */
  MHD_USE_TLS = 2,

  /** @deprecated */
  MHD_USE_SSL = 2,
#if 0
  /* let's do this later once versions that define MHD_USE_TLS a more widely deployed. */
#define MHD_USE_SSL \
  _MHD_DEPR_IN_MACRO ("Value MHD_USE_SSL is deprecated, use MHD_USE_TLS") \
  MHD_USE_TLS
#endif

  /**
   * Run using one thread per connection.
   * Must be used only with #MHD_USE_INTERNAL_POLLING_THREAD.
   */
  MHD_USE_THREAD_PER_CONNECTION = 4,

  /**
   * Run using an internal thread (or thread pool) for sockets sending
   * and receiving and data processing. Without this flag MHD will not
   * run automatically in background thread(s).
   * If this flag is set, #MHD_run() and #MHD_run_from_select() couldn't
   * be used.
   * This flag is set explicitly by #MHD_USE_POLL_INTERNAL_THREAD and
   * by #MHD_USE_EPOLL_INTERNAL_THREAD.
   */
  MHD_USE_INTERNAL_POLLING_THREAD = 8,

  /** @deprecated */
  MHD_USE_SELECT_INTERNALLY = 8,
#if 0 /* Will be marked for real deprecation later. */
#define MHD_USE_SELECT_INTERNALLY \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_USE_SELECT_INTERNALLY is deprecated, use MHD_USE_INTERNAL_POLLING_THREAD instead") \
  MHD_USE_INTERNAL_POLLING_THREAD
#endif /* 0 */

  /**
   * Run using the IPv6 protocol (otherwise, MHD will just support
   * IPv4).  If you want MHD to support IPv4 and IPv6 using a single
   * socket, pass #MHD_USE_DUAL_STACK, otherwise, if you only pass
   * this option, MHD will try to bind to IPv6-only (resulting in
   * no IPv4 support).
   */
  MHD_USE_IPv6 = 16,

  /**
   * Be pedantic about the protocol (as opposed to as tolerant as
   * possible).  Specifically, at the moment, this flag causes MHD to
   * reject HTTP 1.1 connections without a "Host" header.  This is
   * required by the standard, but of course in violation of the "be
   * as liberal as possible in what you accept" norm.  It is
   * recommended to turn this ON if you are testing clients against
   * MHD, and OFF in production.
   */
  MHD_USE_PEDANTIC_CHECKS = 32,
#if 0 /* Will be marked for real deprecation later. */
#define MHD_USE_PEDANTIC_CHECKS \
  _MHD_DEPR_IN_MACRO ( \
    "Flag MHD_USE_PEDANTIC_CHECKS is deprecated, use option MHD_OPTION_STRICT_FOR_CLIENT instead") \
  32
#endif /* 0 */

  /**
   * Use `poll()` instead of `select()`. This allows sockets with `fd >=
   * FD_SETSIZE`.  This option is not compatible with using an
   * 'external' polling mode (as there is no API to get the file
   * descriptors for the external poll() from MHD) and must also not
   * be used in combination with #MHD_USE_EPOLL.
   * @sa ::MHD_FEATURE_POLL, #MHD_USE_POLL_INTERNAL_THREAD
   */
  MHD_USE_POLL = 64,

  /**
   * Run using an internal thread (or thread pool) doing `poll()`.
   * @sa ::MHD_FEATURE_POLL, #MHD_USE_POLL, #MHD_USE_INTERNAL_POLLING_THREAD
   */
  MHD_USE_POLL_INTERNAL_THREAD = MHD_USE_POLL | MHD_USE_INTERNAL_POLLING_THREAD,

  /** @deprecated */
  MHD_USE_POLL_INTERNALLY = MHD_USE_POLL | MHD_USE_INTERNAL_POLLING_THREAD,
#if 0 /* Will be marked for real deprecation later. */
#define MHD_USE_POLL_INTERNALLY \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_USE_POLL_INTERNALLY is deprecated, use MHD_USE_POLL_INTERNAL_THREAD instead") \
  MHD_USE_POLL_INTERNAL_THREAD
#endif /* 0 */

  /**
   * Suppress (automatically) adding the 'Date:' header to HTTP responses.
   * This option should ONLY be used on systems that do not have a clock
   * and that DO provide other mechanisms for cache control.  See also
   * RFC 2616, section 14.18 (exception 3).
   */
  MHD_USE_SUPPRESS_DATE_NO_CLOCK = 128,

  /** @deprecated */
  MHD_SUPPRESS_DATE_NO_CLOCK = 128,
#if 0 /* Will be marked for real deprecation later. */
#define MHD_SUPPRESS_DATE_NO_CLOCK \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_SUPPRESS_DATE_NO_CLOCK is deprecated, use MHD_USE_SUPPRESS_DATE_NO_CLOCK instead") \
  MHD_USE_SUPPRESS_DATE_NO_CLOCK
#endif /* 0 */

  /**
   * Run without a listen socket.  This option only makes sense if
   * #MHD_add_connection is to be used exclusively to connect HTTP
   * clients to the HTTP server.  This option is incompatible with
   * using a thread pool; if it is used, #MHD_OPTION_THREAD_POOL_SIZE
   * is ignored.
   */
  MHD_USE_NO_LISTEN_SOCKET = 256,

  /**
   * Use `epoll()` instead of `select()` or `poll()` for the event loop.
   * This option is only available on some systems; using the option on
   * systems without epoll will cause #MHD_start_daemon to fail.  Using
   * this option is not supported with #MHD_USE_THREAD_PER_CONNECTION.
   * @sa ::MHD_FEATURE_EPOLL
   */
  MHD_USE_EPOLL = 512,

  /** @deprecated */
  MHD_USE_EPOLL_LINUX_ONLY = 512,
#if 0 /* Will be marked for real deprecation later. */
#define MHD_USE_EPOLL_LINUX_ONLY \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_USE_EPOLL_LINUX_ONLY is deprecated, use MHD_USE_EPOLL") \
  MHD_USE_EPOLL
#endif /* 0 */

  /**
   * Run using an internal thread (or thread pool) doing `epoll()`.
   * This option is only available on certain platforms; using the option on
   * platform without `epoll` support will cause #MHD_start_daemon to fail.
   * @sa ::MHD_FEATURE_EPOLL, #MHD_USE_EPOLL, #MHD_USE_INTERNAL_POLLING_THREAD
   */
  MHD_USE_EPOLL_INTERNAL_THREAD = MHD_USE_EPOLL
                                  | MHD_USE_INTERNAL_POLLING_THREAD,

  /** @deprecated */
  MHD_USE_EPOLL_INTERNALLY = MHD_USE_EPOLL | MHD_USE_INTERNAL_POLLING_THREAD,
  /** @deprecated */
  MHD_USE_EPOLL_INTERNALLY_LINUX_ONLY = MHD_USE_EPOLL
                                        | MHD_USE_INTERNAL_POLLING_THREAD,
#if 0 /* Will be marked for real deprecation later. */
#define MHD_USE_EPOLL_INTERNALLY \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_USE_EPOLL_INTERNALLY is deprecated, use MHD_USE_EPOLL_INTERNAL_THREAD") \
  MHD_USE_EPOLL_INTERNAL_THREAD
  /** @deprecated */
#define MHD_USE_EPOLL_INTERNALLY_LINUX_ONLY \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_USE_EPOLL_INTERNALLY_LINUX_ONLY is deprecated, use MHD_USE_EPOLL_INTERNAL_THREAD") \
  MHD_USE_EPOLL_INTERNAL_THREAD
#endif /* 0 */

  /**
   * Use inter-thread communication channel.
   * #MHD_USE_ITC can be used with #MHD_USE_INTERNAL_POLLING_THREAD
   * and is ignored with any "external" mode.
   * It's required for use of #MHD_quiesce_daemon
   * or #MHD_add_connection.
   * This option is enforced by #MHD_ALLOW_SUSPEND_RESUME or
   * #MHD_USE_NO_LISTEN_SOCKET.
   * #MHD_USE_ITC is always used automatically on platforms
   * where select()/poll()/other ignore shutdown of listen
   * socket.
   */
  MHD_USE_ITC = 1024,

  /** @deprecated */
  MHD_USE_PIPE_FOR_SHUTDOWN = 1024,
#if 0 /* Will be marked for real deprecation later. */
#define MHD_USE_PIPE_FOR_SHUTDOWN \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_USE_PIPE_FOR_SHUTDOWN is deprecated, use MHD_USE_ITC") \
  MHD_USE_ITC
#endif /* 0 */

  /**
   * Use a single socket for IPv4 and IPv6.
   */
  MHD_USE_DUAL_STACK = MHD_USE_IPv6 | 2048,

  /**
   * Enable `turbo`.  Disables certain calls to `shutdown()`,
   * enables aggressive non-blocking optimistic reads and
   * other potentially unsafe optimizations.
   * Most effects only happen with #MHD_USE_EPOLL.
   */
  MHD_USE_TURBO = 4096,

  /** @deprecated */
  MHD_USE_EPOLL_TURBO = 4096,
#if 0 /* Will be marked for real deprecation later. */
#define MHD_USE_EPOLL_TURBO \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_USE_EPOLL_TURBO is deprecated, use MHD_USE_TURBO") \
  MHD_USE_TURBO
#endif /* 0 */

  /**
   * Enable suspend/resume functions, which also implies setting up
   * ITC to signal resume.
   */
  MHD_ALLOW_SUSPEND_RESUME = 8192 | MHD_USE_ITC,

  /** @deprecated */
  MHD_USE_SUSPEND_RESUME = 8192 | MHD_USE_ITC,
#if 0 /* Will be marked for real deprecation later. */
#define MHD_USE_SUSPEND_RESUME \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_USE_SUSPEND_RESUME is deprecated, use MHD_ALLOW_SUSPEND_RESUME instead") \
  MHD_ALLOW_SUSPEND_RESUME
#endif /* 0 */

  /**
   * Enable TCP_FASTOPEN option.  This option is only available on Linux with a
   * kernel >= 3.6.  On other systems, using this option cases #MHD_start_daemon
   * to fail.
   */
  MHD_USE_TCP_FASTOPEN = 16384,

  /**
   * You need to set this option if you want to use HTTP "Upgrade".
   * "Upgrade" may require usage of additional internal resources,
   * which we do not want to use unless necessary.
   */
  MHD_ALLOW_UPGRADE = 32768,

  /**
   * Automatically use best available polling function.
   * Choice of polling function is also depend on other daemon options.
   * If #MHD_USE_INTERNAL_POLLING_THREAD is specified then epoll, poll() or
   * select() will be used (listed in decreasing preference order, first
   * function available on system will be used).
   * If #MHD_USE_THREAD_PER_CONNECTION is specified then poll() or select()
   * will be used.
   * If those flags are not specified then epoll or select() will be
   * used (as the only suitable for MHD_get_fdset())
   */
  MHD_USE_AUTO = 65536,

  /**
   * Run using an internal thread (or thread pool) with best available on
   * system polling function.
   * This is combination of #MHD_USE_AUTO and #MHD_USE_INTERNAL_POLLING_THREAD
   * flags.
   */
  MHD_USE_AUTO_INTERNAL_THREAD = MHD_USE_AUTO | MHD_USE_INTERNAL_POLLING_THREAD,

  /**
   * Flag set to enable post-handshake client authentication
   * (only useful in combination with #MHD_USE_TLS).
   */
  MHD_USE_POST_HANDSHAKE_AUTH_SUPPORT = 1U << 17,

  /**
   * Flag set to enable TLS 1.3 early data.  This has
   * security implications, be VERY careful when using this.
   */
  MHD_USE_INSECURE_TLS_EARLY_DATA = 1U << 18

};


/**
 * Type of a callback function used for logging by MHD.
 *
 * @param cls closure
 * @param fm format string (`printf()`-style)
 * @param ap arguments to @a fm
 * @ingroup logging
 */
typedef void
(*MHD_LogCallback)(void *cls,
                   const char *fm,
                   va_list ap);


/**
 * Function called to lookup the pre shared key (@a psk) for a given
 * HTTP connection based on the @a username.
 *
 * @param cls closure
 * @param connection the HTTPS connection
 * @param username the user name claimed by the other side
 * @param[out] psk to be set to the pre-shared-key; should be allocated with malloc(),
 *                 will be freed by MHD
 * @param[out] psk_size to be set to the number of bytes in @a psk
 * @return 0 on success, -1 on errors
 */
typedef int
(*MHD_PskServerCredentialsCallback)(void *cls,
                                    const struct MHD_Connection *connection,
                                    const char *username,
                                    void **psk,
                                    size_t *psk_size);

/**
 * @brief MHD options.
 *
 * Passed in the varargs portion of #MHD_start_daemon.
 */
enum MHD_OPTION
{

  /**
   * No more options / last option.  This is used
   * to terminate the VARARGs list.
   */
  MHD_OPTION_END = 0,

  /**
   * Maximum memory size per connection (followed by a `size_t`).
   * Default is 32 kb (#MHD_POOL_SIZE_DEFAULT).
   * Values above 128k are unlikely to result in much benefit, as half
   * of the memory will be typically used for IO, and TCP buffers are
   * unlikely to support window sizes above 64k on most systems.
   */
  MHD_OPTION_CONNECTION_MEMORY_LIMIT = 1,

  /**
   * Maximum number of concurrent connections to
   * accept (followed by an `unsigned int`).
   */
  MHD_OPTION_CONNECTION_LIMIT = 2,

  /**
   * After how many seconds of inactivity should a
   * connection automatically be timed out? (followed
   * by an `unsigned int`; use zero for no timeout).
   */
  MHD_OPTION_CONNECTION_TIMEOUT = 3,

  /**
   * Register a function that should be called whenever a request has
   * been completed (this can be used for application-specific clean
   * up).  Requests that have never been presented to the application
   * (via #MHD_AccessHandlerCallback) will not result in
   * notifications.
   *
   * This option should be followed by TWO pointers.  First a pointer
   * to a function of type #MHD_RequestCompletedCallback and second a
   * pointer to a closure to pass to the request completed callback.
   * The second pointer maybe NULL.
   */
  MHD_OPTION_NOTIFY_COMPLETED = 4,

  /**
   * Limit on the number of (concurrent) connections made to the
   * server from the same IP address.  Can be used to prevent one
   * IP from taking over all of the allowed connections.  If the
   * same IP tries to establish more than the specified number of
   * connections, they will be immediately rejected.  The option
   * should be followed by an `unsigned int`.  The default is
   * zero, which means no limit on the number of connections
   * from the same IP address.
   */
  MHD_OPTION_PER_IP_CONNECTION_LIMIT = 5,

  /**
   * Bind daemon to the supplied `struct sockaddr`. This option should
   * be followed by a `struct sockaddr *`.  If #MHD_USE_IPv6 is
   * specified, the `struct sockaddr*` should point to a `struct
   * sockaddr_in6`, otherwise to a `struct sockaddr_in`.
   */
  MHD_OPTION_SOCK_ADDR = 6,

  /**
   * Specify a function that should be called before parsing the URI from
   * the client.  The specified callback function can be used for processing
   * the URI (including the options) before it is parsed.  The URI after
   * parsing will no longer contain the options, which maybe inconvenient for
   * logging.  This option should be followed by two arguments, the first
   * one must be of the form
   *
   *     void * my_logger(void *cls, const char *uri, struct MHD_Connection *con)
   *
   * where the return value will be passed as
   * (`* con_cls`) in calls to the #MHD_AccessHandlerCallback
   * when this request is processed later; returning a
   * value of NULL has no special significance (however,
   * note that if you return non-NULL, you can no longer
   * rely on the first call to the access handler having
   * `NULL == *con_cls` on entry;)
   * "cls" will be set to the second argument following
   * #MHD_OPTION_URI_LOG_CALLBACK.  Finally, uri will
   * be the 0-terminated URI of the request.
   *
   * Note that during the time of this call, most of the connection's
   * state is not initialized (as we have not yet parsed the headers).
   * However, information about the connecting client (IP, socket)
   * is available.
   *
   * The specified function is called only once per request, therefore some
   * programmers may use it to instantiate their own request objects, freeing
   * them in the notifier #MHD_OPTION_NOTIFY_COMPLETED.
   */
  MHD_OPTION_URI_LOG_CALLBACK = 7,

  /**
   * Memory pointer for the private key (key.pem) to be used by the
   * HTTPS daemon.  This option should be followed by a
   * `const char *` argument.
   * This should be used in conjunction with #MHD_OPTION_HTTPS_MEM_CERT.
   */
  MHD_OPTION_HTTPS_MEM_KEY = 8,

  /**
   * Memory pointer for the certificate (cert.pem) to be used by the
   * HTTPS daemon.  This option should be followed by a
   * `const char *` argument.
   * This should be used in conjunction with #MHD_OPTION_HTTPS_MEM_KEY.
   */
  MHD_OPTION_HTTPS_MEM_CERT = 9,

  /**
   * Daemon credentials type.
   * Followed by an argument of type
   * `gnutls_credentials_type_t`.
   */
  MHD_OPTION_HTTPS_CRED_TYPE = 10,

  /**
   * Memory pointer to a `const char *` specifying the
   * cipher algorithm (default: "NORMAL").
   */
  MHD_OPTION_HTTPS_PRIORITIES = 11,

  /**
   * Pass a listen socket for MHD to use (systemd-style).  If this
   * option is used, MHD will not open its own listen socket(s). The
   * argument passed must be of type `MHD_socket` and refer to an
   * existing socket that has been bound to a port and is listening.
   */
  MHD_OPTION_LISTEN_SOCKET = 12,

  /**
   * Use the given function for logging error messages.  This option
   * must be followed by two arguments; the first must be a pointer to
   * a function of type #MHD_LogCallback and the second a pointer
   * `void *` which will be passed as the first argument to the log
   * callback.
   *
   * Note that MHD will not generate any log messages
   * if it was compiled without the "--enable-messages"
   * flag being set.
   */
  MHD_OPTION_EXTERNAL_LOGGER = 13,

  /**
   * Number (`unsigned int`) of threads in thread pool. Enable
   * thread pooling by setting this value to to something
   * greater than 1. Currently, thread mode must be
   * #MHD_USE_INTERNAL_POLLING_THREAD if thread pooling is enabled
   * (#MHD_start_daemon returns NULL for an unsupported thread
   * mode).
   */
  MHD_OPTION_THREAD_POOL_SIZE = 14,

  /**
   * Additional options given in an array of `struct MHD_OptionItem`.
   * The array must be terminated with an entry `{MHD_OPTION_END, 0, NULL}`.
   * An example for code using #MHD_OPTION_ARRAY is:
   *
   *     struct MHD_OptionItem ops[] = {
   *       { MHD_OPTION_CONNECTION_LIMIT, 100, NULL },
   *       { MHD_OPTION_CONNECTION_TIMEOUT, 10, NULL },
   *       { MHD_OPTION_END, 0, NULL }
   *     };
   *     d = MHD_start_daemon (0, 8080, NULL, NULL, dh, NULL,
   *                           MHD_OPTION_ARRAY, ops,
   *                           MHD_OPTION_END);
   *
   * For options that expect a single pointer argument, the
   * second member of the `struct MHD_OptionItem` is ignored.
   * For options that expect two pointer arguments, the first
   * argument must be cast to `intptr_t`.
   */
  MHD_OPTION_ARRAY = 15,

  /**
   * Specify a function that should be called for unescaping escape
   * sequences in URIs and URI arguments.  Note that this function
   * will NOT be used by the `struct MHD_PostProcessor`.  If this
   * option is not specified, the default method will be used which
   * decodes escape sequences of the form "%HH".  This option should
   * be followed by two arguments, the first one must be of the form
   *
   *     size_t my_unescaper(void *cls,
   *                         struct MHD_Connection *c,
   *                         char *s)
   *
   * where the return value must be the length of the value left in
   * "s" (without the 0-terminator) and "s" should be updated.  Note
   * that the unescape function must not lengthen "s" (the result must
   * be shorter than the input and must still be 0-terminated).
   * However, it may also include binary zeros before the
   * 0-termination.  "cls" will be set to the second argument
   * following #MHD_OPTION_UNESCAPE_CALLBACK.
   */
  MHD_OPTION_UNESCAPE_CALLBACK = 16,

  /**
   * Memory pointer for the random values to be used by the Digest
   * Auth module. This option should be followed by two arguments.
   * First an integer of type  `size_t` which specifies the size
   * of the buffer pointed to by the second argument in bytes.
   * Note that the application must ensure that the buffer of the
   * second argument remains allocated and unmodified while the
   * deamon is running.
   */
  MHD_OPTION_DIGEST_AUTH_RANDOM = 17,

  /**
   * Size of the internal array holding the map of the nonce and
   * the nonce counter. This option should be followed by an `unsigend int`
   * argument.
   */
  MHD_OPTION_NONCE_NC_SIZE = 18,

  /**
   * Desired size of the stack for threads created by MHD. Followed
   * by an argument of type `size_t`.  Use 0 for system default.
   */
  MHD_OPTION_THREAD_STACK_SIZE = 19,

  /**
   * Memory pointer for the certificate (ca.pem) to be used by the
   * HTTPS daemon for client authentication.
   * This option should be followed by a `const char *` argument.
   */
  MHD_OPTION_HTTPS_MEM_TRUST = 20,

  /**
   * Increment to use for growing the read buffer (followed by a
   * `size_t`). Must fit within #MHD_OPTION_CONNECTION_MEMORY_LIMIT.
   */
  MHD_OPTION_CONNECTION_MEMORY_INCREMENT = 21,

  /**
   * Use a callback to determine which X.509 certificate should be
   * used for a given HTTPS connection.  This option should be
   * followed by a argument of type `gnutls_certificate_retrieve_function2 *`.
   * This option provides an
   * alternative to #MHD_OPTION_HTTPS_MEM_KEY,
   * #MHD_OPTION_HTTPS_MEM_CERT.  You must use this version if
   * multiple domains are to be hosted at the same IP address using
   * TLS's Server Name Indication (SNI) extension.  In this case,
   * the callback is expected to select the correct certificate
   * based on the SNI information provided.  The callback is expected
   * to access the SNI data using `gnutls_server_name_get()`.
   * Using this option requires GnuTLS 3.0 or higher.
   */
  MHD_OPTION_HTTPS_CERT_CALLBACK = 22,

  /**
   * When using #MHD_USE_TCP_FASTOPEN, this option changes the default TCP
   * fastopen queue length of 50.  Note that having a larger queue size can
   * cause resource exhaustion attack as the TCP stack has to now allocate
   * resources for the SYN packet along with its DATA.  This option should be
   * followed by an `unsigned int` argument.
   */
  MHD_OPTION_TCP_FASTOPEN_QUEUE_SIZE = 23,

  /**
   * Memory pointer for the Diffie-Hellman parameters (dh.pem) to be used by the
   * HTTPS daemon for key exchange.
   * This option must be followed by a `const char *` argument.
   */
  MHD_OPTION_HTTPS_MEM_DHPARAMS = 24,

  /**
   * If present and set to true, allow reusing address:port socket
   * (by using SO_REUSEPORT on most platform, or platform-specific ways).
   * If present and set to false, disallow reusing address:port socket
   * (does nothing on most plaform, but uses SO_EXCLUSIVEADDRUSE on Windows).
   * This option must be followed by a `unsigned int` argument.
   */
  MHD_OPTION_LISTENING_ADDRESS_REUSE = 25,

  /**
   * Memory pointer for a password that decrypts the private key (key.pem)
   * to be used by the HTTPS daemon. This option should be followed by a
   * `const char *` argument.
   * This should be used in conjunction with #MHD_OPTION_HTTPS_MEM_KEY.
   * @sa ::MHD_FEATURE_HTTPS_KEY_PASSWORD
   */
  MHD_OPTION_HTTPS_KEY_PASSWORD = 26,

  /**
   * Register a function that should be called whenever a connection is
   * started or closed.
   *
   * This option should be followed by TWO pointers.  First a pointer
   * to a function of type #MHD_NotifyConnectionCallback and second a
   * pointer to a closure to pass to the request completed callback.
   * The second pointer maybe NULL.
   */
  MHD_OPTION_NOTIFY_CONNECTION = 27,

  /**
   * Allow to change maximum length of the queue of pending connections on
   * listen socket. If not present than default platform-specific SOMAXCONN
   * value is used. This option should be followed by an `unsigned int`
   * argument.
   */
  MHD_OPTION_LISTEN_BACKLOG_SIZE = 28,

  /**
   * If set to 1 - be strict about the protocol.  Use -1 to be
   * as tolerant as possible.
   *
   * Specifically, at the moment, at 1 this flag
   * causes MHD to reject HTTP 1.1 connections without a "Host" header,
   * and to disallow spaces in the URL or (at -1) in HTTP header key strings.
   *
   * These are required by some versions of the standard, but of
   * course in violation of the "be as liberal as possible in what you
   * accept" norm.  It is recommended to set this to 1 if you are
   * testing clients against MHD, and 0 in production.  This option
   * should be followed by an `int` argument.
   */
  MHD_OPTION_STRICT_FOR_CLIENT = 29,

  /**
   * This should be a pointer to callback of type
   * gnutls_psk_server_credentials_function that will be given to
   * gnutls_psk_set_server_credentials_function. It is used to
   * retrieve the shared key for a given username.
   */
  MHD_OPTION_GNUTLS_PSK_CRED_HANDLER = 30,

  /**
   * Use a callback to determine which X.509 certificate should be
   * used for a given HTTPS connection.  This option should be
   * followed by a argument of type `gnutls_certificate_retrieve_function3 *`.
   * This option provides an
   * alternative/extension to #MHD_OPTION_HTTPS_CERT_CALLBACK.
   * You must use this version if you want to use OCSP stapling.
   * Using this option requires GnuTLS 3.6.3 or higher.
   */
  MHD_OPTION_HTTPS_CERT_CALLBACK2 = 31,

  /**
   * Allows the application to disable certain sanity precautions
   * in MHD. With these, the client can break the HTTP protocol,
   * so this should never be used in production. The options are,
   * however, useful for testing HTTP clients against "broken"
   * server implementations.
   * This argument must be followed by an "unsigned int", corresponding
   * to an `enum MHD_DisableSanityCheck`.
   */
  MHD_OPTION_SERVER_INSANITY = 32
};


/**
 * Bitfield for the #MHD_OPTION_SERVER_INSANITY specifying
 * which santiy checks should be disabled.
 */
enum MHD_DisableSanityCheck
{
  /**
   * All sanity checks are enabled.
   */
  MHD_DSC_SANE = 0

};


/**
 * Entry in an #MHD_OPTION_ARRAY.
 */
struct MHD_OptionItem
{
  /**
   * Which option is being given.  Use #MHD_OPTION_END
   * to terminate the array.
   */
  enum MHD_OPTION option;

  /**
   * Option value (for integer arguments, and for options requiring
   * two pointer arguments); should be 0 for options that take no
   * arguments or only a single pointer argument.
   */
  intptr_t value;

  /**
   * Pointer option value (use NULL for options taking no arguments
   * or only an integer option).
   */
  void *ptr_value;

};


/**
 * The `enum MHD_ValueKind` specifies the source of
 * the key-value pairs in the HTTP protocol.
 */
enum MHD_ValueKind
{

  /**
   * Response header
   * @deprecated
   */
  MHD_RESPONSE_HEADER_KIND = 0,
#define MHD_RESPONSE_HEADER_KIND \
  _MHD_DEPR_IN_MACRO ( \
    "Value MHD_RESPONSE_HEADER_KIND is deprecated and not used") \
  MHD_RESPONSE_HEADER_KIND

  /**
   * HTTP header (request/response).
   */
  MHD_HEADER_KIND = 1,

  /**
   * Cookies.  Note that the original HTTP header containing
   * the cookie(s) will still be available and intact.
   */
  MHD_COOKIE_KIND = 2,

  /**
   * POST data.  This is available only if a content encoding
   * supported by MHD is used (currently only URL encoding),
   * and only if the posted content fits within the available
   * memory pool.  Note that in that case, the upload data
   * given to the #MHD_AccessHandlerCallback will be
   * empty (since it has already been processed).
   */
  MHD_POSTDATA_KIND = 4,

  /**
   * GET (URI) arguments.
   */
  MHD_GET_ARGUMENT_KIND = 8,

  /**
   * HTTP footer (only for HTTP 1.1 chunked encodings).
   */
  MHD_FOOTER_KIND = 16
};


/**
 * The `enum MHD_RequestTerminationCode` specifies reasons
 * why a request has been terminated (or completed).
 * @ingroup request
 */
enum MHD_RequestTerminationCode
{

  /**
   * We finished sending the response.
   * @ingroup request
   */
  MHD_REQUEST_TERMINATED_COMPLETED_OK = 0,

  /**
   * Error handling the connection (resources
   * exhausted, other side closed connection,
   * application error accepting request, etc.)
   * @ingroup request
   */
  MHD_REQUEST_TERMINATED_WITH_ERROR = 1,

  /**
   * No activity on the connection for the number
   * of seconds specified using
   * #MHD_OPTION_CONNECTION_TIMEOUT.
   * @ingroup request
   */
  MHD_REQUEST_TERMINATED_TIMEOUT_REACHED = 2,

  /**
   * We had to close the session since MHD was being
   * shut down.
   * @ingroup request
   */
  MHD_REQUEST_TERMINATED_DAEMON_SHUTDOWN = 3,

  /**
   * We tried to read additional data, but the other side closed the
   * connection.  This error is similar to
   * #MHD_REQUEST_TERMINATED_WITH_ERROR, but specific to the case where
   * the connection died because the other side did not send expected
   * data.
   * @ingroup request
   */
  MHD_REQUEST_TERMINATED_READ_ERROR = 4,

  /**
   * The client terminated the connection by closing the socket
   * for writing (TCP half-closed); MHD aborted sending the
   * response according to RFC 2616, section 8.1.4.
   * @ingroup request
   */
  MHD_REQUEST_TERMINATED_CLIENT_ABORT = 5

};


/**
 * The `enum MHD_ConnectionNotificationCode` specifies types
 * of connection notifications.
 * @ingroup request
 */
enum MHD_ConnectionNotificationCode
{

  /**
   * A new connection has been started.
   * @ingroup request
   */
  MHD_CONNECTION_NOTIFY_STARTED = 0,

  /**
   * A connection is closed.
   * @ingroup request
   */
  MHD_CONNECTION_NOTIFY_CLOSED = 1

};


/**
 * Information about a connection.
 */
union MHD_ConnectionInfo
{

  /**
   * Cipher algorithm used, of type "enum gnutls_cipher_algorithm".
   */
  int /* enum gnutls_cipher_algorithm */ cipher_algorithm;

  /**
   * Protocol used, of type "enum gnutls_protocol".
   */
  int /* enum gnutls_protocol */ protocol;

  /**
   * The suspended status of a connection.
   */
  int /* MHD_YES or MHD_NO */ suspended;

  /**
   * Amount of second that connection could spend in idle state
   * before automatically disconnected.
   * Zero for no timeout (unlimited idle time).
   */
  unsigned int connection_timeout;

  /**
   * Connect socket
   */
  MHD_socket connect_fd;

  /**
   * Size of the client's HTTP header.
   */
  size_t header_size;

  /**
   * GNUtls session handle, of type "gnutls_session_t".
   */
  void * /* gnutls_session_t */ tls_session;

  /**
   * GNUtls client certificate handle, of type "gnutls_x509_crt_t".
   */
  void * /* gnutls_x509_crt_t */ client_cert;

  /**
   * Address information for the client.
   */
  struct sockaddr *client_addr;

  /**
   * Which daemon manages this connection (useful in case there are many
   * daemons running).
   */
  struct MHD_Daemon *daemon;

  /**
   * Socket-specific client context.  Points to the same address as
   * the "socket_context" of the #MHD_NotifyConnectionCallback.
   */
  void *socket_context;
};


/**
 * Values of this enum are used to specify what
 * information about a connection is desired.
 * @ingroup request
 */
enum MHD_ConnectionInfoType
{
  /**
   * What cipher algorithm is being used.
   * Takes no extra arguments.
   * @ingroup request
   */
  MHD_CONNECTION_INFO_CIPHER_ALGO,

  /**
   *
   * Takes no extra arguments.
   * @ingroup request
   */
  MHD_CONNECTION_INFO_PROTOCOL,

  /**
   * Obtain IP address of the client.  Takes no extra arguments.
   * Returns essentially a `struct sockaddr **` (since the API returns
   * a `union MHD_ConnectionInfo *` and that union contains a `struct
   * sockaddr *`).
   * @ingroup request
   */
  MHD_CONNECTION_INFO_CLIENT_ADDRESS,

  /**
   * Get the gnuTLS session handle.
   * @ingroup request
   */
  MHD_CONNECTION_INFO_GNUTLS_SESSION,

  /**
   * Get the gnuTLS client certificate handle.  Dysfunctional (never
   * implemented, deprecated).  Use #MHD_CONNECTION_INFO_GNUTLS_SESSION
   * to get the `gnutls_session_t` and then call
   * gnutls_certificate_get_peers().
   */
  MHD_CONNECTION_INFO_GNUTLS_CLIENT_CERT,

  /**
   * Get the `struct MHD_Daemon *` responsible for managing this connection.
   * @ingroup request
   */
  MHD_CONNECTION_INFO_DAEMON,

  /**
   * Request the file descriptor for the connection socket.
   * No extra arguments should be passed.
   * @ingroup request
   */
  MHD_CONNECTION_INFO_CONNECTION_FD,

  /**
   * Returns the client-specific pointer to a `void *` that was (possibly)
   * set during a #MHD_NotifyConnectionCallback when the socket was
   * first accepted.  Note that this is NOT the same as the "con_cls"
   * argument of the #MHD_AccessHandlerCallback.  The "con_cls" is
   * fresh for each HTTP request, while the "socket_context" is fresh
   * for each socket.
   */
  MHD_CONNECTION_INFO_SOCKET_CONTEXT,

  /**
   * Check whether the connection is suspended.
   * @ingroup request
   */
  MHD_CONNECTION_INFO_CONNECTION_SUSPENDED,

  /**
   * Get connection timeout
   * @ingroup request
   */
  MHD_CONNECTION_INFO_CONNECTION_TIMEOUT,

  /**
   * Return length of the client's HTTP request header.
   * @ingroup request
   */
  MHD_CONNECTION_INFO_REQUEST_HEADER_SIZE
};


/**
 * Values of this enum are used to specify what
 * information about a deamon is desired.
 */
enum MHD_DaemonInfoType
{
  /**
   * No longer supported (will return NULL).
   */
  MHD_DAEMON_INFO_KEY_SIZE,

  /**
   * No longer supported (will return NULL).
   */
  MHD_DAEMON_INFO_MAC_KEY_SIZE,

  /**
   * Request the file descriptor for the listening socket.
   * No extra arguments should be passed.
   */
  MHD_DAEMON_INFO_LISTEN_FD,

  /**
   * Request the file descriptor for the external epoll.
   * No extra arguments should be passed.
   * Waiting on epoll FD must not block longer than value
   * returned by #MHD_get_timeout().
   */
  MHD_DAEMON_INFO_EPOLL_FD_LINUX_ONLY,
  MHD_DAEMON_INFO_EPOLL_FD = MHD_DAEMON_INFO_EPOLL_FD_LINUX_ONLY,

  /**
   * Request the number of current connections handled by the daemon.
   * No extra arguments should be passed.
   * Note: when using MHD in external polling mode, this type of request
   * could be used only when #MHD_run()/#MHD_run_from_select is not
   * working in other thread at the same time.
   */
  MHD_DAEMON_INFO_CURRENT_CONNECTIONS,

  /**
   * Request the daemon flags.
   * No extra arguments should be passed.
   * Note: flags may differ from original 'flags' specified for
   * daemon, especially if #MHD_USE_AUTO was set.
   */
  MHD_DAEMON_INFO_FLAGS,

  /**
   * Request the port number of daemon's listen socket.
   * No extra arguments should be passed.
   * Note: if port '0' was specified for #MHD_start_daemon(), returned
   * value will be real port number.
   */
  MHD_DAEMON_INFO_BIND_PORT
};


/**
 * Callback for serious error condition. The default action is to print
 * an error message and `abort()`.
 *
 * @param cls user specified value
 * @param file where the error occured
 * @param line where the error occured
 * @param reason error detail, may be NULL
 * @ingroup logging
 */
typedef void
(*MHD_PanicCallback) (void *cls,
                      const char *file,
                      unsigned int line,
                      const char *reason);

/**
 * Allow or deny a client to connect.
 *
 * @param cls closure
 * @param addr address information from the client
 * @param addrlen length of @a addr
 * @return #MHD_YES if connection is allowed, #MHD_NO if not
 */
typedef int
(*MHD_AcceptPolicyCallback) (void *cls,
                             const struct sockaddr *addr,
                             socklen_t addrlen);


/**
 * A client has requested the given url using the given method
 * (#MHD_HTTP_METHOD_GET, #MHD_HTTP_METHOD_PUT,
 * #MHD_HTTP_METHOD_DELETE, #MHD_HTTP_METHOD_POST, etc).  The callback
 * must call MHD callbacks to provide content to give back to the
 * client and return an HTTP status code (i.e. #MHD_HTTP_OK,
 * #MHD_HTTP_NOT_FOUND, etc.).
 *
 * @param cls argument given together with the function
 *        pointer when the handler was registered with MHD
 * @param url the requested url
 * @param method the HTTP method used (#MHD_HTTP_METHOD_GET,
 *        #MHD_HTTP_METHOD_PUT, etc.)
 * @param version the HTTP version string (i.e.
 *        #MHD_HTTP_VERSION_1_1)
 * @param upload_data the data being uploaded (excluding HEADERS,
 *        for a POST that fits into memory and that is encoded
 *        with a supported encoding, the POST data will NOT be
 *        given in upload_data and is instead available as
 *        part of #MHD_get_connection_values; very large POST
 *        data *will* be made available incrementally in
 *        @a upload_data)
 * @param[in,out] upload_data_size set initially to the size of the
 *        @a upload_data provided; the method must update this
 *        value to the number of bytes NOT processed;
 * @param[in,out] con_cls pointer that the callback can set to some
 *        address and that will be preserved by MHD for future
 *        calls for this request; since the access handler may
 *        be called many times (i.e., for a PUT/POST operation
 *        with plenty of upload data) this allows the application
 *        to easily associate some request-specific state.
 *        If necessary, this state can be cleaned up in the
 *        global #MHD_RequestCompletedCallback (which
 *        can be set with the #MHD_OPTION_NOTIFY_COMPLETED).
 *        Initially, `*con_cls` will be NULL.
 * @return #MHD_YES if the connection was handled successfully,
 *         #MHD_NO if the socket must be closed due to a serios
 *         error while handling the request
 */
typedef int
(*MHD_AccessHandlerCallback) (void *cls,
                              struct MHD_Connection *connection,
                              const char *url,
                              const char *method,
                              const char *version,
                              const char *upload_data,
                              size_t *upload_data_size,
                              void **con_cls);


/**
 * Signature of the callback used by MHD to notify the
 * application about completed requests.
 *
 * @param cls client-defined closure
 * @param connection connection handle
 * @param con_cls value as set by the last call to
 *        the #MHD_AccessHandlerCallback
 * @param toe reason for request termination
 * @see #MHD_OPTION_NOTIFY_COMPLETED
 * @ingroup request
 */
typedef void
(*MHD_RequestCompletedCallback) (void *cls,
                                 struct MHD_Connection *connection,
                                 void **con_cls,
                                 enum MHD_RequestTerminationCode toe);


/**
 * Signature of the callback used by MHD to notify the
 * application about started/stopped connections
 *
 * @param cls client-defined closure
 * @param connection connection handle
 * @param socket_context socket-specific pointer where the
 *                       client can associate some state specific
 *                       to the TCP connection; note that this is
 *                       different from the "con_cls" which is per
 *                       HTTP request.  The client can initialize
 *                       during #MHD_CONNECTION_NOTIFY_STARTED and
 *                       cleanup during #MHD_CONNECTION_NOTIFY_CLOSED
 *                       and access in the meantime using
 *                       #MHD_CONNECTION_INFO_SOCKET_CONTEXT.
 * @param toe reason for connection notification
 * @see #MHD_OPTION_NOTIFY_CONNECTION
 * @ingroup request
 */
typedef void
(*MHD_NotifyConnectionCallback) (void *cls,
                                 struct MHD_Connection *connection,
                                 void **socket_context,
                                 enum MHD_ConnectionNotificationCode toe);


/**
 * Iterator over key-value pairs.  This iterator
 * can be used to iterate over all of the cookies,
 * headers, or POST-data fields of a request, and
 * also to iterate over the headers that have been
 * added to a response.
 *
 * @param cls closure
 * @param kind kind of the header we are looking at
 * @param key key for the value, can be an empty string
 * @param value corresponding value, can be NULL
 * @return #MHD_YES to continue iterating,
 *         #MHD_NO to abort the iteration
 * @ingroup request
 */
typedef int
(*MHD_KeyValueIterator) (void *cls,
                         enum MHD_ValueKind kind,
                         const char *key,
                         const char *value);


/**
 * Iterator over key-value pairs with size parameters.
 * This iterator can be used to iterate over all of
 * the cookies, headers, or POST-data fields of a
 * request, and also to iterate over the headers that
 * have been added to a response.
 * @note Available since #MHD_VERSION 0x00096303
 *
 * @param cls closure
 * @param kind kind of the header we are looking at
 * @param key key for the value, can be an empty string
 * @param value corresponding value, can be NULL
 * @param value_size number of bytes in @a value, NEW since #MHD_VERSION 0x00096301;
 *                   for C-strings, the length excludes the 0-terminator
 * @return #MHD_YES to continue iterating,
 *         #MHD_NO to abort the iteration
 * @ingroup request
 */
typedef int
(*MHD_KeyValueIteratorN) (void *cls,
                          enum MHD_ValueKind kind,
                          const char *key,
                          size_t key_size,
                          const char *value,
                          size_t value_size);


/**
 * Callback used by libmicrohttpd in order to obtain content.  The
 * callback is to copy at most @a max bytes of content into @a buf.  The
 * total number of bytes that has been placed into @a buf should be
 * returned.
 *
 * Note that returning zero will cause libmicrohttpd to try again.
 * Thus, returning zero should only be used in conjunction
 * with MHD_suspend_connection() to avoid busy waiting.
 *
 * @param cls extra argument to the callback
 * @param pos position in the datastream to access;
 *        note that if a `struct MHD_Response` object is re-used,
 *        it is possible for the same content reader to
 *        be queried multiple times for the same data;
 *        however, if a `struct MHD_Response` is not re-used,
 *        libmicrohttpd guarantees that "pos" will be
 *        the sum of all non-negative return values
 *        obtained from the content reader so far.
 * @param buf where to copy the data
 * @param max maximum number of bytes to copy to @a buf (size of @a buf)
 * @return number of bytes written to @a buf;
 *  0 is legal unless we are running in internal select mode (since
 *    this would cause busy-waiting); 0 in external select mode
 *    will cause this function to be called again once the external
 *    select calls MHD again;
 *  #MHD_CONTENT_READER_END_OF_STREAM (-1) for the regular
 *    end of transmission (with chunked encoding, MHD will then
 *    terminate the chunk and send any HTTP footers that might be
 *    present; without chunked encoding and given an unknown
 *    response size, MHD will simply close the connection; note
 *    that while returning #MHD_CONTENT_READER_END_OF_STREAM is not technically
 *    legal if a response size was specified, MHD accepts this
 *    and treats it just as #MHD_CONTENT_READER_END_WITH_ERROR;
 *  #MHD_CONTENT_READER_END_WITH_ERROR (-2) to indicate a server
 *    error generating the response; this will cause MHD to simply
 *    close the connection immediately.  If a response size was
 *    given or if chunked encoding is in use, this will indicate
 *    an error to the client.  Note, however, that if the client
 *    does not know a response size and chunked encoding is not in
 *    use, then clients will not be able to tell the difference between
 *    #MHD_CONTENT_READER_END_WITH_ERROR and #MHD_CONTENT_READER_END_OF_STREAM.
 *    This is not a limitation of MHD but rather of the HTTP protocol.
 */
typedef ssize_t
(*MHD_ContentReaderCallback) (void *cls,
                              uint64_t pos,
                              char *buf,
                              size_t max);


/**
 * This method is called by libmicrohttpd if we
 * are done with a content reader.  It should
 * be used to free resources associated with the
 * content reader.
 *
 * @param cls closure
 * @ingroup response
 */
typedef void
(*MHD_ContentReaderFreeCallback) (void *cls);


/**
 * Iterator over key-value pairs where the value
 * maybe made available in increments and/or may
 * not be zero-terminated.  Used for processing
 * POST data.
 *
 * @param cls user-specified closure
 * @param kind type of the value, always #MHD_POSTDATA_KIND when called from MHD
 * @param key 0-terminated key for the value
 * @param filename name of the uploaded file, NULL if not known
 * @param content_type mime-type of the data, NULL if not known
 * @param transfer_encoding encoding of the data, NULL if not known
 * @param data pointer to @a size bytes of data at the
 *              specified offset
 * @param off offset of data in the overall value
 * @param size number of bytes in @a data available
 * @return #MHD_YES to continue iterating,
 *         #MHD_NO to abort the iteration
 */
typedef int
(*MHD_PostDataIterator) (void *cls,
                         enum MHD_ValueKind kind,
                         const char *key,
                         const char *filename,
                         const char *content_type,
                         const char *transfer_encoding,
                         const char *data,
                         uint64_t off,
                         size_t size);

/* **************** Daemon handling functions ***************** */

/**
 * Start a webserver on the given port.
 *
 * @param flags combination of `enum MHD_FLAG` values
 * @param port port to bind to (in host byte order),
 *        use '0' to bind to random free port,
 *        ignored if MHD_OPTION_SOCK_ADDR or
 *        MHD_OPTION_LISTEN_SOCKET is provided
 *        or MHD_USE_NO_LISTEN_SOCKET is specified
 * @param apc callback to call to check which clients
 *        will be allowed to connect; you can pass NULL
 *        in which case connections from any IP will be
 *        accepted
 * @param apc_cls extra argument to apc
 * @param dh handler called for all requests (repeatedly)
 * @param dh_cls extra argument to @a dh
 * @param ap list of options (type-value pairs,
 *        terminated with #MHD_OPTION_END).
 * @return NULL on error, handle to daemon on success
 * @ingroup event
 */
_MHD_EXTERN struct MHD_Daemon *
MHD_start_daemon_va (unsigned int flags,
                     uint16_t port,
                     MHD_AcceptPolicyCallback apc, void *apc_cls,
                     MHD_AccessHandlerCallback dh, void *dh_cls,
                     va_list ap);


/**
 * Start a webserver on the given port.  Variadic version of
 * #MHD_start_daemon_va.
 *
 * @param flags combination of `enum MHD_FLAG` values
 * @param port port to bind to (in host byte order),
 *        use '0' to bind to random free port,
 *        ignored if MHD_OPTION_SOCK_ADDR or
 *        MHD_OPTION_LISTEN_SOCKET is provided
 *        or MHD_USE_NO_LISTEN_SOCKET is specified
 * @param apc callback to call to check which clients
 *        will be allowed to connect; you can pass NULL
 *        in which case connections from any IP will be
 *        accepted
 * @param apc_cls extra argument to apc
 * @param dh handler called for all requests (repeatedly)
 * @param dh_cls extra argument to @a dh
 * @return NULL on error, handle to daemon on success
 * @ingroup event
 */
_MHD_EXTERN struct MHD_Daemon *
MHD_start_daemon (unsigned int flags,
                  uint16_t port,
                  MHD_AcceptPolicyCallback apc, void *apc_cls,
                  MHD_AccessHandlerCallback dh, void *dh_cls,
                  ...);


/**
 * Stop accepting connections from the listening socket.  Allows
 * clients to continue processing, but stops accepting new
 * connections.  Note that the caller is responsible for closing the
 * returned socket; however, if MHD is run using threads (anything but
 * external select mode), it must not be closed until AFTER
 * #MHD_stop_daemon has been called (as it is theoretically possible
 * that an existing thread is still using it).
 *
 * Note that some thread modes require the caller to have passed
 * #MHD_USE_ITC when using this API.  If this daemon is
 * in one of those modes and this option was not given to
 * #MHD_start_daemon, this function will return #MHD_INVALID_SOCKET.
 *
 * @param daemon daemon to stop accepting new connections for
 * @return old listen socket on success, #MHD_INVALID_SOCKET if
 *         the daemon was already not listening anymore
 * @ingroup specialized
 */
_MHD_EXTERN MHD_socket
MHD_quiesce_daemon (struct MHD_Daemon *daemon);


/**
 * Shutdown an HTTP daemon.
 *
 * @param daemon daemon to stop
 * @ingroup event
 */
_MHD_EXTERN void
MHD_stop_daemon (struct MHD_Daemon *daemon);


/**
 * Add another client connection to the set of connections managed by
 * MHD.  This API is usually not needed (since MHD will accept inbound
 * connections on the server socket).  Use this API in special cases,
 * for example if your HTTP server is behind NAT and needs to connect
 * out to the HTTP client, or if you are building a proxy.
 *
 * If you use this API in conjunction with a internal select or a
 * thread pool, you must set the option
 * #MHD_USE_ITC to ensure that the freshly added
 * connection is immediately processed by MHD.
 *
 * The given client socket will be managed (and closed!) by MHD after
 * this call and must no longer be used directly by the application
 * afterwards.
 *
 * @param daemon daemon that manages the connection
 * @param client_socket socket to manage (MHD will expect
 *        to receive an HTTP request from this socket next).
 * @param addr IP address of the client
 * @param addrlen number of bytes in @a addr
 * @return #MHD_YES on success, #MHD_NO if this daemon could
 *        not handle the connection (i.e. `malloc()` failed, etc).
 *        The socket will be closed in any case; `errno` is
 *        set to indicate further details about the error.
 * @ingroup specialized
 */
_MHD_EXTERN int
MHD_add_connection (struct MHD_Daemon *daemon,
                    MHD_socket client_socket,
                    const struct sockaddr *addr,
                    socklen_t addrlen);


/**
 * Obtain the `select()` sets for this daemon.
 * Daemon's FDs will be added to fd_sets. To get only
 * daemon FDs in fd_sets, call FD_ZERO for each fd_set
 * before calling this function. FD_SETSIZE is assumed
 * to be platform's default.
 *
 * This function should only be called in when MHD is configured to
 * use external select with 'select()' or with 'epoll'.
 * In the latter case, it will only add the single 'epoll()' file
 * descriptor used by MHD to the sets.
 * It's necessary to use #MHD_get_timeout() in combination with
 * this function.
 *
 * This function must be called only for daemon started
 * without #MHD_USE_INTERNAL_POLLING_THREAD flag.
 *
 * @param daemon daemon to get sets from
 * @param read_fd_set read set
 * @param write_fd_set write set
 * @param except_fd_set except set
 * @param max_fd increased to largest FD added (if larger
 *               than existing value); can be NULL
 * @return #MHD_YES on success, #MHD_NO if this
 *         daemon was not started with the right
 *         options for this call or any FD didn't
 *         fit fd_set.
 * @ingroup event
 */
_MHD_EXTERN int
MHD_get_fdset (struct MHD_Daemon *daemon,
               fd_set *read_fd_set,
               fd_set *write_fd_set,
               fd_set *except_fd_set,
               MHD_socket *max_fd);


/**
 * Obtain the `select()` sets for this daemon.
 * Daemon's FDs will be added to fd_sets. To get only
 * daemon FDs in fd_sets, call FD_ZERO for each fd_set
 * before calling this function.
 *
 * Passing custom FD_SETSIZE as @a fd_setsize allow usage of
 * larger/smaller than platform's default fd_sets.
 *
 * This function should only be called in when MHD is configured to
 * use external select with 'select()' or with 'epoll'.
 * In the latter case, it will only add the single 'epoll' file
 * descriptor used by MHD to the sets.
 * It's necessary to use #MHD_get_timeout() in combination with
 * this function.
 *
 * This function must be called only for daemon started
 * without #MHD_USE_INTERNAL_POLLING_THREAD flag.
 *
 * @param daemon daemon to get sets from
 * @param read_fd_set read set
 * @param write_fd_set write set
 * @param except_fd_set except set
 * @param max_fd increased to largest FD added (if larger
 *               than existing value); can be NULL
 * @param fd_setsize value of FD_SETSIZE
 * @return #MHD_YES on success, #MHD_NO if this
 *         daemon was not started with the right
 *         options for this call or any FD didn't
 *         fit fd_set.
 * @ingroup event
 */
_MHD_EXTERN int
MHD_get_fdset2 (struct MHD_Daemon *daemon,
                fd_set *read_fd_set,
                fd_set *write_fd_set,
                fd_set *except_fd_set,
                MHD_socket *max_fd,
                unsigned int fd_setsize);


/**
 * Obtain the `select()` sets for this daemon.
 * Daemon's FDs will be added to fd_sets. To get only
 * daemon FDs in fd_sets, call FD_ZERO for each fd_set
 * before calling this function. Size of fd_set is
 * determined by current value of FD_SETSIZE.
 * It's necessary to use #MHD_get_timeout() in combination with
 * this function.
 *
 * This function could be called only for daemon started
 * without #MHD_USE_INTERNAL_POLLING_THREAD flag.
 *
 * @param daemon daemon to get sets from
 * @param read_fd_set read set
 * @param write_fd_set write set
 * @param except_fd_set except set
 * @param max_fd increased to largest FD added (if larger
 *               than existing value); can be NULL
 * @return #MHD_YES on success, #MHD_NO if this
 *         daemon was not started with the right
 *         options for this call or any FD didn't
 *         fit fd_set.
 * @ingroup event
 */
#define MHD_get_fdset(daemon,read_fd_set,write_fd_set,except_fd_set,max_fd) \
  MHD_get_fdset2 ((daemon),(read_fd_set),(write_fd_set),(except_fd_set), \
                  (max_fd),FD_SETSIZE)


/**
 * Obtain timeout value for polling function for this daemon.
 * This function set value to amount of milliseconds for which polling
 * function (`select()` or `poll()`) should at most block, not the
 * timeout value set for connections.
 * It is important to always use this function, even if connection
 * timeout is not set, as in some cases MHD may already have more
 * data to process on next turn (data pending in TLS buffers,
 * connections are already ready with epoll etc.) and returned timeout
 * will be zero.
 *
 * @param daemon daemon to query for timeout
 * @param timeout set to the timeout (in milliseconds)
 * @return #MHD_YES on success, #MHD_NO if timeouts are
 *        not used (or no connections exist that would
 *        necessitate the use of a timeout right now).
 * @ingroup event
 */
_MHD_EXTERN int
MHD_get_timeout (struct MHD_Daemon *daemon,
                 MHD_UNSIGNED_LONG_LONG *timeout);


/**
 * Run webserver operations (without blocking unless in client
 * callbacks).  This method should be called by clients in combination
 * with #MHD_get_fdset if the client-controlled select method is used and
 * #MHD_get_timeout().
 *
 * This function is a convenience method, which is useful if the
 * fd_sets from #MHD_get_fdset were not directly passed to `select()`;
 * with this function, MHD will internally do the appropriate `select()`
 * call itself again.  While it is always safe to call #MHD_run (if
 * #MHD_USE_INTERNAL_POLLING_THREAD is not set), you should call
 * #MHD_run_from_select if performance is important (as it saves an
 * expensive call to `select()`).
 *
 * @param daemon daemon to run
 * @return #MHD_YES on success, #MHD_NO if this
 *         daemon was not started with the right
 *         options for this call.
 * @ingroup event
 */
_MHD_EXTERN int
MHD_run (struct MHD_Daemon *daemon);


/**
 * Run webserver operations. This method should be called by clients
 * in combination with #MHD_get_fdset and #MHD_get_timeout() if the
 * client-controlled select method is used.
 *
 * You can use this function instead of #MHD_run if you called
 * `select()` on the result from #MHD_get_fdset.  File descriptors in
 * the sets that are not controlled by MHD will be ignored.  Calling
 * this function instead of #MHD_run is more efficient as MHD will
 * not have to call `select()` again to determine which operations are
 * ready.
 *
 * This function cannot be used with daemon started with
 * #MHD_USE_INTERNAL_POLLING_THREAD flag.
 *
 * @param daemon daemon to run select loop for
 * @param read_fd_set read set
 * @param write_fd_set write set
 * @param except_fd_set except set
 * @return #MHD_NO on serious errors, #MHD_YES on success
 * @ingroup event
 */
_MHD_EXTERN int
MHD_run_from_select (struct MHD_Daemon *daemon,
                     const fd_set *read_fd_set,
                     const fd_set *write_fd_set,
                     const fd_set *except_fd_set);


/* **************** Connection handling functions ***************** */

/**
 * Get all of the headers from the request.
 *
 * @param connection connection to get values from
 * @param kind types of values to iterate over, can be a bitmask
 * @param iterator callback to call on each header;
 *        maybe NULL (then just count headers)
 * @param iterator_cls extra argument to @a iterator
 * @return number of entries iterated over,
 *         -1 if connection is NULL.
 * @ingroup request
 */
_MHD_EXTERN int
MHD_get_connection_values (struct MHD_Connection *connection,
                           enum MHD_ValueKind kind,
                           MHD_KeyValueIterator iterator,
                           void *iterator_cls);


/**
 * Get all of the headers from the request.
 *
 * @param connection connection to get values from
 * @param kind types of values to iterate over, can be a bitmask
 * @param iterator callback to call on each header;
 *        maybe NULL (then just count headers)
 * @param iterator_cls extra argument to @a iterator
 * @return number of entries iterated over,
 *         -1 if connection is NULL.
 * @ingroup request
 */
_MHD_EXTERN int
MHD_get_connection_values_n (struct MHD_Connection *connection,
                             enum MHD_ValueKind kind,
                             MHD_KeyValueIteratorN iterator,
                             void *iterator_cls);


/**
 * This function can be used to add an entry to the HTTP headers of a
 * connection (so that the #MHD_get_connection_values function will
 * return them -- and the `struct MHD_PostProcessor` will also see
 * them).  This maybe required in certain situations (see Mantis
 * #1399) where (broken) HTTP implementations fail to supply values

 * needed by the post processor (or other parts of the application).
 *
 * This function MUST only be called from within the
 * #MHD_AccessHandlerCallback (otherwise, access maybe improperly
 * synchronized).  Furthermore, the client must guarantee that the key
 * and value arguments are 0-terminated strings that are NOT freed
 * until the connection is closed.  (The easiest way to do this is by
 * passing only arguments to permanently allocated strings.).
 *
 * @param connection the connection for which a
 *  value should be set
 * @param kind kind of the value
 * @param key key for the value
 * @param value the value itself
 * @return #MHD_NO if the operation could not be
 *         performed due to insufficient memory;
 *         #MHD_YES on success
 * @ingroup request
 */
_MHD_EXTERN int
MHD_set_connection_value (struct MHD_Connection *connection,
                          enum MHD_ValueKind kind,
                          const char *key,
                          const char *value);


/**
 * This function can be used to add an arbitrary entry to connection.
 * This function could add entry with binary zero, which is allowed
 * for #MHD_GET_ARGUMENT_KIND. For other kind on entries it is
 * recommended to use #MHD_set_connection_value.
 *
 * This function MUST only be called from within the
 * #MHD_AccessHandlerCallback (otherwise, access maybe improperly
 * synchronized).  Furthermore, the client must guarantee that the key
 * and value arguments are 0-terminated strings that are NOT freed
 * until the connection is closed.  (The easiest way to do this is by
 * passing only arguments to permanently allocated strings.).
 *
 * @param connection the connection for which a
 *  value should be set
 * @param kind kind of the value
 * @param key key for the value, must be zero-terminated
 * @param key_size number of bytes in @a key (excluding 0-terminator)
 * @param value the value itself, must be zero-terminated
 * @param value_size number of bytes in @a value (excluding 0-terminator)
 * @return #MHD_NO if the operation could not be
 *         performed due to insufficient memory;
 *         #MHD_YES on success
 * @ingroup request
 */
int
MHD_set_connection_value_n (struct MHD_Connection *connection,
                            enum MHD_ValueKind kind,
                            const char *key,
                            size_t key_size,
                            const char *value,
                            size_t value_size);


/**
 * Sets the global error handler to a different implementation.  @a cb
 * will only be called in the case of typically fatal, serious
 * internal consistency issues.  These issues should only arise in the
 * case of serious memory corruption or similar problems with the
 * architecture.  While @a cb is allowed to return and MHD will then
 * try to continue, this is never safe.
 *
 * The default implementation that is used if no panic function is set
 * simply prints an error message and calls `abort()`.  Alternative
 * implementations might call `exit()` or other similar functions.
 *
 * @param cb new error handler
 * @param cls passed to @a cb
 * @ingroup logging
 */
_MHD_EXTERN void
MHD_set_panic_func (MHD_PanicCallback cb, void *cls);


/**
 * Process escape sequences ('%HH') Updates val in place; the
 * result should be UTF-8 encoded and cannot be larger than the input.
 * The result must also still be 0-terminated.
 *
 * @param val value to unescape (modified in the process)
 * @return length of the resulting val (`strlen(val)` may be
 *  shorter afterwards due to elimination of escape sequences)
 */
_MHD_EXTERN size_t
MHD_http_unescape (char *val);


/**
 * Get a particular header value.  If multiple
 * values match the kind, return any one of them.
 *
 * @param connection connection to get values from
 * @param kind what kind of value are we looking for
 * @param key the header to look for, NULL to lookup 'trailing' value without a key
 * @return NULL if no such item was found
 * @ingroup request
 */
_MHD_EXTERN const char *
MHD_lookup_connection_value (struct MHD_Connection *connection,
                             enum MHD_ValueKind kind,
                             const char *key);


/**
 * Get a particular header value.  If multiple
 * values match the kind, return any one of them.
 * @note Since MHD_VERSION 0x00096304
 *
 * @param connection connection to get values from
 * @param kind what kind of value are we looking for
 * @param key the header to look for, NULL to lookup 'trailing' value without a key
 * @param key_size the length of @a key in bytes
 * @param[out] value_ptr the pointer to variable, which will be set to found value,
 *                       will not be updated if key not found,
 *                       could be NULL to just check for presence of @a key
 * @param[out] value_size_ptr the pointer variable, which will set to found value,
 *                            will not be updated if key not found,
 *                            could be NULL
 * @return #MHD_YES if key is found,
 *         #MHD_NO otherwise.
 * @ingroup request
 */
_MHD_EXTERN int
MHD_lookup_connection_value_n (struct MHD_Connection *connection,
                               enum MHD_ValueKind kind,
                               const char *key,
                               size_t key_size,
                               const char **value_ptr,
                               size_t *value_size_ptr);


/**
 * Queue a response to be transmitted to the client (as soon as
 * possible but after #MHD_AccessHandlerCallback returns).
 *
 * @param connection the connection identifying the client
 * @param status_code HTTP status code (i.e. #MHD_HTTP_OK)
 * @param response response to transmit
 * @return #MHD_NO on error (i.e. reply already sent),
 *         #MHD_YES on success or if message has been queued
 * @ingroup response
 */
_MHD_EXTERN int
MHD_queue_response (struct MHD_Connection *connection,
                    unsigned int status_code,
                    struct MHD_Response *response);


/**
 * Suspend handling of network data for a given connection.  This can
 * be used to dequeue a connection from MHD's event loop for a while.
 *
 * If you use this API in conjunction with a internal select or a
 * thread pool, you must set the option #MHD_USE_ITC to
 * ensure that a resumed connection is immediately processed by MHD.
 *
 * Suspended connections continue to count against the total number of
 * connections allowed (per daemon, as well as per IP, if such limits
 * are set).  Suspended connections will NOT time out; timeouts will
 * restart when the connection handling is resumed.  While a
 * connection is suspended, MHD will not detect disconnects by the
 * client.
 *
 * The only safe time to suspend a connection is from the
 * #MHD_AccessHandlerCallback.
 *
 * Finally, it is an API violation to call #MHD_stop_daemon while
 * having suspended connections (this will at least create memory and
 * socket leaks or lead to undefined behavior).  You must explicitly
 * resume all connections before stopping the daemon.
 *
 * @param connection the connection to suspend
 */
_MHD_EXTERN void
MHD_suspend_connection (struct MHD_Connection *connection);


/**
 * Resume handling of network data for suspended connection.  It is
 * safe to resume a suspended connection at any time.  Calling this
 * function on a connection that was not previously suspended will
 * result in undefined behavior.
 *
 * If you are using this function in ``external'' select mode, you must
 * make sure to run #MHD_run() and #MHD_get_timeout() afterwards (before
 * again calling #MHD_get_fdset()), as otherwise the change may not be
 * reflected in the set returned by #MHD_get_fdset() and you may end up
 * with a connection that is stuck until the next network activity.
 *
 * @param connection the connection to resume
 */
_MHD_EXTERN void
MHD_resume_connection (struct MHD_Connection *connection);


/* **************** Response manipulation functions ***************** */


/**
 * Flags for special handling of responses.
 */
enum MHD_ResponseFlags
{
  /**
   * Default: no special flags.
   */
  MHD_RF_NONE = 0,

  /**
   * Only respond in conservative HTTP 1.0-mode.   In particular,
   * do not (automatically) sent "Connection" headers and always
   * close the connection after generating the response.
   * By default, MHD will respond using the same HTTP version which
   * was set in the request. You can also set the
   * #MHD_RF_HTTP_VERSION_1_0_RESPONSE flag to force version 1.0
   * in the response.
   */
  MHD_RF_HTTP_VERSION_1_0_ONLY = 1,

  /**
   * Only respond in HTTP 1.0-mode. Contrary to the
   * #MHD_RF_HTTP_VERSION_1_0_ONLY flag, the response's HTTP version will
   * always be set to 1.0 and "Connection" headers are still supported.
   */
  MHD_RF_HTTP_VERSION_1_0_RESPONSE = 2,

  /**
   * Disable sanity check preventing clients from manually
   * setting the HTTP content length option.
   */
  MHD_RF_INSANITY_HEADER_CONTENT_LENGTH = 4


};


/**
 * MHD options (for future extensions).
 */
enum MHD_ResponseOptions
{
  /**
   * End of the list of options.
   */
  MHD_RO_END = 0
};


/**
 * Set special flags and options for a response.
 *
 * @param response the response to modify
 * @param flags to set for the response
 * @param ... #MHD_RO_END terminated list of options
 * @return #MHD_YES on success, #MHD_NO on error
 */
_MHD_EXTERN int
MHD_set_response_options (struct MHD_Response *response,
                          enum MHD_ResponseFlags flags,
                          ...);


/**
 * Create a response object.  The response object can be extended with
 * header information and then be used any number of times.
 *
 * @param size size of the data portion of the response, #MHD_SIZE_UNKNOWN for unknown
 * @param block_size preferred block size for querying crc (advisory only,
 *                   MHD may still call @a crc using smaller chunks); this
 *                   is essentially the buffer size used for IO, clients
 *                   should pick a value that is appropriate for IO and
 *                   memory performance requirements
 * @param crc callback to use to obtain response data
 * @param crc_cls extra argument to @a crc
 * @param crfc callback to call to free @a crc_cls resources
 * @return NULL on error (i.e. invalid arguments, out of memory)
 * @ingroup response
 */
_MHD_EXTERN struct MHD_Response *
MHD_create_response_from_callback (uint64_t size,
                                   size_t block_size,
                                   MHD_ContentReaderCallback crc, void *crc_cls,
                                   MHD_ContentReaderFreeCallback crfc);


/**
 * Create a response object.  The response object can be extended with
 * header information and then be used any number of times.
 *
 * @param size size of the @a data portion of the response
 * @param data the data itself
 * @param must_free libmicrohttpd should free data when done
 * @param must_copy libmicrohttpd must make a copy of @a data
 *        right away, the data maybe released anytime after
 *        this call returns
 * @return NULL on error (i.e. invalid arguments, out of memory)
 * @deprecated use #MHD_create_response_from_buffer instead
 * @ingroup response
 */
_MHD_DEPR_FUNC (
  "MHD_create_response_from_data() is deprecated, use MHD_create_response_from_buffer()") \
  _MHD_EXTERN struct MHD_Response *
MHD_create_response_from_data (size_t size,
                               void *data,
                               int must_free,
                               int must_copy);


/**
 * Specification for how MHD should treat the memory buffer
 * given for the response.
 * @ingroup response
 */
enum MHD_ResponseMemoryMode
{

  /**
   * Buffer is a persistent (static/global) buffer that won't change
   * for at least the lifetime of the response, MHD should just use
   * it, not free it, not copy it, just keep an alias to it.
   * @ingroup response
   */
  MHD_RESPMEM_PERSISTENT,

  /**
   * Buffer is heap-allocated with `malloc()` (or equivalent) and
   * should be freed by MHD after processing the response has
   * concluded (response reference counter reaches zero).
   * @ingroup response
   */
  MHD_RESPMEM_MUST_FREE,

  /**
   * Buffer is in transient memory, but not on the heap (for example,
   * on the stack or non-`malloc()` allocated) and only valid during the
   * call to #MHD_create_response_from_buffer.  MHD must make its
   * own private copy of the data for processing.
   * @ingroup response
   */
  MHD_RESPMEM_MUST_COPY

};


/**
 * Create a response object.  The response object can be extended with
 * header information and then be used any number of times.
 *
 * @param size size of the data portion of the response
 * @param buffer size bytes containing the response's data portion
 * @param mode flags for buffer management
 * @return NULL on error (i.e. invalid arguments, out of memory)
 * @ingroup response
 */
_MHD_EXTERN struct MHD_Response *
MHD_create_response_from_buffer (size_t size,
                                 void *buffer,
                                 enum MHD_ResponseMemoryMode mode);


/**
 * Create a response object.  The response object can be extended with
 * header information and then be used any number of times.
 *
 * @param size size of the data portion of the response
 * @param buffer size bytes containing the response's data portion
 * @param crfc function to call to free the @a buffer
 * @return NULL on error (i.e. invalid arguments, out of memory)
 * @ingroup response
 */
_MHD_EXTERN struct MHD_Response *
MHD_create_response_from_buffer_with_free_callback (size_t size,
                                                    void *buffer,
                                                    MHD_ContentReaderFreeCallback
                                                    crfc);


/**
 * Create a response object.  The response object can be extended with
 * header information and then be used any number of times.
 *
 * @param size size of the data portion of the response
 * @param fd file descriptor referring to a file on disk with the
 *        data; will be closed when response is destroyed;
 *        fd should be in 'blocking' mode
 * @return NULL on error (i.e. invalid arguments, out of memory)
 * @ingroup response
 */
_MHD_EXTERN struct MHD_Response *
MHD_create_response_from_fd (size_t size,
                             int fd);


/**
 * Create a response object.  The response object can be extended with
 * header information and then be used any number of times.
 *
 * @param size size of the data portion of the response;
 *        sizes larger than 2 GiB may be not supported by OS or
 *        MHD build; see ::MHD_FEATURE_LARGE_FILE
 * @param fd file descriptor referring to a file on disk with the
 *        data; will be closed when response is destroyed;
 *        fd should be in 'blocking' mode
 * @return NULL on error (i.e. invalid arguments, out of memory)
 * @ingroup response
 */
_MHD_EXTERN struct MHD_Response *
MHD_create_response_from_fd64 (uint64_t size,
                               int fd);


/**
 * Create a response object.  The response object can be extended with
 * header information and then be used any number of times.
 *
 * @param size size of the data portion of the response
 * @param fd file descriptor referring to a file on disk with the
 *        data; will be closed when response is destroyed;
 *        fd should be in 'blocking' mode
 * @param offset offset to start reading from in the file;
 *        Be careful! `off_t` may have been compiled to be a
 *        64-bit variable for MHD, in which case your application
 *        also has to be compiled using the same options! Read
 *        the MHD manual for more details.
 * @return NULL on error (i.e. invalid arguments, out of memory)
 * @ingroup response
 */
_MHD_DEPR_FUNC (
  "Function MHD_create_response_from_fd_at_offset() is deprecated, use MHD_create_response_from_fd_at_offset64()") \
  _MHD_EXTERN struct MHD_Response *
MHD_create_response_from_fd_at_offset (size_t size,
                                       int fd,
                                       off_t offset);

#if ! defined(_MHD_NO_DEPR_IN_MACRO) || defined(_MHD_NO_DEPR_FUNC)
/* Substitute MHD_create_response_from_fd_at_offset64() instead of MHD_create_response_from_fd_at_offset()
   to minimize potential problems with different off_t sizes */
#define MHD_create_response_from_fd_at_offset(size,fd,offset) \
  _MHD_DEPR_IN_MACRO ( \
    "Usage of MHD_create_response_from_fd_at_offset() is deprecated, use MHD_create_response_from_fd_at_offset64()") \
  MHD_create_response_from_fd_at_offset64 ((size),(fd),(offset))
#endif /* !_MHD_NO_DEPR_IN_MACRO || _MHD_NO_DEPR_FUNC */


/**
 * Create a response object.  The response object can be extended with
 * header information and then be used any number of times.
 *
 * @param size size of the data portion of the response;
 *        sizes larger than 2 GiB may be not supported by OS or
 *        MHD build; see ::MHD_FEATURE_LARGE_FILE
 * @param fd file descriptor referring to a file on disk with the
 *        data; will be closed when response is destroyed;
 *        fd should be in 'blocking' mode
 * @param offset offset to start reading from in the file;
 *        reading file beyond 2 GiB may be not supported by OS or
 *        MHD build; see ::MHD_FEATURE_LARGE_FILE
 * @return NULL on error (i.e. invalid arguments, out of memory)
 * @ingroup response
 */
_MHD_EXTERN struct MHD_Response *
MHD_create_response_from_fd_at_offset64 (uint64_t size,
                                         int fd,
                                         uint64_t offset);


/**
 * Enumeration for actions MHD should perform on the underlying socket
 * of the upgrade.  This API is not finalized, and in particular
 * the final set of actions is yet to be decided. This is just an
 * idea for what we might want.
 */
enum MHD_UpgradeAction
{

  /**
   * Close the socket, the application is done with it.
   *
   * Takes no extra arguments.
   */
  MHD_UPGRADE_ACTION_CLOSE = 0,

  /**
   * Enable CORKing on the underlying socket.
   */
  MHD_UPGRADE_ACTION_CORK_ON = 1,

  /**
   * Disable CORKing on the underlying socket.
   */
  MHD_UPGRADE_ACTION_CORK_OFF = 2

};


/**
 * Handle given to the application to manage special
 * actions relating to MHD responses that "upgrade"
 * the HTTP protocol (i.e. to WebSockets).
 */
struct MHD_UpgradeResponseHandle;


/**
 * This connection-specific callback is provided by MHD to
 * applications (unusual) during the #MHD_UpgradeHandler.
 * It allows applications to perform 'special' actions on
 * the underlying socket from the upgrade.
 *
 * @param urh the handle identifying the connection to perform
 *            the upgrade @a action on.
 * @param action which action should be performed
 * @param ... arguments to the action (depends on the action)
 * @return #MHD_NO on error, #MHD_YES on success
 */
_MHD_EXTERN int
MHD_upgrade_action (struct MHD_UpgradeResponseHandle *urh,
                    enum MHD_UpgradeAction action,
                    ...);


/**
 * Function called after a protocol "upgrade" response was sent
 * successfully and the socket should now be controlled by some
 * protocol other than HTTP.
 *
 * Any data already received on the socket will be made available in
 * @e extra_in.  This can happen if the application sent extra data
 * before MHD send the upgrade response.  The application should
 * treat data from @a extra_in as if it had read it from the socket.
 *
 * Note that the application must not close() @a sock directly,
 * but instead use #MHD_upgrade_action() for special operations
 * on @a sock.
 *
 * Data forwarding to "upgraded" @a sock will be started as soon
 * as this function return.
 *
 * Except when in 'thread-per-connection' mode, implementations
 * of this function should never block (as it will still be called
 * from within the main event loop).
 *
 * @param cls closure, whatever was given to #MHD_create_response_for_upgrade().
 * @param connection original HTTP connection handle,
 *                   giving the function a last chance
 *                   to inspect the original HTTP request
 * @param con_cls last value left in `con_cls` of the `MHD_AccessHandlerCallback`
 * @param extra_in if we happened to have read bytes after the
 *                 HTTP header already (because the client sent
 *                 more than the HTTP header of the request before
 *                 we sent the upgrade response),
 *                 these are the extra bytes already read from @a sock
 *                 by MHD.  The application should treat these as if
 *                 it had read them from @a sock.
 * @param extra_in_size number of bytes in @a extra_in
 * @param sock socket to use for bi-directional communication
 *        with the client.  For HTTPS, this may not be a socket
 *        that is directly connected to the client and thus certain
 *        operations (TCP-specific setsockopt(), getsockopt(), etc.)
 *        may not work as expected (as the socket could be from a
 *        socketpair() or a TCP-loopback).  The application is expected
 *        to perform read()/recv() and write()/send() calls on the socket.
 *        The application may also call shutdown(), but must not call
 *        close() directly.
 * @param urh argument for #MHD_upgrade_action()s on this @a connection.
 *        Applications must eventually use this callback to (indirectly)
 *        perform the close() action on the @a sock.
 */
typedef void
(*MHD_UpgradeHandler)(void *cls,
                      struct MHD_Connection *connection,
                      void *con_cls,
                      const char *extra_in,
                      size_t extra_in_size,
                      MHD_socket sock,
                      struct MHD_UpgradeResponseHandle *urh);


/**
 * Create a response object that can be used for 101 UPGRADE
 * responses, for example to implement WebSockets.  After sending the
 * response, control over the data stream is given to the callback (which
 * can then, for example, start some bi-directional communication).
 * If the response is queued for multiple connections, the callback
 * will be called for each connection.  The callback
 * will ONLY be called after the response header was successfully passed
 * to the OS; if there are communication errors before, the usual MHD
 * connection error handling code will be performed.
 *
 * Setting the correct HTTP code (i.e. MHD_HTTP_SWITCHING_PROTOCOLS)
 * and setting correct HTTP headers for the upgrade must be done
 * manually (this way, it is possible to implement most existing
 * WebSocket versions using this API; in fact, this API might be useful
 * for any protocol switch, not just WebSockets).  Note that
 * draft-ietf-hybi-thewebsocketprotocol-00 cannot be implemented this
 * way as the header "HTTP/1.1 101 WebSocket Protocol Handshake"
 * cannot be generated; instead, MHD will always produce "HTTP/1.1 101
 * Switching Protocols" (if the response code 101 is used).
 *
 * As usual, the response object can be extended with header
 * information and then be used any number of times (as long as the
 * header information is not connection-specific).
 *
 * @param upgrade_handler function to call with the "upgraded" socket
 * @param upgrade_handler_cls closure for @a upgrade_handler
 * @return NULL on error (i.e. invalid arguments, out of memory)
 */
_MHD_EXTERN struct MHD_Response *
MHD_create_response_for_upgrade (MHD_UpgradeHandler upgrade_handler,
                                 void *upgrade_handler_cls);


/**
 * Destroy a response object and associated resources.  Note that
 * libmicrohttpd may keep some of the resources around if the response
 * is still in the queue for some clients, so the memory may not
 * necessarily be freed immediatley.
 *
 * @param response response to destroy
 * @ingroup response
 */
_MHD_EXTERN void
MHD_destroy_response (struct MHD_Response *response);


/**
 * Add a header line to the response.
 *
 * @param response response to add a header to
 * @param header the header to add
 * @param content value to add
 * @return #MHD_NO on error (i.e. invalid header or content format),
 *         or out of memory
 * @ingroup response
 */
_MHD_EXTERN int
MHD_add_response_header (struct MHD_Response *response,
                         const char *header,
                         const char *content);


/**
 * Add a footer line to the response.
 *
 * @param response response to remove a header from
 * @param footer the footer to delete
 * @param content value to delete
 * @return #MHD_NO on error (i.e. invalid footer or content format).
 * @ingroup response
 */
_MHD_EXTERN int
MHD_add_response_footer (struct MHD_Response *response,
                         const char *footer,
                         const char *content);


/**
 * Delete a header (or footer) line from the response.
 *
 * @param response response to remove a header from
 * @param header the header to delete
 * @param content value to delete
 * @return #MHD_NO on error (no such header known)
 * @ingroup response
 */
_MHD_EXTERN int
MHD_del_response_header (struct MHD_Response *response,
                         const char *header,
                         const char *content);


/**
 * Get all of the headers (and footers) added to a response.
 *
 * @param response response to query
 * @param iterator callback to call on each header;
 *        maybe NULL (then just count headers)
 * @param iterator_cls extra argument to @a iterator
 * @return number of entries iterated over
 * @ingroup response
 */
_MHD_EXTERN int
MHD_get_response_headers (struct MHD_Response *response,
                          MHD_KeyValueIterator iterator,
                          void *iterator_cls);


/**
 * Get a particular header (or footer) from the response.
 *
 * @param response response to query
 * @param key which header to get
 * @return NULL if header does not exist
 * @ingroup response
 */
_MHD_EXTERN const char *
MHD_get_response_header (struct MHD_Response *response,
                         const char *key);


/* ********************** PostProcessor functions ********************** */

/**
 * Create a `struct MHD_PostProcessor`.
 *
 * A `struct MHD_PostProcessor` can be used to (incrementally) parse
 * the data portion of a POST request.  Note that some buggy browsers
 * fail to set the encoding type.  If you want to support those, you
 * may have to call #MHD_set_connection_value with the proper encoding
 * type before creating a post processor (if no supported encoding
 * type is set, this function will fail).
 *
 * @param connection the connection on which the POST is
 *        happening (used to determine the POST format)
 * @param buffer_size maximum number of bytes to use for
 *        internal buffering (used only for the parsing,
 *        specifically the parsing of the keys).  A
 *        tiny value (256-1024) should be sufficient.
 *        Do NOT use a value smaller than 256.  For good
 *        performance, use 32 or 64k (i.e. 65536).
 * @param iter iterator to be called with the parsed data,
 *        Must NOT be NULL.
 * @param iter_cls first argument to @a iter
 * @return NULL on error (out of memory, unsupported encoding),
 *         otherwise a PP handle
 * @ingroup request
 */
_MHD_EXTERN struct MHD_PostProcessor *
MHD_create_post_processor (struct MHD_Connection *connection,
                           size_t buffer_size,
                           MHD_PostDataIterator iter, void *iter_cls);


/**
 * Parse and process POST data.  Call this function when POST data is
 * available (usually during an #MHD_AccessHandlerCallback) with the
 * "upload_data" and "upload_data_size".  Whenever possible, this will
 * then cause calls to the #MHD_PostDataIterator.
 *
 * @param pp the post processor
 * @param post_data @a post_data_len bytes of POST data
 * @param post_data_len length of @a post_data
 * @return #MHD_YES on success, #MHD_NO on error
 *         (out-of-memory, iterator aborted, parse error)
 * @ingroup request
 */
_MHD_EXTERN int
MHD_post_process (struct MHD_PostProcessor *pp,
                  const char *post_data, size_t post_data_len);


/**
 * Release PostProcessor resources.
 *
 * @param pp the PostProcessor to destroy
 * @return #MHD_YES if processing completed nicely,
 *         #MHD_NO if there were spurious characters / formatting
 *                problems; it is common to ignore the return
 *                value of this function
 * @ingroup request
 */
_MHD_EXTERN int
MHD_destroy_post_processor (struct MHD_PostProcessor *pp);


/* ********************* Digest Authentication functions *************** */


/**
 * Constant to indicate that the nonce of the provided
 * authentication code was wrong.
 * @ingroup authentication
 */
#define MHD_INVALID_NONCE -1


/**
 * Get the username from the authorization header sent by the client
 *
 * @param connection The MHD connection structure
 * @return NULL if no username could be found, a pointer
 *      to the username if found, free using #MHD_free().
 * @ingroup authentication
 */
_MHD_EXTERN char *
MHD_digest_auth_get_username (struct MHD_Connection *connection);


/**
 * Free the memory given by @a ptr. Calls "free(ptr)".  This function
 * should be used to free the username returned by
 * #MHD_digest_auth_get_username().
 * @note Since v0.9.56
 *
 * @param ptr pointer to free.
 */
_MHD_EXTERN void
MHD_free (void *ptr);


/**
 * Which digest algorithm should MHD use for HTTP digest authentication?
 */
enum MHD_DigestAuthAlgorithm
{

  /**
   * MHD should pick (currently defaults to SHA-256).
   */
  MHD_DIGEST_ALG_AUTO = 0,

  /**
   * Force use of MD5.
   */
  MHD_DIGEST_ALG_MD5,

  /**
   * Force use of SHA-256.
   */
  MHD_DIGEST_ALG_SHA256

};


/**
 * Authenticates the authorization header sent by the client.
 *
 * @param connection The MHD connection structure
 * @param realm The realm presented to the client
 * @param username The username needs to be authenticated
 * @param password The password used in the authentication
 * @param nonce_timeout The amount of time for a nonce to be
 *      invalid in seconds
 * @param algo digest algorithms allowed for verification
 * @return #MHD_YES if authenticated, #MHD_NO if not,
 *      #MHD_INVALID_NONCE if nonce is invalid
 * @ingroup authentication
 */
_MHD_EXTERN int
MHD_digest_auth_check2 (struct MHD_Connection *connection,
                        const char *realm,
                        const char *username,
                        const char *password,
                        unsigned int nonce_timeout,
                        enum MHD_DigestAuthAlgorithm algo);


/**
 * Authenticates the authorization header sent by the client.
 * Uses #MHD_DIGEST_ALG_MD5 (for now, for backwards-compatibility).
 * Note that this MAY change to #MHD_DIGEST_ALG_AUTO in the future.
 * If you want to be sure you get MD5, use #MHD_digest_auth_check2()
 * and specifiy MD5 explicitly.
 *
 * @param connection The MHD connection structure
 * @param realm The realm presented to the client
 * @param username The username needs to be authenticated
 * @param password The password used in the authentication
 * @param nonce_timeout The amount of time for a nonce to be
 *      invalid in seconds
 * @return #MHD_YES if authenticated, #MHD_NO if not,
 *      #MHD_INVALID_NONCE if nonce is invalid
 * @ingroup authentication
 * @deprecated use MHD_digest_auth_check2()
 */
_MHD_EXTERN int
MHD_digest_auth_check (struct MHD_Connection *connection,
                       const char *realm,
                       const char *username,
                       const char *password,
                       unsigned int nonce_timeout);


/**
 * Authenticates the authorization header sent by the client.
 *
 * @param connection The MHD connection structure
 * @param realm The realm presented to the client
 * @param username The username needs to be authenticated
 * @param digest An `unsigned char *' pointer to the binary MD5 sum
 *      for the precalculated hash value "username:realm:password"
 *      of @a digest_size bytes
 * @param digest_size number of bytes in @a digest (size must match @a algo!)
 * @param nonce_timeout The amount of time for a nonce to be
 *      invalid in seconds
 * @param algo digest algorithms allowed for verification
 * @return #MHD_YES if authenticated, #MHD_NO if not,
 *      #MHD_INVALID_NONCE if nonce is invalid
 * @ingroup authentication
 */
_MHD_EXTERN int
MHD_digest_auth_check_digest2 (struct MHD_Connection *connection,
                               const char *realm,
                               const char *username,
                               const uint8_t *digest,
                               size_t digest_size,
                               unsigned int nonce_timeout,
                               enum MHD_DigestAuthAlgorithm algo);


/**
 * Authenticates the authorization header sent by the client
 * Uses #MHD_DIGEST_ALG_MD5 (required, as @a digest is of fixed
 * size).
 *
 * @param connection The MHD connection structure
 * @param realm The realm presented to the client
 * @param username The username needs to be authenticated
 * @param digest An `unsigned char *' pointer to the binary hash
 *    for the precalculated hash value "username:realm:password";
 *    length must be #MHD_MD5_DIGEST_SIZE bytes
 * @param nonce_timeout The amount of time for a nonce to be
 *      invalid in seconds
 * @return #MHD_YES if authenticated, #MHD_NO if not,
 *      #MHD_INVALID_NONCE if nonce is invalid
 * @ingroup authentication
 * @deprecated use #MHD_digest_auth_check_digest2()
 */
_MHD_EXTERN int
MHD_digest_auth_check_digest (struct MHD_Connection *connection,
                              const char *realm,
                              const char *username,
                              const uint8_t digest[MHD_MD5_DIGEST_SIZE],
                              unsigned int nonce_timeout);


/**
 * Queues a response to request authentication from the client
 *
 * @param connection The MHD connection structure
 * @param realm the realm presented to the client
 * @param opaque string to user for opaque value
 * @param response reply to send; should contain the "access denied"
 *        body; note that this function will set the "WWW Authenticate"
 *        header and that the caller should not do this
 * @param signal_stale #MHD_YES if the nonce is invalid to add
 *      'stale=true' to the authentication header
 * @param algo digest algorithm to use
 * @return #MHD_YES on success, #MHD_NO otherwise
 * @ingroup authentication
 */
_MHD_EXTERN int
MHD_queue_auth_fail_response2 (struct MHD_Connection *connection,
                               const char *realm,
                               const char *opaque,
                               struct MHD_Response *response,
                               int signal_stale,
                               enum MHD_DigestAuthAlgorithm algo);


/**
 * Queues a response to request authentication from the client
 * For now uses MD5 (for backwards-compatibility). Still, if you
 * need to be sure, use #MHD_queue_fail_auth_response2().
 *
 * @param connection The MHD connection structure
 * @param realm The realm presented to the client
 * @param opaque string to user for opaque value
 * @param response reply to send; should contain the "access denied"
 *        body; note that this function will set the "WWW Authenticate"
 *        header and that the caller should not do this
 * @param signal_stale #MHD_YES if the nonce is invalid to add
 *      'stale=true' to the authentication header
 * @return #MHD_YES on success, #MHD_NO otherwise
 * @ingroup authentication
 * @deprecated use MHD_queue_auth_fail_response2()
 */
_MHD_EXTERN int
MHD_queue_auth_fail_response (struct MHD_Connection *connection,
                              const char *realm,
                              const char *opaque,
                              struct MHD_Response *response,
                              int signal_stale);


/**
 * Get the username and password from the basic authorization header sent by the client
 *
 * @param connection The MHD connection structure
 * @param[out] password a pointer for the password, free using #MHD_free().
 * @return NULL if no username could be found, a pointer
 *      to the username if found, free using #MHD_free().
 * @ingroup authentication
 */
_MHD_EXTERN char *
MHD_basic_auth_get_username_password (struct MHD_Connection *connection,
                                      char**password);


/**
 * Queues a response to request basic authentication from the client
 * The given response object is expected to include the payload for
 * the response; the "WWW-Authenticate" header will be added and the
 * response queued with the 'UNAUTHORIZED' status code.
 *
 * @param connection The MHD connection structure
 * @param realm the realm presented to the client
 * @param response response object to modify and queue
 * @return #MHD_YES on success, #MHD_NO otherwise
 * @ingroup authentication
 */
_MHD_EXTERN int
MHD_queue_basic_auth_fail_response (struct MHD_Connection *connection,
                                    const char *realm,
                                    struct MHD_Response *response);

/* ********************** generic query functions ********************** */


/**
 * Obtain information about the given connection.
 *
 * @param connection what connection to get information about
 * @param info_type what information is desired?
 * @param ... depends on @a info_type
 * @return NULL if this information is not available
 *         (or if the @a info_type is unknown)
 * @ingroup specialized
 */
_MHD_EXTERN const union MHD_ConnectionInfo *
MHD_get_connection_info (struct MHD_Connection *connection,
                         enum MHD_ConnectionInfoType info_type,
                         ...);


/**
 * MHD connection options.  Given to #MHD_set_connection_option to
 * set custom options for a particular connection.
 */
enum MHD_CONNECTION_OPTION
{

  /**
   * Set a custom timeout for the given connection.  Specified
   * as the number of seconds, given as an `unsigned int`.  Use
   * zero for no timeout.
   * If timeout was set to zero (or unset) before, setup of new value by
   * MHD_set_connection_option() will reset timeout timer.
   */
  MHD_CONNECTION_OPTION_TIMEOUT

};


/**
 * Set a custom option for the given connection, overriding defaults.
 *
 * @param connection connection to modify
 * @param option option to set
 * @param ... arguments to the option, depending on the option type
 * @return #MHD_YES on success, #MHD_NO if setting the option failed
 * @ingroup specialized
 */
_MHD_EXTERN int
MHD_set_connection_option (struct MHD_Connection *connection,
                           enum MHD_CONNECTION_OPTION option,
                           ...);


/**
 * Information about an MHD daemon.
 */
union MHD_DaemonInfo
{
  /**
   * Size of the key, no longer supported.
   * @deprecated
   */
  size_t key_size;

  /**
   * Size of the mac key, no longer supported.
   * @deprecated
   */
  size_t mac_key_size;

  /**
   * Socket, returned for #MHD_DAEMON_INFO_LISTEN_FD.
   */
  MHD_socket listen_fd;

  /**
   * Bind port number, returned for #MHD_DAEMON_INFO_BIND_PORT.
   */
  uint16_t port;

  /**
   * epoll FD, returned for #MHD_DAEMON_INFO_EPOLL_FD.
   */
  int epoll_fd;

  /**
   * Number of active connections, for #MHD_DAEMON_INFO_CURRENT_CONNECTIONS.
   */
  unsigned int num_connections;

  /**
   * Combination of #MHD_FLAG values, for #MHD_DAEMON_INFO_FLAGS.
   * This value is actually a bitfield.
   * Note: flags may differ from original 'flags' specified for
   * daemon, especially if #MHD_USE_AUTO was set.
   */
  enum MHD_FLAG flags;
};


/**
 * Obtain information about the given daemon
 * (not fully implemented!).
 *
 * @param daemon what daemon to get information about
 * @param info_type what information is desired?
 * @param ... depends on @a info_type
 * @return NULL if this information is not available
 *         (or if the @a info_type is unknown)
 * @ingroup specialized
 */
_MHD_EXTERN const union MHD_DaemonInfo *
MHD_get_daemon_info (struct MHD_Daemon *daemon,
                     enum MHD_DaemonInfoType info_type,
                     ...);


/**
 * Obtain the version of this library
 *
 * @return static version string, e.g. "0.9.9"
 * @ingroup specialized
 */
_MHD_EXTERN const char*
MHD_get_version (void);


/**
 * Types of information about MHD features,
 * used by #MHD_is_feature_supported().
 */
enum MHD_FEATURE
{
  /**
   * Get whether messages are supported. If supported then in debug
   * mode messages can be printed to stderr or to external logger.
   */
  MHD_FEATURE_MESSAGES = 1,

  /**
   * Get whether HTTPS is supported.  If supported then flag
   * #MHD_USE_TLS and options #MHD_OPTION_HTTPS_MEM_KEY,
   * #MHD_OPTION_HTTPS_MEM_CERT, #MHD_OPTION_HTTPS_MEM_TRUST,
   * #MHD_OPTION_HTTPS_MEM_DHPARAMS, #MHD_OPTION_HTTPS_CRED_TYPE,
   * #MHD_OPTION_HTTPS_PRIORITIES can be used.
   */
  MHD_FEATURE_TLS = 2,
  MHD_FEATURE_SSL = 2,

  /**
   * Get whether option #MHD_OPTION_HTTPS_CERT_CALLBACK is
   * supported.
   */
  MHD_FEATURE_HTTPS_CERT_CALLBACK = 3,

  /**
   * Get whether IPv6 is supported. If supported then flag
   * #MHD_USE_IPv6 can be used.
   */
  MHD_FEATURE_IPv6 = 4,

  /**
   * Get whether IPv6 without IPv4 is supported. If not supported
   * then IPv4 is always enabled in IPv6 sockets and
   * flag #MHD_USE_DUAL_STACK if always used when #MHD_USE_IPv6 is
   * specified.
   */
  MHD_FEATURE_IPv6_ONLY = 5,

  /**
   * Get whether `poll()` is supported. If supported then flag
   * #MHD_USE_POLL can be used.
   */
  MHD_FEATURE_POLL = 6,

  /**
   * Get whether `epoll()` is supported. If supported then Flags
   * #MHD_USE_EPOLL and
   * #MHD_USE_EPOLL_INTERNAL_THREAD can be used.
   */
  MHD_FEATURE_EPOLL = 7,

  /**
   * Get whether shutdown on listen socket to signal other
   * threads is supported. If not supported flag
   * #MHD_USE_ITC is automatically forced.
   */
  MHD_FEATURE_SHUTDOWN_LISTEN_SOCKET = 8,

  /**
   * Get whether socketpair is used internally instead of pipe to
   * signal other threads.
   */
  MHD_FEATURE_SOCKETPAIR = 9,

  /**
   * Get whether TCP Fast Open is supported. If supported then
   * flag #MHD_USE_TCP_FASTOPEN and option
   * #MHD_OPTION_TCP_FASTOPEN_QUEUE_SIZE can be used.
   */
  MHD_FEATURE_TCP_FASTOPEN = 10,

  /**
   * Get whether HTTP Basic authorization is supported. If supported
   * then functions #MHD_basic_auth_get_username_password and
   * #MHD_queue_basic_auth_fail_response can be used.
   */
  MHD_FEATURE_BASIC_AUTH = 11,

  /**
   * Get whether HTTP Digest authorization is supported. If
   * supported then options #MHD_OPTION_DIGEST_AUTH_RANDOM,
   * #MHD_OPTION_NONCE_NC_SIZE and
   * #MHD_digest_auth_check() can be used.
   */
  MHD_FEATURE_DIGEST_AUTH = 12,

  /**
   * Get whether postprocessor is supported. If supported then
   * functions #MHD_create_post_processor(), #MHD_post_process() and
   * #MHD_destroy_post_processor() can
   * be used.
   */
  MHD_FEATURE_POSTPROCESSOR = 13,

  /**
  * Get whether password encrypted private key for HTTPS daemon is
  * supported. If supported then option
  * ::MHD_OPTION_HTTPS_KEY_PASSWORD can be used.
  */
  MHD_FEATURE_HTTPS_KEY_PASSWORD = 14,

  /**
   * Get whether reading files beyond 2 GiB boundary is supported.
   * If supported then #MHD_create_response_from_fd(),
   * #MHD_create_response_from_fd64 #MHD_create_response_from_fd_at_offset()
   * and #MHD_create_response_from_fd_at_offset64() can be used with sizes and
   * offsets larger than 2 GiB. If not supported value of size+offset is
   * limited to 2 GiB.
   */
  MHD_FEATURE_LARGE_FILE = 15,

  /**
   * Get whether MHD set names on generated threads.
   */
  MHD_FEATURE_THREAD_NAMES = 16,
  MHD_THREAD_NAMES = 16,

  /**
   * Get whether HTTP "Upgrade" is supported.
   * If supported then #MHD_ALLOW_UPGRADE, #MHD_upgrade_action() and
   * #MHD_create_response_for_upgrade() can be used.
   */
  MHD_FEATURE_UPGRADE = 17,

  /**
   * Get whether it's safe to use same FD for multiple calls of
   * #MHD_create_response_from_fd() and whether it's safe to use single
   * response generated by #MHD_create_response_from_fd() with multiple
   * connections at same time.
   * If #MHD_is_feature_supported() return #MHD_NO for this feature then
   * usage of responses with same file FD in multiple parallel threads may
   * results in incorrect data sent to remote client.
   * It's always safe to use same file FD in multiple responses if MHD
   * is run in any single thread mode.
   */
  MHD_FEATURE_RESPONSES_SHARED_FD = 18,

  /**
   * Get whether MHD support automatic detection of bind port number.
   * @sa #MHD_DAEMON_INFO_BIND_PORT
   */
  MHD_FEATURE_AUTODETECT_BIND_PORT = 19,

  /**
   * Get whether MHD support SIGPIPE suppression.
   * If SIGPIPE suppression is not supported, application must handle
   * SIGPIPE signal by itself.
   */
  MHD_FEATURE_AUTOSUPPRESS_SIGPIPE = 20,

  /**
   * Get whether MHD use system's sendfile() function to send
   * file-FD based responses over non-TLS connections.
   * @note Since v0.9.56
   */
  MHD_FEATURE_SENDFILE = 21,

  /**
   * Get whether MHD supports threads.
   */
  MHD_FEATURE_THREADS = 22,

  /**
   * Get whether option #MHD_OPTION_HTTPS_CERT_CALLBACK2 is
   * supported.
   */
  MHD_FEATURE_HTTPS_CERT_CALLBACK2 = 23
};


/**
 * Get information about supported MHD features.
 * Indicate that MHD was compiled with or without support for
 * particular feature. Some features require additional support
 * by kernel. Kernel support is not checked by this function.
 *
 * @param feature type of requested information
 * @return #MHD_YES if feature is supported by MHD, #MHD_NO if
 * feature is not supported or feature is unknown.
 * @ingroup specialized
 */
_MHD_EXTERN int
MHD_is_feature_supported (enum MHD_FEATURE feature);


#if 0                           /* keep Emacsens' auto-indent happy */
{
#endif
#ifdef __cplusplus
}
#endif

#endif