githubmirror/nghttp2

src/template.h
409 строк12 KB
Tatsuhiro Tsujikawa
src: Review the use of iterator and range concepts
22 мар 2026, 17:17
22 мар 2026, 17:17dc1ac54
/*
 * nghttp2 - HTTP/2 C Library
 *
 * Copyright (c) 2015 Tatsuhiro Tsujikawa
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
#ifndef TEMPLATE_H
#define TEMPLATE_H

#include "nghttp2_config.h"

#include <cstdint>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <memory>
#include <array>
#include <functional>
#include <typeinfo>
#include <algorithm>
#include <ostream>
#include <utility>
#include <span>
#include <string_view>
#include <compare>
#include <type_traits>

namespace nghttp2 {

template <std::integral T>
[[nodiscard]] constexpr auto as_unsigned(T n) noexcept {
  return static_cast<std::make_unsigned_t<T>>(n);
}

template <std::unsigned_integral T>
[[nodiscard]] constexpr auto as_signed(T n) noexcept {
  return static_cast<std::make_signed_t<T>>(n);
}

template <typename T, size_t N> constexpr size_t array_size(T (&)[N]) {
  return N;
}

template <typename T, size_t N> constexpr size_t str_size(T (&)[N]) {
  return N - 1;
}

template <std::invocable F> struct Defer {
  using Invocable = std::decay_t<F>;

  template <typename G>
  [[nodiscard]] explicit Defer(G &&g) noexcept(
    std::is_nothrow_constructible_v<Invocable, G &&>)
    : f{std::forward<G>(g)} {}
  ~Defer() { f(); }

  Defer(Defer &&o) = delete;
  Defer(const Defer &) = delete;
  Defer &operator=(const Defer &) = delete;
  Defer &operator=(Defer &&) = delete;

  Invocable f;
};

template <std::invocable F> [[nodiscard]] Defer<std::decay_t<F>> defer(F &&f) {
  return Defer<std::decay_t<F>>(std::forward<F>(f));
}

template <typename T, typename F> bool test_flags(T t, F flags) {
  return (t & flags) == flags;
}

// doubly linked list of element T*.  T must have field T *dlprev and
// T *dlnext, which point to previous element and next element in the
// list respectively.
template <typename T> struct DList {
  DList() : head(nullptr), tail(nullptr), len(0) {}

  DList(const DList &) = delete;
  DList &operator=(const DList &) = delete;

  DList(DList &&other) noexcept
    : head{std::exchange(other.head, nullptr)},
      tail{std::exchange(other.tail, nullptr)},
      len{std::exchange(other.len, 0)} {}

  DList &operator=(DList &&other) noexcept {
    if (this == &other) {
      return *this;
    }
    head = std::exchange(other.head, nullptr);
    tail = std::exchange(other.tail, nullptr);
    len = std::exchange(other.len, 0);

    return *this;
  }

  void append(T *t) {
    ++len;
    if (tail) {
      tail->dlnext = t;
      t->dlprev = tail;
      tail = t;
      return;
    }
    head = tail = t;
  }

  void remove(T *t) {
    --len;
    auto p = t->dlprev;
    auto n = t->dlnext;
    if (p) {
      p->dlnext = n;
    } else {
      head = n;
    }
    if (n) {
      n->dlprev = p;
    } else {
      tail = p;
    }
    t->dlprev = t->dlnext = nullptr;
  }

  bool empty() const { return head == nullptr; }

  size_t size() const { return len; }

  T *head, *tail;
  size_t len;
};

template <typename T> void dlist_delete_all(DList<T> &dl) {
  for (auto e = dl.head; e;) {
    auto next = e->dlnext;
    delete e;
    e = next;
  }
}

// User-defined literals for K, M, and G (powers of 1024)

constexpr unsigned long long operator"" _k(unsigned long long k) {
  return k * 1024;
}

constexpr unsigned long long operator"" _m(unsigned long long m) {
  return m * 1024 * 1024;
}

constexpr unsigned long long operator"" _g(unsigned long long g) {
  return g * 1024 * 1024 * 1024;
}

// User-defined literals for time, converted into double in seconds

// hours
constexpr double operator"" _h(unsigned long long h) {
  return static_cast<double>(h * 60 * 60);
}

// minutes
constexpr double operator"" _min(unsigned long long min) {
  return static_cast<double>(min * 60);
}

// seconds
constexpr double operator"" _s(unsigned long long s) {
  return static_cast<double>(s);
}

// milliseconds
constexpr double operator"" _ms(unsigned long long ms) {
  return static_cast<double>(ms) / 1000.;
}

// ImmutableString represents string that is immutable unlike
// std::string.  It has c_str() and size() functions to mimic
// std::string.  It manages buffer by itself.  Just like std::string,
// c_str() returns NULL-terminated string, but NULL character may
// appear before the final terminal NULL.
class ImmutableString {
public:
  using traits_type = std::char_traits<char>;
  using value_type = traits_type::char_type;
  using allocator_type = std::allocator<char>;
  using size_type = std::allocator_traits<allocator_type>::size_type;
  using difference_type =
    std::allocator_traits<allocator_type>::difference_type;
  using const_reference = const value_type &;
  using const_pointer = const value_type *;
  using const_iterator = const_pointer;
  using const_reverse_iterator = std::reverse_iterator<const_iterator>;

  constexpr ImmutableString() noexcept : len(0), base("") {}

  constexpr ImmutableString(const char *s, size_t slen)
    : len(slen), base(copystr(s, s + len)) {}

  constexpr explicit ImmutableString(const char *s)
    : len(traits_type::length(s)), base(copystr(s, s + len)) {}

  ImmutableString(std::nullptr_t) = delete;

  template <std::ranges::sized_range R>
  requires(std::is_same_v<std::ranges::range_value_t<R>, value_type> &&
           !std::is_same_v<std::remove_cvref_t<R>, ImmutableString> &&
           !std::is_array_v<std::remove_cvref_t<R>>)
  constexpr explicit ImmutableString(R &&r)
    : len(std::ranges::size(r)), base(copystr(std::forward<R>(r))) {}

  template <std::forward_iterator I>
  requires(std::is_same_v<std::iter_value_t<I>, value_type>)
  constexpr ImmutableString(I first, I last)
    : len(as_unsigned(std::ranges::distance(first, last))),
      base(copystr(std::move(first), std::move(last))) {}

  constexpr ImmutableString(const ImmutableString &other)
    : len(other.len), base(copystr(other)) {}

  constexpr ImmutableString(ImmutableString &&other) noexcept
    : len{std::exchange(other.len, 0)}, base{std::exchange(other.base, "")} {}

  constexpr ~ImmutableString() {
    if (len) {
      delete[] base;
    }
  }

  constexpr ImmutableString &operator=(const ImmutableString &other) {
    if (this == &other) {
      return *this;
    }
    if (len) {
      delete[] base;
    }
    len = other.len;
    base = copystr(other);
    return *this;
  }
  constexpr ImmutableString &operator=(ImmutableString &&other) noexcept {
    if (this == &other) {
      return *this;
    }
    if (len) {
      delete[] base;
    }
    len = std::exchange(other.len, 0);
    base = std::exchange(other.base, "");
    return *this;
  }

  constexpr const_iterator begin() const noexcept { return base; }
  constexpr const_iterator cbegin() const noexcept { return base; }

  constexpr const_iterator end() const noexcept { return base + len; }
  constexpr const_iterator cend() const noexcept { return base + len; }

  constexpr const_reverse_iterator rbegin() const noexcept {
    return const_reverse_iterator{base + len};
  }
  constexpr const_reverse_iterator crbegin() const noexcept {
    return const_reverse_iterator{base + len};
  }

  constexpr const_reverse_iterator rend() const noexcept {
    return const_reverse_iterator{base};
  }
  constexpr const_reverse_iterator crend() const noexcept {
    return const_reverse_iterator{base};
  }

  constexpr const_pointer c_str() const noexcept { return base; }
  constexpr const_pointer data() const noexcept { return base; }
  constexpr size_type size() const noexcept { return len; }
  constexpr bool empty() const noexcept { return len == 0; }
  constexpr const_reference operator[](size_type pos) const noexcept {
    return *(base + pos);
  }

private:
  template <std::forward_iterator I>
  constexpr const char *copystr(I first, I last) {
    auto len = static_cast<size_t>(std::ranges::distance(first, last));
    if (len == 0) {
      return "";
    }
    auto res = new char[len + 1];
    *std::ranges::copy(first, last, res).out = '\0';
    return res;
  }

  template <std::ranges::forward_range R>
  requires(!std::is_array_v<std::remove_cvref_t<R>>)
  constexpr const char *copystr(R &&r) {
    return copystr(std::ranges::begin(r), std::ranges::end(r));
  }

  size_type len;
  const char *base;
};

inline bool operator==(const ImmutableString &lhs, const ImmutableString &rhs) {
  return std::ranges::equal(lhs, rhs);
}

inline std::ostream &operator<<(std::ostream &o, const ImmutableString &s) {
  return o.write(s.c_str(), static_cast<std::streamsize>(s.size()));
}

inline std::string &operator+=(std::string &lhs, const ImmutableString &rhs) {
  lhs.append(rhs.c_str(), rhs.size());
  return lhs;
}

inline bool operator==(const ImmutableString &lhs, std::string_view rhs) {
  return std::ranges::equal(lhs, rhs);
}

inline std::strong_ordering operator<=>(const ImmutableString &lhs,
                                        const ImmutableString &rhs) noexcept {
  return std::string_view{lhs.data(), lhs.size()} <=>
         std::string_view{rhs.data(), rhs.size()};
}

constexpr ImmutableString operator""_is(const char *str, size_t len) {
  return {str, len};
}

template <typename T, std::size_t N>
[[nodiscard]] auto as_uint8_span(std::span<T, N> s) noexcept {
  return std::span<const uint8_t, N == std::dynamic_extent ? std::dynamic_extent
                                                           : N * sizeof(T)>{
    reinterpret_cast<const uint8_t *>(s.data()), s.size_bytes()};
}

template <typename T, std::size_t N>
[[nodiscard]] auto as_writable_uint8_span(std::span<T, N> s) noexcept {
  return std::span<uint8_t, N == std::dynamic_extent ? std::dynamic_extent
                                                     : N * sizeof(T)>{
    reinterpret_cast<uint8_t *>(s.data()), s.size_bytes()};
}

template <typename R>
requires(std::ranges::contiguous_range<R> && std::ranges::sized_range<R> &&
         std::ranges::borrowed_range<R> &&
         !std::is_array_v<std::remove_cvref_t<R>> &&
         sizeof(std::ranges::range_value_t<R>) ==
           sizeof(std::string_view::value_type))
[[nodiscard]] std::string_view as_string_view(R &&r) {
  return std::string_view{
    reinterpret_cast<std::string_view::const_pointer>(std::ranges::data(r)),
    std::ranges::size(r)};
}

// Returns std::string_view over a given range [|first|, |last|).
template <std::contiguous_iterator I>
requires(sizeof(std::iter_value_t<I>) == sizeof(std::string_view::value_type))
[[nodiscard]] std::string_view as_string_view(I first, I last) {
  return std::string_view{
    reinterpret_cast<std::string_view::const_pointer>(std::to_address(first)),
    static_cast<size_t>(std::ranges::distance(first, last))};
}

// Returns std::string_view over a given range [|first|, |first| + |n|).
template <std::contiguous_iterator I>
requires(sizeof(std::iter_value_t<I>) == sizeof(std::string_view::value_type))
[[nodiscard]] std::string_view as_string_view(I first, size_t n) {
  return std::string_view{
    reinterpret_cast<std::string_view::const_pointer>(std::to_address(first)),
    n};
}

inline int run_app(std::function<int(int, char **)> app, int argc,
                   char **argv) {
  try {
    return app(argc, argv);
  } catch (const std::bad_alloc &) {
    fputs("Out of memory\n", stderr);
  } catch (const std::exception &x) {
    fprintf(stderr, "Caught %s:\n%s\n", typeid(x).name(), x.what());
  } catch (...) {
    fputs("Unknown exception caught\n", stderr);
  }
  return EXIT_FAILURE;
}

} // namespace nghttp2

#endif // !defined(TEMPLATE_H)