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v2.8
lib/tempname.c
343 строки
9 KB
Paul Eggert
diffutils 2.7.7
03 дек 2001, 16:56
03 дек 2001, 16:56
0ac2866
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/* Copyright (C) 1991-1999, 2000, 2001 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C 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. The GNU C 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 the GNU C Library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. */ #if HAVE_CONFIG_H # include <config.h> #endif #include <sys/types.h> #include <assert.h> #include <errno.h> #ifndef __set_errno # define __set_errno(Val) errno = (Val) #endif #include <stdio.h> #ifndef P_tmpdir # define P_tmpdir "/tmp" #endif #ifndef TMP_MAX # define TMP_MAX 238328 #endif #ifndef __GT_FILE # define __GT_FILE 0 # define __GT_BIGFILE 1 # define __GT_DIR 2 # define __GT_NOCREATE 3 #endif #if STDC_HEADERS || _LIBC # include <stddef.h> # include <string.h> #endif #include <stdlib.h> #if HAVE_FCNTL_H || _LIBC # include <fcntl.h> #endif #if HAVE_SYS_TIME_H || _LIBC # include <sys/time.h> #endif #if HAVE_STDINT_H || _LIBC # include <stdint.h> #endif #if HAVE_UNISTD_H || _LIBC # include <unistd.h> #endif #include <sys/stat.h> #if STAT_MACROS_BROKEN # undef S_ISDIR #endif #if !defined S_ISDIR && defined S_IFDIR # define S_ISDIR(mode) (((mode) & S_IFMT) == S_IFDIR) #endif #if !S_IRUSR && S_IREAD # define S_IRUSR S_IREAD #endif #if !S_IRUSR # define S_IRUSR 00400 #endif #if !S_IWUSR && S_IWRITE # define S_IWUSR S_IWRITE #endif #if !S_IWUSR # define S_IWUSR 00200 #endif #if !S_IXUSR && S_IEXEC # define S_IXUSR S_IEXEC #endif #if !S_IXUSR # define S_IXUSR 00100 #endif #if _LIBC # define struct_stat64 struct stat64 #else # define struct_stat64 struct stat # define __getpid getpid # define __gettimeofday gettimeofday # define __mkdir mkdir # define __open open # define __open64 open # define __lxstat64(version, path, buf) lstat (path, buf) # define __xstat64(version, path, buf) stat (path, buf) #endif #if ! (HAVE___SECURE_GETENV || _LIBC) # define __secure_getenv getenv #endif #ifdef _LIBC # include <hp-timing.h> # if HP_TIMING_AVAIL # define RANDOM_BITS(Var) \ if (__builtin_expect (value == UINT64_C (0), 0)) \ { \ /* If this is the first time this function is used initialize \ the variable we accumulate the value in to some somewhat \ random value. If we'd not do this programs at startup time \ might have a reduced set of possible names, at least on slow \ machines. */ \ struct timeval tv; \ __gettimeofday (&tv, NULL); \ value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; \ } \ HP_TIMING_NOW (Var) # endif #endif /* Use the widest available unsigned type if uint64_t is not available. The algorithm below extracts a number less than 62**6 (approximately 2**35.725) from uint64_t, so ancient hosts where uintmax_t is only 32 bits lose about 3.725 bits of randomness, which is better than not having mkstemp at all. */ #if !defined UINT64_MAX && !defined uint64_t # define uint64_t uintmax_t #endif /* Return nonzero if DIR is an existent directory. */ static int direxists (const char *dir) { struct_stat64 buf; return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode); } /* Path search algorithm, for tmpnam, tmpfile, etc. If DIR is non-null and exists, uses it; otherwise uses the first of $TMPDIR, P_tmpdir, /tmp that exists. Copies into TMPL a template suitable for use with mk[s]temp. Will fail (-1) if DIR is non-null and doesn't exist, none of the searched dirs exists, or there's not enough space in TMPL. */ int __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx, int try_tmpdir) { const char *d; size_t dlen, plen; if (!pfx || !pfx[0]) { pfx = "file"; plen = 4; } else { plen = strlen (pfx); if (plen > 5) plen = 5; } if (try_tmpdir) { d = __secure_getenv ("TMPDIR"); if (d != NULL && direxists (d)) dir = d; else if (dir != NULL && direxists (dir)) /* nothing */ ; else dir = NULL; } if (dir == NULL) { if (direxists (P_tmpdir)) dir = P_tmpdir; else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp")) dir = "/tmp"; else { __set_errno (ENOENT); return -1; } } dlen = strlen (dir); while (dlen > 1 && dir[dlen - 1] == '/') dlen--; /* remove trailing slashes */ /* check we have room for "${dir}/${pfx}XXXXXX\0" */ if (tmpl_len < dlen + 1 + plen + 6 + 1) { __set_errno (EINVAL); return -1; } sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx); return 0; } /* These are the characters used in temporary filenames. */ static const char letters[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; /* Generate a temporary file name based on TMPL. TMPL must match the rules for mk[s]temp (i.e. end in "XXXXXX"). The name constructed does not exist at the time of the call to __gen_tempname. TMPL is overwritten with the result. KIND may be one of: __GT_NOCREATE: simply verify that the name does not exist at the time of the call. __GT_FILE: create the file using open(O_CREAT|O_EXCL) and return a read-write fd. The file is mode 0600. __GT_BIGFILE: same as __GT_FILE but use open64(). __GT_DIR: create a directory, which will be mode 0700. We use a clever algorithm to get hard-to-predict names. */ int __gen_tempname (char *tmpl, int kind) { int len; char *XXXXXX; static uint64_t value; uint64_t random_time_bits; unsigned int count; int fd = -1; int save_errno = errno; struct_stat64 st; /* A lower bound on the number of temporary files to attempt to generate. The maximum total number of temporary file names that can exist for a given template is 62**6. It should never be necessary to try all these combinations. Instead if a reasonable number of names is tried (we define reasonable as 62**3) fail to give the system administrator the chance to remove the problems. */ unsigned int attempts_min = 62 * 62 * 62; /* The number of times to attempt to generate a temporary file. To conform to POSIX, this must be no smaller than TMP_MAX. */ unsigned int attempts = attempts_min < TMP_MAX ? TMP_MAX : attempts_min; len = strlen (tmpl); if (len < 6 || strcmp (&tmpl[len - 6], "XXXXXX")) { __set_errno (EINVAL); return -1; } /* This is where the Xs start. */ XXXXXX = &tmpl[len - 6]; /* Get some more or less random data. */ #ifdef RANDOM_BITS RANDOM_BITS (random_time_bits); #else # if HAVE_GETTIMEOFDAY || _LIBC { struct timeval tv; __gettimeofday (&tv, NULL); random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec; } # else random_time_bits = time (NULL); # endif #endif value += random_time_bits ^ __getpid (); for (count = 0; count < attempts; value += 7777, ++count) { uint64_t v = value; /* Fill in the random bits. */ XXXXXX[0] = letters[v % 62]; v /= 62; XXXXXX[1] = letters[v % 62]; v /= 62; XXXXXX[2] = letters[v % 62]; v /= 62; XXXXXX[3] = letters[v % 62]; v /= 62; XXXXXX[4] = letters[v % 62]; v /= 62; XXXXXX[5] = letters[v % 62]; switch (kind) { case __GT_FILE: fd = __open (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR); break; case __GT_BIGFILE: fd = __open64 (tmpl, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR); break; case __GT_DIR: fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR); break; case __GT_NOCREATE: /* This case is backward from the other three. __gen_tempname succeeds if __xstat fails because the name does not exist. Note the continue to bypass the common logic at the bottom of the loop. */ if (__lxstat64 (_STAT_VER, tmpl, &st) < 0) { if (errno == ENOENT) { __set_errno (save_errno); return 0; } else /* Give up now. */ return -1; } continue; default: assert (! "invalid KIND in __gen_tempname"); } if (fd >= 0) { __set_errno (save_errno); return fd; } else if (errno != EEXIST) return -1; } /* We got out of the loop because we ran out of combinations to try. */ __set_errno (EEXIST); return -1; }