u-tools/apps/tar/gnu/tempname.c

   1 /* -*- buffer-read-only: t -*- vi: set ro: */
   2 /* DO NOT EDIT! GENERATED AUTOMATICALLY! */
   3 /* tempname.c - generate the name of a temporary file.
   4
   5    Copyright (C) 1991-2003, 2005-2007, 2009-2011 Free Software Foundation, Inc.
   6
   7    This program is free software: you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 /* Extracted from glibc sysdeps/posix/tempname.c.  See also tmpdir.c.  */
  21
  22 #if !_LIBC
  23 # include <config.h>
  24 # include "tempname.h"
  25 #endif
  26
  27 #include <sys/types.h>
  28 #include <assert.h>
  29
  30 #include <errno.h>
  31 #ifndef __set_errno
  32 # define __set_errno(Val) errno = (Val)
  33 #endif
  34
  35 #include <stdio.h>
  36 #ifndef P_tmpdir
  37 # define P_tmpdir "/tmp"
  38 #endif
  39 #ifndef TMP_MAX
  40 # define TMP_MAX 238328
  41 #endif
  42 #ifndef __GT_FILE
  43 # define __GT_FILE      0
  44 # define __GT_DIR       1
  45 # define __GT_NOCREATE  2
  46 #endif
  47 #if !_LIBC && (GT_FILE != __GT_FILE || GT_DIR != __GT_DIR       \
  48                || GT_NOCREATE != __GT_NOCREATE)
  49 # error report this to bug-gnulib@gnu.org
  50 #endif
  51
  52 #include <stddef.h>
  53 #include <stdlib.h>
  54 #include <string.h>
  55
  56 #include <fcntl.h>
  57 #include <sys/time.h>
  58 #include <stdint.h>
  59 #include <unistd.h>
  60
  61 #include <sys/stat.h>
  62
  63 #if _LIBC
  64 # define struct_stat64 struct stat64
  65 #else
  66 # define struct_stat64 struct stat
  67 # define __gen_tempname gen_tempname
  68 # define __getpid getpid
  69 # define __gettimeofday gettimeofday
  70 # define __mkdir mkdir
  71 # define __open open
  72 # define __open64 open
  73 # define __lxstat64(version, file, buf) lstat (file, buf)
  74 # define __xstat64(version, file, buf) stat (file, buf)
  75 #endif
  76
  77 #if ! (HAVE___SECURE_GETENV || _LIBC)
  78 # define __secure_getenv getenv
  79 #endif
  80
  81 #ifdef _LIBC
  82 # include <hp-timing.h>
  83 # if HP_TIMING_AVAIL
  84 #  define RANDOM_BITS(Var) \
  85   if (__builtin_expect (value == UINT64_C (0), 0))                            \
  86     {                                                                         \
  87       /* If this is the first time this function is used initialize           \
  88          the variable we accumulate the value in to some somewhat             \
  89          random value.  If we'd not do this programs at startup time          \
  90          might have a reduced set of possible names, at least on slow         \
  91          machines.  */                                                        \
  92       struct timeval tv;                                                      \
  93       __gettimeofday (&tv, NULL);                                             \
  94       value = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;                      \
  95     }                                                                         \
  96   HP_TIMING_NOW (Var)
  97 # endif
  98 #endif
  99
 100 /* Use the widest available unsigned type if uint64_t is not
 101    available.  The algorithm below extracts a number less than 62**6
 102    (approximately 2**35.725) from uint64_t, so ancient hosts where
 103    uintmax_t is only 32 bits lose about 3.725 bits of randomness,
 104    which is better than not having mkstemp at all.  */
 105 #if !defined UINT64_MAX && !defined uint64_t
 106 # define uint64_t uintmax_t
 107 #endif
 108
 109 #if _LIBC
 110 /* Return nonzero if DIR is an existent directory.  */
 111 static int
 112 direxists (const char *dir)
 113 {
 114   struct_stat64 buf;
 115   return __xstat64 (_STAT_VER, dir, &buf) == 0 && S_ISDIR (buf.st_mode);
 116 }
 117
 118 /* Path search algorithm, for tmpnam, tmpfile, etc.  If DIR is
 119    non-null and exists, uses it; otherwise uses the first of $TMPDIR,
 120    P_tmpdir, /tmp that exists.  Copies into TMPL a template suitable
 121    for use with mk[s]temp.  Will fail (-1) if DIR is non-null and
 122    doesn't exist, none of the searched dirs exists, or there's not
 123    enough space in TMPL. */
 124 int
 125 __path_search (char *tmpl, size_t tmpl_len, const char *dir, const char *pfx,
 126                int try_tmpdir)
 127 {
 128   const char *d;
 129   size_t dlen, plen;
 130
 131   if (!pfx || !pfx[0])
 132     {
 133       pfx = "file";
 134       plen = 4;
 135     }
 136   else
 137     {
 138       plen = strlen (pfx);
 139       if (plen > 5)
 140         plen = 5;
 141     }
 142
 143   if (try_tmpdir)
 144     {
 145       d = __secure_getenv ("TMPDIR");
 146       if (d != NULL && direxists (d))
 147         dir = d;
 148       else if (dir != NULL && direxists (dir))
 149         /* nothing */ ;
 150       else
 151         dir = NULL;
 152     }
 153   if (dir == NULL)
 154     {
 155       if (direxists (P_tmpdir))
 156         dir = P_tmpdir;
 157       else if (strcmp (P_tmpdir, "/tmp") != 0 && direxists ("/tmp"))
 158         dir = "/tmp";
 159       else
 160         {
 161           __set_errno (ENOENT);
 162           return -1;
 163         }
 164     }
 165
 166   dlen = strlen (dir);
 167   while (dlen > 1 && dir[dlen - 1] == '/')
 168     dlen--;                     /* remove trailing slashes */
 169
 170   /* check we have room for "${dir}/${pfx}XXXXXX\0" */
 171   if (tmpl_len < dlen + 1 + plen + 6 + 1)
 172     {
 173       __set_errno (EINVAL);
 174       return -1;
 175     }
 176
 177   sprintf (tmpl, "%.*s/%.*sXXXXXX", (int) dlen, dir, (int) plen, pfx);
 178   return 0;
 179 }
 180 #endif /* _LIBC */
 181
 182 /* These are the characters used in temporary file names.  */
 183 static const char letters[] =
 184 "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
 185
 186 /* Generate a temporary file name based on TMPL.  TMPL must match the
 187    rules for mk[s]temp (i.e. end in "XXXXXX", possibly with a suffix).
 188    The name constructed does not exist at the time of the call to
 189    __gen_tempname.  TMPL is overwritten with the result.
 190
 191    KIND may be one of:
 192    __GT_NOCREATE:       simply verify that the name does not exist
 193                         at the time of the call.
 194    __GT_FILE:           create the file using open(O_CREAT|O_EXCL)
 195                         and return a read-write fd.  The file is mode 0600.
 196    __GT_DIR:            create a directory, which will be mode 0700.
 197
 198    We use a clever algorithm to get hard-to-predict names. */
 199 int
 200 __gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
 201 {
 202   int len;
 203   char *XXXXXX;
 204   static uint64_t value;
 205   uint64_t random_time_bits;
 206   unsigned int count;
 207   int fd = -1;
 208   int save_errno = errno;
 209   struct_stat64 st;
 210
 211   /* A lower bound on the number of temporary files to attempt to
 212      generate.  The maximum total number of temporary file names that
 213      can exist for a given template is 62**6.  It should never be
 214      necessary to try all these combinations.  Instead if a reasonable
 215      number of names is tried (we define reasonable as 62**3) fail to
 216      give the system administrator the chance to remove the problems.  */
 217 #define ATTEMPTS_MIN (62 * 62 * 62)
 218
 219   /* The number of times to attempt to generate a temporary file.  To
 220      conform to POSIX, this must be no smaller than TMP_MAX.  */
 221 #if ATTEMPTS_MIN < TMP_MAX
 222   unsigned int attempts = TMP_MAX;
 223 #else
 224   unsigned int attempts = ATTEMPTS_MIN;
 225 #endif
 226
 227   len = strlen (tmpl);
 228   if (len < 6 + suffixlen || memcmp (&tmpl[len - 6 - suffixlen], "XXXXXX", 6))
 229     {
 230       __set_errno (EINVAL);
 231       return -1;
 232     }
 233
 234   /* This is where the Xs start.  */
 235   XXXXXX = &tmpl[len - 6 - suffixlen];
 236
 237   /* Get some more or less random data.  */
 238 #ifdef RANDOM_BITS
 239   RANDOM_BITS (random_time_bits);
 240 #else
 241   {
 242     struct timeval tv;
 243     __gettimeofday (&tv, NULL);
 244     random_time_bits = ((uint64_t) tv.tv_usec << 16) ^ tv.tv_sec;
 245   }
 246 #endif
 247   value += random_time_bits ^ __getpid ();
 248
 249   for (count = 0; count < attempts; value += 7777, ++count)
 250     {
 251       uint64_t v = value;
 252
 253       /* Fill in the random bits.  */
 254       XXXXXX[0] = letters[v % 62];
 255       v /= 62;
 256       XXXXXX[1] = letters[v % 62];
 257       v /= 62;
 258       XXXXXX[2] = letters[v % 62];
 259       v /= 62;
 260       XXXXXX[3] = letters[v % 62];
 261       v /= 62;
 262       XXXXXX[4] = letters[v % 62];
 263       v /= 62;
 264       XXXXXX[5] = letters[v % 62];
 265
 266       switch (kind)
 267         {
 268         case __GT_FILE:
 269           fd = __open (tmpl,
 270                        (flags & ~O_ACCMODE)
 271                        | O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
 272           break;
 273
 274         case __GT_DIR:
 275           fd = __mkdir (tmpl, S_IRUSR | S_IWUSR | S_IXUSR);
 276           break;
 277
 278         case __GT_NOCREATE:
 279           /* This case is backward from the other three.  __gen_tempname
 280              succeeds if __xstat fails because the name does not exist.
 281              Note the continue to bypass the common logic at the bottom
 282              of the loop.  */
 283           if (__lxstat64 (_STAT_VER, tmpl, &st) < 0)
 284             {
 285               if (errno == ENOENT)
 286                 {
 287                   __set_errno (save_errno);
 288                   return 0;
 289                 }
 290               else
 291                 /* Give up now. */
 292                 return -1;
 293             }
 294           continue;
 295
 296         default:
 297           assert (! "invalid KIND in __gen_tempname");
 298           abort ();
 299         }
 300
 301       if (fd >= 0)
 302         {
 303           __set_errno (save_errno);
 304           return fd;
 305         }
 306       else if (errno != EEXIST)
 307         return -1;
 308     }
 309
 310   /* We got out of the loop because we ran out of combinations to try.  */
 311   __set_errno (EEXIST);
 312   return -1;
 313 }