sysdeps/posix/tempname.c

   1 /* Copyright (C) 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <errno.h>
  21 #include <stddef.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <sys/types.h>
  26 #include <sys/stat.h>
  27 #include <fcntl.h>
  28 #include <unistd.h>
  29
  30 #ifdef USE_IN_LIBIO
  31 # include "libioP.h"
  32 # include <libio.h>
  33 #endif
  34
  35 /* Return nonzero if DIR is an existent directory.  */
  36 static int
  37 DEFUN(diraccess, (dir), CONST char *dir)
  38 {
  39   struct stat buf;
  40   return __stat (dir, &buf) == 0 && S_ISDIR (buf.st_mode);
  41 }
  42
  43 /* Return nonzero if FILE exists.  */
  44 static int
  45 DEFUN(exists, (file), CONST char *file)
  46 {
  47   /* We can stat the file even if we can't read its data.  */
  48   struct stat st;
  49   int save = errno;
  50   if (__stat (file, &st) == 0)
  51     return 1;
  52   else
  53     {
  54       /* We report that the file exists if stat failed for a reason other
  55          than nonexistence.  In this case, it may or may not exist, and we
  56          don't know; but reporting that it does exist will never cause any
  57          trouble, while reporting that it doesn't exist when it does would
  58          violate the interface of __stdio_gen_tempname.  */
  59       int exists = errno != ENOENT;
  60       errno = save;
  61       return exists;
  62     }
  63 }
  64
  65
  66 /* These are the characters used in temporary filenames.  */
  67 static CONST char letters[] =
  68   "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
  69
  70 /* Generate a temporary filename and return it (in a static buffer).  If
  71    STREAMPTR is not NULL, open a stream "w+b" on the file and set
  72    *STREAMPTR to it.  If DIR_SEARCH is nonzero, DIR and PFX are used as
  73    described for tempnam.  If not, a temporary filename in P_tmpdir with no
  74    special prefix is generated.  If LENPTR is not NULL, *LENPTR is set the
  75    to length (including the terminating '\0') of the resultant filename,
  76    which is returned.  This goes through a cyclic pattern of all possible
  77    filenames consisting of five decimal digits of the current pid and three
  78    of the characters in `letters'.  Data for tempnam and tmpnam is kept
  79    separate, but when tempnam is using P_tmpdir and no prefix (i.e, it is
  80    identical to tmpnam), the same data is used.  Each potential filename is
  81    tested for an already-existing file of the same name, and no name of an
  82    existing file will be returned.  When the cycle reaches its end
  83    (12345ZZZ), NULL is returned.  */
  84 char *
  85 DEFUN(__stdio_gen_tempname, (dir, pfx, dir_search, lenptr, streamptr),
  86       CONST char *dir AND CONST char *pfx AND
  87       int dir_search AND size_t *lenptr AND
  88       FILE **streamptr)
  89 {
  90   int saverrno = errno;
  91   static CONST char tmpdir[] = P_tmpdir;
  92   static size_t indices[2];
  93   size_t *idx;
  94   static char buf[FILENAME_MAX];
  95   static pid_t oldpid = (pid_t) 0;
  96   pid_t pid = __getpid();
  97   register size_t len, plen, dlen;
  98
  99   if (dir_search)
 100     {
 101       register CONST char *d = getenv ("TMPDIR");
 102       if (d != NULL && !diraccess (d))
 103         d = NULL;
 104       if (d == NULL && dir != NULL && diraccess (dir))
 105         d = dir;
 106       if (d == NULL && diraccess (tmpdir))
 107         d = tmpdir;
 108       if (d == NULL && diraccess ("/tmp"))
 109         d = "/tmp";
 110       if (d == NULL)
 111         {
 112           errno = ENOENT;
 113           return NULL;
 114         }
 115       dir = d;
 116     }
 117   else
 118     dir = tmpdir;
 119
 120   dlen = strlen (dir);
 121
 122  /* Remove trailing slashes from the directory name.  */
 123   while (dlen > 1 && dir[dlen - 1] == '/')
 124     --dlen;
 125
 126   if (pfx != NULL && *pfx != '\0')
 127     {
 128       plen = strlen (pfx);
 129       if (plen > 5)
 130         plen = 5;
 131     }
 132   else
 133     plen = 0;
 134
 135   if (dir != tmpdir && !strcmp (dir, tmpdir))
 136     dir = tmpdir;
 137   idx = &indices[(plen == 0 && dir == tmpdir) ? 1 : 0];
 138
 139   if (pid != oldpid)
 140     {
 141       oldpid = pid;
 142       indices[0] = indices[1] = 0;
 143     }
 144
 145   len = dlen + 1 + plen + 5 + 3;
 146   while (*idx < ((sizeof (letters) - 1) * (sizeof (letters) - 1) *
 147                  (sizeof (letters) - 1)))
 148     {
 149       const size_t i = (*idx)++;
 150
 151       /* Construct a file name and see if it already exists.
 152
 153          We use a single counter in *IDX to cycle each of three
 154          character positions through each of 62 possible letters.  */
 155
 156       if (sizeof (buf) < len ||
 157           sprintf (buf, "%.*s/%.*s%.5d%c%c%c",
 158                    (int) dlen, dir, (int) plen,
 159                    pfx, pid % 100000,
 160                    letters[i % (sizeof (letters) - 1)],
 161                    letters[(i / (sizeof (letters) - 1))
 162                            % (sizeof (letters) - 1)],
 163                    letters[(i / ((sizeof (letters) - 1) *
 164                                  (sizeof (letters) - 1)))
 165                            % (sizeof (letters) - 1)]
 166                    ) != (int) len)
 167         return NULL;
 168
 169       if (streamptr != NULL)
 170         {
 171           /* Try to create the file atomically.  */
 172           int fd = __open (buf, O_RDWR|O_CREAT|O_EXCL, 0666);
 173           if (fd >= 0)
 174             {
 175               /* We got a new file that did not previously exist.
 176                  Create a stream for it.  */
 177 #ifdef USE_IN_LIBIO
 178               int save;
 179               struct _IO_FILE_plus *fp;
 180
 181               fp = (struct _IO_FILE_plus *)
 182                 malloc(sizeof (struct _IO_FILE_plus));
 183               if (fp == NULL)
 184                 {
 185                   /* We lost trying to create a stream (out of memory?).
 186                      Nothing to do but remove the file, close the descriptor,
 187                      and return failure.  */
 188                   save = errno;
 189                 lose:
 190                   (void) remove (buf);
 191                   (void) __close (fd);
 192                   errno = save;
 193                   return NULL;
 194                 }
 195               _IO_init (&fp->file, 0);
 196               _IO_JUMPS (&fp->file) = &_IO_file_jumps;
 197               _IO_file_init (&fp->file);
 198 # if !_IO_UNIFIED_JUMPTABLES
 199               fp->vtable = NULL;
 200 # endif
 201               if (_IO_file_attach (&fp->file, fd) == NULL)
 202                 {
 203                   save = errno;
 204                   free (fp);
 205                   goto lose;
 206                 }
 207               fp->file._flags &= ~_IO_DELETE_DONT_CLOSE;
 208               fp->file._IO_file_flags = 0;
 209
 210               *streamptr = (FILE *) fp;
 211 #else
 212               *streamptr = __newstream ();
 213               if (*streamptr == NULL)
 214                 {
 215                   /* We lost trying to create a stream (out of memory?).
 216                      Nothing to do but remove the file, close the descriptor,
 217                      and return failure.  */
 218                   const int save = errno;
 219                   (void) remove (buf);
 220                   (void) __close (fd);
 221                   errno = save;
 222                   return NULL;
 223                 }
 224               (*streamptr)->__cookie = (PTR) (long int) fd;
 225               (*streamptr)->__mode.__write = 1;
 226               (*streamptr)->__mode.__read = 1;
 227               (*streamptr)->__mode.__binary = 1;
 228 #endif
 229             }
 230           else
 231             continue;
 232         }
 233       else if (exists (buf))
 234         continue;
 235
 236       /* If the file already existed we have continued the loop above,
 237          so we only get here when we have a winning name to return.  */
 238
 239       errno = saverrno;
 240
 241       if (lenptr != NULL)
 242         *lenptr = len + 1;
 243       return buf;
 244     }
 245
 246   /* We got out of the loop because we ran out of combinations to try.  */
 247   errno = EEXIST;               /* ? */
 248   return NULL;
 249 }