summary refs log tree commit diff
path: root/sysdeps/posix/tempname.c
blob: bb921c172f6d64a3826e5bb9b84c2d1b629ae07b (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
/* Copyright (C) 1991, 92, 93, 94, 95, 96 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 Library General Public License as
published by the Free Software Foundation; either version 2 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
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#ifdef USE_IN_LIBIO
# include "libioP.h"
# include <libio.h>
#endif

/* Return nonzero if DIR is an existent directory.  */
static int
diraccess (const char *dir)
{
  struct stat buf;
  return __stat (dir, &buf) == 0 && S_ISDIR (buf.st_mode);
}

/* Return nonzero if FILE exists.  */
static int
exists (const char *file)
{
  /* We can stat the file even if we can't read its data.  */
  struct stat st;
  int save = errno;
  if (__stat (file, &st) == 0)
    return 1;
  else
    {
      /* We report that the file exists if stat failed for a reason other
	 than nonexistence.  In this case, it may or may not exist, and we
	 don't know; but reporting that it does exist will never cause any
	 trouble, while reporting that it doesn't exist when it does would
	 violate the interface of __stdio_gen_tempname.  */
      int exists = errno != ENOENT;
      __set_errno (save);
      return exists;
    }
}


/* These are the characters used in temporary filenames.  */
static const char letters[] =
  "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

/* Generate a temporary filename and return it (in a static buffer).  If
   STREAMPTR is not NULL, open a stream "w+b" on the file and set
   *STREAMPTR to it.  If DIR_SEARCH is nonzero, DIR and PFX are used as
   described for tempnam.  If not, a temporary filename in P_tmpdir with no
   special prefix is generated.  If LENPTR is not NULL, *LENPTR is set the
   to length (including the terminating '\0') of the resultant filename,
   which is returned.  This goes through a cyclic pattern of all possible
   filenames consisting of five decimal digits of the current pid and three
   of the characters in `letters'.  Data for tempnam and tmpnam is kept
   separate, but when tempnam is using P_tmpdir and no prefix (i.e, it is
   identical to tmpnam), the same data is used.  Each potential filename is
   tested for an already-existing file of the same name, and no name of an
   existing file will be returned.  When the cycle reaches its end
   (12345ZZZ), NULL is returned.  */
char *
__stdio_gen_tempname (char *buf, size_t bufsize, const char *dir,
		      const char *pfx, int dir_search, size_t *lenptr,
		      FILE **streamptr)
{
  int saverrno = errno;
  static const char tmpdir[] = P_tmpdir;
  static size_t indices[2];
  size_t *idx;
#if 0
  static pid_t oldpid = (pid_t) 0;
#endif
  pid_t pid = __getpid();
  register size_t len, plen, dlen;
  int wrapped;

  if (dir_search)
    {
      register const char *d = __secure_getenv ("TMPDIR");
      if (d != NULL && !diraccess (d))
	d = NULL;
      if (d == NULL && dir != NULL && diraccess (dir))
	d = dir;
      if (d == NULL && diraccess (tmpdir))
	d = tmpdir;
      if (d == NULL && diraccess ("/tmp"))
	d = "/tmp";
      if (d == NULL)
	{
	  __set_errno (ENOENT);
	  return NULL;
	}
      dir = d;
    }
  else
    dir = tmpdir;

  dlen = strlen (dir);

 /* Remove trailing slashes from the directory name.  */
  while (dlen > 1 && dir[dlen - 1] == '/')
    --dlen;

  if (pfx != NULL && *pfx != '\0')
    {
      plen = strlen (pfx);
      if (plen > 5)
	plen = 5;
    }
  else
    plen = 0;

  if (dir != tmpdir && !strcmp (dir, tmpdir))
    dir = tmpdir;
  idx = &indices[(plen == 0 && dir == tmpdir) ? 1 : 0];

#if 0
  /* XXX Is this ever useful???  At least when using a thread package
     which uses different PIDs for the threads it is not helpful.  */
  if (pid != oldpid)
    {
      oldpid = pid;
      indices[0] = indices[1] = 0;
    }
#endif

  wrapped = 0; /* We have not yet wrapped around the index counter.  */
  len = dlen + 1 + plen + 5 + 3;
  while (1)
    {
      size_t i;

      if (*idx >= ((sizeof (letters) - 1) * (sizeof (letters) - 1) *
		   (sizeof (letters) - 1)))
	{
	  if (wrapped)
	    /* We really wrapped around this call.  Can't believe it
	       but nevertheless stop the endless loop.  */
	    break;

	  indices[0] = indices[1] = 0;
	  wrapped = 1;
	}

      i = (*idx)++;

      /* Construct a file name and see if it already exists.

	 We use a single counter in *IDX to cycle each of three
	 character positions through each of 62 possible letters.  */

      if (__snprintf (buf, bufsize, "%.*s/%.*s%.5d%c%c%c",
		      (int) dlen, dir, (int) plen,
		      pfx, pid % 100000,
		      letters[i % (sizeof (letters) - 1)],
		      letters[(i / (sizeof (letters) - 1))
			     % (sizeof (letters) - 1)],
		      letters[(i / ((sizeof (letters) - 1) *
				    (sizeof (letters) - 1)))
			     % (sizeof (letters) - 1)]
		    ) != (int) len)
	return NULL;

      if (streamptr != NULL)
	{
	  /* Try to create the file atomically.  */
	  int fd = __open (buf, O_RDWR|O_CREAT|O_EXCL, 0666);
	  if (fd >= 0)
	    {
	      /* We got a new file that did not previously exist.
		 Create a stream for it.  */
#ifdef USE_IN_LIBIO
	      int save;
	      struct locked_FILE
		{
		  struct _IO_FILE_plus fp;
#ifdef _IO_MTSAFE_IO
		  _IO_lock_t lock;
#endif
		} *new_f;
	      struct _IO_FILE_plus *fp;

	      new_f = (struct locked_FILE *)
		malloc (sizeof (struct locked_FILE));
	      if (new_f == NULL)
		{
		  /* We lost trying to create a stream (out of memory?).
		     Nothing to do but remove the file, close the descriptor,
		     and return failure.  */
		  save = errno;
		lose:
		  (void) remove (buf);
		  (void) __close (fd);
		  __set_errno (save);
		  return NULL;
		}
	      fp = &new_f->fp;
#ifdef _IO_MTSAFE_IO
	      fp->file._lock = &new_f->lock;
#endif
	      _IO_init (&fp->file, 0);
	      _IO_JUMPS (&fp->file) = &_IO_file_jumps;
	      _IO_file_init (&fp->file);
# if !_IO_UNIFIED_JUMPTABLES
	      fp->vtable = NULL;
# endif
	      if (_IO_file_attach (&fp->file, fd) == NULL)
		{
		  save = errno;
		  free (fp);
		  goto lose;
		}
	      fp->file._flags &= ~_IO_DELETE_DONT_CLOSE;

	      *streamptr = (FILE *) fp;
#else
	      *streamptr = __newstream ();
	      if (*streamptr == NULL)
		{
		  /* We lost trying to create a stream (out of memory?).
		     Nothing to do but remove the file, close the descriptor,
		     and return failure.  */
		  const int save = errno;
		  (void) remove (buf);
		  (void) __close (fd);
		  __set_errno (save);
		  return NULL;
		}
	      (*streamptr)->__cookie = (__ptr_t) (long int) fd;
	      (*streamptr)->__mode.__write = 1;
	      (*streamptr)->__mode.__read = 1;
	      (*streamptr)->__mode.__binary = 1;
#endif
	    }
#if defined EMFILE || defined ENFILE || defined EINTR
	  else if (0
# ifdef EMFILE
		   || errno == EMFILE
# endif
# ifdef ENFILE
		   || errno == ENFILE
# endif
# ifdef EINTR
		   || errno == EINTR
# endif
		   )
	    /* We cannot open anymore files since all descriptors are
	       used or because we got a signal.  */
	    return NULL;
#endif
	  else
	    continue;
	}
      else if (exists (buf))
	continue;

      /* If the file already existed we have continued the loop above,
	 so we only get here when we have a winning name to return.  */

      __set_errno (saverrno);

      if (lenptr != NULL)
	*lenptr = len + 1;
      return buf;
    }

  /* We got out of the loop because we ran out of combinations to try.  */
  __set_errno (EEXIST);		/* ? */
  return NULL;
}