1/*-
2 * Copyright (c) 1990, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#include <errno.h>
34#include <signal.h>
35#include <stdio.h>
36#include <stdlib.h>
37#include <sys/stat.h>
38#include <sys/types.h>
39#include <unistd.h>
40
41#include "private/ErrnoRestorer.h"
42
43class ScopedSignalBlocker {
44 public:
45  ScopedSignalBlocker() {
46    sigset_t set;
47    sigfillset(&set);
48    sigprocmask(SIG_BLOCK, &set, &old_set_);
49  }
50
51  ~ScopedSignalBlocker() {
52    sigprocmask(SIG_SETMASK, &old_set_, NULL);
53  }
54
55 private:
56  sigset_t old_set_;
57};
58
59static FILE* __tmpfile_dir(const char* tmp_dir) {
60  char buf[PATH_MAX];
61  int path_length = snprintf(buf, sizeof(buf), "%s/tmp.XXXXXXXXXX", tmp_dir);
62  if (path_length >= static_cast<int>(sizeof(buf))) {
63    return NULL;
64  }
65
66  int fd;
67  {
68    ScopedSignalBlocker ssb;
69    fd = mkstemp(buf);
70    if (fd == -1) {
71      return NULL;
72    }
73
74    // Unlink the file now so that it's removed when closed.
75    unlink(buf);
76
77    // Can we still use the file now it's unlinked?
78    // File systems without hard link support won't have the usual Unix semantics.
79    struct stat sb;
80    int rc = fstat(fd, &sb);
81    if (rc == -1) {
82      ErrnoRestorer errno_restorer;
83      close(fd);
84      return NULL;
85    }
86  }
87
88  // Turn the file descriptor into a FILE*.
89  FILE* fp = fdopen(fd, "w+");
90  if (fp != NULL) {
91    return fp;
92  }
93
94  // Failure. Clean up. We already unlinked, so we just need to close.
95  ErrnoRestorer errno_restorer;
96  close(fd);
97  return NULL;
98}
99
100FILE* tmpfile() {
101  // TODO: get this app's temporary directory from the framework ("/data/data/app/cache").
102
103  // $EXTERNAL_STORAGE turns out not to be very useful because it doesn't support hard links.
104  // This means we can't do the usual trick of calling unlink before handing the file back.
105
106  FILE* fp = __tmpfile_dir("/data/local/tmp");
107  if (fp == NULL) {
108    // P_tmpdir is "/tmp/", but POSIX explicitly says that tmpdir(3) should try P_tmpdir before
109    // giving up. This is potentially useful for bionic on the host anyway.
110    fp = __tmpfile_dir(P_tmpdir);
111  }
112  return fp;
113}
114