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      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 
     43 class 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 
     59 static FILE* __tmpfile_dir(const char* tmp_dir) {
     60   char* path = NULL;
     61   if (asprintf(&path, "%s/tmp.XXXXXXXXXX", tmp_dir) == -1) {
     62     return NULL;
     63   }
     64 
     65   int fd;
     66   {
     67     ScopedSignalBlocker ssb;
     68     fd = mkstemp(path);
     69     if (fd == -1) {
     70       free(path);
     71       return NULL;
     72     }
     73 
     74     // Unlink the file now so that it's removed when closed.
     75     unlink(path);
     76     free(path);
     77 
     78     // Can we still use the file now it's unlinked?
     79     // File systems without hard link support won't have the usual Unix semantics.
     80     struct stat sb;
     81     int rc = fstat(fd, &sb);
     82     if (rc == -1) {
     83       ErrnoRestorer errno_restorer;
     84       close(fd);
     85       return NULL;
     86     }
     87   }
     88 
     89   // Turn the file descriptor into a FILE*.
     90   FILE* fp = fdopen(fd, "w+");
     91   if (fp != NULL) {
     92     return fp;
     93   }
     94 
     95   // Failure. Clean up. We already unlinked, so we just need to close.
     96   ErrnoRestorer errno_restorer;
     97   close(fd);
     98   return NULL;
     99 }
    100 
    101 FILE* tmpfile() {
    102   // TODO: get this app's temporary directory from the framework ("/data/data/app/cache").
    103 
    104   // $EXTERNAL_STORAGE turns out not to be very useful because it doesn't support hard links.
    105   // This means we can't do the usual trick of calling unlink before handing the file back.
    106 
    107   FILE* fp = __tmpfile_dir("/data/local/tmp");
    108   if (fp == NULL) {
    109     // P_tmpdir is "/tmp/", but POSIX explicitly says that tmpdir(3) should try P_tmpdir before
    110     // giving up. This is potentially useful for bionic on the host anyway.
    111     fp = __tmpfile_dir(P_tmpdir);
    112   }
    113   return fp;
    114 }
    115 __strong_alias(tmpfile64, tmpfile);
    116