lib/tmpfile.c

   1 /* Create a temporary file.
   2    Copyright (C) 2007, 2009-2017 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program 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
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Ben Pfaff. */
  18
  19 #include <config.h>
  20
  21 /* Specification.  */
  22 #include <stdio.h>
  23
  24 /* This replacement is used only on native Windows platforms.  */
  25
  26 #include <errno.h>
  27 #include <fcntl.h>
  28 #include <string.h>
  29 #include <sys/stat.h>
  30
  31 #include <io.h>
  32
  33 #define WIN32_LEAN_AND_MEAN  /* avoid including junk */
  34 #include <windows.h>
  35
  36 #include "pathmax.h"
  37 #include "tempname.h"
  38 #include "tmpdir.h"
  39
  40 /* PATH_MAX is guaranteed to be defined, because this replacement is only
  41    used on native Windows.  */
  42
  43 /* On Windows, opening a file with _O_TEMPORARY has the effect of passing
  44    the FILE_FLAG_DELETE_ON_CLOSE flag to CreateFile(), which has the effect
  45    of deleting the file when it is closed - even when the program crashes.
  46    But (according to the Cygwin sources) it works only on Windows NT or newer.
  47    So we cache the info whether we are running on Windows NT or newer.  */
  48
  49 static bool
  50 supports_delete_on_close ()
  51 {
  52   static int known; /* 1 = yes, -1 = no, 0 = unknown */
  53   if (!known)
  54     {
  55       OSVERSIONINFO v;
  56
  57       /* According to
  58          <http://msdn.microsoft.com/en-us/library/windows/desktop/ms724451(v=vs.85).aspx>
  59          this structure must be initialized as follows:  */
  60       v.dwOSVersionInfoSize = sizeof (OSVERSIONINFO);
  61
  62       if (GetVersionEx (&v))
  63         known = (v.dwPlatformId == VER_PLATFORM_WIN32_NT ? 1 : -1);
  64       else
  65         known = -1;
  66     }
  67   return (known > 0);
  68 }
  69
  70 FILE *
  71 tmpfile (void)
  72 {
  73   char dir[PATH_MAX];
  74   DWORD retval;
  75
  76   /* Find Windows temporary file directory.
  77      We provide this as the directory argument to path_search because Windows
  78      defines P_tmpdir to "\\" and will therefore try to put all temporary files
  79      in the root directory (unless $TMPDIR is set). */
  80   retval = GetTempPath (PATH_MAX, dir);
  81   if (retval > 0 && retval < PATH_MAX)
  82     {
  83       char xtemplate[PATH_MAX];
  84
  85       if (path_search (xtemplate, PATH_MAX, dir, NULL, true) >= 0)
  86         {
  87           size_t len = strlen (xtemplate);
  88           int o_temporary = (supports_delete_on_close () ? _O_TEMPORARY : 0);
  89           int fd;
  90
  91           do
  92             {
  93               memcpy (&xtemplate[len - 6], "XXXXXX", 6);
  94               if (gen_tempname (xtemplate, 0, 0, GT_NOCREATE) < 0)
  95                 {
  96                   fd = -1;
  97                   break;
  98                 }
  99
 100               fd = _open (xtemplate,
 101                           _O_CREAT | _O_EXCL | o_temporary
 102                           | _O_RDWR | _O_BINARY,
 103                           _S_IREAD | _S_IWRITE);
 104             }
 105           while (fd < 0 && errno == EEXIST);
 106
 107           if (fd >= 0)
 108             {
 109               FILE *fp = _fdopen (fd, "w+b");
 110
 111               if (fp != NULL)
 112                 return fp;
 113               else
 114                 {
 115                   int saved_errno = errno;
 116                   _close (fd);
 117                   errno = saved_errno;
 118                 }
 119             }
 120         }
 121     }
 122   else
 123     {
 124       if (retval > 0)
 125         errno = ENAMETOOLONG;
 126       else
 127         /* Ideally this should translate GetLastError () to an errno value.  */
 128         errno = ENOENT;
 129     }
 130
 131   return NULL;
 132 }