newlib/libc/stdio/tmpnam.c

   1 /*
   2  * tmpname.c
   3  * Original Author:     G. Haley
   4  */
   5 /*
   6 FUNCTION
   7 <<tmpnam>>, <<tempnam>>---name for a temporary file
   8
   9 INDEX
  10         tmpnam
  11 INDEX
  12         tempnam
  13 INDEX
  14         _tmpnam_r
  15 INDEX
  16         _tempnam_r
  17
  18 SYNOPSIS
  19         #include <stdio.h>
  20         char *tmpnam(char *<[s]>);
  21         char *tempnam(char *<[dir]>, char *<[pfx]>);
  22         char *_tmpnam_r(struct _reent *<[reent]>, char *<[s]>);
  23         char *_tempnam_r(struct _reent *<[reent]>, char *<[dir]>, char *<[pfx]>);
  24
  25 DESCRIPTION
  26 Use either of these functions to generate a name for a temporary file.
  27 The generated name is guaranteed to avoid collision with other files
  28 (for up to <<TMP_MAX>> calls of either function).
  29
  30 <<tmpnam>> generates file names with the value of <<P_tmpdir>>
  31 (defined in `<<stdio.h>>') as the leading directory component of the path.
  32
  33 You can use the <<tmpnam>> argument <[s]> to specify a suitable area
  34 of memory for the generated filename; otherwise, you can call
  35 <<tmpnam(NULL)>> to use an internal static buffer.
  36
  37 <<tempnam>> allows you more control over the generated filename: you
  38 can use the argument <[dir]> to specify the path to a directory for
  39 temporary files, and you can use the argument <[pfx]> to specify a
  40 prefix for the base filename.
  41
  42 If <[dir]> is <<NULL>>, <<tempnam>> will attempt to use the value of
  43 environment variable <<TMPDIR>> instead; if there is no such value,
  44 <<tempnam>> uses the value of <<P_tmpdir>> (defined in `<<stdio.h>>').
  45
  46 If you don't need any particular prefix to the basename of temporary
  47 files, you can pass <<NULL>> as the <[pfx]> argument to <<tempnam>>.
  48
  49 <<_tmpnam_r>> and <<_tempnam_r>> are reentrant versions of <<tmpnam>>
  50 and <<tempnam>> respectively.  The extra argument <[reent]> is a
  51 pointer to a reentrancy structure.
  52
  53 WARNINGS
  54 The generated filenames are suitable for temporary files, but do not
  55 in themselves make files temporary.  Files with these names must still
  56 be explicitly removed when you no longer want them.
  57
  58 If you supply your own data area <[s]> for <<tmpnam>>, you must ensure
  59 that it has room for at least <<L_tmpnam>> elements of type <<char>>.
  60
  61 RETURNS
  62 Both <<tmpnam>> and <<tempnam>> return a pointer to the newly
  63 generated filename.
  64
  65 PORTABILITY
  66 ANSI C requires <<tmpnam>>, but does not specify the use of
  67 <<P_tmpdir>>.  The System V Interface Definition (Issue 2) requires
  68 both <<tmpnam>> and <<tempnam>>.
  69
  70 Supporting OS subroutines required: <<close>>,  <<fstat>>, <<getpid>>,
  71 <<isatty>>, <<lseek>>, <<open>>, <<read>>, <<sbrk>>, <<write>>.
  72
  73 The global pointer <<environ>> is also required.
  74 */
  75
  76 #include <_ansi.h>
  77 #include <reent.h>
  78 #include <stdio.h>
  79 #include <stdlib.h>
  80 #include <string.h>
  81 #include <fcntl.h>
  82 #include <reent.h>
  83 #include <errno.h>
  84
  85 #ifdef _REENT_THREAD_LOCAL
  86 _Thread_local int _tls_inc;
  87 _Thread_local char _tls_emergency[_REENT_EMERGENCY_SIZE];
  88 #endif
  89
  90 /* Try to open the file specified, if it can't be opened then try
  91    another one.  Return nonzero if successful, otherwise zero.  */
  92
  93 static int
  94 worker (struct _reent *ptr,
  95        char *result,
  96        const char *part1,
  97        const char *part2,
  98        int part3,
  99        int *part4)
 100 {
 101   /*  Generate the filename and make sure that there isn't one called
 102       it already.  */
 103
 104   while (1)
 105     {
 106       int t;
 107       _sprintf_r (ptr, result, "%s/%s%x.%x", part1, part2, part3, *part4);
 108       (*part4)++;
 109       t = _open_r (ptr, result, O_RDONLY, 0);
 110       if (t == -1)
 111         {
 112           if (_REENT_ERRNO(ptr) == ENOSYS)
 113             {
 114               result[0] = '\0';
 115               return 0;
 116             }
 117           break;
 118         }
 119       _close_r (ptr, t);
 120     }
 121   return 1;
 122 }
 123
 124 char *
 125 _tmpnam_r (struct _reent *p,
 126        char *s)
 127 {
 128   char *result;
 129   int pid;
 130
 131   if (s == NULL)
 132     {
 133       /* ANSI states we must use an internal static buffer if s is NULL */
 134       _REENT_CHECK_EMERGENCY(p);
 135       result = _REENT_EMERGENCY(p);
 136     }
 137   else
 138     {
 139       result = s;
 140     }
 141   pid = _getpid_r (p);
 142
 143   if (worker (p, result, P_tmpdir, "t", pid, &_REENT_INC(p)))
 144     {
 145       _REENT_INC(p)++;
 146       return result;
 147     }
 148
 149   return NULL;
 150 }
 151
 152 char *
 153 _tempnam_r (struct _reent *p,
 154        const char *dir,
 155        const char *pfx)
 156 {
 157   char *filename;
 158   int length;
 159   const char *prefix = (pfx) ? pfx : "";
 160   if (dir == NULL && (dir = getenv ("TMPDIR")) == NULL)
 161     dir = P_tmpdir;
 162
 163   /* two 8 digit numbers + . / */
 164   length = strlen (dir) + strlen (prefix) + (4 * sizeof (int)) + 2 + 1;
 165
 166   filename = _malloc_r (p, length);
 167   if (filename)
 168     {
 169       if (! worker (p, filename, dir, prefix,
 170                     _getpid_r (p) ^ (int) (_POINTER_INT) p, &_REENT_INC(p)))
 171         return NULL;
 172     }
 173   return filename;
 174 }
 175
 176 #ifndef _REENT_ONLY
 177
 178 char *
 179 tempnam (const char *dir,
 180        const char *pfx)
 181 {
 182   return _tempnam_r (_REENT, dir, pfx);
 183 }
 184
 185 char *
 186 tmpnam (char *s)
 187 {
 188   return _tmpnam_r (_REENT, s);
 189 }
 190
 191 #endif