stdio/memstream.c

   1 /* Copyright (C) 1991, 1992, 1994 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library 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 GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23
  24 struct memstream_info
  25   {
  26     char **buffer;
  27     size_t *bufsize;
  28   };
  29
  30 /* Enlarge STREAM's buffer.  */
  31 static void
  32 DEFUN(enlarge_buffer, (stream, c),
  33       register FILE *stream AND int c)
  34 {
  35   struct memstream_info *info = (struct memstream_info *) stream->__cookie;
  36   size_t need;
  37
  38   if (stream->__put_limit != stream->__buffer)
  39     /* Record how much has actually been written into the buffer.  */
  40     *info->bufsize = stream->__bufp - stream->__buffer;
  41
  42   if (stream->__target != -1
  43       && stream->__target > *info->bufsize)
  44     /* Our target (where the buffer maps to) is always zero except when
  45        the user just did a SEEK_END fseek.  If he sought within the
  46        buffer, we need do nothing and will zero the target below.  If he
  47        sought past the end of the object, grow and zero-fill the buffer
  48        up to the target address.  */
  49     need = stream->__target;
  50   else
  51     need = *info->bufsize;
  52
  53   /* We always need an extra character in the buffer.  Either we are
  54      writing C, or we are flushing and need to write a NUL terminator.  */
  55   ++need;
  56
  57   if (stream->__bufsize < need)
  58     {
  59       /* Enlarge the buffer.  */
  60       char *newbuf;
  61       size_t newsize;
  62       if (stream->__bufsize * 2 < need)
  63         newsize = need;
  64       else
  65         newsize = stream->__bufsize * 2;
  66       newbuf = (char *) realloc ((PTR) stream->__buffer, newsize);
  67       if (newbuf == NULL)
  68         {
  69           stream->__error = 1;
  70           return;
  71         }
  72       *info->buffer = stream->__buffer = newbuf;
  73       stream->__bufsize = newsize;
  74     }
  75
  76   stream->__target = stream->__offset = 0;
  77   stream->__get_limit = stream->__bufp = stream->__buffer + *info->bufsize;
  78   stream->__put_limit = stream->__buffer + stream->__bufsize;
  79
  80   need -= stream->__bufp - stream->__buffer + 1;
  81   if (need > 0)
  82     {
  83       /* We are extending the buffer after an fseek; zero-fill new space.  */
  84       bzero (stream->__bufp, need);
  85       stream->__bufp += need;
  86     }
  87
  88   if (c != EOF)
  89     *stream->__bufp++ = (unsigned char) c;
  90   else
  91     *stream->__bufp = '\0';
  92 }
  93
  94 /* Seek function for memstreams.
  95    There is no external state to munge.  */
  96
  97 static int
  98 DEFUN(seek, (cookie, pos, whence),
  99       PTR cookie AND fpos_t *pos AND int whence)
 100 {
 101   switch (whence)
 102     {
 103     case SEEK_SET:
 104     case SEEK_CUR:
 105       return 0;
 106
 107     case SEEK_END:
 108       /* Return the position relative to the end of the object.
 109          fseek has just flushed us, so the info is consistent.  */
 110       *pos += *((struct memstream_info *) cookie)->bufsize;
 111       return 0;
 112
 113     default:
 114       __libc_fatal ("memstream::seek called with bogus WHENCE\n");
 115       return -1;
 116     }
 117 }
 118
 119 static int
 120 DEFUN(free_info, (cookie), PTR cookie)
 121 {
 122 #if 0
 123   struct memstream_info *info = (struct memstream_info *) cookie;
 124   char *buf;
 125
 126   buf = (char *) realloc ((PTR) *info->buffer, *info->bufsize);
 127   if (buf != NULL)
 128     *info->buffer = buf;
 129 #endif
 130
 131   free (cookie);
 132
 133   return 0;
 134 }
 135 \f
 136 /* Open a stream that writes into a malloc'd buffer that is expanded as
 137    necessary.  *BUFLOC and *SIZELOC are updated with the buffer's location
 138    and the number of characters written on fflush or fclose.  */
 139 FILE *
 140 DEFUN(open_memstream, (bufloc, sizeloc),
 141       char **bufloc AND size_t *sizeloc)
 142 {
 143   FILE *stream;
 144   struct memstream_info *info;
 145
 146   if (bufloc == NULL || sizeloc == NULL)
 147     {
 148       errno = EINVAL;
 149       return NULL;
 150     }
 151
 152   stream = fmemopen ((char *) NULL, BUFSIZ, "w+");
 153   if (stream == NULL)
 154     return NULL;
 155
 156   info = (struct memstream_info *) malloc (sizeof (struct memstream_info));
 157   if (info == NULL)
 158     {
 159       int save = errno;
 160       (void) fclose (stream);
 161       errno = save;
 162       return NULL;
 163     }
 164
 165   stream->__room_funcs.__output = enlarge_buffer;
 166   stream->__io_funcs.__seek = seek;
 167   stream->__io_funcs.__close = free_info;
 168   stream->__cookie = (PTR) info;
 169   stream->__userbuf = 1;
 170
 171   info->buffer = bufloc;
 172   info->bufsize = sizeloc;
 173
 174   *bufloc = stream->__buffer;
 175
 176   return stream;
 177 }