util/membuf.c

   1 /* membuf.c - A simple implementation of a dynamic buffer
   2  *      Copyright (C) 2001, 2003 Free Software Foundation, Inc.
   3  *
   4  * This file is part of GnuPG.
   5  *
   6  * GnuPG is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * GnuPG is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  19  * USA.
  20  */
  21
  22 #include <config.h>
  23 #include <stdlib.h>
  24 #include <errno.h>
  25 #include <string.h>
  26
  27 #include "util.h"
  28
  29
  30 /* A simple implementation of a dynamic buffer.  Use init_membuf() to
  31    create a buffer, put_membuf to append bytes and get_membuf to
  32    release and return the buffer.  Allocation errors are detected but
  33    only returned at the final get_membuf(), this helps not to clutter
  34    the code with out of core checks.  */
  35
  36 void
  37 init_membuf (membuf_t *mb, int initiallen)
  38 {
  39   mb->len = 0;
  40   mb->size = initiallen;
  41   mb->out_of_core = 0;
  42   mb->buf = xmalloc (initiallen);
  43   if (!mb->buf)
  44       mb->out_of_core = errno;
  45 }
  46
  47
  48 void
  49 put_membuf (membuf_t *mb, const void *buf, size_t len)
  50 {
  51   if (mb->out_of_core)
  52     return;
  53
  54   if (mb->len + len >= mb->size)
  55     {
  56       char *p;
  57
  58       mb->size += len + 1024;
  59       p = xrealloc (mb->buf, mb->size);
  60       mb->buf = p;
  61     }
  62   memcpy (mb->buf + mb->len, buf, len);
  63   mb->len += len;
  64 }
  65
  66
  67 void *
  68 get_membuf (membuf_t *mb, size_t *len)
  69 {
  70   char *p;
  71
  72   if (mb->out_of_core)
  73     {
  74       xfree (mb->buf);
  75       mb->buf = NULL;
  76       return NULL;
  77     }
  78
  79   p = mb->buf;
  80   *len = mb->len;
  81   mb->buf = NULL;
  82   mb->out_of_core = ENOMEM; /* hack to make sure it won't get reused. */
  83   return p;
  84 }