common/membuf.c

   1 /* membuf.c - A simple implementation of a dynamic buffer.
   2  * Copyright (C) 2001, 2003, 2009 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 3 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, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <config.h>
  21 #include <stdlib.h>
  22 #include <errno.h>
  23
  24 #include "membuf.h"
  25
  26 #include "util.h"
  27
  28
  29 /* A simple implementation of a dynamic buffer.  Use init_membuf() to
  30    create a buffer, put_membuf to append bytes and get_membuf to
  31    release and return the buffer.  Allocation errors are detected but
  32    only returned at the final get_membuf(), this helps not to clutter
  33    the code with out of core checks.  */
  34
  35 void
  36 init_membuf (membuf_t *mb, int initiallen)
  37 {
  38   mb->len = 0;
  39   mb->size = initiallen;
  40   mb->out_of_core = 0;
  41   mb->buf = xtrymalloc (initiallen);
  42   if (!mb->buf)
  43     mb->out_of_core = errno;
  44 }
  45
  46 /* Same as init_membuf but allocates the buffer in secure memory.  */
  47 void
  48 init_membuf_secure (membuf_t *mb, int initiallen)
  49 {
  50   mb->len = 0;
  51   mb->size = initiallen;
  52   mb->out_of_core = 0;
  53   mb->buf = xtrymalloc_secure (initiallen);
  54   if (!mb->buf)
  55     mb->out_of_core = errno;
  56 }
  57
  58
  59 void
  60 put_membuf (membuf_t *mb, const void *buf, size_t len)
  61 {
  62   if (mb->out_of_core)
  63     return;
  64
  65   if (mb->len + len >= mb->size)
  66     {
  67       char *p;
  68
  69       mb->size += len + 1024;
  70       p = xtryrealloc (mb->buf, mb->size);
  71       if (!p)
  72         {
  73           mb->out_of_core = errno ? errno : ENOMEM;
  74           /* Wipe out what we already accumulated.  This is required
  75              in case we are storing sensitive data here.  The membuf
  76              API does not provide another way to cleanup after an
  77              error. */
  78           wipememory (mb->buf, mb->len);
  79           return;
  80         }
  81       mb->buf = p;
  82     }
  83   memcpy (mb->buf + mb->len, buf, len);
  84   mb->len += len;
  85 }
  86
  87
  88 void
  89 put_membuf_str (membuf_t *mb, const char *string)
  90 {
  91   put_membuf (mb, string, strlen (string));
  92 }
  93
  94
  95 void *
  96 get_membuf (membuf_t *mb, size_t *len)
  97 {
  98   char *p;
  99
 100   if (mb->out_of_core)
 101     {
 102       if (mb->buf)
 103         {
 104           wipememory (mb->buf, mb->len);
 105           xfree (mb->buf);
 106           mb->buf = NULL;
 107         }
 108       errno = mb->out_of_core;
 109       return NULL;
 110     }
 111
 112   p = mb->buf;
 113   if (len)
 114     *len = mb->len;
 115   mb->buf = NULL;
 116   mb->out_of_core = ENOMEM; /* hack to make sure it won't get reused. */
 117   return p;
 118 }