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/* crc32-tvb.c
* CRC-32 tvbuff routines
*
* $Id$
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Credits:
*
* Table from Solomon Peachy
* Routine from Chris Waters
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include <glib.h>
#include <epan/tvbuff.h>
#include <wsutil/crc32.h>
guint32
crc32_ccitt_tvb(tvbuff_t *tvb, guint len)
{
const guint8* buf;
tvb_ensure_bytes_exist(tvb, 0, len); /* len == -1 not allowed */
buf = tvb_get_ptr(tvb, 0, len);
return ( crc32_ccitt_seed(buf, len, CRC32_CCITT_SEED) );
}
guint32
crc32_ccitt_tvb_offset(tvbuff_t *tvb, guint offset, guint len)
{
const guint8* buf;
tvb_ensure_bytes_exist(tvb, offset, len); /* len == -1 not allowed */
buf = tvb_get_ptr(tvb, offset, len);
return ( crc32_ccitt(buf, len) );
}
guint32
crc32_ccitt_tvb_seed(tvbuff_t *tvb, guint len, guint32 seed)
{
const guint8* buf;
tvb_ensure_bytes_exist(tvb, 0, len); /* len == -1 not allowed */
buf = tvb_get_ptr(tvb, 0, len);
return ( crc32_ccitt_seed(buf, len, seed) );
}
guint32
crc32_ccitt_tvb_offset_seed(tvbuff_t *tvb, guint offset, guint len,
guint32 seed)
{
const guint8* buf;
tvb_ensure_bytes_exist(tvb, offset, len); /* len == -1 not allowed */
buf = tvb_get_ptr(tvb, offset, len);
return ( crc32_ccitt_seed(buf, len, seed) );
}
/*
* IEEE 802.x version (Ethernet and 802.11, at least) - byte-swap
* the result of "crc32()".
*
* XXX - does this mean we should fetch the Ethernet and 802.11
* FCS with "tvb_get_letohl()" rather than "tvb_get_ntohl()",
* or is fetching it big-endian and byte-swapping the CRC done
* to cope with 802.x sending stuff out in reverse bit order?
*/
guint32
crc32_802_tvb(tvbuff_t *tvb, guint len)
{
guint32 c_crc;
c_crc = crc32_ccitt_tvb(tvb, len);
/* Byte reverse. */
c_crc = ((unsigned char)(c_crc>>0)<<24) |
((unsigned char)(c_crc>>8)<<16) |
((unsigned char)(c_crc>>16)<<8) |
((unsigned char)(c_crc>>24)<<0);
return ( c_crc );
}
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