/* crc8.c
 * Implementation CRC-8 declarations and routines
 *
 * 2011 Roland Knall <rknall@gmail.com>
 *
 * $Id: crc8.c 39726 2011-11-03 20:58:29Z stig $
 *
 * 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.
 */


#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <glib.h>
#include <wsutil/crc8.h>

/* @brief Precompiled table for CRC8 values for the polynom 0x2F */
static const guint8 crc8_precompiled_2F[256] =
{
	0x00, 0x2F, 0x5E, 0x71, 0xBC, 0x93, 0xE2, 0xCD,
	0x57, 0x78, 0x09, 0x26, 0xEB, 0xC4, 0xB5, 0x9A,
	0xAE, 0x81, 0xF0, 0xDF, 0x12, 0x3D, 0x4C, 0x63,
	0xF9, 0xD6, 0xA7, 0x88, 0x45, 0x6A, 0x1B, 0x34,
	0x73, 0x5C, 0x2D, 0x02, 0xCF, 0xE0, 0x91, 0xBE,
	0x24, 0x0B, 0x7A, 0x55, 0x98, 0xB7, 0xC6, 0xE9,
	0xDD, 0xF2, 0x83, 0xAC, 0x61, 0x4E, 0x3F, 0x10,
	0x8A, 0xA5, 0xD4, 0xFB, 0x36, 0x19, 0x68, 0x47,
	0xE6, 0xC9, 0xB8, 0x97, 0x5A, 0x75, 0x04, 0x2B,
	0xB1, 0x9E, 0xEF, 0xC0, 0x0D, 0x22, 0x53, 0x7C,
	0x48, 0x67, 0x16, 0x39, 0xF4, 0xDB, 0xAA, 0x85,
	0x1F, 0x30, 0x41, 0x6E, 0xA3, 0x8C, 0xFD, 0xD2,
	0x95, 0xBA, 0xCB, 0xE4, 0x29, 0x06, 0x77, 0x58,
	0xC2, 0xED, 0x9C, 0xB3, 0x7E, 0x51, 0x20, 0x0F,
	0x3B, 0x14, 0x65, 0x4A, 0x87, 0xA8, 0xD9, 0xF6,
	0x6C, 0x43, 0x32, 0x1D, 0xD0, 0xFF, 0x8E, 0xA1,
	0xE3, 0xCC, 0xBD, 0x92, 0x5F, 0x70, 0x01, 0x2E,
	0xB4, 0x9B, 0xEA, 0xC5, 0x08, 0x27, 0x56, 0x79,
	0x4D, 0x62, 0x13, 0x3C, 0xF1, 0xDE, 0xAF, 0x80,
	0x1A, 0x35, 0x44, 0x6B, 0xA6, 0x89, 0xF8, 0xD7,
	0x90, 0xBF, 0xCE, 0xE1, 0x2C, 0x03, 0x72, 0x5D,
	0xC7, 0xE8, 0x99, 0xB6, 0x7B, 0x54, 0x25, 0x0A,
	0x3E, 0x11, 0x60, 0x4F, 0x82, 0xAD, 0xDC, 0xF3,
	0x69, 0x46, 0x37, 0x18, 0xD5, 0xFA, 0x8B, 0xA4,
	0x05, 0x2A, 0x5B, 0x74, 0xB9, 0x96, 0xE7, 0xC8,
	0x52, 0x7D, 0x0C, 0x23, 0xEE, 0xC1, 0xB0, 0x9F,
	0xAB, 0x84, 0xF5, 0xDA, 0x17, 0x38, 0x49, 0x66,
	0xFC, 0xD3, 0xA2, 0x8D, 0x40, 0x6F, 0x1E, 0x31,
	0x76, 0x59, 0x28, 0x07, 0xCA, 0xE5, 0x94, 0xBB,
	0x21, 0x0E, 0x7F, 0x50, 0x9D, 0xB2, 0xC3, 0xEC,
	0xD8, 0xF7, 0x86, 0xA9, 0x64, 0x4B, 0x3A, 0x15,
	0x8F, 0xA0, 0xD1, 0xFE, 0x33, 0x1C, 0x6D, 0x42
};


/** Calculates a CRC8 checksum for the given buffer with the polynom
 *  stored in the crc_table
 * @param buf a pointer to a buffer of the given length
 * @param len the length of the given buffer
 * @param seed The seed to use.
 * @param crc_table a table storing 256 entries for crc8 checksums
 * @return the CRC8 checksum for the buffer
 */
static guint8 crc8_precompiled(guint8 *buf, guint32 len, guint8 seed, const guint8 crc_table[])
{
    guint8 crc;

    crc = seed;
    while(len-- > 0)
        crc = crc_table[(guint8)(*buf++) ^ crc];

    return crc;
}

/** Calculates a CRC8 checksum for the given buffer with the polynom
 *  0x2F using the precompiled CRC table
 * @param buf a pointer to a buffer of the given length
 * @param len the length of the given buffer
 * @param seed The seed to use.
 * @return the CRC8 checksum for the buffer
 */
guint8 crc8_0x2F(guint8 *buf, guint32 len, guint8 seed)
{
    return crc8_precompiled(buf, len, seed, crc8_precompiled_2F);
}
