/*
	checksum.c

	(description)

	Copyright (C) 1996-1997  Id Software, Inc.

	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:

		Free Software Foundation, Inc.
		59 Temple Place - Suite 330
		Boston, MA  02111-1307, USA

	$Id$
*/

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif
#include "checksum.h"
#include "crc.h"

static byte chktbl[1024 + 4] = {
0x78,0xd2,0x94,0xe3,0x41,0xec,0xd6,0xd5,0xcb,0xfc,0xdb,0x8a,0x4b,0xcc,0x85,0x01,
0x23,0xd2,0xe5,0xf2,0x29,0xa7,0x45,0x94,0x4a,0x62,0xe3,0xa5,0x6f,0x3f,0xe1,0x7a,
0x64,0xed,0x5c,0x99,0x29,0x87,0xa8,0x78,0x59,0x0d,0xaa,0x0f,0x25,0x0a,0x5c,0x58,
0xfb,0x00,0xa7,0xa8,0x8a,0x1d,0x86,0x80,0xc5,0x1f,0xd2,0x28,0x69,0x71,0x58,0xc3,
0x51,0x90,0xe1,0xf8,0x6a,0xf3,0x8f,0xb0,0x68,0xdf,0x95,0x40,0x5c,0xe4,0x24,0x6b,
0x29,0x19,0x71,0x3f,0x42,0x63,0x6c,0x48,0xe7,0xad,0xa8,0x4b,0x91,0x8f,0x42,0x36,
0x34,0xe7,0x32,0x55,0x59,0x2d,0x36,0x38,0x38,0x59,0x9b,0x08,0x16,0x4d,0x8d,0xf8,
0x0a,0xa4,0x52,0x01,0xbb,0x52,0xa9,0xfd,0x40,0x18,0x97,0x37,0xff,0xc9,0x82,0x27,
0xb2,0x64,0x60,0xce,0x00,0xd9,0x04,0xf0,0x9e,0x99,0xbd,0xce,0x8f,0x90,0x4a,0xdd,
0xe1,0xec,0x19,0x14,0xb1,0xfb,0xca,0x1e,0x98,0x0f,0xd4,0xcb,0x80,0xd6,0x05,0x63,
0xfd,0xa0,0x74,0xa6,0x86,0xf6,0x19,0x98,0x76,0x27,0x68,0xf7,0xe9,0x09,0x9a,0xf2,
0x2e,0x42,0xe1,0xbe,0x64,0x48,0x2a,0x74,0x30,0xbb,0x07,0xcc,0x1f,0xd4,0x91,0x9d,
0xac,0x55,0x53,0x25,0xb9,0x64,0xf7,0x58,0x4c,0x34,0x16,0xbc,0xf6,0x12,0x2b,0x65,
0x68,0x25,0x2e,0x29,0x1f,0xbb,0xb9,0xee,0x6d,0x0c,0x8e,0xbb,0xd2,0x5f,0x1d,0x8f,
0xc1,0x39,0xf9,0x8d,0xc0,0x39,0x75,0xcf,0x25,0x17,0xbe,0x96,0xaf,0x98,0x9f,0x5f,
0x65,0x15,0xc4,0x62,0xf8,0x55,0xfc,0xab,0x54,0xcf,0xdc,0x14,0x06,0xc8,0xfc,0x42,
0xd3,0xf0,0xad,0x10,0x08,0xcd,0xd4,0x11,0xbb,0xca,0x67,0xc6,0x48,0x5f,0x9d,0x59,
0xe3,0xe8,0x53,0x67,0x27,0x2d,0x34,0x9e,0x9e,0x24,0x29,0xdb,0x69,0x99,0x86,0xf9,
0x20,0xb5,0xbb,0x5b,0xb0,0xf9,0xc3,0x67,0xad,0x1c,0x9c,0xf7,0xcc,0xef,0xce,0x69,
0xe0,0x26,0x8f,0x79,0xbd,0xca,0x10,0x17,0xda,0xa9,0x88,0x57,0x9b,0x15,0x24,0xba,
0x84,0xd0,0xeb,0x4d,0x14,0xf5,0xfc,0xe6,0x51,0x6c,0x6f,0x64,0x6b,0x73,0xec,0x85,
0xf1,0x6f,0xe1,0x67,0x25,0x10,0x77,0x32,0x9e,0x85,0x6e,0x69,0xb1,0x83,0x00,0xe4,
0x13,0xa4,0x45,0x34,0x3b,0x40,0xff,0x41,0x82,0x89,0x79,0x57,0xfd,0xd2,0x8e,0xe8,
0xfc,0x1d,0x19,0x21,0x12,0x00,0xd7,0x66,0xe5,0xc7,0x10,0x1d,0xcb,0x75,0xe8,0xfa,
0xb6,0xee,0x7b,0x2f,0x1a,0x25,0x24,0xb9,0x9f,0x1d,0x78,0xfb,0x84,0xd0,0x17,0x05,
0x71,0xb3,0xc8,0x18,0xff,0x62,0xee,0xed,0x53,0xab,0x78,0xd3,0x65,0x2d,0xbb,0xc7,
0xc1,0xe7,0x70,0xa2,0x43,0x2c,0x7c,0xc7,0x16,0x04,0xd2,0x45,0xd5,0x6b,0x6c,0x7a,
0x5e,0xa1,0x50,0x2e,0x31,0x5b,0xcc,0xe8,0x65,0x8b,0x16,0x85,0xbf,0x82,0x83,0xfb,
0xde,0x9f,0x36,0x48,0x32,0x79,0xd6,0x9b,0xfb,0x52,0x45,0xbf,0x43,0xf7,0x0b,0x0b,
0x19,0x19,0x31,0xc3,0x85,0xec,0x1d,0x8c,0x20,0xf0,0x3a,0xfa,0x80,0x4d,0x2c,0x7d,
0xac,0x60,0x09,0xc0,0x40,0xee,0xb9,0xeb,0x13,0x5b,0xe8,0x2b,0xb1,0x20,0xf0,0xce,
0x4c,0xbd,0xc6,0x04,0x86,0x70,0xc6,0x33,0xc3,0x15,0x0f,0x65,0x19,0xfd,0xc2,0xd3,

// map checksum goes here
0x00,0x00,0x00,0x00
};

#if 0
/*
====================
COM_BlockSequenceCheckByte

For proxy protecting
====================
*/
byte	COM_BlockSequenceCheckByte (byte *base, int length, int sequence, unsigned mapchecksum)
{
	int		checksum;
	byte	*p;

	if (last_mapchecksum != mapchecksum) {
		last_mapchecksum = mapchecksum;
		chktbl[1024] = (mapchecksum & 0xff000000) >> 24;
		chktbl[1025] = (mapchecksum & 0x00ff0000) >> 16;
		chktbl[1026] = (mapchecksum & 0x0000ff00) >> 8;
		chktbl[1027] = (mapchecksum & 0x000000ff);

		Com_BlockFullChecksum (chktbl, sizeof(chktbl), chkbuf);
	}

	p = chktbl + (sequence % (sizeof(chktbl) - 8));

	if (length > 60)
		length = 60;
	memcpy (chkbuf + 16, base, length);

	length += 16;

	chkbuf[length] = (sequence & 0xff) ^ p[0];
	chkbuf[length+1] = p[1];
	chkbuf[length+2] = ((sequence>>8) & 0xff) ^ p[2];
	chkbuf[length+3] = p[3];

	length += 4;

	checksum = LittleLong(Com_BlockChecksum (chkbuf, length));

	checksum &= 0xff;

	return checksum;
}
#endif

/*
====================
COM_BlockSequenceCRCByte

For proxy protecting
====================
*/
byte	COM_BlockSequenceCRCByte (byte *base, int length, int sequence)
{
	unsigned short crc;
	byte	*p;
	byte chkb[60 + 4];

	p = chktbl + (sequence % (sizeof(chktbl) - 8));

	if (length > 60)
		length = 60;
	memcpy (chkb, base, length);

	chkb[length] = (sequence & 0xff) ^ p[0];
	chkb[length+1] = p[1];
	chkb[length+2] = ((sequence>>8) & 0xff) ^ p[2];
	chkb[length+3] = p[3];

	length += 4;

	crc = CRC_Block(chkb, length);

	crc &= 0xff;

	return (byte) crc;
}