crc.c File Reference

#include "shared/shared.h"

Go to the source code of this file.

Macros
#define	CRC_INIT_VALUE   0xffff
#define	CRC_XOR_VALUE   0x0000

Functions
static uint16_t	CRC_Block (byte *start, size_t count)
byte	COM_BlockSequenceCRCByte (byte *base, size_t length, int sequence)

Variables
static const uint16_t	crctable [256]
static const byte	chktbl [1024]

Macro Definition Documentation

CRC_INIT_VALUE

#define CRC_INIT_VALUE   0xffff

Definition at line 26 of file crc.c.

CRC_XOR_VALUE

#define CRC_XOR_VALUE   0x0000

Definition at line 27 of file crc.c.

Function Documentation

COM_BlockSequenceCRCByte()

byte COM_BlockSequenceCRCByte	(	byte *	base,
		size_t	length,
		int	sequence
	)

Definition at line 148 of file crc.c.

{
    int     n;
    const byte  *p;
    int     x;
    byte chkb[60 + 4];
    unsigned short crc;
 
    if (sequence < 0)
        Com_Error(ERR_DROP, "%s: sequence < 0", __func__);
 
    p = chktbl + (sequence % (sizeof(chktbl) - 4));
 
    if (length > 60)
        length = 60;
    memcpy(chkb, base, length);
 
    chkb[length] = p[0];
    chkb[length + 1] = p[1];
    chkb[length + 2] = p[2];
    chkb[length + 3] = p[3];
 
    length += 4;
 
    crc = CRC_Block(chkb, length);
 
    for (x = 0, n = 0; n < length; n++)
        x += chkb[n];
 
    crc = (crc ^ x) & 0xff;
 
    return crc;
}

Referenced by CL_SendDefaultCmd().

CRC_Block()

static uint16_t CRC_Block ( byte *  start, size_t  count  )

static

Definition at line 64 of file crc.c.

{
    uint16_t    crc = CRC_INIT_VALUE;
 
    while (count--)
        crc = (crc << 8) ^ crctable[(crc >> 8) ^ *start++];
 
    return crc;
}

Referenced by COM_BlockSequenceCRCByte().

Variable Documentation

chktbl

const byte chktbl[1024]

static

Definition at line 74 of file crc.c.

Referenced by COM_BlockSequenceCRCByte().

crctable

const uint16_t crctable[256]

static

Definition at line 29 of file crc.c.

Referenced by CRC_Block().