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/*
* $Id: crc32.c,v 1.1.1.1 2002/03/28 00:02:10 andrew_belov Exp $
* ---------------------------------------------------------------------------
* This file contains CRC32 calculation routines.
*
*/
#include "arj.h"
DEBUGHDR(__FILE__) /* Debug information block */
#define CRCPOLY 0xEDB88320L /* CRC32 polynomial */
#define UPDATE_CRC(r, c) crc32tab[((unsigned char)(r)^(unsigned char)(c))&0xFF]^(r>>CHAR_BIT)
unsigned long crc32term;
#ifdef ASM8086
unsigned short crc32tab_lo[256];
unsigned short crc32tab_hi[256];
static unsigned short xbp;
#else
unsigned long crc32tab[256];
#endif
/* CRC32 initialization */
void build_crc32_table()
{
#ifdef ASM8086
asm{
push si
push di
xor di, di
jmp short lt_0
}
loop_ch:
asm{
mov dx, di
xor ax, ax
mov si, 8
or si, si
jmp short lt_1
}
loop_term:
asm{
test dx, 1
jz lt_next
shr ax, 1
rcr dx, 1
xor dx, 8320h
xor ax, 0EDB8h
jmp short lt_next_c
}
lt_next:
asm{
shr ax, 1
rcr dx, 1
}
lt_next_c:
asm{
dec si
}
lt_1:
asm{
jg loop_term
mov bx, di
shl bx, 1
mov word ptr crc32tab_lo[bx], dx
mov word ptr crc32tab_hi[bx], ax
inc di
}
lt_0:
asm{
cmp di, 0FFh
jbe loop_ch
pop di
pop si
}
#else
unsigned int i, j;
unsigned long r;
for(i=0; i<=UCHAR_MAX; i++)
{
r=i;
for(j=CHAR_BIT; j>0; j--)
{
if(r&1)
r=(r>>1)^CRCPOLY;
else
r>>=1;
}
crc32tab[i]=r;
}
#endif
}
/* Calculates CRC32 for a given block */
void crc32_for_block(char *block, unsigned int b_size)
{
#ifdef ASM8086
asm{
push si
push di
cld
mov word ptr xbp, bp
mov bx, offset crc32tab_lo
mov cl, 4
shr bx, cl
mov cx, word ptr crc32term[0]
mov dx, word ptr crc32term[2]
mov si, block
mov di, b_size
push ds
mov ax, ds
mov es, ax
add ax, bx
xor bx, bx
mov bp, di
and di, 3
push di
shr bp, 1
shr bp, 1
jz lt_shloop
}
lt_accterm:
#if COMPILER==BCC
asm{
db 26h, 0ADh
}
#else
asm{
lods word ptr es:[si]
}
#endif
asm{
mov bl, cl
xor bl, al
mov cl, ch
mov ch, dl
mov dl, dh
mov dh, bh
mov di, bx
shl di, 1
xor cx, crc32tab_lo[di]
xor dx, crc32tab_hi[di]
mov bl, cl
xor bl, ah
mov cl, ch
mov ch, dl
mov dl, dh
mov dh, bh
mov di, bx
shl di, 1
xor cx, crc32tab_lo[di]
xor dx, crc32tab_hi[di]
}
#if COMPILER==BCC
asm{
db 26h, 0ADh
}
#else
asm{
lods word ptr es:[si]
}
#endif
asm{
mov bl, cl
xor bl, al
mov cl, ch
mov ch, dl
mov dl, dh
mov dh, bh
mov di, bx
shl di, 1
xor cx, crc32tab_lo[di]
xor dx, crc32tab_hi[di]
mov bl, cl
xor bl, ah
mov cl, ch
mov ch, dl
mov dl, dh
mov dh, bh
mov di, bx
shl di, 1
xor cx, crc32tab_lo[di]
xor dx, crc32tab_hi[di]
dec bp
jnz lt_accterm
}
lt_shloop:
asm{
pop bp
or bp, bp
jz lt_exit
}
lt_shift:
#if COMPILER==BCC
asm{
db 26h, 0ACh
}
#else
asm{
lods byte ptr es:[si]
}
#endif
asm{
mov bl, cl
xor bl, al
mov cl, ch
mov ch, dl
mov dl, dh
mov dh, bh
mov di, bx
shl di, 1
xor cx, crc32tab_lo[di]
xor dx, crc32tab_hi[di]
dec bp
jnz lt_shift
}
lt_exit:
asm{
pop ds
mov word ptr crc32term[0], cx
mov word ptr crc32term[2], dx
pop di
pop si
mov bp, word ptr xbp
}
#else
while(b_size--)
crc32term=UPDATE_CRC(crc32term, *block++);
#endif
}
#if SFX_LEVEL>=ARJSFX||defined(REARJ)||defined(REGISTER)||defined(ARJUTIL)
/* Calculates CRC32 for a given ASCIIz string */
void crc32_for_string(char *sptr)
{
#ifdef ASM8086
asm{
push si
push di
cld
xor bx, bx
mov si, sptr
mov cx, word ptr crc32term[0]
mov dx, word ptr crc32term[2]
jmp short str_nchar
}
stracc:
asm{
mov bl, cl
xor bl, al
mov cl, ch
mov ch, dl
mov dl, dh
mov dh, bh
mov di, bx
shl di, 1
xor cx, word ptr crc32tab_lo[di]
xor dx, word ptr crc32tab_hi[di]
}
str_nchar:
asm{
lodsb
or al, al
jnz stracc
mov word ptr crc32term[0], cx
mov word ptr crc32term[2], dx
pop di
pop si
}
#else
while(*sptr!='\0')
crc32term=UPDATE_CRC(crc32term, (unsigned char)(*sptr++));
#endif
}
/* Evaluates CRC32 based on character and term given */
unsigned long crc32_for_char(unsigned long crc32_term, unsigned char newc)
{
#ifdef ASM8086
asm{
mov ax, word ptr crc32_term
mov dx, word ptr crc32_term+2
mov bl, al
mov al, ah
mov ah, dl
mov dl, dh
mov dh, 0
xor bl, newc
mov bh, 0
shl bx, 1
xor ax, word ptr crc32tab_lo[bx]
xor dx, word ptr crc32tab_hi[bx]
}
#else
return(UPDATE_CRC(crc32_term, newc));
#endif
}
#endif
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