;===========================================================================
; Copyright (c) 1990-2007 Info-ZIP. All rights reserved.
;
; See the accompanying file LICENSE, version 2000-Apr-09 or later
; (the contents of which are also included in zip.h) for terms of use.
; If, for some reason, all these files are missing, the Info-ZIP license
; also may be found at: ftp://ftp.info-zip.org/pub/infozip/license.html
;===========================================================================
; crc_i386.asm, optimized CRC calculation function for Zip and UnZip,
; created by Paul Kienitz and Christian Spieler. Last revised 07 Jan 2007.
;
; Revised 06-Oct-96, Scott Field (sfield@microsoft.com)
; fixed to assemble with masm by not using .model directive which makes
; assumptions about segment alignment. Also,
; avoid using loop, and j[e]cxz where possible. Use mov + inc, rather
; than lodsb, and other misc. changes resulting in the following performance
; increases:
;
; unrolled loops NO_UNROLLED_LOOPS
; *8 >8 <8 *8 >8 <8
;
; +54% +42% +35% +82% +52% +25%
;
; first item in each table is input buffer length, even multiple of 8
; second item in each table is input buffer length, > 8
; third item in each table is input buffer length, < 8
;
; Revised 02-Apr-97, Chr. Spieler, based on Rodney Brown (rdb@cmutual.com.au)
; Incorporated Rodney Brown's 32-bit-reads optimization as found in the
; UNIX AS source crc_i386.S. This new code can be disabled by defining
; the macro symbol NO_32_BIT_LOADS.
;
; Revised 12-Oct-97, Chr. Spieler, based on Rodney Brown (rdb@cmutual.com.au)
; Incorporated Rodney Brown's additional tweaks for 32-bit-optimized CPUs
; (like the Pentium Pro, Pentium II, and probably some Pentium clones).
; This optimization is controlled by the macro symbol __686 and is disabled
; by default. (This default is based on the assumption that most users
; do not yet work on a Pentium Pro or Pentium II machine ...)
;
; Revised 25-Mar-98, Cosmin Truta (cosmint@cs.ubbcluj.ro)
; Working without .model directive caused tasm32 version 5.0 to produce
; bad object code. The optimized alignments can be optionally disabled
; by defining NO_ALIGN, thus allowing to use .model flat. There is no need
; to define this macro if using other versions of tasm.
;
; Revised 16-Jan-2005, Cosmin Truta (cosmint@cs.ubbcluj.ro)
; Enabled the 686 build by default, because there are hardly any pre-686 CPUs
; in serious use nowadays. (See the 12-Oct-97 note above.)
;
; Revised 03-Jan-2006, Chr. Spieler
; Enlarged unrolling loops to "do 16 bytes per turn"; optimized access to
; data buffer in loop body (adjust pointer only once in loop body and use
; offsets to access each item); added additional support for the "unfolded
; tables" optimization variant (enabled by IZ_CRCOPTIM_UNFOLDTBL).
;
; Revised 07-Jan-2007, Chr. Spieler
; Recognize additional conditional flag CRC_TABLE_ONLY that prevents
; compilation of the crc32() function.
;
; FLAT memory model assumed.
;
; Loop unrolling can be disabled by defining the macro NO_UNROLLED_LOOPS.
; This results in shorter code at the expense of reduced performance.
;
;==============================================================================
;
; Do NOT assemble this source if external crc32 routine from zlib gets used,
; or only the precomputed CRC_32_Table is needed.
;
IFNDEF USE_ZLIB
IFNDEF CRC_TABLE_ONLY
;
.386p
name crc_i386
IFDEF NO_ALIGN
.model flat
ENDIF
IFNDEF PRE_686
IFNDEF __686
__686 EQU 1 ; optimize for Pentium Pro, Pentium II and compatible CPUs
ENDIF
ENDIF
extrn _get_crc_table:near ; ZCONST ulg near *get_crc_table(void);
;
IFNDEF NO_STD_STACKFRAME
; Use a `standard' stack frame setup on routine entry and exit.
; Actually, this option is set as default, because it results
; in smaller code !!
STD_ENTRY MACRO
push ebp
mov ebp,esp
ENDM
Arg1 EQU 08H[ebp]
Arg2 EQU 0CH[ebp]
Arg3 EQU 10H[ebp]
STD_LEAVE MACRO
pop ebp
ENDM
ELSE ; NO_STD_STACKFRAME
STD_ENTRY MACRO
ENDM
Arg1 EQU 18H[esp]
Arg2 EQU 1CH[esp]
Arg3 EQU 20H[esp]
STD_LEAVE MACRO
ENDM
ENDIF ; ?NO_STD_STACKFRAME
; These two (three) macros make up the loop body of the CRC32 cruncher.
; registers modified:
; eax : crc value "c"
; esi : pointer to next data byte (or dword) "buf++"
; registers read:
; edi : pointer to base of crc_table array
; scratch registers:
; ebx : index into crc_table array
; (requires upper three bytes = 0 when __686 is undefined)
IFNDEF __686 ; optimize for 386, 486, Pentium
Do_CRC MACRO
mov bl,al ; tmp = c & 0xFF
shr eax,8 ; c = (c >> 8)
xor eax,[edi+ebx*4] ; ^ table[tmp]
ENDM
ELSE ; __686 : optimize for Pentium Pro, Pentium II and compatible CPUs
Do_CRC MACRO
movzx ebx,al ; tmp = c & 0xFF
shr eax,8 ; c = (c >> 8)
xor eax,[edi+ebx*4] ; ^ table[tmp]
ENDM
ENDIF ; ?__686
Do_CRC_byte MACRO
xor al, byte ptr [esi] ; c ^= *buf
inc esi ; buf++
Do_CRC ; c = (c >> 8) ^ table[c & 0xFF]
ENDM
Do_CRC_byteof MACRO ofs
xor al, byte ptr [esi+ofs] ; c ^= *(buf+ofs)
Do_CRC ; c = (c >> 8) ^ table[c & 0xFF]
ENDM
IFNDEF NO_32_BIT_LOADS
IFDEF IZ_CRCOPTIM_UNFOLDTBL
; the edx register is needed in crc calculation
SavLen EQU Arg3
UpdCRC_dword MACRO
movzx ebx,al ; tmp = c & 0xFF
mov edx,[edi+ebx*4+3072] ; table[256*3+tmp]
movzx ebx,ah ; tmp = (c>>8) & 0xFF
shr eax,16 ;
xor edx,[edi+ebx*4+2048] ; ^ table[256*2+tmp]
movzx ebx,al ; tmp = (c>>16) & 0xFF
shr eax,8 ; tmp = (c>>24)
xor edx,[edi+ebx*4+1024] ; ^ table[256*1+tmp]
mov eax,[edi+eax*4] ; ^ table[256*0+tmp]
xor eax,edx ; ..
ENDM
UpdCRC_dword_sh MACRO dwPtrIncr
movzx ebx,al ; tmp = c & 0xFF
mov edx,[edi+ebx*4+3072] ; table[256*3+tmp]
movzx ebx,ah ; tmp = (c>>8) & 0xFF
xor edx,[edi+ebx*4+2048] ; ^ table[256*2+tmp]
shr eax,16 ;
movzx ebx,al ; tmp = (c>>16) & 0xFF
add esi, 4*dwPtrIncr ; ((ulg *)buf) += dwPtrIncr
shr eax,8 ; tmp = (c>>24)
xor edx,[edi+ebx*4+1024] ; ^ table[256*1+tmp]
mov eax,[edi+eax*4] ; ^ table[256*0+tmp]
xor eax,edx ; ..
ENDM
ELSE ; IZ_CRCOPTIM_UNFOLDTBL
; the edx register is not needed anywhere else
SavLen EQU edx
UpdCRC_dword MACRO
Do_CRC
Do_CRC
Do_CRC
Do_CRC
ENDM
UpdCRC_dword_sh MACRO dwPtrIncr
Do_CRC
Do_CRC
add esi, 4*dwPtrIncr ; ((ulg *)buf) += dwPtrIncr
Do_CRC
Do_CRC
ENDM
ENDIF ; ?IZ_CRCOPTIM_UNFOLDTBL
Do_CRC_dword MACRO
xor eax, dword ptr [esi] ; c ^= *(ulg *)buf
UpdCRC_dword_sh 1 ; ... ((ulg *)buf)++
ENDM
Do_CRC_4dword MACRO
xor eax, dword ptr [esi] ; c ^= *(ulg *)buf
UpdCRC_dword
xor eax, dword ptr [esi+4] ; c ^= *((ulg *)buf+1)
UpdCRC_dword
xor eax, dword ptr [esi+8] ; c ^= *((ulg *)buf+2)
UpdCRC_dword
xor eax, dword ptr [esi+12] ; c ^= *((ulg *)buf]+3
UpdCRC_dword_sh 4 ; ... ((ulg *)buf)+=4
ENDM
ENDIF ; !NO_32_BIT_LOADS
IFNDEF NO_ALIGN
_TEXT segment use32 para public 'CODE'
ELSE
_TEXT segment use32
ENDIF
assume CS: _TEXT
public _crc32
_crc32 proc near ; ulg crc32(ulg crc, ZCONST uch *buf, extent len)
STD_ENTRY
push edi
push esi
push ebx
push edx
push ecx
mov esi,Arg2 ; 2nd arg: uch *buf
sub eax,eax ;> if (!buf)
test esi,esi ;> return 0;
jz fine ;> else {
call _get_crc_table
mov edi,eax
mov eax,Arg1 ; 1st arg: ulg crc
IFNDEF __686
sub ebx,ebx ; ebx=0; make bl usable as a dword
ENDIF
mov ecx,Arg3 ; 3rd arg: extent len
not eax ;> c = ~crc;
test ecx,ecx
IFNDEF NO_UNROLLED_LOOPS
jz bail
IFNDEF NO_32_BIT_LOADS
align_loop:
test esi,3 ; align buf pointer on next
jz SHORT aligned_now ; dword boundary
Do_CRC_byte
dec ecx
jnz align_loop
aligned_now:
ENDIF ; !NO_32_BIT_LOADS
mov SavLen,ecx ; save current len for later
shr ecx,4 ; ecx = len / 16
jz No_Sixteens
IFNDEF NO_ALIGN
; align loop head at start of 486 internal cache line !!
align 16
ENDIF
Next_Sixteen:
IFNDEF NO_32_BIT_LOADS
Do_CRC_4dword
ELSE ; NO_32_BIT_LOADS
Do_CRC_byteof 0
Do_CRC_byteof 1
Do_CRC_byteof 2
Do_CRC_byteof 3
Do_CRC_byteof 4
Do_CRC_byteof 5
Do_CRC_byteof 6
Do_CRC_byteof 7
Do_CRC_byteof 8
Do_CRC_byteof 9
Do_CRC_byteof 10
Do_CRC_byteof 11
Do_CRC_byteof 12
Do_CRC_byteof 13
Do_CRC_byteof 14
Do_CRC_byteof 15
add esi, 16 ; buf += 16
ENDIF ; ?NO_32_BIT_LOADS
dec ecx
jnz Next_Sixteen
No_Sixteens:
mov ecx,SavLen
and ecx,00000000FH ; ecx = len % 16
IFNDEF NO_32_BIT_LOADS
shr ecx,2 ; ecx = len / 4
jz SHORT No_Fours
Next_Four:
Do_CRC_dword
dec ecx
jnz Next_Four
No_Fours:
mov ecx,SavLen
and ecx,000000003H ; ecx = len % 4
ENDIF ; !NO_32_BIT_LOADS
ENDIF ; !NO_UNROLLED_LOOPS
jz SHORT bail ;> if (len)
IFNDEF NO_ALIGN
; align loop head at start of 486 internal cache line !!
align 16
ENDIF
loupe: ;> do {
Do_CRC_byte ; c = CRC32(c,*buf++,crctab);
dec ecx ;> } while (--len);
jnz loupe
bail: ;> }
not eax ;> return ~c;
fine:
pop ecx
pop edx
pop ebx
pop esi
pop edi
STD_LEAVE
ret
_crc32 endp
_TEXT ends
;
ENDIF ; !CRC_TABLE_ONLY
ENDIF ; !USE_ZLIB
;
end