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/*
Copyright (c) 1990-2005 Info-ZIP. All rights reserved.
See the accompanying file LICENSE, version 2004-May-22 or later
(the contents of which are also included in zip.h) for terms of use.
If, for some reason, both of these files are missing, the Info-ZIP license
also may be found at: ftp://ftp.info-zip.org/pub/infozip/license.html
*/
/* crc_i386.c -- Microsoft 32-bit C/C++ adaptation of crc_i386.asm
* Created by Rodney Brown from crc_i386.asm, modified by Chr. Spieler.
*
* Original coded (in crc_i386.asm) and put into the public domain
* by Paul Kienitz and Christian Spieler.
*
* 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 16-Nov-97, Chr. Spieler: Made code compatible with Borland C++
* 32-bit, removed unneeded kludge for potentially unknown movzx mnemonic,
* confirmed correct working with MS VC++ (32-bit).
*
* Revised 22-May-98, Peter Kunath, Chr. Spieler: The 16-Nov-97 revision broke
* MSVC 5.0. Inside preprocessor macros, each instruction is enclosed in its
* own __asm {...} construct. For MSVC, a "#pragma warning" was added to
* shut up the "no return value" warning message.
*
* Revised 13-Dec-98, Chr. Spieler: Modified path to "zip.h" header file.
*
* Revised 16-Jan-2005, Cosmin Truta: Added the ASM_CRC guard, for easier
* switching between ASM vs. non-ASM builds, when handling makefiles.
* Also 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.)
*
* 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.
*
*/
#include "../zip.h"
#if defined(ASM_CRC) && !defined(USE_ZLIB)
#if !defined(PRE_686) && !defined(__686)
# define __686
#endif
#ifndef ZCONST
# define ZCONST const
#endif
/* Select wether the following inline-assember code is supported. */
#if (defined(_MSC_VER) && _MSC_VER >= 700)
#if (defined(_M_IX86) && _M_IX86 >= 300)
# define MSC_INLINE_ASM_32BIT_SUPPORT
/* Disable warning for no return value, typical of asm functions */
# pragma warning( disable : 4035 )
#endif
#endif
#if (defined(__BORLANDC__) && __BORLANDC__ >= 452)
# define MSC_INLINE_ASM_32BIT_SUPPORT
#endif
#ifdef MSC_INLINE_ASM_32BIT_SUPPORT
/* This code is intended for Microsoft C/C++ (32-bit) compatible compilers. */
/*
* 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
#define Do_CRC { \
__asm { mov bl, al }; \
__asm { shr eax, 8 }; \
__asm { xor eax, [edi+ebx*4] }; }
#else /* __686 */
#define Do_CRC { \
__asm { movzx ebx, al }; \
__asm { shr eax, 8 }; \
__asm { xor eax, [edi+ebx*4] }; }
#endif /* ?__686 */
#define Do_CRC_byte { \
__asm { xor al, byte ptr [esi] }; \
__asm { inc esi }; \
Do_CRC; }
#ifndef NO_32_BIT_LOADS
#define Do_CRC_dword { \
__asm { xor eax, dword ptr [esi] }; \
__asm { add esi, 4 }; \
Do_CRC; \
Do_CRC; \
Do_CRC; \
Do_CRC; }
#endif /* !NO_32_BIT_LOADS */
/* ========================================================================= */
ulg crc32(crc, buf, len)
ulg crc; /* crc shift register */
ZCONST uch *buf; /* pointer to bytes to pump through */
extent len; /* number of bytes in buf[] */
/* Run a set of bytes through the crc shift register. If buf is a NULL
pointer, then initialize the crc shift register contents instead.
Return the current crc in either case. */
{
__asm {
push edx
push ecx
mov esi,buf ;/* 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,crc ;/* 1st arg: ulg crc */
#ifndef __686
sub ebx,ebx ;/* ebx=0; => bl usable as a dword */
#endif
mov ecx,len ;/* 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 aligned_now ;/* dword boundary */
}
Do_CRC_byte ;
__asm {
dec ecx
jnz align_loop
aligned_now:
# endif /* !NO_32_BIT_LOADS */
mov edx,ecx ;/* save len in edx */
shr ecx,3 ;/* ecx = len / 8 */
jz No_Eights
; align loop head at start of 486 internal cache line !!
align 16
Next_Eight:
}
# ifndef NO_32_BIT_LOADS
Do_CRC_dword ;
Do_CRC_dword ;
# else /* NO_32_BIT_LOADS */
Do_CRC_byte ;
Do_CRC_byte ;
Do_CRC_byte ;
Do_CRC_byte ;
Do_CRC_byte ;
Do_CRC_byte ;
Do_CRC_byte ;
Do_CRC_byte ;
# endif /* ?NO_32_BIT_LOADS */
__asm {
dec ecx
jnz Next_Eight
No_Eights:
mov ecx,edx
and ecx,000000007H ;/* ecx = len % 8 */
#endif /* !NO_UNROLLED_LOOPS */
jz bail ;/*> if (len) */
; align loop head at start of 486 internal cache line !!
align 16
loupe: ;/*> do { */
}
Do_CRC_byte ;/* c = CRC32(c, *buf++); */
__asm {
dec ecx ;/*> } while (--len); */
jnz loupe
bail: ;/*> } */
not eax ;/*> return ~c; */
fine:
pop ecx
pop edx
}
#ifdef NEED_RETURN
return _EAX;
#endif
}
#endif /* MSC_INLINE_ASM_32BIT_SUPPORT */
#if (defined(_MSC_VER) && _MSC_VER >= 700)
#if (defined(_M_IX86) && _M_IX86 >= 300)
/* Reenable missing return value warning */
# pragma warning( default : 4035 )
#endif
#endif
#endif /* ASM_CRC && !USE_ZLIB */
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