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Diffstat (limited to 'msdos/crc_i86.asm')
| -rw-r--r-- | msdos/crc_i86.asm | 464 |
1 files changed, 464 insertions, 0 deletions
diff --git a/msdos/crc_i86.asm b/msdos/crc_i86.asm new file mode 100644 index 0000000..12e85ee --- /dev/null +++ b/msdos/crc_i86.asm @@ -0,0 +1,464 @@ +;=========================================================================== +; Copyright (c) 1990-1999 Info-ZIP. All rights reserved. +; +; See the accompanying file LICENSE, version 1999-Oct-05 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.cdrom.com/pub/infozip/license.html +;=========================================================================== +; Created by Christian Spieler, last modified 24 Dec 1998. +; + TITLE crc_i86.asm + NAME crc_i86 +; +; Optimized 8086 assembler version of the CRC32 calculation loop, intended +; for real mode Info-ZIP programs (Zip 2.1, UnZip 5.2, and later versions). +; Supported compilers are Microsoft C (DOS real mode) and Borland C(++) +; (Turbo C). Watcom C (16bit) should also work. +; This module was inspired by a similar module for the Amiga (Paul Kienitz). +; +; It replaces the `ulg crc32(ulg crc, ZCONST uch *buf, extent len)' function +; in crc32.c. +; +; In March/April 1997, the code has been revised to incorporate Rodney Brown's +; ideas for optimized access to the data buffer. For 8086 real mode code, +; the data buffer is now accessed by aligned word-wide read operations. +; This new optimization may be turned off by defining the macro switch +; NO_16_BIT_LOADS. +; +; In December 1998, the loop branch commands were changed from "loop dest" +; into "dec cx; jnz dest". On modern systems (486 and newer), the latter +; code is usually much faster (e.g. 1 clock cycle compared to 5 for "loop" +; on Pentium MMX). For the 286, the penalty of "dec cx; jnz" is one clock +; cycle (12 vs. 11 cycles); on an 8088 the cycle counts are 22 (dec cx; jnz) +; vs. 18 (loop). I decided to optimize for newer CPU models by default, because +; I expect that old 80286 or 8088 dinosaurier machines may be rarely used +; nowadays. In case you want optimum performance for these old CPU models +; you should define the OPTIMIZE_286_88 macro switch on the assembler's +; command line. +; Likewise, "jcxz" was replaced by "jz", because the latter is faster on +; 486 and newer CPUs (without any penalty on 80286 and older CPU models). +; +; The code in this module should work with all kinds of C memory models +; (except Borland's __HUGE__ model), as long as the following +; restrictions are not violated: +; +; - The implementation assumes that the char buffer is confined to a +; 64k segment. The pointer `s' to the buffer must be in a format that +; all bytes can be accessed by manipulating the offset part, only. +; This means: +; + no huge pointers +; + char buffer size < 64 kByte +; +; - Since the buffer size argument `n' is of type `size_t' (= unsigned short) +; for this routine, the char buffer size is limited to less than 64 kByte, +; anyway. So, the assumption above should be easily fulfilled. +; +;============================================================================== +; +; Do NOT assemble this source if external crc32 routine from zlib gets used. +; +ifndef USE_ZLIB +; +; Setup of amount of assemble time informational messages: +; +ifdef DEBUG + VERBOSE_INFO EQU 1 +else + ifdef _AS_MSG_ + VERBOSE_INFO EQU 1 + else + VERBOSE_INFO EQU 0 + endif +endif +; +; Selection of memory model, and initialization of memory model +; related macros: +; +ifndef __SMALL__ + ifndef __COMPACT__ + ifndef __MEDIUM__ + ifndef __LARGE__ + ifndef __HUGE__ +; __SMALL__ EQU 1 + endif + endif + endif + endif +endif + +ifdef __HUGE__ +; .MODEL Huge + @CodeSize EQU 1 + @DataSize EQU 1 + Save_DS EQU 1 + if VERBOSE_INFO + if1 + %out Assembling for C, Huge memory model + endif + endif +else + ifdef __LARGE__ +; .MODEL Large + @CodeSize EQU 1 + @DataSize EQU 1 + if VERBOSE_INFO + if1 + %out Assembling for C, Large memory model + endif + endif + else + ifdef __COMPACT__ +; .MODEL Compact + @CodeSize EQU 0 + @DataSize EQU 1 + if VERBOSE_INFO + if1 + %out Assembling for C, Compact memory model + endif + endif + else + ifdef __MEDIUM__ +; .MODEL Medium + @CodeSize EQU 1 + @DataSize EQU 0 + if VERBOSE_INFO + if1 + %out Assembling for C, Medium memory model + endif + endif + else +; .MODEL Small + @CodeSize EQU 0 + @DataSize EQU 0 + if VERBOSE_INFO + if1 + %out Assembling for C, Small memory model + endif + endif + endif + endif + endif +endif + +if @CodeSize + LCOD_OFS EQU 2 +else + LCOD_OFS EQU 0 +endif + +IF @DataSize + LDAT_OFS EQU 2 +else + LDAT_OFS EQU 0 +endif + +ifdef Save_DS +; (di,si,ds)+(size, return address) + SAVE_REGS EQU 6+(4+LCOD_OFS) +else +; (di,si)+(size, return address) + SAVE_REGS EQU 4+(4+LCOD_OFS) +endif + +; +; Selection of the supported CPU instruction set and initialization +; of CPU type related macros: +; +ifdef __586 + Use_286_code EQU 1 + Align_Size EQU 4 ; dword alignment on Pentium + Alig_PARA EQU 1 ; paragraph aligned code segment +else +ifdef __486 + Use_286_code EQU 1 + Align_Size EQU 4 ; dword alignment on 32 bit processors + Alig_PARA EQU 1 ; paragraph aligned code segment +else +ifdef __386 + Use_286_code EQU 1 + Align_Size EQU 4 ; dword alignment on 32 bit processors + Alig_PARA EQU 1 ; paragraph aligned code segment +else +ifdef __286 + Use_286_code EQU 1 + Align_Size EQU 2 ; word alignment on 16 bit processors + Alig_PARA EQU 0 ; word aligned code segment +else +ifdef __186 + Use_186_code EQU 1 + Align_Size EQU 2 ; word alignment on 16 bit processors + Alig_PARA EQU 0 ; word aligned code segment +else + Align_Size EQU 2 ; word alignment on 16 bit processors + Alig_PARA EQU 0 ; word aligned code segment +endif ;?__186 +endif ;?__286 +endif ;?__386 +endif ;?__486 +endif ;?__586 + +ifdef Use_286_code + .286 + Have_80x86 EQU 1 +else +ifdef Use_186_code + .186 + Have_80x86 EQU 1 +else + .8086 + Have_80x86 EQU 0 +endif ;?Use_186_code +endif ;?Use_286_code + +; +; Declare the segments used in this module: +; +if @CodeSize +if Alig_PARA +CRC32_TEXT SEGMENT PARA PUBLIC 'CODE' +else +CRC32_TEXT SEGMENT WORD PUBLIC 'CODE' +endif +CRC32_TEXT ENDS +else ;!@CodeSize +if Alig_PARA +_TEXT SEGMENT PARA PUBLIC 'CODE' +else +_TEXT SEGMENT WORD PUBLIC 'CODE' +endif +_TEXT ENDS +endif ;?@CodeSize +_DATA SEGMENT WORD PUBLIC 'DATA' +_DATA ENDS +_BSS SEGMENT WORD PUBLIC 'BSS' +_BSS ENDS +DGROUP GROUP _BSS, _DATA +if @DataSize + ASSUME DS: nothing, SS: DGROUP +else + ASSUME DS: DGROUP, SS: DGROUP +endif + +if @CodeSize +EXTRN _get_crc_table:FAR +else +EXTRN _get_crc_table:NEAR +endif + + +Do_CRC MACRO + mov bl,al + sub bh,bh +if Have_80x86 + shl bx,2 +else + shl bx,1 + shl bx,1 +endif + mov al,ah + mov ah,dl + mov dl,dh + sub dh,dh + xor ax,WORD PTR [bx][si] + xor dx,WORD PTR [bx+2][si] + ENDM +; +Do_1 MACRO +if @DataSize + xor al,BYTE PTR es:[di] +else + xor al,BYTE PTR [di] +endif + inc di + Do_CRC + ENDM +; +Do_2 MACRO +ifndef NO_16_BIT_LOADS +if @DataSize + xor ax,WORD PTR es:[di] +else + xor ax,WORD PTR [di] +endif + add di,2 + Do_CRC + Do_CRC +else + Do_1 + Do_1 +endif + ENDM +; +Do_4 MACRO + Do_2 + Do_2 + ENDM +; + +IF @CodeSize +CRC32_TEXT SEGMENT + ASSUME CS: CRC32_TEXT +else +_TEXT SEGMENT + ASSUME CS: _TEXT +endif +; Line 37 + +; +;ulg crc32(ulg crc, +; ZCONST uch *buf, +; extend len) +; + PUBLIC _crc32 +if @CodeSize +_crc32 PROC FAR +else +_crc32 PROC NEAR +endif +if Have_80x86 + enter WORD PTR 0,0 +else + push bp + mov bp,sp +endif + push di + push si +if @DataSize +; crc = 4+LCOD_OFS DWORD (unsigned long) +; buf = 8+LCOD_OFS DWORD PTR BYTE (uch *) +; len = 12+LCOD_OFS WORD (unsigned int) +else +; crc = 4+LCOD_OFS DWORD (unsigned long) +; buf = 8+LCOD_OFS WORD PTR BYTE (uch *) +; len = 10+LCOD_OFS WORD (unsigned int) +endif +; +if @DataSize + mov ax,WORD PTR [bp+8+LCOD_OFS] ; buf + or ax,WORD PTR [bp+10+LCOD_OFS] ; == NULL ? +else + cmp WORD PTR [bp+8+LCOD_OFS],0 ; buf == NULL ? +endif + jne crc_update + sub ax,ax ; crc = 0 + cwd +ifndef NO_UNROLLED_LOOPS + jmp fine +else + jmp SHORT fine +endif +; +crc_update: + call _get_crc_table +; When used with compilers that conform to the Microsoft/Borland standard +; C calling convention, model-dependent handling is not needed, because +; _get_crc_table returns NEAR pointer. +; But Watcom C is different and does not allow one to assume DS pointing to +; DGROUP. So, we load DS with DGROUP, to be safe. +;if @DataSize +; push ds +; mov ds,dx +; ASSUME DS: nothing +;endif + mov si,ax ;crc_table +if @DataSize + push ds + mov ax,SEG DGROUP + mov ds,ax + ASSUME DS: DGROUP +endif +; + mov ax,WORD PTR [bp+4+LCOD_OFS] ;crc + mov dx,WORD PTR [bp+6+LCOD_OFS] + not ax + not dx +if @DataSize + les di,DWORD PTR [bp+8+LCOD_OFS] ;buf + mov cx,WORD PTR [bp+12+LCOD_OFS] ;len +else + mov di,WORD PTR [bp+8+LCOD_OFS] ;buf + mov cx,WORD PTR [bp+10+LCOD_OFS] ;len +endif +; +ifndef NO_UNROLLED_LOOPS +ifndef NO_16_BIT_LOADS + test cx,cx + jnz start + jmp done +start: test di,1 + jz is_wordaligned + dec cx + Do_1 + mov WORD PTR [bp+10+LDAT_OFS+LCOD_OFS],cx +is_wordaligned: +endif ; !NO_16_BIT_LOADS +if Have_80x86 + shr cx,2 +else + shr cx,1 + shr cx,1 +endif + jz No_Fours +; + align Align_Size ; align destination of branch +Next_Four: + Do_4 +ifndef OPTIMIZE_286_88 + dec cx ; on 286, "loop Next_Four" needs 11 + jnz Next_Four ; clocks, one less than this code +else + loop Next_Four +endif +; +No_Fours: +if @DataSize + mov cx,WORD PTR [bp+12+LCOD_OFS] ;len +else + mov cx,WORD PTR [bp+10+LCOD_OFS] ;len +endif + and cx,00003H +endif ; !NO_UNROLLED_LOOPS + jz done +; + align Align_Size ; align destination of branch +Next_Byte: + Do_1 +ifndef OPTIMIZE_286_88 + dec cx ; on 286, "loop Next_Four" needs 11 + jnz Next_Byte ; clocks, one less than this code +else + loop Next_Four +endif +; +done: +if @DataSize + pop ds +; ASSUME DS: DGROUP + ASSUME DS: nothing +endif + not ax + not dx +; +fine: + pop si + pop di +if Have_80x86 + leave +else + mov sp,bp + pop bp +endif + ret + +_crc32 ENDP + +if @CodeSize +CRC32_TEXT ENDS +else +_TEXT ENDS +endif +; +endif ;!USE_ZLIB +; +END |