145 lines
4.0 KiB
ArmAsm
145 lines
4.0 KiB
ArmAsm
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;===========================================================================
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; Copyright (c) 1990-2000 Info-ZIP. All rights reserved.
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;
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; See the accompanying file LICENSE, version 2000-Apr-09 or later
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; (the contents of which are also included in zip.h) for terms of use.
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; If, for some reason, all these files are missing, the Info-ZIP license
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; also may be found at: ftp://ftp.info-zip.org/pub/infozip/license.html
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;===========================================================================
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; crc_68 created by Paul Kienitz, last modified 04 Jan 96.
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;
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; Return an updated 32 bit CRC value, given the old value and a block of data.
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; The CRC table used to compute the value is gotten by calling get_crc_table().
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; This replaces the older updcrc() function used in Zip and fUnZip. The
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; prototype of the function is:
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;
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; ulg crc32(ulg crcval, uch *text, extent textlen);
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;
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; On the Amiga, type extent is always unsigned long, not unsigned int, because
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; int can be short or long at whim, but size_t is long.
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;
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; If using this source on a non-Amiga 680x0 system, note that we treat
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; a0/a1/d0/d1 as scratch registers not preserved across function calls.
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; We do not bother to support registerized arguments for crc32() -- the
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; textlen parm is usually large enough so that savings outside the loop
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; are pointless.
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;
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; Define NO_UNROLLED_LOOPS to use a simple short loop which might be more
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; efficient on certain machines with dinky instruction caches ('020?), or for
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; processing short strings. If loops are unrolled, the textlen parm must be
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; less than 512K; if not unrolled, it must be less than 64K.
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;
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; 1999/09/23: for Human68k: Modified by Shimazaki Ryo.
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xdef _crc32 ; (ulg val, uch *buf, extent bufsize)
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DO_CRC0 MACRO
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moveq #0,ltemp
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move.b (textbuf)+,ltemp
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eor.b crcval,ltemp
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lsl.w #2,ltemp
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move.l (crc_table,ltemp.w),ltemp
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lsr.l #8,crcval
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eor.l ltemp,crcval
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ENDM
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DO_CRC2 MACRO
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move.b (textbuf)+,btemp
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eor.b crcval,btemp
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lsr.l #8,crcval
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move.l (crc_table,btemp.w*4),ltemp
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eor.l ltemp,crcval
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ENDM
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crc_table reg a0 array of unsigned long
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crcval reg d0 unsigned long initial value
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textbuf reg a1 array of unsigned char
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textbufsize reg d1 unsigned long (count of bytes in textbuf)
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btemp reg d2
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ltemp reg d3
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xref _get_crc_table ; ulg *get_crc_table(void)
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quad
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_crc32:
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move.l 8(sp),d0
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bne.s valid
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;;;;; moveq #0,d0
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rts
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valid: movem.l btemp/ltemp,-(sp)
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jsr _get_crc_table
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movea.l d0,crc_table
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move.l 12(sp),crcval
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move.l 16(sp),textbuf
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move.l 20(sp),textbufsize
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not.l crcval
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ifdef NO_UNROLLED_LOOPS
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if CPU==68000
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bra.s decr
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loop: DO_CRC0
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decr: dbra textbufsize,loop
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bra.s done
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else
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twenty: moveq #0,btemp
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bra.s decr2
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loop2: DO_CRC2
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decr2: dbra textbufsize,loop2
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endif
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ELSE ; !NO_UNROLLED_LOOPS
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if CPU==68000
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moveq #7,btemp
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and textbufsize,btemp
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lsr.l #3,textbufsize
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bra decr8
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loop8: DO_CRC0
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DO_CRC0
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DO_CRC0
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DO_CRC0
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DO_CRC0
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DO_CRC0
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DO_CRC0
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DO_CRC0
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decr8: dbra textbufsize,loop8
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bra.s decr1
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loop1: DO_CRC0
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decr1: dbra btemp,loop1
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bra done
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else
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twenty: moveq #0,btemp
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move.l textbufsize,-(sp)
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lsr.l #3,textbufsize
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bra decr82
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quad
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loop82: DO_CRC2
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DO_CRC2
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DO_CRC2
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DO_CRC2
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DO_CRC2
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DO_CRC2
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DO_CRC2
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DO_CRC2
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decr82: dbra textbufsize,loop82
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moveq #7,textbufsize
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and.l (sp)+,textbufsize
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bra.s decr12
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loop12: DO_CRC2
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decr12: dbra textbufsize,loop12
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endif
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ENDC ; ?NO_UNROLLED_LOOPS
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done: movem.l (sp)+,btemp/ltemp
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not.l crcval
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;;;;; move.l crcval,d0 ; crcval already is d0
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rts
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