; XFD external slave for SZDD files (C) 2000 Stuart Caie ; $VER: SZDD.asm 1.3 (29.06.2000) ; v1.1: better xfd name, eliminated 4k buffer ; v1.2: better header text, no code changed ; v1.3: off-by-one error fixed, spaces-vs-nulls error fixed ; ; Files in the SZDD file format are created with Microsoft's COMPRESS.EXE ; program, and decompressed with Microsoft's EXPAND.EXE program. The file, ; when compressed, usually has an underscore as the last character in its ; filename, ie HELLO.EX_ or VBRUN666.DL_ ; ; File header format: ; 4 bytes : "SZDD" (0x53,0x5A,0x44,0x44) - magic ID ; 4 bytes : 0x88,0xF0,0x27,0x33 - more magic ID ; 1 byte : compression mode - only 'A' (0x41) known ; 1 byte : the character missing from the end of the filename (0=unknown) ; 4 bytes : A,B,C,D. unpacked size of file is (D<<24)|(C<<16)|(B<<8)|(A) ; n bytes : the compressed data ; ; The compressed data format is basically LZSS ; - one control byte, whose bits dictate the format of the next 8 elements, ; in the order of LSB to MSB: ; - if a bit is set, the next element is a single byte literal ; - otherwise, the next element is a repeat: two bytes, %AAAAAAAA %BBBBCCCC ; where offset = %BBBBAAAAAAAA and length is %CCCC + 3 ; - this repeats until enough data has been unpacked ; ; A 4096 byte wraparound buffer must be kept by the decruncher. A wraparound ; pointer starts at 4096-16 and each outputted byte must be written at that ; position and the pointer advanced by one. The offsets of the compressed ; data refer to an absolute position in this buffer, which may be before the ; current pointer, or after it. The buffer's initial state is that all ; elements are the space character (0x20). ; ; Also, it seems that there can often be superfluous data at the end of a ; file - I can only go by the uncompressed size, so I can only really test ; running out of source data. Some files end in the middle of a run, so I ; can't test if they exactly reach the endpoint and no more. ; ; This code was based on code found in a document describing the Windows Help ; file format, written by M. Winterhoff <100326.2776@compuserve.com>. ; SZDD_WNDSIZE=4096 SZDD_WNDMASK=4095 SZDD_MINLEN=14 SZDD_OVERRUN=144 include exec/memory.i include libraries/xfdmaster.i include lvo/exec_lib.i IFD TEST include xfdExeHead.a ENDC ForeMan dc.l $70FF4E75,XFDF_ID ; id dc.w XFDF_VERSION ; foreman version dcb.w 5,0 ; reserved stuff dc.l SZDDslv ; first slave SZDDslv dc.l 0 dc.w XFDS_VERSION,39 dc.l SZDDnam dc.w XFDPFF_DATA!XFDPFF_RECOGLEN!XFDPFF_USERTARGET,0 dc.l SZDD_recog,SZDD_decrunch,0,0 dc.l 0,SZDD_MINLEN SZDD_recog cmp.l #"SZDD",(a0) bne.s .fail move.l 10(a0),d0 rol.w #8,d0 swap d0 rol.w #8,d0 move.l d0,xfdrr_FinalTargetLen(a1) add.l #SZDD_OVERRUN,d0 move.l d0,xfdrr_MinTargetLen(a1) moveq #1,d0 ; return success rts .fail moveq #0,d0 rts SZDD_decrunch movem.l d2-d7/a2-a6,-(sp) move.l a0,a4 ; a4 = BufferInfo move.l xfdbi_SourceBuffer(a4),a0 ; a0 = src move.l a0,a2 adda.l xfdbi_SourceBufLen(a4),a2 ; a2 = ends adda.w #14,a0 move.l xfdbi_UserTargetBuf(a4),a1 ; a1 = dest move.l a1,a3 adda.l xfdbi_TargetBufSaveLen(a4),a3 ; a3 = endd move.l a1,d3 ; d3 = start move.w #SZDD_WNDSIZE-16,d7 ; d7 = posn move.w #SZDD_WNDMASK,d6 ; d6 = bufmask .mainlp move.b (a0)+,d5 ; d5 = bits moveq #0,d4 ; d4 = mask .bitlp btst.b d4,d5 beq.s .rep ; literal move.b (a0)+,(a1)+ addq.w #1,d7 bra.s .nxtbit .rep ; repeat moveq #0,d0 move.b (a0)+,d0 ; d0 = offset move.b (a0)+,d1 ; d1 = length moveq #0,d2 move.b d1,d2 asl.w #4,d2 move.b #0,d2 or.w d2,d0 andi.w #$f,d1 addq.b #3,d1 and.w d6,d7 cmp.w d0,d7 bhi.s .noadd ; if (offset <= posn) don't add WNDSIZE add.w #SZDD_WNDSIZE,d7; [or bset #12,d7 - but that's no shorter] .noadd lea (a1,d0.w),a5 ; a5 = rep, = dest+offset-posn suba.w d7,a5 add.w d1,d7 ; posn += length .clr cmp.l a5,d3 ; if rep >= base, stop doing clearing bls.s .noclr move.b #' ',(a1)+ ; clear one byte addq.l #1,a5 subq.w #1,d1 ; length-- beq.s .nxtbit bra.s .clr .noclr move.b (a5)+,(a1)+ ; *dest++=*rep++ subq.w #1,d1 ; while (length--) bne.s .noclr .nxtbit cmp.l a1,a3 ; if dest >= endd, stop now bcs.s .done addq.l #1,d4 ; next bit, from 0-7 cmp.b #8,d4 bcs.s .bitlp ; if d4<8, goto .bitlp cmp.l a0,a2 bcc.s .mainlp ; if src < ends, go back to main loop .corupt move.w #XFDERR_CORRUPTEDDATA,xfdbi_Error(a4) moveq #0,d0 bra.s .exit .done clr.w xfdbi_Error(a4) moveq #1,d0 .exit movem.l (sp)+,d2-d7/a2-a6 rts SZDDnam dc.b '(SZDD) Microsoft Data Cruncher',0 dc.b '$VER: SZDD 1.3 (29.06.2000) by ',0