Power Programmierung/Power-Programmierung (Tewi)(1994).iso/magazine/drdobbs/ddjcompr/comp2_as/comp2.asm

Assembly Source File | 1991-04-29 | 4KB | 202 lines

; Copyright 1991 by Jussi Puttonen, Timo Raita and Jukka Teuhola

; Written by Jussi Puttonen, 19.4.1991 at University of Turku, Finland
; Algorithms suggested by Timo Raita and Jukka Teuhola


InFile    equ    0
OutFile    equ    1

ReadBufferSize        equ    16384
WriteBufferSize    equ    16384

stack segment stack 'stack'
        db 1024 dup (?)
stack ends

data segment para public 'data'

FailString    db    'COMP failed.', 10,13, '$'

        align

ReadBuffer    db    ReadBufferSize dup (?)
ReadBufferEnd    label byte
ReadSize        dw    ?
        align

WriteBuffer    db    WriteBufferSize dup (?)
WriteBufferEnd    label byte
ExtraWriteBuffer db 10 dup (?)

data ends

table segment para public 'data'
    db    8000h dup (' ')
    db    8000h dup (' ')
table ends

code segment para public 'code'
    assume cs:code, ds:data, es:table

; FlushBuffer must be called at the end of the program

WriteBlock:    push    ax
            push    bx
            push    cx
            push    dx
            mov    ah, 40h
            mov    bx, OutFile
            mov    cx, WriteBufferSize
            lea    dx, WriteBuffer
            int    21h

; take care of the ExtraWriteBuffer
            mov    cx, di
            mov    di, offset WriteBuffer
            sub    cx, offset WriteBufferEnd
            je    ExtraHandled
            mov    bx, offset WriteBufferEnd
ExtraCopyLoop:    mov    al, ds:[bx]
            mov    ds:[di], al
            inc    bx
            inc    di
            loop    ExtraCopyLoop
ExtraHandled:    pop    dx
            pop    cx
            pop    bx
            pop    ax
            ret

FlushBuffer    proc
            mov    ah, 40h
            mov    bx, OutFile
            mov    cx, di
            lea    dx, WriteBuffer
            sub    cx, dx
            int    21h
            ret
FlushBuffer    endp

; register use:
;   bx    address
;   si    pointer to ReadBuffer
;   di    pointer to WriteBuffer
;   dl    Bits
;   bp    SavedWriteLoc

jProcessLastBytes:
            jmp    ProcessLastBytes
Start:        cld
            mov    ax, data
            mov    ds, ax
            mov    ax, table
            mov    es, ax

            mov    bx, 0
            mov    di, offset WriteBuffer

ReadBlockLoop:    mov    dx, offset ReadBuffer
            mov    si, dx                ; to be used in ProcessBlockLoop
            push    bx
            mov    bx, InFile
            mov    ah, 3Fh
            mov    cx, ReadBufferSize
            int    21h
            jnc    ReadSuccess
            jmp    fail
ReadSuccess:    pop    bx
            mov    ReadSize, ax
            mov    cl, 3
            shr    ax, cl
            je    jProcessLastBytes
            mov    cx, ax

ProcessByte    macro SourceReg,BitVal
            local over
            cmp    SourceReg, es:[bx]
            je    over
            or    dl, BitVal
            mov    es:[bx], SourceReg
            mov    ds:[di], SourceReg
            inc    di
over:        mov    bh, bl
            mov    bl, SourceReg
            endm


ProcessBlockLoop:
            mov bp, di
            inc di
            xor dl, dl
            lodsw
            ProcessByte al, 80h
            ProcessByte ah, 40h
            lodsw
            ProcessByte al, 20h
            ProcessByte ah, 10h
            lodsw
            ProcessByte al, 08h
            ProcessByte ah, 04h
            lodsw
            ProcessByte al, 02h
            ProcessByte ah, 01h

            mov    ds:[bp], dl

            cmp    di, offset WriteBufferEnd
            jb    NoWriteBlock
            call    WriteBlock
NoWriteBlock:    loop    jProcessBlockLoop
            jmp    jNext1
jProcessBlockLoop:
            jmp    ProcessBlockLoop
jNext1:        mov    ax, ReadSize
            cmp    ax, ReadBufferSize
            jne    ProcessLastBytes
            jmp    ReadBlockLoop
ProcessLastBytes:
            mov    cx, ReadSize
            and    cx, 7
            je    Finish
            mov    bp, di
            inc    di
LastByteLoop:    lodsb
            shl    dl, 1
            cmp    al, es:[bx]
            je    over
            inc    dl
            mov    es:[bx], al
            mov    ds:[di], al
            inc    di
over:        mov    bh, bl
            mov    bl, al
            loop    LastByteLoop

            mov    cx, 8
            sub    cx, ReadSize
            and    cx, 7
            je    NoShift
ShiftLoop:    shl    dl, 1
            inc    dl
            loop    ShiftLoop

NoShift:        mov    ds:[bp], dl

Finish:        call    FlushBuffer

            mov    ax, 4c00h
            int    21h

fail:        mov    dx, offset FailString
            mov    ah, 9
            int    21h
            mov    ax, 4c01h
            int    21h


            code ends

        end Start