Power-Programmierung/CD1.mdf/magazine/drdobbs/ddjcompr/comp2_as/decomp2.asm

Assembly Source File | 1991-04-29 | 4KB | 242 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    'DECOMP failed.', 10,13, '$'

        align

ReadBuffer    db    ReadBufferSize dup (?)
ReadBufferEnd    label byte
ReadEnd        dw    offset ReadBufferEnd

        align

WriteBuffer    db    WriteBufferSize dup (?)
WriteBufferEnd    label byte

nine            dw    9

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

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


jProcessWithChecks:
            jmp    ProcessWithChecks

start:        cld
            mov    ax, data
            mov    ds, ax
            mov    ax, table
            mov    es, ax

; si contains pointer to ReadBuffer
            mov    si, offset ReadBufferEnd
; di contains pointer to WriteBuffer
            mov    di, offset WriteBuffer
; bx contains the Addr
            mov    bx, 0

ReadLoop:        mov    ax, ReadEnd
            sub    ax, si
            xor    dx, dx
            div    nine
            cmp    ax, 1
            jbe    jProcessWithChecks
            mov    dx, ax
            dec    dx

            mov    ax, offset WriteBufferEnd
            sub    ax, di
            mov    cl, 3
            shr    ax, cl
            cmp    ax, 1
            jbe    jProcessWithChecks
            dec    ax
            mov    cx, ax

            cmp    cx, dx
            jbe    MinFound
            mov    cx, dx
MinFound:

ByteLoop:        lodsb
            mov    dl, al
ProcessBit    macro
            local zerobit, over
            shl    dl, 1
            jnc    zerobit
            lodsb
            mov    es:[bx], al
            jmp    short over
zerobit:        mov    al, es:[bx]
over:        mov    bh, bl
            mov    bl, al
            mov    ds:[di], al
            inc    di
            endm

            ProcessBit
            ProcessBit
            ProcessBit
            ProcessBit
            ProcessBit
            ProcessBit
            ProcessBit
            ProcessBit

            loop    jByteLoop
            jmp    ReadLoop
jByteLoop:    jmp    ByteLoop

ProcessWithChecks:
; read a byte
        cmp    si, ReadEnd
        jb    noreadblock$1
        push    bx
        mov    dx, offset ReadBuffer
        mov    si, dx
        mov    bx, InFile
        mov    ah, 3Fh
        mov    cx, ReadBufferSize
        int    21h
        pop    bx
        jnc    readsuccess$1
        jmp    fail
readsuccess$1:
        or    ax, ax
        jne    notready$1
        jmp    ready
notready$1:
        add    ax, offset ReadBuffer
        mov    ReadEnd, ax
noreadblock$1:
        lodsb
;
        mov    dl, al
        mov    cx, 8
bitloop:
        shl    dl, 1
        jnc    zerobit
onebit:
; read a byte
        cmp    si, ReadEnd
        jb    noreadblock$2
        push    bx
        push    cx
        push    dx
        mov    dx, offset ReadBuffer
        mov    si, dx
        mov    bx, InFile
        mov    ah, 3Fh
        mov    cx, ReadBufferSize
        int    21h
        pop    dx
        pop    cx
        pop    bx
        jnc    readsuccess$2
        jmp    fail
readsuccess$2:
        or    ax, ax
        jne    notready$2
        jmp    ready
notready$2:
        add    ax, offset ReadBuffer
        mov    ReadEnd, ax
noreadblock$2:
        lodsb
;
        mov    es:[bx], al
        mov    bh, bl
        mov    bl, al
; Write a byte
        cmp    di, offset WriteBufferEnd
        jb    nowriteblock$1
        call    WriteBlock
nowriteblock$1:
        mov    ds:[di], al
        inc    di
;
        loop    bitloop
        jmp    ReadLoop

zerobit:
        mov    al, es:[bx]
        mov    bh, bl
        mov    bl, al
; Write a byte
        cmp    di, offset WriteBufferEnd
        jb    nowriteblock$2
        call    WriteBlock
nowriteblock$2:
        mov    ds:[di], al
        inc    di
;
        loop    bitloop
        jmp    ReadLoop


ready:    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