Extra libs: ap.lib

aPLib support with apultra.

1 files changed, 177 insertions, 0 deletions

diff --git a/tools/apultra/asm/8088/aplib_8088_small.S b/tools/apultra/asm/8088/aplib_8088_small.S
new file mode 100644
index 0000000..542991e
--- /dev/null
+++ b/tools/apultra/asm/8088/aplib_8088_small.S
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+;  aplib_8088_small.S - size-optimized aPLib decompressor for 8088 - 145 bytes

+;

+;  Copyright (C) 2019 Emmanuel Marty

+;

+;  This software is provided 'as-is', without any express or implied

+;  warranty.  In no event will the authors be held liable for any damages

+;  arising from the use of this software.

+;

+;  Permission is granted to anyone to use this software for any purpose,

+;  including commercial applications, and to alter it and redistribute it

+;  freely, subject to the following restrictions:

+;

+;  1. The origin of this software must not be misrepresented; you must not

+;     claim that you wrote the original software. If you use this software

+;     in a product, an acknowledgment in the product documentation would be

+;     appreciated but is not required.

+;  2. Altered source versions must be plainly marked as such, and must not be

+;     misrepresented as being the original software.

+;  3. This notice may not be removed or altered from any source distribution.

+

+        segment .text

+        bits 16

+

+;  ---------------------------------------------------------------------------

+;  Decompress aPLib data

+;  inputs:

+;  * ds:si: compressed aPLib data

+;  * es:di: output buffer

+;  output:

+;  * ax:    decompressed size

+;  ---------------------------------------------------------------------------

+

+apl_decompress:

+        push    di              ; remember decompression offset

+        cld                     ; make string operations go forward

+

+        ; === register map ===

+        ; al: bit queue

+        ; ah: unused, but value is trashed

+        ; bx: follows_literal

+        ; cx: scratch register for reading gamma2 codes and storing copy length

+        ; dx: match offset (and rep-offset)

+        ; si: input (compressed data) pointer

+        ; di: output (decompressed data) pointer

+        ; bp: offset of .get_bit 

+

+        mov     al,080H         ; clear bit queue(al) and set high bit to move into carry

+        xor     dx,dx           ; invalidate rep offset

+        mov     bp,.get_bit     ; load offset of .get_bit, to be used with call bp

+

+.literal:

+        movsb                   ; read and write literal byte

+.next_command_after_literal:

+        mov     bx,03H          ; set follows_literal(bx) to 3

+

+.next_command:

+        call    bp              ; read 'literal or match' bit

+        jnc     .literal        ; if 0: literal

+                                

+                                ; 1x: match

+

+        call    bp              ; read '8+n bits or other type' bit

+        jc      .other          ; 11x: other type of match

+

+                                ; 10: 8+n bits match

+        call    .get_gamma2     ; read gamma2-coded high offset bits

+        sub     cx,bx           ; high offset bits == 2 when follows_literal == 3 ?

+                                ; (a gamma2 value is always >= 2, so substracting follows_literal when it

+                                ; is == 2 will never result in a negative value)

+        jae     .not_repmatch   ; if not, not a rep-match

+

+        call    .get_gamma2     ; read match length

+        jmp     short .got_len  ; go copy

+

+.not_repmatch:

+        mov     dh,cl           ; transfer high offset bits to dh

+        mov     dl,[si]         ; read low offset byte in dl

+        inc     si

+

+        call    .get_gamma2     ; read match length

+        cmp     dh,07DH         ; offset >= 32000 ?

+        jae     .increase_len_by2 ; if so, increase match len by 2

+        cmp     dh,05H          ; offset >= 1280 ?

+        jae     .increase_len_by1 ; if so, increase match len by 1

+        cmp     dx,0080H        ; offset < 128 ?

+        jae     .got_len        ; if so, increase match len by 2, otherwise it would be a 7+1 copy

+.increase_len_by2:

+        inc     cx              ; increase length

+.increase_len_by1:

+        inc     cx              ; increase length

+

+        ; copy cx bytes from match offset dx

+

+.got_len:

+        push    ds              ; save ds:si (current pointer to compressed data)

+        push    si

+

+        push    es

+        pop     ds

+        mov     si,di           ; point to destination in es:di - offset in dx

+        sub     si,dx

+        rep     movsb           ; copy matched bytes

+

+        pop     si              ; restore ds:si

+        pop     ds

+

+        mov     bl,02H          ; set follows_literal to 2 (bx is unmodified by match commands)

+        jmp     short .next_command

+

+        ; read gamma2-coded value into cx

+

+.get_gamma2:

+        xor     cx,cx           ; initialize to 1 so that value will start at 2

+        inc     cx              ; when shifted left in the adc below

+

+.gamma2_loop:

+        call    .get_dibits     ; read data bit, shift into cx, read continuation bit

+        jc      .gamma2_loop    ; loop until a zero continuation bit is read

+

+        ret

+

+        ; handle 7 bits offset + 1 bit len or 4 bits offset / 1 byte copy

+

+.other:

+        xor     cx,cx

+        call    bp              ; read '7+1 match or short literal' bit

+        jc      .short_literal  ; 111: 4 bit offset for 1-byte copy

+

+                                ; 110: 7 bits offset + 1 bit length

+                                

+        mov     dl,[si]         ; read offset + length in dl

+        inc     si

+

+        inc     cx              ; prepare cx for length below

+        shr     dl,1            ; shift len bit into carry, and offset in place

+        je      .done           ; if zero offset: EOD

+        adc     cx,cx           ; len in cx: 1*2 + carry bit = 2 or 3

+

+        xor     dh,dh           ; clear high bits of offset

+        jmp     short .got_len

+

+        ; 4 bits offset / 1 byte copy

+

+.short_literal:

+        call    .get_dibits     ; read 2 offset bits

+        adc     cx,cx

+        call    .get_dibits     ; read 2 offset bits

+        adc     cx,cx

+        xchg    ax,cx           ; preserve bit queue in cx, put offset in ax

+        jz      .write_zero     ; if offset is 0, write a zero byte

+

+                                ; short offset 1-15

+        mov     bx,di           ; point to destination in es:di - offset in ax

+        sub     bx,ax           ; we trash bx, it will be reset to 3 when we loop

+        mov     al,[es:bx]      ; read byte from short offset

+.write_zero:

+        stosb                   ; copy matched byte

+        xchg    ax,cx           ; restore bit queue in al

+        jmp     .next_command_after_literal

+

+.done:

+        pop     ax              ; retrieve the original decompression offset

+        xchg    di,ax           ; compute decompressed size

+        sub     ax,di

+        ret

+

+.get_dibits:

+        call    bp              ; read data bit

+        adc     cx,cx           ; shift into cx

+

+.get_bit:

+        add     al,al           ; shift bit queue, and high bit into carry

+        jnz     .got_bit        ; queue not empty, bits remain

+        lodsb                   ; read 8 new bits

+        adc     al,al           ; shift bit queue, and high bit into carry

+.got_bit:

+        ret