mirror of
https://github.com/emmanuel-marty/lzsa.git
synced 2024-11-25 10:30:45 +00:00
121 lines
4.3 KiB
NASM
121 lines
4.3 KiB
NASM
; decompress_small_v1.asm - space-efficient decompressor implementation for x86
|
|
;
|
|
; 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 32
|
|
|
|
; ---------------------------------------------------------------------------
|
|
; Decompress raw LZSA1 block
|
|
; inputs:
|
|
; * esi: raw LZSA1 block
|
|
; * edi: output buffer
|
|
; output:
|
|
; * eax: decompressed size
|
|
; ---------------------------------------------------------------------------
|
|
|
|
%ifndef BIN
|
|
global lzsa1_decompress
|
|
global _lzsa1_decompress
|
|
%endif
|
|
|
|
lzsa1_decompress:
|
|
_lzsa1_decompress:
|
|
pushad
|
|
|
|
;mov edi, [esp+32+4] ; edi = outbuf
|
|
;mov esi, [esp+32+8] ; esi = inbuf
|
|
|
|
xor ecx, ecx
|
|
.decode_token:
|
|
mul ecx
|
|
lodsb ; read token byte: O|LLL|MMMM
|
|
mov dl, al ; keep token in dl
|
|
|
|
and al, 070H ; isolate literals length in token (LLL)
|
|
shr al, 4 ; shift literals length into place
|
|
|
|
cmp al, 07H ; LITERALS_RUN_LEN?
|
|
jne .got_literals ; no, we have the full literals count from the token, go copy
|
|
|
|
lodsb ; grab extra length byte
|
|
add al, 07H ; add LITERALS_RUN_LEN
|
|
jnc .got_literals ; if no overflow, we have the full literals count, go copy
|
|
jne .mid_literals
|
|
|
|
lodsw ; grab 16-bit extra length
|
|
jmp .got_literals
|
|
|
|
.mid_literals:
|
|
lodsb ; grab single extra length byte
|
|
inc ah ; add 256
|
|
|
|
.got_literals:
|
|
xchg ecx, eax
|
|
rep movsb ; copy cx literals from ds:si to es:di
|
|
|
|
test dl, dl ; check match offset size in token (O bit)
|
|
js .get_long_offset
|
|
|
|
dec ecx
|
|
xchg eax, ecx ; clear ah - cx is zero from the rep movsb above
|
|
lodsb
|
|
jmp .get_match_length
|
|
|
|
.get_long_offset:
|
|
lodsw ; Get 2-byte match offset
|
|
|
|
.get_match_length:
|
|
xchg eax, edx ; edx: match offset eax: original token
|
|
and al, 0FH ; isolate match length in token (MMMM)
|
|
add al, 3 ; add MIN_MATCH_SIZE
|
|
|
|
cmp al, 012H ; MATCH_RUN_LEN?
|
|
jne .got_matchlen ; no, we have the full match length from the token, go copy
|
|
|
|
lodsb ; grab extra length byte
|
|
add al,012H ; add MIN_MATCH_SIZE + MATCH_RUN_LEN
|
|
jnc .got_matchlen ; if no overflow, we have the entire length
|
|
jne .mid_matchlen
|
|
|
|
lodsw ; grab 16-bit length
|
|
test eax, eax ; bail if we hit EOD
|
|
je .done_decompressing
|
|
jmp .got_matchlen
|
|
|
|
.mid_matchlen:
|
|
lodsb ; grab single extra length byte
|
|
inc ah ; add 256
|
|
|
|
.got_matchlen:
|
|
xchg ecx, eax ; copy match length into ecx
|
|
xchg esi, eax
|
|
mov esi, edi ; esi now points at back reference in output data
|
|
movsx edx, dx ; sign-extend dx to 32-bits.
|
|
add esi, edx
|
|
rep movsb ; copy match
|
|
xchg esi, eax ; restore esi
|
|
jmp .decode_token ; go decode another token
|
|
|
|
.done_decompressing:
|
|
sub edi, [esp+32+4]
|
|
mov [esp+28], edi ; eax = decompressed size
|
|
popad
|
|
ret ; done
|