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depacker.asm
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depacker.asm
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; This file is distributed under a BSD license. See LICENSE.txt for details.
; kkrunchy depacker
bits 32
%define ModelSizes 2+1+32+256+256+256
struc dataArea
.src resd 1
.csub resd 1
.range resd 1
.move resd 1
.r0 resd 1
.cmodel resd 2 ; code models
.pmodel resd 1 ; prev match model
.mmodel resd 32 ; match low models
.lmodel resd 256 ; literal model
.gmodel resd 256 ; gamma 0 model
.hmodel resd 256 ; gamma 1 model
.rest resd 1024-ModelSizes ; padding
.size:
endstruc
section .text
; ----------------------------------------------------------------------------
DePacker mov ebp, 'WORK'
; initialize pointers and state
mov dword [ebp + dataArea.src], 'ESI0'
dec dword [ebp + dataArea.range]
mov byte [ebp + dataArea.move], 5
; initialize models
lea edi, [ebp + dataArea.cmodel]
xor eax, eax
mov ah, 1024/256
mov ecx, eax
rep stosd
mov edi, 'EDI0'
push edi
mov esi, DecodeBit + ('R' << 24) + ('P' << 16)
.literal xor ecx, ecx
inc ecx
dec dword [ebp + dataArea.move]
.litbit lea ebx, [ebp + dataArea.lmodel + ecx * 4]
call esi
adc cl, cl
jnc .litbit
inc dword [ebp + dataArea.move]
xchg eax, ecx
stosb
or ecx, byte -1
.getcode lea ebx, [ebp + dataArea.cmodel + 4 + ecx * 4]
call esi
jz .literal
; match
jecxz .noprev
lea ebx, [ebp + dataArea.pmodel]
call esi
jz .noprev
lea ebx, [ebp + dataArea.hmodel]
call DeGamma
mov eax, [ebp + dataArea.r0]
jmp short .copy
.noprev lea ebx, [ebp + dataArea.gmodel]
call DeGamma
dec ecx
dec ecx
js .end
lea ebx, [ebp + dataArea.mmodel]
jz .nonext
add ebx, byte 16*4
.nonext xor edx, edx
inc edx
.mtree call DeBitTree
lea ecx, [eax + ecx * 2]
test dl, 16
jz .mtree
inc ecx
xchg eax, ecx
lea ebx, [ebp + dataArea.hmodel]
call DeGamma
cmp eax, 2048
sbb ecx, byte -1
cmp eax, byte 96
sbb ecx, byte -1
.copy mov [ebp + dataArea.r0], eax
push esi
mov esi, edi
sub esi, eax
rep movsb
pop esi
jmp short .getcode
; imports
.end mov esi, 'IMPO'
mov ebx, 'LLIB'
push ebp
.iloop inc esi
lodsd
test eax, eax
jz .iend
xchg eax, edi
push esi
call [ebx]
test eax, eax
jz .ierr
xchg eax, ebp
.lfunc lodsb
test al, al
jnz .lfunc
cmp [esi], al
je .iloop
js .iord
push esi
.iget push ebp
call [ebx+4]
stosd
test eax, eax
jnz .lfunc
.ierr inc eax
pop ebx
pop ecx
ret
.iord inc esi
xor eax, eax
lodsw
push eax
jmp short .iget
.iend pop ebp
ret
; ----------------------------------------------------------------------------
DecodeBit push ecx ; in ebx=model.
mov eax, [ebp + dataArea.range]
shr eax, 11
mov ecx, [ebp + dataArea.src]
imul eax, [ebx] ; now eax=bound
mov ecx, [ecx]
bswap ecx
sub ecx, [ebp + dataArea.csub]
cmp eax, ecx
mov ecx, [ebp + dataArea.move]
jbe .one
mov [ebp + dataArea.range], eax
xor eax, eax
mov ah, 2048/256
sub eax, [ebx]
shr eax, cl
add [ebx], eax
xor eax, eax
jmp short .renorm
.one add [ebp + dataArea.csub], eax
sub [ebp + dataArea.range], eax
mov eax, [ebx]
shr eax, cl
sub [ebx], eax
or eax, byte -1
.renorm test byte [ebp + dataArea.range + 3], 0xff ; range<(1<<24)?
jnz .norenorm
; renormalize
inc dword [ebp + dataArea.src]
shl dword [ebp + dataArea.range], 8
shl dword [ebp + dataArea.csub], 8
.norenorm shr eax, 31
pop ecx
ret
; out: eax = bit; z-flag = bit is zero; c-flag = bit
; ----------------------------------------------------------------------------
DeBitTree push ebx
lea ebx, [ebx + edx * 4]
call esi
pop ebx
adc dl, dl
ret
; ----------------------------------------------------------------------------
DeGamma push eax ; in ebx=model
xor ecx, ecx
inc ecx
mov edx, ecx
.loop call DeBitTree
call DeBitTree
lea ecx, [eax + ecx * 2]
test dl, 2
jnz .loop
pop eax
ret
; out ecx=value; edx destroyed.
; ----------------------------------------------------------------------------