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rom_decrunch.s
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rom_decrunch.s
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# ByteKiller decrunch code for PSX by Silpheed of Hitmen
#
# Ever so slightly tweaked for Unirom, 2013, 2020 ~Sickle
#
# BK_Decrunch
# a0 - src
# a1 - dest
#======================================================
# Decrunch - Omnomnom
#======================================================
BK_Decrunch:
addiu $sp, $sp, -0x4
sw $ra, 0($sp)
move $t0, $a0 # t0 = source address
nop
lw $t2, 0($a0) # t2 = uncompressed size
move $t1, $a1 # t1 = write address
lw $t3, 4($a0) # t3 = compressed size
addu $t2, $t2, $t1 # t2 = uncompressed size + write address (end of write)
addu $t0, $t0, $t3 # t3 = compressed size + read address ( end of read )
addiu $t0, $t0, -4 # t0 = end of read address -4#
lw $t3, 0($t0) # preload first word from t0 ( srcend -4 )
nop
#======================================================
# BK_mainloop
#======================================================
BK_mainloop:
jal BK_getnextbit
nop
beq $0, $v0, _BK_part2
nop
li $a0, 2
jal BK_readbits
nop
slti $t4, $v0, 2
beq $0, $t4, _BK_skip1
nop
addiu $a0, $v0, 9
addiu $a1, $v0, 2
jal BK_dodupl
nop
b _BK_endloop
nop
_BK_skip1:
addiu $t4, $v0, -3
bne $0, $t4, _BK_skip2
nop
li $a0, 8
li $a1, 8
jal BK_dojmp
nop
b _BK_endloop
nop
_BK_skip2:
jal BK_readbits
li $a0, 8
move $a1, $v0
li $a0, 12
jal BK_dodupl
nop
b _BK_endloop
nop
_BK_part2:
jal BK_getnextbit
nop
beq $0, $v0, _BK_skip3
nop
li $a0, 8
li $a1, 1
jal BK_dodupl
nop
b _BK_endloop
nop
_BK_skip3:
li $a0, 3
move $a1, $0
jal BK_dojmp
nop
_BK_endloop:
bne $t2, $t1, BK_mainloop
nop
lw $ra, 0($sp)
nop
jr $ra
addiu $sp, $sp, -0x4
#======================================================
# BK_getnextbit
#======================================================
BK_getnextbit:
addiu $sp, $sp, -0x4
sw $ra, 0($sp)
nop
andi $v0, $t3, 1
srl $t3, $t3, 1
bne $0, $t3, _BK_gnbend
nop
addiu $t0, $t0, -4
lw $t3, 0($t0)
nop
andi $v0, $t3, 1
srl $t3, $t3, 1
lui $t5, 0x8000
or $t3, $t3, $t5
_BK_gnbend:
lw $ra, 0($sp)
nop
jr $ra
addiu $sp, $sp, 0x4
#======================================================
# BK_readbits
#======================================================
BK_readbits:
addiu $sp, $sp, -0x4
sw $ra, 0($sp)
nop
move $v1, $zero
_BK_rbloop:
beq $0, $a0, _BK_rbend
nop
addiu $a0, $a0, -1
sll $v1, $v1, 1
jal BK_getnextbit
nop
or $v1, $v1, $v0
b _BK_rbloop
nop
_BK_rbend:
move $v0, $v1
lw $ra, 0($sp)
nop
jr $ra
addiu $sp, $sp, 0x4
#======================================================
# BK_dojmp
#======================================================
BK_dojmp:
addiu $sp, $sp, -0x4
sw $ra, 0($sp)
nop
jal BK_readbits
nop
addu $t4, $v0, $a1
addiu $t4, $t4, 1
nop
_BK_djloop:
beq $0, $t4, _BK_djend
nop
addiu $t4, $t4, -1
li $a0, 8
addiu $t2, $t2, -1
nop
jal BK_readbits
nop
sb $v0, 0($t2)
nop
b _BK_djloop
nop
_BK_djend:
lw $ra, 0($sp)
nop
jr $ra
addiu $sp, $sp, 0x4
#======================================================
# BK_dodupl
#======================================================
BK_dodupl:
addiu $sp, $sp, -0x4
sw $ra, 0($sp)
nop
move $t7, $ra
addiu $a1, $a1, 1
jal BK_readbits
nop
_BK_ddloop:
beq $0, $a1, _BK_ddend
nop
addiu $a1, $a1, -1
addiu $t2, $t2, -1
addu $t4, $t2, $v0
lb $t4, 0($t4)
nop
sb $t4, 0($t2)
nop
b _BK_ddloop
nop
_BK_ddend:
lw $ra, 0($sp)
nop
jr $ra
addiu $sp, $sp, 0x4