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Rearrange match offset code to save 2 bytes in 6809 LZSA depacker

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This commit is contained in:
Doug Masten 2020-06-21 01:09:15 -05:00
parent 7f0316b81c
commit b5b8ca556a
1 changed files with 4 additions and 5 deletions
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9
asm/6809/unlzsa1.s
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@ -1,4 +1,4 @@
; unlzsa1.s - 6809 decompression routine for raw LZSA1 - 111 bytes
; unlzsa1.s - 6809 decompression routine for raw LZSA1 - 109 bytes
; compress with lzsa -r <original_file> <compressed_file>
;
; in: x = start of compressed data
@ -25,8 +25,7 @@
decompress_lzsa1 equ lz1token
lz1bigof ldb ,x+ ; O set: load long 16 bit (negative, signed) offset
lda ,x+ ; (little endian)
lz1bigof lda ,x+ ; O set: load MSB 16-bit (negative, signed) offest
lz1gotof leau d,y ; put backreference start address in U (dst+offset)
puls b ; restore token
@ -97,9 +96,9 @@ lz1cpylt lda ,u+ ; copy literal byte
bne lz1cpylt ; loop until all literal bytes are copied
tfr u,x
lz1nolt ldb ,s ; get token again, don't pop it from the stack
lz1nolt ldb ,x+ ; load either 8-bit or LSB 16-bit offset (negative, signed)
lda ,s ; get token again, don't pop it from the stack
bmi lz1bigof ; test O bit (small or large offset)
ldb ,x+ ; O clear: load 8 bit (negative, signed) offset
lda #$ff ; set high 8 bits
bra lz1gotof