6502
/
zlib6502
mirror of https://github.com/pfusik/zlib6502.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

Shorten by one byte.

This commit is contained in:
Piotr Fusik 2017-02-07 17:46:10 +01:00
parent fd18d5618d
commit 8498d8fde7
2 changed files with 31 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
README.md
View File

@ -15,7 +15,7 @@ Use [xasm](https://github.com/pfusik/xasm).
The routine uses three memory areas:
* `inflate` - code and constants (502 bytes)
* `inflate` - code and constants (501 bytes)
* `inflate_data` - uninitialized data (764 bytes)
* `inflate_zp` - variables on zero page

58
inflate.asx
View File

@ -4,7 +4,7 @@
; Compile with xasm (http://xasm.atari.org/), for example:
; xasm inflate.asx /l /d:inflate=$b700 /d:inflate_data=$b900 /d:inflate_zp=$f0
; inflate is 502 bytes of code and constants
; inflate is 501 bytes of code and constants
; inflate_data is 764 bytes of uninitialized data
; inflate_zp is 10 bytes on page zero
@ -69,7 +69,6 @@ inflate_blockLoop
jsr getBits
lsr @
php
tax
bne inflateCompressed
; Copy uncompressed block
@ -82,9 +81,7 @@ inflate_blockLoop
bcs inflateStored_firstByte
inflateStored_copyByte
jsr getByte
inflateStoreByte
jsr storeByte
bcc inflateCodes_loop
inflateStored_firstByte
inx
bne inflateStored_copyByte
@ -97,35 +94,42 @@ inflate_nextBlock
rts
inflateCompressed
; A=1: fixed block, initialize with fixed codes
; A=2: dynamic block, start by clearing all code length
; A=3: invalid compressed data, not handled here
eor #2
; Decompress a block with fixed Huffman trees:
; ldy #0
inflateCompressed_setCodeLengths
tax
beq inflateCompressed_setLiteralCodeLength
; fixed Huffman literal codes:
; :144 dta 8
; :112 dta 9
; :24 dta 7
; :6 dta 8
; :2 dta 8 ; codes with no meaning
; :30 dta 5+DISTANCE_TREE
; ldy #0
inflateFixed_setCodeLengths
lda #4
cpy #144
rol @
inflateCompressed_setLiteralCodeLength
sta literalSymbolCodeLength,y
cpy #CONTROL_SYMBOLS
bcs inflateFixed_noControlSymbol
beq inflateCompressed_setControlCodeLength
; fixed Huffman control codes:
; :24 dta 7
; :6 dta 8
; :2 dta 8 ; meaningless codes
; :30 dta 5+DISTANCE_TREE
lda #5+DISTANCE_TREE
cpy #LENGTH_SYMBOLS
bcs inflateFixed_setControlCodeLength
bcs inflateCompressed_setControlCodeLength
cpy #24
adc #2-DISTANCE_TREE
inflateFixed_setControlCodeLength
sta controlSymbolCodeLength,y
inflateFixed_noControlSymbol
inflateCompressed_setControlCodeLength
cpy #CONTROL_SYMBOLS
scs:sta controlSymbolCodeLength,y
iny
bne inflateFixed_setCodeLengths
bne inflateCompressed_setCodeLengths
dex
beq inflateCodes
tax
bne inflateCodes
; Decompress a block reading Huffman trees first
@ -173,7 +177,7 @@ inflateDynamic_controlSymbolCodeLength
cpx inflateDynamic_primaryCodes
bcc inflateDynamic_storeControl
; the code lengths we skip here were zero-initialized
; in inflateDynamic_clearCodeLengths
; in inflateCompressed_setControlCodeLength
sne:ldx #LENGTH_SYMBOLS
ora #DISTANCE_TREE
inflateDynamic_storeControl
@ -187,9 +191,13 @@ inflateDynamic_storeControl
; Decompress a block
inflateCodes
jsr buildHuffmanTree
; jmp inflateCodes_loop
beq inflateCodes_loop
inflateCodes_literal
jsr storeByte
inflateCodes_loop
jsr fetchPrimaryCode
bcc inflateStoreByte
bcc inflateCodes_literal
beq inflate_nextBlock
; Copy sequence from look-behind buffer
; ldy #0
@ -244,12 +252,6 @@ inflateCodes_copyByte
buildTempHuffmanTree
; ldy #0
tya
inflateDynamic_clearCodeLengths
sta literalSymbolCodeLength,y
sta literalSymbolCodeLength+TOTAL_SYMBOLS-256,y
iny
bne inflateDynamic_clearCodeLengths
; numberOfPrimaryCodes = 257 + getBits(5)
; numberOfDistanceCodes = 1 + getBits(5)
; numberOfTemporaryCodes = 4 + getBits(4)