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Make the routine ROM-friendly - the initialized data is now constant. Shorten by four bytes.

This commit is contained in:
Piotr Fusik 2017-02-07 15:04:19 +01:00
parent bc8b90cf24
commit e5dfc7db2f
2 changed files with 15 additions and 14 deletions
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2
README.md
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@ -15,7 +15,7 @@ Use [xasm](https://github.com/pfusik/xasm).
The routine uses three memory areas:
* `inflate` - code and initialized data (508 bytes)
* `inflate` - code and constants (504 bytes)
* `inflate_data` - uninitialized data (764 bytes)
* `inflate_zp` - variables on zero page

27
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 508 bytes of code and initialized data
; inflate is 504 bytes of code and constants
; inflate_data is 764 bytes of uninitialized data
; inflate_zp is 10 bytes on page zero
@ -24,13 +24,13 @@ inflateStoredBlock_pageCounter equ inflate_zp+5 ; 1 byte
inflateCodes_sourcePointer equ inflate_zp+6 ; 2 bytes
inflateDynamicBlock_lengthIndex equ inflate_zp+6 ; 1 byte
inflateDynamicBlock_lastLength equ inflate_zp+7 ; 1 byte
inflateDynamicBlock_lastLength equ inflate_zp+7 ; 1 byte
inflateDynamicBlock_tempCodes equ inflate_zp+7 ; 1 byte
inflateCodes_lengthMinus2 equ inflate_zp+8 ; 1 byte
inflateDynamicBlock_allCodes equ inflate_zp+8 ; 1 byte
inflateCodes_primaryCodes equ inflate_zp+9 ; 1 byte
inflateDynamicBlock_primaryCodes equ inflate_zp+9 ; 1 byte
; Argument values for getBits
@ -123,7 +123,6 @@ inflateFixedBlock_setControlCodeLength
inflateFixedBlock_noControlSymbol
iny
bne inflateFixedBlock_setCodeLengths
mva #LENGTH_SYMBOLS inflateCodes_primaryCodes
dex
beq inflateCodes
@ -142,11 +141,11 @@ inflateDynamicBlock_decodeLength
; Fetch a temporary code
jsr fetchPrimaryCode
; Temporary code 0..15: put this length
tax
bpl inflateDynamicBlock_verbatimLength
; Temporary code 16: repeat last length 3 + getBits(2) times
; Temporary code 17: put zero length 3 + getBits(3) times
; Temporary code 18: put zero length 11 + getBits(7) times
tax
jsr getBits
; sec
adc #1
@ -171,8 +170,13 @@ inflateDynamicBlock_storeNext
; jmp inflateDynamicBlock_decodeLength
beq inflateDynamicBlock_decodeLength
inflateDynamicBlock_controlSymbolCodeLength
cpx inflateCodes_primaryCodes
scc:ora #DISTANCE_TREE
cpx inflateDynamicBlock_primaryCodes
bcc inflateDynamicBlock_storeControl
; the code lengths we skip here were zero-initialized
; in inflateDynamicBlock_clearCodeLengths
sne:ldx #LENGTH_SYMBOLS
ora #DISTANCE_TREE
inflateDynamicBlock_storeControl
sta controlSymbolCodeLength,x+
cpx inflateDynamicBlock_allCodes
bcc inflateDynamicBlock_storeNext
@ -186,7 +190,6 @@ inflateCodes
inflateCodes_loop
jsr fetchPrimaryCode
bcc inflateStoreByte
tax
beq inflate_nextBlock
; Copy sequence from look-behind buffer
; ldy #0
@ -211,9 +214,6 @@ inflateCodes_setSequenceLength
sta inflateCodes_lengthMinus2
ldx #DISTANCE_TREE
jsr fetchCode
; sec
sbc inflateCodes_primaryCodes
tax
cmp #4
bcc inflateCodes_setOffsetLowByte
inc getBits_base
@ -260,7 +260,6 @@ inflateDynamicBlock_getHeader
; sec
adc inflateDynamicBlock_headerBase-1,x
sta inflateDynamicBlock_tempCodes-1,x
sta inflateDynamicBlock_headerBase+1
dex
bne inflateDynamicBlock_getHeader
@ -353,6 +352,8 @@ fetchCode_control
adc nBitCode_controlOffset-1,x
tax
lda codeToControlSymbol-1,x
and #$1f ; make distance symbols zero-based
tax
sec
rts
@ -422,7 +423,7 @@ tempCodeLengthOrder
dta GET_2_BITS,GET_3_BITS,GET_7_BITS,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15
inflateDynamicBlock_headerBits dta GET_4_BITS,GET_5_BITS,GET_5_BITS
inflateDynamicBlock_headerBase dta 3,0,0 ; second byte is modified at runtime!
inflateDynamicBlock_headerBase dta 3,LENGTH_SYMBOLS,0
org inflate_data