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fasterer v2

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This commit is contained in:
Peter Ferrie 2020-01-06 22:24:07 -08:00
parent fb7e03030f
commit 45b91ddaa2
1 changed files with 105 additions and 3 deletions
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108
asm/6502/decompress_faster_v2.asm
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@ -10,7 +10,7 @@
; Optional code is presented for two minor 6502 optimizations that break
; compatibility with the current LZSA2 format standard.
;
; The code is 241 bytes for the small version, and 256 bytes for the normal.
; The code is 241 bytes for the small version, and 268 bytes for the normal.
;
; Copyright John Brandwood 2019.
;
@ -85,6 +85,13 @@ LZSA_SHORT_CP = 1
LZSA_FROM_BANK = 0
;
; We will read from or write to $FFFF. This prevents the
; use of the "INC ptrhi / BNE" trick and reduces speed.
;
LZSA_USE_FFFF = 0
;
; Macro to increment the source pointer to the next page.
;
@ -190,13 +197,41 @@ DECOMPRESS_LZSA2_FAST:
lzsa2_unpack: ldy #0 ; Initialize source index.
sty <lzsa_nibflg ; Initialize nibble buffer.
!if !(LZSA_FROM_BANK | LZSA_NO_INLINE | LZSA_USE_FFFF) {
beq .cp_length ; always taken
.incsrc1:
inc <lzsa_srcptr + 1
bne .resume_src1 ; always taken
.incsrc2:
inc <lzsa_srcptr + 1
bne .resume_src2 ; always taken
.incdst:
inc <lzsa_dstptr + 1
bne .resume_dst ; always taken
}
;
; Copy bytes from compressed source data.
;
.cp_length: ldx #$00 ; Hi-byte of length or offset.
!if (LZSA_FROM_BANK | LZSA_NO_INLINE | LZSA_USE_FFFF) {
+LZSA_GET_SRC
} else {
lda (lzsa_srcptr),y
inc <lzsa_srcptr + 0
beq .incsrc1
.resume_src1:
}
sta <lzsa_cmdbuf ; Preserve this for later.
and #$18 ; Extract literal length.
beq .lz_offset ; Skip directly to match?
@ -222,12 +257,27 @@ lzsa2_unpack: ldy #0 ; Initialize source index.
.cp_page: lda (lzsa_srcptr),y
sta (lzsa_dstptr),y
inc <lzsa_srcptr + 0
!if (LZSA_FROM_BANK | LZSA_NO_INLINE | LZSA_USE_FFFF) {
bne .skip1
inc <lzsa_srcptr + 1
.skip1: inc <lzsa_dstptr + 0
bne .skip2
inc <lzsa_dstptr + 1
.skip2: dex
.skip2:
} else {
beq .incsrc2
.resume_src2:
inc <lzsa_dstptr + 0
beq .incdst
.resume_dst:
}
dex
bne .cp_page
dec <lzsa_length ; Any full pages left to copy?
bne .cp_page
@ -374,7 +424,19 @@ lzsa2_unpack: ldy #0 ; Initialize source index.
.get_16_bits: jsr lzsa2_get_byte ; Get hi-byte of offset.
tax
.get_low8: +LZSA_GET_SRC ; Get lo-byte of offset.
.get_low8:
!if (LZSA_FROM_BANK | LZSA_NO_INLINE | LZSA_USE_FFFF) {
+LZSA_GET_SRC ; Get lo-byte of offset.
} else {
lda (lzsa_srcptr),y
inc <lzsa_srcptr + 0
beq .incsrc3
.resume_src3:
}
.set_offset: stx <lzsa_offset + 1 ; Save new offset.
sta <lzsa_offset + 0
@ -424,6 +486,14 @@ lzsa2_unpack: ldy #0 ; Initialize source index.
jmp .cp_length ; Loop around to the beginning.
!if !(LZSA_FROM_BANK | LZSA_NO_INLINE | LZSA_USE_FFFF) {
.incsrc3:
inc <lzsa_srcptr + 1
bne .resume_src3 ; always taken
}
;
; Lookup tables to differentiate literal and match lengths.
;
@ -496,7 +566,19 @@ lzsa2_get_nibble:
bcs .got_nibble
inc <lzsa_nibflg ; Reset the flag.
!if (LZSA_FROM_BANK | LZSA_NO_INLINE | LZSA_USE_FFFF) {
+LZSA_GET_SRC
} else {
lda (lzsa_srcptr),y
inc <lzsa_srcptr + 0
beq .incsrc4
.resume_src4:
}
sta <lzsa_nibble ; Preserve for next time.
lsr ; Extract the hi-nibble.
lsr
@ -514,7 +596,19 @@ lzsa2_get_nibble:
lzsa2_new_nibble:
inc <lzsa_nibflg ; Reset the flag.
!if (LZSA_FROM_BANK | LZSA_NO_INLINE | LZSA_USE_FFFF) {
+LZSA_GET_SRC
} else {
lda (lzsa_srcptr),y
inc <lzsa_srcptr + 0
beq .incsrc4
.resume_src4:
}
sta <lzsa_nibble ; Preserve for next time.
lsr ; Extract the hi-nibble.
lsr
@ -528,3 +622,11 @@ lzsa2_new_nibble:
rts
}
!if !(LZSA_FROM_BANK | LZSA_NO_INLINE | LZSA_USE_FFFF) {
.incsrc4:
inc <lzsa_srcptr + 1
bne .resume_src4 ; always taken
}