dranke/upkr
1
0
Fork 0
mirror of https://github.com/exoticorn/upkr.git synced 2026-01-20 11:36:42 +01:00
Code Issues Projects Releases Wiki Activity

z80_unpacker: optimisation: -1B in decode_number (fwd 170B / rev 167B)

Browse Source 
slightly slower code, ROM unpack is back to ~22.6s
This commit is contained in:
Peter Helcmanovsky (Ped)
2022-09-19 13:20:44 +02:00
parent e1f9fa143a
commit a8fd3dc573
2 changed files with 3 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

BIN
z80_unpacker/example/example.sna
View File

Binary file not shown.

7
z80_unpacker/unpack.asm
View File

@@ -301,13 +301,12 @@ decode_number:
; BC = probs+context_index-1
; A' = upkr_current_byte (!!! init to 0x80 at start, not 0x00)
; return length in DE, CF=0
ld de,$7FFF ; length = 0 with positional-stop-bit
jr .loop_entry
ld de,$FFFF ; length = 0 with positional-stop-bit
or a ; CF=0 to skip getting data bit and use only `rr d : rr e` to fix init DE
.loop:
call inc_c_decode_bit ; context_index + 1
call c,inc_c_decode_bit ; get data bit, context_index + 1 / if CF=0 just add stop bit into DE init
rr d
rr e ; DE = length = (length >> 1) | (bit << 15);
.loop_entry:
call inc_c_decode_bit ; context_index += 2
jr c,.loop
.fix_bit_pos: