uzix/zx-midiplayer
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file_get_next_byte: tiny optimization

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Eugene Lozovoy
2023-05-25 18:42:24 +03:00
parent 4c6372cb90
commit d545c9fc0e
2 changed files with 28 additions and 20 deletions
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1
README.md
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@ -24,4 +24,5 @@ You may use addon with builtin MIDI synthesizer or connect an external one to yo
- Handle last entry in playlist
- Implement FAT32 support
- Implement DivMMC, ZXMMC and Z-Controller support
- Support for >64Kb files
- Correctly handle TRDOS-less environment

47
src/file.asm
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@ -8,8 +8,11 @@
; 6 110 slow
; 7 111 altscr slow slow
file_pages:
db #10, #14, #16, #13
file_page0 equ #10
file_page1 equ #14
file_page2 equ #16
file_page3 equ #13
file_pages: db file_page0, file_page1, file_page2, file_page3
file_base_addr equ #c000
file_page_size equ #4000
@ -21,26 +24,30 @@ file_page_size equ #4000
; OUT - F - garbage
; OUT - BC - garbage
file_get_next_byte:
ld a, h ; compare requested page with current page
and #c0 ; ...
.pg:cp #0f ; ... self modifying code! see bellow and file_load
jp z, .get ; ...
ld a, h ; compare requested page with current page
and #c0 ; ...
.pg:cp #0f ; ... self modifying code! see bellow and file_load
jp z, .get ; ...
.switch_page:
ld (.pg+1), a ;
ld bc, #7ffd ;
or a : jp nz, 1f : ld a, (file_pages+0) : out (c), a : jp .get ;
1: cp #40 : jp nz, 1f : ld a, (file_pages+1) : out (c), a : jp .get ;
1: cp #80 : jp nz, 1f : ld a, (file_pages+2) : out (c), a : jp .get ;
1: ld a, (file_pages+3) : out (c), a : jp .get ;
ld (.pg+1), a ;
.4 rrca ; A = 0/4/8/12
ld (.A+1), a ;
.A jr $ ;
ld a, file_page0 : jr 1f ; 2 bytes + 2 bytes
ld a, file_page1 : jr 1f ;
ld a, file_page2 : jr 1f ;
ld a, file_page3 ;
1: ld bc, #7ffd ;
out (c), a ;
.get:
ld a, h ; position = position[5:0]
and #3f ; ...
add high file_base_addr ; A = *(base_addr + position)
ld b, a ; ...
ld c, l ; ...
ld a, (bc) ; ...
inc hl ; position++
ret ;
ld a, h ; position = position[5:0]
and #3f ; ...
add high file_base_addr ; A = *(base_addr + position)
ld b, a ; ...
ld c, l ; ...
ld a, (bc) ; ...
inc hl ; position++
ret ;