6502 command stream player, part 1

doesn't work

src/asm/6502/stream.s

@@ -0,0 +1,187 @@
+; Furnace Command Stream player for 6502 architecture
+; written by tildearrow
+
+; usage:
+; call fcsInit - this sets A to 0 on success or 1 on failure
+; call fcsTick on every frame/tick/whatever
+; - call your dispatch implementation's tick function afterwards
+
+; notes:
+; - short pointers only
+; - little-endian only!
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+; constants
+FCS_MAX_CHANS=8 ; maximum number of channels (up to 127, but see below!)
+FCS_MAX_STACK=16 ; stack depth per channel (FCS_MAX_STACK*FCS_MAX_CHAN<256)
+
+; player constants - change if necessary
+fcsAddrBase=$20 ; player state address base
+fcsGlobalStack=$200 ; player stack (best placed in a page)
+fcsPtr=$8000 ; pointer to command stream
+fcsVolMax=fcsVolMaxExample ; pointer to max channel volume array
+
+; calculated from player constants
+fcsDelays=fcsPtr+8
+fcsSpeedDial=fcsPtr+24
+
+; command call table
+; - see src/engine/dispatch.h for a list of commands to be potentially handled
+;   - do not implement HINT commands - the player will never send these
+;   - no need to implement commands not pertaining to the target system
+; - a zero pointer means "don't handle"
+fcsCmdTable=fcsCmdTableExample
+
+; variables
+; these may be read by your command handling routines
+fcsArg0=fcsAddrBase ; int
+fcsArg1=fcsAddrBase+4 ; int
+; something else
+fcsTicks=fcsAddrBase+8 ; short
+; temporary variables
+fcsSendVolume=fcsAddrBase+10 ; char
+fcsSendPitch=fcsAddrBase+11 ; char
+; channel state
+chanPC=fcsAddrBase+16 ; short
+chanTicks=fcsAddrBase+16+(FCS_MAX_CHAN*2) ; short
+chanStackPtr=fcsAddrBase+16+(FCS_MAX_CHAN*4) ; char
+
+; may be used for driver detection
+fcsDriverInfo:
+  .byte "Furnace"
+  .byte 0
+
+; x: channel*2 (for speed... char variables are interleaved)
+; read commands
+fcsChannelCmd:
+  ; read next byte
+
+  ; process and read arguments
+
+  ; end
+  rts
+
+; x: channel*2
+; stuff that goes after command reading
+fcsChannelPost:
+  ; do volume
+
+  ; do pitch
+
+  ; do portamento
+
+  ; do arpeggio
+
+  ; end
+  rts
+
+; x: channel*2
+fcsDoChannel:
+  ; initialize
+  lda #0
+  sta fcsSendVolume
+  sta fcsSendPitch
+
+  ; check whether this channel is halted (PC = 0)
+  lda chanPC,x
+  ora chanPC+1,x
+  beq :+
+  rts
+  ; channel not halted... begin processing
+  ; chanTicks--
+: lda chanTicks,x
+  sec
+  sbc #1
+  sta chanTicks,x
+  bne :+ ; skip if our counter isn't zero
+
+  ; ticks lower is zero; check upper byte
+  ldy chanTicks+1,x
+  beq fcsDoChannelLoop ; go to read commands if it's zero as well
+  ; decrease ticks upper
+  dey
+  sty chanTicks+1,x
+  ; process channel stuff
+  jsr fcsChannelPost
+  rts
+
+  ; ticks is zero... read commands until chanTicks is set
+  fcsDoChannelLoop:
+    lda chanTicks,x
+    ora chanTicks+1,x
+    bne :+ ; get out if chanTicks is no longer zero
+    jsr fcsChannelCmd ; read next command
+    jmp fcsDoChannelLoop
+
+: jsr fcsChannelPost
+  ; end
+  rts
+
+fcsTick:
+  ; update channel state
+  ; for (x=0; x<FCS_MAX_CHANS; x++)
+  ldx #0
+: jsr fcsDoChannel
+  inx
+  inx
+  cpx #FCS_MAX_CHANS*2
+  bne :-
+
+  ; increase tick counter
+  inc fcsTicks
+  bne :+
+  inc fcsTicks+1
+  
+  ; end
+: rts
+
+fcsInit:
+  ; set all tick counters to 1
+  lda #1
+  ldy #0
+  ldx #(FCS_MAX_CHANS*2)-1
+: sty fcsTicks,x
+  dex
+  sta fcsTicks,x
+  dex
+  bne :-
+
+  ; set channel program counters
+  ldx #(FCS_MAX_CHANS*2)-1
+: lda fcsPtr+40,x
+  sta chanPC,x
+  dex
+  bne :-
+
+  ; TODO: relocate and more...
+
+  ; success
+  lda #0
+  rts
+
+; floor(127*sin((x/64)*(2*pi)))
+fcsVibTable:
+  .byte 0, 12, 24, 36, 48, 59, 70, 80, 89, 98, 105, 112, 117, 121, 124, 126
+  .byte 127, 126, 124, 121, 117, 112, 105, 98, 89, 80, 70, 59, 48, 36, 24, 12
+  .byte 0, -12, -24, -36, -48, -59, -70, -80, -89, -98, -105, -112, -117, -121, -124, -126
+  .byte -126, -126, -124, -121, -117, -112, -105, -98, -89, -80, -70, -59, -48, -36, -24, -12
+
+; "dummy" implementation - example only!
+
+fcsDummyFunc:
+  rts
+
+fcsVolMaxExample:
+  .byte 127, 127, 127, 127, 127, 127, 127, 127
+
+; first 64 commands
+fcsCmdTableExample:
+  .word 0, 0, 0, 0, 0, 0, 0, 0
+  .word 0, 0, 0, 0, 0, 0, 0, 0
+  .word 0, 0, 0, 0, 0, 0, 0, 0
+  .word 0, 0, 0, 0, 0, 0, 0, 0
+  .word 0, 0, 0, 0, 0, 0, 0, 0
+  .word 0, 0, 0, 0, 0, 0, 0, 0
+  .word 0, 0, 0, 0, 0, 0, 0, 0
+  .word 0, 0, 0, 0, 0, 0, 0, 0