Applecorn/buffer.s
2022-10-15 10:43:30 +01:00

289 lines
11 KiB
ArmAsm

* BUFFER.S
* Buffer handling code
* Code to call buffer handlers
* ============================
* Flush buffer - to do
* ====================
BUFFLUSHALL RTS
BUFFLUSH RTS
* Attempt to insert byte in buffer, waiting until done or aborted
* ===============================================================
* On entry, X=buffer number
* A=byte to insert
* On exit, CC=Successful
* CS=Aborted with Escape
*
BUFINSERT PHP
BUFINSERTLP SEI ; Disable interrupts
JSR JMPINSV ; Attempt to insert byte
BCC BUFINSERTOK ; If successful exit
JSR ESCPOLL ; We have a foreground keyboard
; so we have to poll the hardware
BMI BUFINSERTBAD ; Escape pending, so abort with CS
CLI ; Allow interrupts for a few cycles
BPL BUFINSERTLP ; And loop around and try again
BUFINSERTOK PLP ; Restore IRQs
CLC ; CC=Ok
RTS
BUFINSERTBAD PLP ; Restore IRQs
SEC ; CS=Aborted
RTS
* OSBYTE &99 - Put byte in buffer checking for Escape
* ===================================================
* On entry, X =buffer number
* Y =character to be written
* On exit, If not Escape character
* X =preserved
* Y =corrupted
* CS=buffer full, couldn't insert
* CC=buffer wasn't full, insertion successful
* If Escape character
* X =corrupted
* Y =corrupted
*
BYTE99 TYA ; A character to write
EOR FXESCCHAR ; Is it current Escape character
ORA FXESCON ; And is it ASCII or Escape
BNE BYTE8A ; If Escape is ASCII or not Escape, insert it
LDA FX200VAR ; Is Escape ignored?
ROR A ; Move bit 0 into Carry to test it
BCS BYTE99A ; Escape completely ignored, exit
JSR BYTE7D ; Set pending Escape
BYTE99A CLC ; Exit with CLC
RTS
* OSBYTE &8E - Insert byte in buffer
* ==================================
* On entry, X =buffer number
* Y =byte to be written
* On exit, X =preserved
* A =preserved
* Y =corrupted
* CS=buffer full, couldn't insert
* CC=buffer wasn't full, insertion successful
*
BYTE8A TYA ; A=character to enter
JMPINSV JMP (INSV) ; Pass on to buffer handler
* OSBYTE &91 - Get byte from Buffer
* =================================
* On entry, X =buffer number
* On exit, X =preserved
* CS=buffer empty
* Y corrupted
* CC=buffer not empty
* Y=byte from buffer
*
BYTE91 CLV ; Clear V
BVC JMPREMV ; Pass on to buffer handler
* OSBYTE &9A - Examine Buffer
* ===========================
* On entry, X =buffer number
* On exit, X =preserved
* CS=buffer empty
* Y corrupted
* CC=buffer not empty
* Y=byte at top of buffer
*
BYTE9A BIT SETV ; Set V
JMPREMV JMP (REMV) ; Pass on to buffer handler
* Buffer handling code, called by INSV, REMV, CNPV
* ================================================
* Location and sizes of buffers
* -----------------------------
BUF4 EQU $0340
BUF4SZ EQU 16
BUF5 EQU $0350
BUF5SZ EQU 16
BUF6 EQU $0360
BUF6SZ EQU 16
BUF7 EQU $0370
BUF7SZ EQU 16
BUF3 EQU $0380
BUF3SZ EQU 64
BUFBASE EQU $03C0 ; Base of buffer workspace
BUF0 EQU $03E0
BUF0SZ EQU 32
BUF2 EQU $0C00 ; Also transient program area
BUF2SZ EQU 192
BUF8 EQU $0CC0 ; Also transient program area
BUF8SZ EQU 64
BUF1 EQU $0D00 ; Also transient program area
BUF1SZ EQU 256
* The buffers are arranged so that an offset of &FF is the last entry, and
* incrementing to &00 passes the end of the buffer. A buffer is empty when
* BUFINP=BUFOUT, and is full when BUFINP+1=BUFOUT.
* BUFFER ADDRESS LOW BYTE LOOKUP TABLE
* ------------------------------------
* start+len
BUFLO DB (BUF0 + BUF0SZ - 256) AND 255 ; keyboard
DB (BUF1 + BUF1SZ - 256) AND 255 ; serial input
DB (BUF2 + BUF2SZ - 256) AND 255 ; serial output
DB (BUF3 + BUF3SZ - 256) AND 255 ; printer
DB (BUF4 + BUF4SZ - 256) AND 255 ; sound 0
DB (BUF5 + BUF5SZ - 256) AND 255 ; sound 1
DB (BUF6 + BUF6SZ - 256) AND 255 ; sound 2
DB (BUF7 + BUF7SZ - 256) AND 255 ; sound 3
DB (BUF8 + BUF8SZ - 256) AND 255 ; speech
* BUFFER ADDRESS HIGH BYTE LOOKUP TABLE
* -------------------------------------
* start+len
BUFHI DB (BUF0 + BUF0SZ - 256) DIV 256 ; keyboard
DB (BUF1 + BUF1SZ - 256) DIV 256 ; serial input
DB (BUF2 + BUF2SZ - 256) DIV 256 ; serial output
DB (BUF3 + BUF3SZ - 256) DIV 256 ; printer
DB (BUF4 + BUF4SZ - 256) DIV 256 ; sound 0
DB (BUF5 + BUF5SZ - 256) DIV 256 ; sound 1
DB (BUF6 + BUF6SZ - 256) DIV 256 ; sound 2
DB (BUF7 + BUF7SZ - 256) DIV 256 ; sound 3
DB (BUF8 + BUF8SZ - 256) DIV 256 ; speech
* BUFFER START ADDRESS OFFSET
* ---------------------------
* len
BUFOFF DB 256-BUF0SZ
DB 256-BUF1SZ
DB 256-BUF2SZ
DB 256-BUF3SZ
DB 256-BUF4SZ
DB 256-BUF5SZ
DB 256-BUF6SZ
DB 256-BUF7SZ
DB 256-BUF8SZ
BUFNUM EQU BUFHI-BUFLO ; Number of buffers
BUFFLG EQU BUFBASE+0*BUFNUM ; Buffer flags
BUFINP EQU BUFBASE+1*BUFNUM ; Input pointers
BUFOUT EQU BUFBASE+2*BUFNUM ; Output pointers
* Get buffer base address
* -----------------------
* On entry, X=buffer number (not checked)
* On exit, (OSINTWS)=>buffer base
BUFADDR LDA BUFLO,X
STA OSINTWS+0 ; Get buffer base address low
LDA BUFHI,X
STA OSINTWS+1 ; Get buffer base address high
RTS
* REMV buffer remove
* ==================
* On entry, X =buffer number
* VS=examine buffer
* VC=remove from buffer
* On exit, X =preserved
* CS=buffer empty
* A,Y corrupted
* CC=buffer not empty
* A=Y=byte from buffer
* If called to remove from buffer, pointers updated
*
BUFREM PHP ; Save flags
SEI ; Disable IRQs
CPX #BUFNUM ; Valid buffer number?
BCS BUFFAIL ; No, return 'empty'
LDA BUFOUT,X ; Get output pointer for buffer X
CMP BUFINP,X ; Compare it to input pointer
BEQ BUFFAIL ; Equal, so buffer is empty
TAY ; Y=output pointer
JSR BUFADDR ; Get buffer base address
LDA (OSINTWS),Y ; Get byte from buffer
BVS BUFREM2 ; If VS, just examine buffer, return
INY ; Otherwise, update buffer pointer
BNE BUFREM1 ; Not zero, not reached end of buffer
LDY BUFOFF,X ; Get offset to start of buffer
BUFREM1 STY BUFOUT,X ; Update the buffer output pointer
BUFREM2 TAY ; Return A=Y=byte from buffer
BUFREMOK PLP ; Restore IRQs
CLC ; CLC=success
RTS
* INSV buffer insert
* ==================
* On entry, X =buffer number
* A =byte to be inserted
* On exit, X =preserved
* A =preserved
* Y =corrupted
* CS=buffer full, couldn't insert
* CC=buffer wasn't full, insertion successful
*
BUFINS PHP ; Save flags
SEI ; Disable IRQs
CPX #BUFNUM ; Valid buffer number?
BCS BUFINS2 ; No, sink it and return 'ok'
PHA ; Save A
LDY BUFINP,X ; Get buffer input pointer
INY ; Otherwise, update buffer pointer
BNE BUFINS1 ; Not zero, not reached end of buffer
LDY BUFOFF,X ; Get offset to start of buffer
BUFINS1 TYA ; A=updated input pointer
CMP BUFOUT,X ; Compare with output pointer
BEQ BUFINS4 ; Same, buffer is full, exit with 'failed'
LDY BUFINP,X ; Get unupdated input pointer back
STA BUFINP,X ; Store updated input pointer
JSR BUFADDR ; Get buffer base address
PLA ; Get the byte back
STA (OSINTWS),Y ; And store it in buffer
BUFINS2 PLP ; Restore IRQs
CLC ; CLC=success
RTS
BUFINS4 PLA ; Restore A
BUFFAIL PLP ; Restore IRQs
SEC ; SEC=failed
RTS
* CNPV count/purge buffer
* =======================
* On entry, X =buffer number
* VC=purge (clear) buffer
* VS=count buffer
* CC=count used space
* CS=count free space
* On exit, XY=size counted
* A =corrupted
*
BUFCNP CPX #BUFNUM ; Valid buffer number?
BCS BUFCNP1 ; No, ignore it
BVC BUFCNT1 ; VS, count buffer
LDA BUFOUT,X ; Set input=output, empty buffer
STA BUFINP,X
BUFCNP1 BVS BUFCNT5 ; Purged, exit
LDX #$00
BEQ BUFCNT4 ; Count, return zero
BUFCNT1 PHP ; Save flags
SEI ; Disable IRQs
SEC ; Prepare for SBC
LDA BUFOUT,X ; Get output pointer
SBC BUFINP,X ; Subtract input pointer
BCS BUFCNT2 ; No overflow, use it
SEC ; Prepare for SBC
SBC BUFOFF,X ; Subtract buffer start offset
BUFCNT2 PLP ; Get flags back, also restore IRQs
BCC BUFCNT3 ; CLC, exit with size counted
CLC ; Prepare for ADC
ADC BUFOFF,X ; Add buffer offset to get NEG(bytes free)
EOR #$FF ; Invert it to get free space
BUFCNT3 TAX ; YX=count
BUFCNT4 LDY #$00 ; All our buffers are <256 bytes
BUFCNT5 RTS