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cc65/libsrc/cbm/read.s
2013-12-23 12:20:28 -05:00

160 lines
3.8 KiB
ArmAsm

;
; 2002-11-16, Ullrich von Bassewitz
; 2013-12-23, Greg King
;
; int read (int fd, void* buf, unsigned count);
;
.export _read
.constructor initstdin
.import SETLFS, OPEN, CHKIN, BASIN, CLRCH, BSOUT, READST
.import rwcommon
.import popax
.importzp ptr1, ptr2, ptr3, tmp1, tmp2, tmp3
.include "cbm.inc"
.include "errno.inc"
.include "fcntl.inc"
.include "filedes.inc"
;--------------------------------------------------------------------------
; initstdin: Open the stdin file descriptors for the keyboard
.segment "INIT"
.proc initstdin
lda #LFN_READ
sta fdtab+STDIN_FILENO
lda #STDIN_FILENO + LFN_OFFS
ldx #CBMDEV_KBD
stx unittab+STDIN_FILENO
ldy #$FF
jsr SETLFS
jmp OPEN ; Will always succeed
.endproc
;--------------------------------------------------------------------------
; _read
.code
.proc _read
jsr rwcommon ; Pop params, check handle
bcs invalidfd ; Invalid handle
; Check if the LFN is valid and the file is open for writing
adc #LFN_OFFS ; Carry is already clear
tax
lda fdtab-LFN_OFFS,x; Get flags for this handle
tay
and #LFN_READ ; File open for writing?
beq invalidfd
; Check the EOF flag. If it is set, don't read anything
tya ; Get flags again
bmi eof
; Remember the device number.
ldy unittab-LFN_OFFS,x
sty unit
; Valid lfn. Make it the input file
jsr CHKIN
bcc @L3 ; Branch if ok
jmp __mappederrno ; Store into __oserror, map to errno, return -1
; Read the next byte
@L0: jsr BASIN
sta tmp1 ; Save the input byte
ldx unit
bne @L0_1 ; Not keyboard/screen-editor
cmp #$0D ; Is it a Carriage Return?
bne @L0_1
jsr BSOUT ; Yes, echo it (because editor didn't)
@L0_1: jsr READST ; Read the IEEE status
sta tmp3 ; Save it
and #%10111111 ; Check anything but the EOI bit
bne devnotpresent ; Assume device not present
; Store the byte just read
ldy #0
lda tmp1
sta (ptr2),y
inc ptr2
bne @L1
inc ptr2+1 ; *buf++ = A;
; Increment the byte count
@L1: inc ptr3
bne @L2
inc ptr3+1
; Get the status again and check the EOI bit
@L2: lda tmp3
and #%01000000 ; Check for EOI
bne @L4 ; Jump if end of file reached
; Decrement the count
@L3: inc ptr1
bne @L0
inc ptr1+1
bne @L0
beq done ; Branch always
; Set the EOI flag and bail out
@L4: ldx tmp2 ; Get the handle
lda #LFN_EOF
ora fdtab,x
sta fdtab,x
; Read done, close the input channel
done: jsr CLRCH
; Clear _oserror and return the number of chars read
eof: lda #0
sta __oserror
lda ptr3
ldx ptr3+1
rts
; Error entry: Device not present
devnotpresent:
lda #ENODEV
jmp __directerrno ; Sets _errno, clears _oserror, returns -1
; Error entry: The given file descriptor is not valid or not open
invalidfd:
lda #EBADF
jmp __directerrno ; Sets _errno, clears _oserror, returns -1
.endproc
;--------------------------------------------------------------------------
.bss
unit: .res 1