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|
;
; Low level file I/O routines, ONLY for module loading OR sth similar
;
; Maciej 'YTM/Elysium' Witkowiak <ytm@elysium.pl>
; 25.12.2002
;
; only ONE opened file at a time, only O_RDONLY flag
; int open (const char* name, int flags, ...); /* May take a mode argument */
; int __fastcall__ close (int fd);
; int __fastcall__ read (int fd, void* buf, unsigned count);
FILEDES = 3 ; first free to use file descriptor
.importzp ptr1, ptr2, ptr3, tmp1
.import addysp, popax, popptr1
.import __oserror
.import _FindFile, _ReadByte
.export _open, _close, _read
.include "geossym.inc"
.include "const.inc"
.include "errno.inc"
.include "fcntl.inc"
_open:
cpy #4 ; correct # of arguments (bytes)?
beq @parmok ; parameter count ok
tya ; parm count < 4 shouldn't be needed to be...
sec ; ...checked (it generates a c compiler warning)
sbc #4
tay
jsr addysp ; fix stack, throw away unused parameters
; Parameters ok. Pop the flags and save them into tmp3
@parmok:
jsr popax ; Get flags
sta tmp1
jsr popptr1 ; Get name
lda filedesc ; is there a file already open?
bne @alreadyopen
lda tmp1 ; check open mode
and #(O_RDWR | O_CREAT)
cmp #O_RDONLY ; only O_RDONLY is valid
bne @badmode
lda ptr1
ldx ptr1+1
jsr _FindFile ; try to find the file
tax
bne @oserror
lda dirEntryBuf + OFF_DE_TR_SC ; tr&se for ReadByte (r1)
sta f_track
lda dirEntryBuf + OFF_DE_TR_SC + 1
sta f_sector
lda #<diskBlkBuf ; buffer for ReadByte (r4)
sta f_buffer
lda #>diskBlkBuf
sta f_buffer+1
ldx #0 ; offset for ReadByte (r5)
stx f_offset
stx f_offset+1
lda #0 ; clear errors
sta __oserror
jsr __seterrno
lda #FILEDES ; return fd
sta filedesc
rts
@badmode:
lda #EINVAL ; invalid parameters - invalid open mode
.byte $2c ; skip
@alreadyopen:
lda #EMFILE ; too many opened files (there can be only one)
jmp __directerrno ; set errno, clear oserror, return -1
@oserror:
jmp __mappederrno ; set platform error code, return -1
_close:
lda #0
sta __oserror
jsr __seterrno ; clear errors
lda #0 ; clear fd
sta filedesc
tax
rts
_read:
; a/x - number of bytes
; popax - buffer ptr
; popax - fd, must be == to the above one
; return -1+__oserror or number of bytes read
eor #$ff
sta ptr1
txa
eor #$ff
sta ptr1+1 ; -(# of bytes to read)-1
jsr popax
sta ptr2
stx ptr2+1 ; buffer ptr
jsr popax
cmp #FILEDES ; lo-byte == FILEDES
bne @filenotopen
txa ; hi-byte == 0
beq @fileok ; fd must be == FILEDES
@filenotopen:
lda #EBADF
jmp __directerrno ; Sets _errno, clears _oserror, returns -1
@fileok:
lda #0
sta ptr3
sta ptr3+1 ; put 0 into ptr3 (number of bytes read)
sta __oserror ; clear error flags
jsr __seterrno
lda f_track ; restore stuff for ReadByte
ldx f_sector
sta r1L
stx r1H
lda f_buffer
ldx f_buffer+1
sta r4L
stx r4H
lda f_offset
ldx f_offset+1
sta r5L
stx r5H
clc
bcc @L3 ; branch always
@L0: jsr _ReadByte
ldy #0 ; store the byte
sta (ptr2),y
inc ptr2 ; increment target address
bne @L1
inc ptr2+1
@L1: inc ptr3 ; increment byte count
bne @L2
inc ptr3+1
@L2: lda __oserror ; was there error ?
beq @L3
cmp #BFR_OVERFLOW ; EOF?
beq @done ; yes, we're done
jmp __mappederrno ; no, we're screwed
@L3: inc ptr1 ; decrement the count
bne @L0
inc ptr1+1
bne @L0
@done:
lda r1L ; preserve data for ReadByte
ldx r1H
sta f_track
stx f_sector
lda r4L
ldx r4H
sta f_buffer
stx f_buffer+1
lda r5L
ldx r5H
sta f_offset
stx f_offset+1
lda ptr3 ; return byte count
ldx ptr3+1
rts
.bss
filedesc:
.res 1 ; file open flag - 0 (no file opened) or 1
f_track:
.res 1 ; values preserved for ReadByte
f_sector:
.res 1
f_offset:
.res 2
f_buffer:
.res 2
|
