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185 lines
3.4 KiB
ArmAsm
185 lines
3.4 KiB
ArmAsm
;
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; Low level file I/O routines, ONLY for module loading OR sth similar
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;
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; Maciej 'YTM/Elysium' Witkowiak <ytm@elysium.pl>
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; 25.12.2002
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;
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; only ONE opened file at a time, only O_RDONLY flag
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; int open (const char* name, int flags, ...); /* May take a mode argument */
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; int __fastcall__ close (int fd);
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; int __fastcall__ read (int fd, void* buf, unsigned count);
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FILEDES = 3 ; first free to use file descriptor
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.include "../inc/geossym.inc"
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.include "../inc/const.inc"
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.include "fcntl.inc"
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.importzp ptr1, ptr2, ptr3, tmp1
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.import addysp, popax
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.import __oserror
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.import _FindFile, _ReadByte
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.export _open, _close, _read
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;--------------------------------------------------------------------------
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; _open
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_open:
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cpy #4 ; correct # of arguments (bytes)?
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beq @parmok ; parameter count ok
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tya ; parm count < 4 shouldn't be needed to be...
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sec ; ...checked (it generates a c compiler warning)
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sbc #4
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tay
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jsr addysp ; fix stack, throw away unused parameters
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; Parameters ok. Pop the flags and save them into tmp3
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@parmok:
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jsr popax ; Get flags
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sta tmp1
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jsr popax ; Get name
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sta ptr1
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stx ptr1+1
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lda filedesc ; is there a file already open?
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bne @alreadyopen
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lda tmp1 ; check open mode
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and #(O_RDWR | O_CREAT)
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cmp #O_RDONLY ; only O_RDONLY is valid
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bne @badmode
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lda ptr1
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ldx ptr1+1
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jsr _FindFile ; try to find the file
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bne @error
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lda dirEntryBuf + OFF_DE_TR_SC ; tr&se for ReadByte (r1)
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sta f_track
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lda dirEntryBuf + OFF_DE_TR_SC + 1
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sta f_sector
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lda #<diskBlkBuf ; buffer for ReadByte (r4)
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sta f_buffer
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lda #>diskBlkBuf
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sta f_buffer+1
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ldx #0 ; offset for ReadByte (r5)
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stx f_offset
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stx f_offset+1
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lda #FILEDES ; return fd
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sta filedesc
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rts
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@badmode:
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@alreadyopen:
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lda #70 ; no channel
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sta __oserror
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@error:
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lda #$ff
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tax
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rts
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_close:
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lda #0 ; clear fd
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sta filedesc
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tax
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rts
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_read:
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; a/x - number of bytes
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; popax - buffer ptr
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; popax - fd, must be == to the above one
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; return -1+__oserror or number of bytes read
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eor #$ff
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sta ptr1
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txa
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eor #$ff
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sta ptr1+1 ; -(# of bytes to read)-1
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jsr popax
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sta ptr2
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stx ptr2+1 ; buffer ptr
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jsr popax
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cmp #FILEDES
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bne @notopen
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txa
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bne @notopen ; fd must be == FILEDES
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lda #0
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sta ptr3
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sta ptr3+1 ; put 0 into ptr3 (number of bytes read)
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lda f_track ; restore stuff for ReadByte
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ldx f_sector
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sta r1L
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stx r1H
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lda f_buffer
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ldx f_buffer+1
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sta r4L
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stx r4H
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lda f_offset
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ldx f_offset+1
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sta r5L
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stx r5H
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clc
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bcc @L3 ; branch always
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@L0: jsr _ReadByte
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ldy #0 ; store the byte
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sta (ptr2),y
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inc ptr2 ; increment target address
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bne @L1
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inc ptr2+1
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@L1: inc ptr3 ; increment byte count
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bne @L2
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inc ptr3+1
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@L2: txa ; was there error ?
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beq @L3
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cmp #BFR_OVERFLOW ; EOF?
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bne @error
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beq @done
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@L3: inc ptr1 ; decrement the count
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bne @L0
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inc ptr1+1
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bne @L0
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@done:
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lda r1L ; preserve data for ReadByte
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ldx r1H
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sta f_track
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stx f_sector
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lda r4L
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ldx r4H
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sta f_buffer
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stx f_buffer+1
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lda r5L
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ldx r5H
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sta f_offset
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stx f_offset+1
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lda ptr3 ; return byte count
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ldx ptr3+1
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rts
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@notopen:
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lda #61 ; File not open
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@error:
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sta __oserror
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lda #$ff
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tax
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rts
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.bss
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filedesc: .res 1 ; file open flag - 0 (no file opened) or 1
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f_track: .res 1 ; values preserved for ReadByte
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f_sector: .res 1
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f_offset: .res 2
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f_buffer: .res 2
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