mirror of https://github.com/cc65/cc65.git
214 lines
5.4 KiB
ArmAsm
214 lines
5.4 KiB
ArmAsm
;
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; Ullrich von Bassewitz, 2002-11-22, 2004-05-14
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;
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; size_t __fastcall__ fread (void* buf, size_t size, size_t count, FILE* file);
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; /* Read from a file */
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;
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.export _fread
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.import _read
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.import pusha0, pushax
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.import incsp4, incsp6
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.import ldaxysp, ldax0sp
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.import pushwysp
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.import tosumulax, tosudivax
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.importzp ptr1, sp
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.include "errno.inc"
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.include "_file.inc"
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.macpack generic
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; ------------------------------------------------------------------------
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; Code
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.proc _fread
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; We will place a pointer to the file descriptor into the register bank
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.import regbank: zp
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file = regbank
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; Save two bytes from the register bank
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ldy file+0
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sty save
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ldy file+1
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sty save+1
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; Save the file pointer into the register bank
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sta file
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stx file+1
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; Check if the file is open
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ldy #_FILE::f_flags
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lda (file),y
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and #_FOPEN ; Is the file open?
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beq @L1 ; Branch if no
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; Check if the stream is in an error state
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lda (file),y ; get file->f_flags again
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and #_FERROR
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beq @L2
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; File not open or in error state
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@L1: lda #EINVAL
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jsr __seterrno ; Set __errno, return zero in A
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tax ; a/x = 0
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jmp @L99 ; Bail out
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; Remember if we have a pushed back character and reset the flag.
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@L2: tax ; X = 0
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lda (file),y
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and #_FPUSHBACK
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beq @L3
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lda (file),y
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and #<~_FPUSHBACK
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sta (file),y ; file->f_flags &= ~_FPUSHBACK;
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inx ; X = 1
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@L3: stx pb
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; Build the stackframe for read()
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ldy #_FILE::f_fd
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lda (file),y
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jsr pusha0 ; file->f_fd
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ldy #9
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jsr pushwysp ; buf
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; Stack is now: buf/size/count/file->fd/buf
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; Calculate the number of bytes to read: count * size
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ldy #7
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jsr pushwysp ; count
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ldy #9
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jsr ldaxysp ; Get size
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jsr tosumulax ; count * size -> a/x
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; Check if count is zero.
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cmp #0
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bne @L4
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cpx #0
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bne @L4
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; Count is zero, drop the stack frame just built and return count
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jsr incsp4 ; Drop file->fd/buf
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jsr ldax0sp ; Get count
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jmp @L99 ; Bail out
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; Check if we have a buffered char from ungetc
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@L4: ldy pb
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beq @L6
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; We have a buffered char from ungetc. Save the low byte from count
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pha
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; Copy the buffer pointer into ptr1, and increment the pointer value passed
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; to read() by one, so read() starts to store data at buf+1.
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ldy #0
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lda (sp),y
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sta ptr1
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add #1
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sta (sp),y
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iny
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lda (sp),y
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sta ptr1+1
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adc #0
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sta (sp),y ; ptr1 = buf++;
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; Get the buffered character and place it as first character into the read
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; buffer.
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ldy #_FILE::f_pushback
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lda (file),y
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ldy #0
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sta (ptr1),y ; *buf = file->f_pushback;
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; Restore the low byte of count and decrement count by one. This may result
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; in count being zero, so check for that.
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pla
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sub #1
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bcs @L5
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dex
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@L5: cmp #0
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bne @L6
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cpx #0
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beq @L8
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; Call read(). This will leave the original 3 params on the stack
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@L6: jsr _read
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; Check for errors in read
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cpx #$FF
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bne @L8
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cmp #$FF
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bne @L8
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; Error in read. Set the stream error flag and bail out. errno has already
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; been set by read(). On entry to label @L7, X must be zero.
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inx ; X = 0
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lda #_FERROR
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@L7: ldy #_FILE::f_flags ; X must be zero here!
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ora (file),y
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sta (file),y
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txa ; a/x = 0
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beq @L99 ; Return zero
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; Read was ok, account for the pushed back character (if any).
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@L8: add pb
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bcc @L9
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inx
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; Check for end of file.
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@L9: cmp #0 ; Zero bytes read?
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bne @L10
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cpx #0
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bne @L10
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; Zero bytes read. Set the EOF flag
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lda #_FEOF
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bne @L7 ; Set flag and return zero
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; Return the number of items successfully read. Since we've checked for
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; bytes == 0 above, size cannot be zero here, so the division is safe.
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@L10: jsr pushax ; Push number of bytes read
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ldy #5
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jsr ldaxysp ; Get size
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jsr tosudivax ; bytes / size -> a/x
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@L99: ldy save ; Restore zp register
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sty file
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ldy save+1
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sty file+1
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jmp incsp6 ; Drop params, return
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.endproc
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; ------------------------------------------------------------------------
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; Data
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.bss
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save: .res 2
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pb: .res 1
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