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100 lines
2.4 KiB
ArmAsm
100 lines
2.4 KiB
ArmAsm
;
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; Ullrich von Bassewitz, 2012-06-01
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;
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; Helper functions for open-/read-/closedir
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.include "dir.inc"
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.include "errno.inc"
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.include "zeropage.inc"
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.import pushax
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.import _read
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;---------------------------------------------------------------------------
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;
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; unsigned char __fastcall__ _dirread1 (DIR* dir, void* buf);
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; /* Read one byte from the directory into the supplied buffer. Makes sure,
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; ** errno is set in case of a short read. Return true if the read was
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; ** successful and false otherwise.
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; */
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__dirread1:
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jsr pushax ; Push buf
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lda #1 ; Load count = 1
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; Run directly into __dirread
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;---------------------------------------------------------------------------
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;
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; unsigned char __fastcall__ _dirread (DIR* dir, void* buf, unsigned char count);
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; /* Read characters from the directory into the supplied buffer. Makes sure,
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; ** errno is set in case of a short read. Return true if the read was
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; ** successful and false otherwise.
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; */
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__dirread:
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; Save count
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pha
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; Replace dir by dir->fd
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ldy #2
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lda (sp),y
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sta ptr1
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iny
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lda (sp),y
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sta ptr1+1
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ldy #DIR::fd+1
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lda (ptr1),y
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pha
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dey
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lda (ptr1),y
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ldy #2
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sta (sp),y
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pla
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iny
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sta (sp),y
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; Get count, save it again, clear the high byte and call read(). By the
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; previous actions, the stack frame is as read() needs it, and read() will
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; also drop it.
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pla
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pha
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ldx #0
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jsr _read
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; Check for errors.
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cpx #$FF
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bne L3
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; read() returned an error, so errno is already set
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pla ; Drop count
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inx ; X = 0
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L1: txa ; Return zero
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L2: rts
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; read() was successful, check number of bytes read. We assume that read will
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; not return more than count, so X is zero if we come here.
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L3: sta tmp1 ; Save returned count
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pla ; Our count
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cmp tmp1
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beq L2 ; Ok, return count
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; Didn't read enough bytes. This is an error for us, but errno is not set
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lda #<EIO
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sta __errno
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stx __errno+1 ; X is zero
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bne L1 ; Branch always
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