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Implement special read function that sets errno in case of a short read. Drop

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_dirskip in favour of the new function.


git-svn-id: svn://svn.cc65.org/cc65/trunk@5672 b7a2c559-68d2-44c3-8de9-860c34a00d81
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uz
2012-06-03 13:59:31 +00:00
parent 9d0a2c3007
commit a83bf3dc04
5 changed files with 91 additions and 79 deletions
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113
libsrc/cbm/dir.s
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@@ -1,92 +1,99 @@
;
; Ullrich von Bassewitz, 2012-06-01
;
; unsigned char __fastcall__ _dirskip (unsigned char count, struct DIR* dir);
; /* Skip bytes from the directory and make sure, errno is set if this isn't
; * possible. Return true if anything is ok and false otherwise. For
; * simplicity we assume that read will never return less than count if there
; * is no error and end-of-file is not reached.
; * Note: count must not be more than 254.
; */
;
; Helper functions for open-/read-/closedir
.include "dir.inc"
.include "errno.inc"
.include "zeropage.inc"
.import pushax
.import _read
.import pushax, pushptr1idx
.import subysp, addysp1
.proc __dirskip
;---------------------------------------------------------------------------
;
; unsigned char __fastcall__ _dirread1 (DIR* dir, void* buf);
; /* Read one byte from the directory into the supplied buffer. Makes sure,
; * errno is set in case of a short read. Return true if the read was
; * successful and false otherwise.
; */
sta ptr1
stx ptr1+1 ; Save dir
__dirread1:
; Get count and allocate space on the stack
jsr pushax ; Push buf
lda #1 ; Load count = 1
ldy #0
; Run directly into __dirread
;---------------------------------------------------------------------------
;
; unsigned char __fastcall__ _dirread (DIR* dir, void* buf, unsigned char count);
; /* Read characters from the directory into the supplied buffer. Makes sure,
; * errno is set in case of a short read. Return true if the read was
; * successful and false otherwise.
; */
__dirread:
; Save count
pha
; Replace dir by dir->fd
ldy #2
lda (sp),y
pha
tay
jsr subysp
; Save current value of sp
lda sp
pha
lda sp+1
pha
; Push dir->fd
sta ptr1
iny
lda (sp),y
sta ptr1+1
ldy #DIR::fd+1
jsr pushptr1idx
; Push pointer to buffer
lda (ptr1),y
pha
dey
lda (ptr1),y
ldy #2
sta (sp),y
pla
tax
pla
jsr pushax
iny
sta (sp),y
; Load count and call read
; Get count, save it again, clear the high byte and call read(). By the
; previous actions, the stack frame is as read() needs it, and read() will
; also drop it.
pla
pha
ldx #0
jsr _read
; Check for errors. In case of errors, errno is already set.
; Check for errors.
cpx #$FF
bne L2
bne L3
; read() returned an error
; read() returned an error, so errno is already set
pla ; Count
tay
lda #0
tax
L1: jmp addysp1 ; Drop buffer plus count
pla ; Drop count
inx ; X = 0
L1: txa ; Return zero
L2: rts
; read() was successful, check number of bytes read. We assume that read will
; not return more than count, so X is zero if we come here.
L2: sta tmp1
pla ; count
tay
L3: sta tmp1 ; Save returned count
pla ; Our count
cmp tmp1
beq L1 ; Drop variables, return count
beq L2 ; Ok, return count
; Didn't read enough bytes. This is an error for us, but errno is not set
lda #<EIO
sta __errno
stx __errno+1
txa ; A=X=0
beq L1 ; Branch always
stx __errno+1 ; X is zero
bne L1 ; Branch always
.endproc