1
0
mirror of https://github.com/cc65/cc65.git synced 2024-12-25 02:29:52 +00:00
cc65/libsrc/cbm/dir.s
uz a83bf3dc04 Implement special read function that sets errno in case of a short read. Drop
_dirskip in favour of the new function.


git-svn-id: svn://svn.cc65.org/cc65/trunk@5672 b7a2c559-68d2-44c3-8de9-860c34a00d81
2012-06-03 13:59:31 +00:00

100 lines
2.4 KiB
ArmAsm

;
; Ullrich von Bassewitz, 2012-06-01
;
; Helper functions for open-/read-/closedir
.include "dir.inc"
.include "errno.inc"
.include "zeropage.inc"
.import pushax
.import _read
;---------------------------------------------------------------------------
;
; 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.
; */
__dirread1:
jsr pushax ; Push buf
lda #1 ; Load count = 1
; 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
sta ptr1
iny
lda (sp),y
sta ptr1+1
ldy #DIR::fd+1
lda (ptr1),y
pha
dey
lda (ptr1),y
ldy #2
sta (sp),y
pla
iny
sta (sp),y
; 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.
cpx #$FF
bne L3
; read() returned an error, so errno is already set
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.
L3: sta tmp1 ; Save returned count
pla ; Our count
cmp tmp1
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 ; X is zero
bne L1 ; Branch always