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cc65/libsrc/common/strncpy.s
cuz cfe7a8c246 Another small improvement
git-svn-id: svn://svn.cc65.org/cc65/trunk@2145 b7a2c559-68d2-44c3-8de9-860c34a00d81
2003-05-04 22:27:20 +00:00

68 lines
1.4 KiB
ArmAsm

;
; Ullrich von Bassewitz, 2003-05-04
;
; char* __fastcall__ strncpy (char* dest, const char* src, unsigned size);
;
.export _strncpy
.import popax
.importzp ptr1, ptr2, tmp1, tmp2, tmp3
.proc _strncpy
eor #$FF
sta tmp1
txa
eor #$FF
sta tmp2 ; Store -size - 1
jsr popax ; get src
sta ptr1
stx ptr1+1
jsr popax ; get dest
sta ptr2
stx ptr2+1
stx tmp3 ; remember for function return
; Copy src -> dest up to size bytes
ldx tmp1 ; Load low byte of ones complement of size
ldy #$00
L1: inx
bne L2
inc tmp2
beq L9
L2: lda (ptr1),y ; Copy one character
sta (ptr2),y
beq L3 ; Bail out if terminator reached
iny
bne L1
inc ptr1+1
inc ptr2+1 ; Bump high bytes
bne L1 ; Branch always
; Fill the remaining bytes. A is zero if we come here
L3: inx
bne L4
inc tmp2
beq L9
L4: sta (ptr2),y
iny
bne L3
inc ptr2+1 ; Bump high byte
bne L3 ; Branch always
; Done, return dest
L9: lda ptr2 ; Get low byte
ldx tmp3 ; Get unchanged high byte
rts
.endproc