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Improved strncpy

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git-svn-id: svn://svn.cc65.org/cc65/trunk@2144 b7a2c559-68d2-44c3-8de9-860c34a00d81
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cuz 2003-05-04 22:21:13 +00:00
parent e9f6a0a3ab
commit c0ca2e2a62
1 changed files with 42 additions and 73 deletions
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115
libsrc/common/strncpy.s
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@ -1,16 +1,20 @@
;
; Ullrich von Bassewitz, 31.05.1998
; Ullrich von Bassewitz, 2003-05-04
;
; char* strncpy (char* dest, const char* src, unsigned size);
; char* __fastcall__ strncpy (char* dest, const char* src, unsigned size);
;
.export _strncpy
.import popax
.importzp ptr1, ptr2, ptr3, tmp1, tmp2
.export _strncpy
.import popax
.importzp ptr1, ptr2, ptr3, tmp1, tmp2
_strncpy:
sta tmp1 ; Save size
stx tmp2
.proc _strncpy
eor #$FF
sta tmp1
txa
eor #$FF
sta tmp2 ; Store -size - 1
jsr popax ; get src
sta ptr1
stx ptr1+1
@ -20,79 +24,44 @@ _strncpy:
sta ptr3 ; remember for function return
stx ptr3+1
; Copy src -> dest up to size bytes
ldx tmp1 ; Load low byte of ones complement of size
ldy #$00
ldx tmp1 ; Low byte of size
beq L1
L1: inx
bne L2
inc tmp2
beq L9
; Copy the first chunk < 256
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
jsr CopyChunk
bcs L3 ; Jump if end of string found
L3: inx
bne L4
inc tmp2
beq L9
; Copy full 256 byte chunks
L4: sta (ptr2),y
iny
bne L3
inc ptr2+1 ; Bump high byte
bne L3 ; Branch always
L1: lda tmp2 ; High byte of size
beq L3
ldx #$00 ; Copy 256 bytes
L2: jsr CopyChunk
bcs L3
dec tmp2
bne L2
beq L9
; Done, return dest
; Fill the remaining space with zeroes. If we come here, the value in X
; is the low byte of the fill count, tmp2 holds the high byte. Y is the index
; into the target string.
L9: lda ptr3
ldx ptr3+1
rts
L3: tax ; Test low byte
beq L4
jsr FillChunk
L4: lda tmp2 ; Test high byte
beq L9
L5: jsr FillChunk
dec tmp2
bne L5
; Done - return a pointer to the string
L9: lda ptr3
ldx ptr3+1
rts
; -------------------------------------------------------------------
; Copy byte count in X from ptr1 to ptr2
.proc CopyChunk
L1: lda (ptr1),y
sta (ptr2),y
beq L3
iny
bne L2
inc ptr1+1
inc ptr2+1
L2: dex
bne L1
clc
rts
L3: sec
rts
.endproc
; -------------------------------------------------------------------
; Fill byte count in X with zeroes
.proc FillChunk
lda #$00
L1: sta (ptr1),y
iny
bne L2
inc ptr1+1
L2: dex
bne L1
rts
.endproc