1
0
mirror of https://github.com/cc65/cc65.git synced 2024-12-25 02:29:52 +00:00

Rewrote memcmp. The old version was buggy, the new one is faster and

hopefully error free.


git-svn-id: svn://svn.cc65.org/cc65/trunk@330 b7a2c559-68d2-44c3-8de9-860c34a00d81
This commit is contained in:
cuz 2000-09-15 17:23:19 +00:00
parent 1b4039be3b
commit d6fb2d94bf

View File

@ -1,5 +1,5 @@
;
; Ullrich von Bassewitz, 09.06.1998
; Ullrich von Bassewitz, 15.09.2000
;
; int memcmp (const void* p1, const void* p2, size_t count);
;
@ -9,46 +9,64 @@
.importzp ptr1, ptr2, ptr3
_memcmp:
sta ptr3 ; Save count
sta ptr3+1
jsr popax ; get p2
; Calculate (-count-1) and store it into ptr3. This is some overhead here but
; saves time in the compare loop
eor #$FF
sta ptr3
txa
eor #$FF
sta ptr3+1
; Get the pointer parameters
jsr popax ; Get p2
sta ptr2
stx ptr2+1
jsr popax ; get p1
jsr popax ; Get p1
sta ptr1
stx ptr1+1
ldy #0
ldx ptr3 ; use X as low counter byte
beq L3
; Loop initialization
L1: lda (ptr1),y
cmp (ptr2),y
bne L5
iny
bne L2
inc ptr1+1
inc ptr2+1
L2: txa
beq L3
dex
jmp L1
L3: lda ptr3+1 ; check high byte
beq L4
dec ptr3+1
dex ; X = $FF
bne L1 ; branch always
ldx ptr3 ; Load low counter byte into X
ldy #$00 ; Initialize pointer
; Memory areas are equal
; Head of compare loop: Test for the end condition
L4: jmp return0
Loop: inx ; Bump low byte of (-count-1)
beq BumpHiCnt ; Jump on overflow
; Do the compare
Comp: lda (ptr1),y
cmp (ptr2),y
bne NotEqual ; Jump if bytes not equal
; Bump the pointers
iny ; Increment pointer
bne Loop
inc ptr1+1 ; Increment high bytes
inc ptr2+1
bne Loop ; Branch always (pointer wrap is illegal)
; Entry on low counter byte overflow
BumpHiCnt:
inc ptr3+1 ; Bump high byte of (-count-1)
bne Comp ; Jump if not done
jmp return0 ; Count is zero, areas are identical
; Not equal, check which one is greater
L5: bcs L6
ldx #$FF
NotEqual:
bcs Greater
ldx #$FF ; Make result negative
rts
L6: ldx #$01
Greater:
ldx #$01 ; Make result positive
rts