From: cuz <cuz@b7a2c559-68d2-44c3-8de9-860c34a00d81>
Date: Tue, 30 Nov 2004 18:47:25 +0000 (+0000)
Subject: Fixed an error and improved the code
X-Git-Tag: V2.12.0~518
X-Git-Url: https://git.sur5r.net/?a=commitdiff_plain;h=08074a2ee311698472fd20b07572ccb38414838d;p=cc65

Fixed an error and improved the code


git-svn-id: svn://svn.cc65.org/cc65/trunk@3317 b7a2c559-68d2-44c3-8de9-860c34a00d81
---

diff --git a/libsrc/common/_swap.s b/libsrc/common/_swap.s
index 7f3f98fa0..7f0b59e94 100644
--- a/libsrc/common/_swap.s
+++ b/libsrc/common/_swap.s
@@ -1,62 +1,55 @@
 ;
-; Ullrich von Bassewitz, 09.12.1998
+; Ullrich von Bassewitz, 1998-12-09, 2004-11-30
 ;
 ; void __fastcall__ _swap (void* p, void* q, size_t size);
 ;
 
-	.export	       	__swap
-	.import		popax
-	.importzp	ptr1, ptr2, ptr3
+      	.export	       	__swap
+      	.import		popax
+      	.importzp	ptr1, ptr2, ptr3
 
 
-__swap:	sta	ptr3		; Save size
-	stx	ptr3+1
+__swap:	eor     #$FF
+        sta	ptr3
+        txa
+        eor     #$FF
+       	sta	ptr3+1          ; Save -(size+1) into ptr3
 
-	jsr	popax		; Get q
-	sta	ptr2
-	stx	ptr2+1
+      	jsr	popax		; Get q
+      	sta	ptr2
+      	stx	ptr2+1
 
-	jsr	popax		; Get p
-	sta	ptr1
-	stx	ptr1+1
+      	jsr	popax		; Get p
+      	sta	ptr1
+      	stx	ptr1+1
 
 ; Prepare for swap
 
-	ldy	#$00
+      	ldy	#$00
 
-; Swap 256 byte blocks
+; Swap loop
 
-	ldx	ptr3+1
-	beq	@L2
+@L1:    inc     ptr3            ; Bump counter low byte
+        beq     @L3             ; Branch on overflow
 
-@L1:	lda	(ptr1),y
-    	tax
-    	lda	(ptr2),y
-    	sta	(ptr1),y
-    	txa
-    	sta	(ptr2),y
-    	iny
-    	bne	@L1
-	dec	ptr3+1
-	bne	@L1
+@L2:    lda	(ptr1),y
+      	tax
+      	lda	(ptr2),y
+      	sta	(ptr1),y
+      	txa
+      	sta	(ptr2),y
+      	iny
+      	bne	@L1
+        inc     ptr1+1
+        inc     ptr2+1
+        bne     @L1             ; Branch always (hopefully)
 
-; Swap remaining bytes (Y is zero)
+; Bump the high counter byte
 
-@L2:	ldx	ptr3
-	beq	@L9
-
-@L3:   	lda	(ptr1),y
-    	tax
-    	lda	(ptr2),y
-    	sta	(ptr1),y
-    	txa
-    	sta	(ptr2),y
-	iny
-    	dec	ptr3
-    	bne	@L3
+@L3:    inc     ptr3+1
+        bne     @L2
 
 ; Done
 
-@L9:	rts
-
+        rts