fixed bug in memcopy

compiler/res/prog8lib/c64/syslib.p8

@@ -500,19 +500,23 @@ sys {
     asmsub memcopy(uword source @R0, uword target @R1, uword count @AY) clobbers(A,X,Y) {
         %asm {{
             ldx  cx16.r0
-            stx  P8ZP_SCRATCH_W1
+            stx  P8ZP_SCRATCH_W1        ; source in ZP
             ldx  cx16.r0+1
             stx  P8ZP_SCRATCH_W1+1
             ldx  cx16.r1
-            stx  P8ZP_SCRATCH_W2
+            stx  P8ZP_SCRATCH_W2        ; target in ZP
             ldx  cx16.r1+1
             stx  P8ZP_SCRATCH_W2+1
             cpy  #0
             bne  _longcopy
-            ; copy <= 255
-            tay
 
-_remainder
+            ; copy <= 255 bytes
+            tay
+            bne  _copyshort
+            rts     ; nothing to copy
+
+_copyshort
+            ; decrease source and target pointers so we can simply index by Y
             lda  P8ZP_SCRATCH_W1
             bne  +
             dec  P8ZP_SCRATCH_W1+1
@@ -521,18 +525,19 @@ _remainder
             bne  +
             dec  P8ZP_SCRATCH_W2+1
 +           dec  P8ZP_SCRATCH_W2
--           lda  (P8ZP_SCRATCH_W1), y
-            sta  (P8ZP_SCRATCH_W2), y
+
+-           lda  (P8ZP_SCRATCH_W1),y
+            sta  (P8ZP_SCRATCH_W2),y
             dey
             bne  -
             rts
 
 _longcopy
-            sta  P8ZP_SCRATCH_B1        ; lsb(count) = remainder
+            sta  P8ZP_SCRATCH_B1        ; lsb(count) = remainder in last page
             tya
             tax                         ; x = num pages (1+)
             ldy  #0
--           lda  (P8ZP_SCRATCH_W1),y    ; copy a page at a time
+-           lda  (P8ZP_SCRATCH_W1),y
             sta  (P8ZP_SCRATCH_W2),y
             iny
             bne  -
@@ -541,7 +546,8 @@ _longcopy
             dex
             bne  -
             ldy  P8ZP_SCRATCH_B1
-            jmp  _remainder
+            bne  _copyshort
+            rts
         }}
     }
 

docs/source/todo.rst

@@ -2,7 +2,6 @@
 TODO
 ====
 
-- fix sys.memcopy()
 - allow  uwordpointer[index] syntax -> transform into @(uwordpointer+index)  allow index to be >255!
 - add offsetof() to get the byte offset of struct members
 - add any2(), all2(), max2(), min2(), reverse2(), sum2(), sort2() that take (array, startindex, length) arguments

examples/test.p8

@@ -8,26 +8,33 @@ main {
 
 
     sub start() {
-        ubyte[] sarray = [11,22,33]
-        ubyte[] tarray = [0,0,0]
+        ; TODO test memcopy
+        ; counts: 0, 1, 2, 254, 255, 256, 257, 512, 1000
 
-        uword target = &tarray
-        uword source = &sarray
-        ubyte bb
-        @(target) = @(source)
-        target++
-        source++
-        @(target) = @(source)
-        target++
-        source++
-        @(target) = @(source)
-        target++
-        source++
+        uword buffer=memory("buffer",1000)
+        uword ones=memory("ones",1000)
 
-        for bb in tarray {
-            txt.print_ub(bb)
-            txt.chrout('\n')
+        sys.memset(buffer, 1000, '.')
+        @(buffer) = '<'
+        @(buffer+255) = '>'
+        @(buffer+256) = '<'
+        @(buffer+511) = '>'
+        @(buffer+512) = '<'
+        @(buffer+767) = '>'
+        @(buffer+768) = '<'
+        @(buffer+999) = '!'
+        sys.memset(ones, 1000, '*')
+
+        txt.clear_screen()
+        txt.print("\n\n\n\n\n\n\n\n\n")
+
+        sys.memcopy(ones, buffer, 999)
+
+        uword scr = $0400
+        uword ix
+        for ix in 0 to 999 {
+            @(scr) = @(buffer+ix)
+            scr++
         }
     }
-
 }