From f8dbfd86f9fa8f615489779fd168316c712abefc Mon Sep 17 00:00:00 2001
From: hugova <hugova@kth.se>
Date: Thu, 15 May 2025 16:11:51 +0200
Subject: [PATCH] rewrite memcpy to work more like c:s implementation

---
 wip-hugo/routines/memory/mem.inc       |  3 +-
 wip-hugo/routines/memory/memcpy.s      | 40 ++++++++++++--------------
 wip-hugo/routines/memory/memcpy_test.s | 24 ++++------------
 wip-hugo/source.s                      |  4 +--
 4 files changed, 29 insertions(+), 42 deletions(-)

diff --git a/wip-hugo/routines/memory/mem.inc b/wip-hugo/routines/memory/mem.inc
index 6d7e188..5ee149f 100644
--- a/wip-hugo/routines/memory/mem.inc
+++ b/wip-hugo/routines/memory/mem.inc
@@ -3,4 +3,5 @@
         ;; public args
         A_start = $D0      ; 16-bit value (uses D1)
         B_start = $D2      ; 16-bit value (uses D3)
-        B_end = $D4        ; 16-bit value (uses D5)
+        length = $D4        ; 16-bit value (uses D5)
+        B_end = length + 0
diff --git a/wip-hugo/routines/memory/memcpy.s b/wip-hugo/routines/memory/memcpy.s
index c9487e7..4001096 100644
--- a/wip-hugo/routines/memory/memcpy.s
+++ b/wip-hugo/routines/memory/memcpy.s
@@ -1,33 +1,31 @@
 ;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-
 
-;;Move memory from B_start B_end to A_start , (implied address)
-;;Modifies A,X and B_start gets modified
+;;Move length bytes from A_start address to lenght bytes starting at B_start.
 .proc memcpy
         .include "mem.inc"
-
-        ;; Let Y + A_start lower nibble represent A_start
-        ;; therefor: A_start = Y - A_start
-        ;; With Y we mean what Y will represent later aka >B_start
-        Sub_16 A_start, A_start + 1, B_start, #$00
-
-        ;;Lets move B_start lover-nibble to Y
-        LDY B_start
-        LDA #$00
-        STA B_start
+        LDY #$00
 loop:
-        Lag_16 B_end, B_end + 1, A, B_start, end_loop
         LDA (B_start), Y
         STA (A_start), Y
-        ;Tip save time by counting downward, fast to check if Y ==0 // hugo
         INY
-        TYA
-        CMP #$ff
+        BEQ y_overflow
+change_length:
+        DEC length
         BNE loop
-        ;; Fix overflow
-        LDY #$00
-        INC A_start + 1
-        INC B_start + 1
+
+        ;;check if length hi byte is 0. if it is end this
+        LDA length + 1
+        BEQ loop_end
+
+        DEC length +1
         JMP loop
-end_loop:
+y_overflow:
+        LDY #$00
+        INC B_start + 1
+        INC A_start + 1
+
+        jmp change_length
+loop_end:
+
 RTS
 .endproc
diff --git a/wip-hugo/routines/memory/memcpy_test.s b/wip-hugo/routines/memory/memcpy_test.s
index 83e9832..9d2e5a8 100644
--- a/wip-hugo/routines/memory/memcpy_test.s
+++ b/wip-hugo/routines/memory/memcpy_test.s
@@ -1,25 +1,13 @@
 ;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-
 ;; test for memcpy
+;; Writes text to half the screen
 .scope memcpy_test
-        charset = $FB
-        code = $FE
-        petski_position = $FE ;16-bit value (uses FF), reuses code:s memory
-        screen_position = $FC ;16-bit value (uses FD)
-
-        Mov_16 B_start, B_start + 1, #<$D000, #>$D000
-        ;#### TEMP INIT DATA ####
-        Mov_16 B_end, B_end + 1,  #<($D000+$1F3F), #>($D000 +$1F3F)
-        LDA #$10
-        STA code
-        LDA #$10
-        STA X_pos
-        STA Y_pos
-
+        .include "mem.inc"
         VIC_bank = $4000
-        VIC_bank_end = VIC_bank + $3FFF
+        Character_generator_ROM = $D000
+        len = $1f40
         Mov_16 A_start, A_start + 1, #<VIC_bank, #>VIC_bank
-        LDA #$00
+        Mov_16 B_start, B_start + 1, #<Character_generator_ROM, #>Character_generator_ROM
+        Mov_16 length,  length  + 1, #<len, #>len
         JSR memcpy
-        STA petski_position
-        jmp exit
 .endscope
diff --git a/wip-hugo/source.s b/wip-hugo/source.s
index 961e672..66e0ec6 100755
--- a/wip-hugo/source.s
+++ b/wip-hugo/source.s
@@ -10,8 +10,8 @@
 
 ;.include "routines/line/line_test.s"
 ;.include "routines/text/char_draw_test.s"
-.include "routines/pixel/pixel_test.s"
-;.include "routines/memory/memcpy_test.s"
+;.include "routines/pixel/pixel_test.s"
+.include "routines/memory/memcpy_test.s"
 ;.include "routines/triangle/triangle_test.s"
 exit:
 JMP exit