fox32rom: Add some convenience routines for copying memory

main.asm

@@ -165,6 +165,7 @@ mount_boot_disk:
     #include "boot.asm"
     #include "background.asm"
     #include "overlay.asm"
+    #include "memory.asm"
     #include "menu.asm"
     #include "submenu.asm"
     #include "event.asm"

memory.asm

@@ -0,0 +1,51 @@
+; memory copy routines
+
+; copy specified number of bytes from source pointer to destination pointer
+; if the source and destination overlap, the behavior is undefined
+; inputs:
+; r0: pointer to source
+; r1: pointer to destinaton
+; r2: number of bytes to copy
+; outputs:
+; none
+copy_memory_bytes:
+    push r0
+    push r1
+    push r31
+
+    mov r31, r2
+copy_memory_bytes_loop:
+    mov.8 [r1], [r0]
+    inc r0
+    inc r1
+    loop copy_memory_bytes_loop
+
+    pop r31
+    pop r1
+    pop r0
+    ret
+
+; copy specified number of words from source pointer to destination pointer
+; if the source and destination overlap, the behavior is undefined
+; inputs:
+; r0: pointer to source
+; r1: pointer to destinaton
+; r2: number of words to copy
+; outputs:
+; none
+copy_memory_words:
+    push r0
+    push r1
+    push r31
+
+    mov r31, r2
+copy_memory_words_loop:
+    mov [r1], [r0]
+    add r0, 4
+    add r1, 4
+    loop copy_memory_words_loop
+
+    pop r31
+    pop r1
+    pop r0
+    ret