From dddfd8b706a5083517d5dbaa9d6c52c53952ea59 Mon Sep 17 00:00:00 2001
From: Ry <ryanst755@gmail.com>
Date: Fri, 25 Mar 2022 18:03:12 -0700
Subject: [PATCH] fox32rom: Add memory compare routines

---
 memory.asm | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 58 insertions(+), 2 deletions(-)

diff --git a/memory.asm b/memory.asm
index a94efa7..573e39e 100644
--- a/memory.asm
+++ b/memory.asm
@@ -1,4 +1,4 @@
-; memory copy routines
+; memory copy/compare routines
 
 ; copy specified number of bytes from source pointer to destination pointer
 ; if the source and destination overlap, the behavior is undefined
@@ -48,4 +48,60 @@ copy_memory_words_loop:
     pop r31
     pop r1
     pop r0
-    ret
\ No newline at end of file
+    ret
+
+; compare specified number of bytes from source pointer with destination pointer
+; inputs:
+; r0: pointer to source
+; r1: pointer to destinaton
+; r2: number of bytes to compare
+; outputs:
+; Z flag
+compare_memory_bytes:
+    push r0
+    push r1
+    push r31
+
+    mov r31, r2
+compare_memory_bytes_loop:
+    cmp.8 [r1], [r0]
+    ifnz jmp compare_memory_bytes_not_equal
+    inc r0
+    inc r1
+    loop compare_memory_bytes_loop
+    ; set Z flag if we reach thie point
+    mov r0, 0
+    cmp r0, 0
+compare_memory_bytes_not_equal:
+    pop r31
+    pop r1
+    pop r0
+    ret
+
+; compare specified number of words from source pointer with destination pointer
+; inputs:
+; r0: pointer to source
+; r1: pointer to destinaton
+; r2: number of words to compare
+; outputs:
+; Z flag
+compare_memory_words:
+    push r0
+    push r1
+    push r31
+
+    mov r31, r2
+compare_memory_words_loop:
+    cmp [r1], [r0]
+    ifnz jmp compare_memory_words_not_equal
+    add r0, 4
+    add r1, 4
+    loop compare_memory_words_loop
+    ; set Z flag if we reach thie point
+    mov r0, 0
+    cmp r0, 0
+compare_memory_words_not_equal:
+    pop r31
+    pop r1
+    pop r0
+    ret