From 4ed9c427f2ba2e4ec0e620f1416aea0e2906f19e Mon Sep 17 00:00:00 2001
From: Jeremiah Orians <jeremiah@pdp10.guru>
Date: Sun, 14 Aug 2016 17:41:16 -0400
Subject: [PATCH] Initial prototype for a copy_string function

---
 Library function prototypes/clear_string.s |  5 +--
 Library function prototypes/copy_string.s  | 39 ++++++++++++++++++++++
 2 files changed, 42 insertions(+), 2 deletions(-)
 create mode 100644 Library function prototypes/copy_string.s

diff --git a/Library function prototypes/clear_string.s b/Library function prototypes/clear_string.s
index ff185d9..b578fad 100644
--- a/Library function prototypes/clear_string.s	
+++ b/Library function prototypes/clear_string.s	
@@ -1,4 +1,5 @@
-	# We will be using R0 and R1 to pass values to the function
+	# We will be using R0 to pass pointer to string
+	# to cleared by the function
 	# R15 will be used as the stack pointer
 :start
 	LOADUI R0 @string
@@ -29,7 +30,7 @@
 	LOADXU8 R0 R1 R2			; Get the byte
 	STOREX8 R3 R1 R2			; Overwrite with a Zero
 	ADDUI R2 R2 1				; Prep for next loop
-	CMPJUMP.NE R0 R3 @clear_byte	; Stop if byte is NULL
+	JUMP.NZ R0 @clear_byte		; Stop if byte is NULL
 ;; Done
 	;; Restore registers
 	POPR R3 R15
diff --git a/Library function prototypes/copy_string.s b/Library function prototypes/copy_string.s
new file mode 100644
index 0000000..f5d23ef
--- /dev/null
+++ b/Library function prototypes/copy_string.s	
@@ -0,0 +1,39 @@
+	# We will be using R0 and R1 to pass values to the function
+	# R15 will be used as the stack pointer
+:start
+	LOADUI R0 @string
+	LOADUI R1 0x100
+	LOADUI R2 33
+	LOADUI R3 44
+	LOADUI R4 55
+	LOADUI R15 0x600
+	CALLI R15 @copy_string
+	HALT
+:string
+	HALT
+	HALT
+	NOP
+
+;;  Our simple string compare function
+:copy_string
+	;; Preserve registers
+	PUSHR R0 R15
+	PUSHR R1 R15
+	PUSHR R2 R15
+	PUSHR R3 R15
+	;; Setup registers
+	MOVE R2 R1
+	MOVE R1 R0
+	LOADUI R3 0
+:copy_byte
+	LOADXU8 R0 R1 R3			; Get the byte
+	STOREX8 R0 R2 R3			; Store the byte
+	ADDUI R3 R3 1				; Prep for next loop
+	JUMP.NZ R0 @copy_byte	; Stop if byte is NULL
+;; Done
+	;; Restore registers
+	POPR R3 R15
+	POPR R2 R15
+	POPR R1 R15
+	POPR R0 R15
+	RET R15