From acd0b8861c4369ca3e53a81e1a73a7287d93c8e7 Mon Sep 17 00:00:00 2001
From: FReenen <git@finnvanreenen.nl>
Date: Sun, 15 Sep 2024 11:05:17 +0200
Subject: [PATCH] w1.2: finish assignment1.2

---
 .../assignment1/{test.s => test.asm}          |  0
 assignment_assembly/assignment2/main.c        | 22 ++++++++
 assignment_assembly/assignment2/mulOne.c      | 50 +++++++++++++++++++
 assignment_assembly/assignment2/multiply.asm  | 16 +++---
 assignment_assembly/readme.md                 | 12 +++++
 5 files changed, 92 insertions(+), 8 deletions(-)
 rename assignment_assembly/assignment1/{test.s => test.asm} (100%)
 create mode 100644 assignment_assembly/assignment2/main.c
 create mode 100644 assignment_assembly/assignment2/mulOne.c

diff --git a/assignment_assembly/assignment1/test.s b/assignment_assembly/assignment1/test.asm
similarity index 100%
rename from assignment_assembly/assignment1/test.s
rename to assignment_assembly/assignment1/test.asm
diff --git a/assignment_assembly/assignment2/main.c b/assignment_assembly/assignment2/main.c
new file mode 100644
index 0000000..dcf975a
--- /dev/null
+++ b/assignment_assembly/assignment2/main.c
@@ -0,0 +1,22 @@
+/* main.c simple program to test assembler program */
+
+#include <stdio.h>
+
+extern int test(int a, int b);
+extern unsigned int multiply(unsigned int a, unsigned int b);
+
+int main(void)
+{
+	extern void initialise_monitor_handles(void);
+	initialise_monitor_handles();
+
+	int a = test(3, 5);
+    printf("Result of test(3, 5) = %d\n", a);
+
+    unsigned int b = multiply(3, 5);
+    printf("Result of multipy(3, 5) = %d\n", b);
+
+	b = multiply(3, 0);
+    printf("Result of multipy(3, 0) = %d\n", b);
+    return 0;
+}
diff --git a/assignment_assembly/assignment2/mulOne.c b/assignment_assembly/assignment2/mulOne.c
new file mode 100644
index 0000000..918fcf0
--- /dev/null
+++ b/assignment_assembly/assignment2/mulOne.c
@@ -0,0 +1,50 @@
+#include <stdio.h>
+
+unsigned int multiply(unsigned int a, unsigned int b);
+
+/**
+ * Multiplies two unsigned int values
+ * @param unsigned int a
+    The value of the multiplier a (0-4294967295)
+ * @param unsigned int b
+    The value of the multiplicand b (0-4294967295)
+ * @return unsigned int
+    The answer of a times b given that a * b < 4294967295
+ */
+
+// // This function must be implemented in LEGv7 Pinky assembly
+// unsigned int multiply(unsigned int a, unsigned int b)
+// {
+//     unsigned int m = 0;
+//     for (unsigned int i = 0; i != a; i++)
+//     {
+//         m = m + b;
+//     }
+//     return m;
+// }
+
+int main()
+{
+    extern void initialise_monitor_handles(void);
+    initialise_monitor_handles();
+
+    unsigned int a[] = {0, 1, 0, 1, 2000,      2,     10000,          1 ,      65535 };
+    unsigned int b[] = {0, 0, 1, 1,    2,  65535,     65535, 4294967295u,      65535 };
+    unsigned int r[] = {0, 0, 0, 1, 4000, 131070, 655350000, 4294967295u, 4294836225u};
+
+    for (size_t i = 0; i != sizeof(a)/sizeof(a[0]); i++)
+    {
+        printf("%u x %u: ", a[i], b[i]);
+        unsigned int result = multiply(a[i], b[i]);
+        unsigned int correct = r[i];
+        if (result != correct)
+        {
+            printf("Failed, function returned %u but the correct answer is %u\n", result, correct);
+        }
+        else
+        {
+            printf("Passed, %u\n", result);
+        }
+    }
+    return 0;
+}
diff --git a/assignment_assembly/assignment2/multiply.asm b/assignment_assembly/assignment2/multiply.asm
index 254282d..dc947c1 100644
--- a/assignment_assembly/assignment2/multiply.asm
+++ b/assignment_assembly/assignment2/multiply.asm
@@ -5,14 +5,14 @@
 	.text
 	.thumb_func
 multiply:
-	MOVS.N	R2, #0
-	ADDS.N	R1, #0
-	BEQ.N	=exit
+	MOVS.N	R2, #0		// set result to 0
+	CMP.N	R1, #0
+	BEQ.N	exit		// goto exit if b == 0
 loop:
-	ADDS.N	R2, R0, R2
-	SUBS.N	R1, #1
-	BNE.N	=exit
-	B.N		=loop
+	ADDS.N	R2, R0, R2	// add a to result
+	SUBS.N	R1, #1		// substract 1 from b
+	BEQ.N	exit		// goto exit if b == 0
+	B.N		loop		// loop otherwise
 exit:
-	MOVS.N	R0, R2
+	MOVS.N	R0, R2		// move result to R0
 	BX.N	LR
diff --git a/assignment_assembly/readme.md b/assignment_assembly/readme.md
index f5f62be..acdd1cd 100644
--- a/assignment_assembly/readme.md
+++ b/assignment_assembly/readme.md
@@ -25,4 +25,16 @@ Hierna werken het nogsteed zoals verwacht.
 
 ## Writeting a simple multiplication program
 
+Om te beginnen heb ik het project van de vorige assignment. Hier heb ik aan *main.c* een paar simpele regels toegevoegd om de basis werking te testen. 
+
+![simpele test code](assignment2/main.c)
+
+Pas toen ik het werkend had kwam ik achter dat ik `a` en `b` heb omgedraaid. Dit maakt gelukkig niet uit in een vermedigvuldiging. Daarnaast heb ik ook `i` weg gewerkt door i.p.v. `i` te verhogen en daarna te vergeleiken met `b` heb ik `b` verlaagd tot het 0 is.
+
+Dit is mijn implementatie:
+
+![asambly implementatie van vermedigvuldiging](assignment2/multiply.asm)
+
+## A smarter tail recursive multiply algorithm
+