From 2aa5b91430b4d9521c53e3095cf94e6b90bab020 Mon Sep 17 00:00:00 2001
From: Johannes Theiner <j.theiner@live.de>
Date: Thu, 3 Jan 2019 11:24:51 +0100
Subject: [PATCH] a5: Dokumentation verbessert

---
 src/c/a5/Makefile   |  7 +------
 src/c/a5/addsub.asm | 18 +++++++-----------
 src/c/a5/flagtest.c | 38 ++++++++++++++++++++++++++++++--------
 src/c/a5/run.sh     |  2 +-
 4 files changed, 39 insertions(+), 26 deletions(-)

diff --git a/src/c/a5/Makefile b/src/c/a5/Makefile
index c040c74..cbf7ad2 100644
--- a/src/c/a5/Makefile
+++ b/src/c/a5/Makefile
@@ -7,14 +7,9 @@ flagtest.o: flagtest.c
 
 # ASM-Modul assemblieren
 addsub.o: addsub.asm
-	nasm -f elf -o addsub.o addsub.asm
+	nasm -f elf -o addsub.o addsub.asm # assemblieren
 
 # Projekt aufraemen 
 clean:
 	@echo 'Ausgabedateien loeschen'
 	rm -f flagtest *.o *~
-
-
-
-
-
diff --git a/src/c/a5/addsub.asm b/src/c/a5/addsub.asm
index 36d4a5c..524d584 100644
--- a/src/c/a5/addsub.asm
+++ b/src/c/a5/addsub.asm
@@ -8,15 +8,14 @@ addsub:
     mov ebp, esp
 
     push ebx
-    push ecx
     push edx
 
     mov eax, 0
 
-    mov bx, word [ebp+16] ;Operation
     mov ax, word [ebp+8] ;op1
+    mov bx, word [ebp+16] ;what
 
-    cmp bx, 0x2b
+    cmp bx, 0x2b;hex code for + symbol
     jne substract
 
     add ax, word [ebp+12] ;op2
@@ -26,21 +25,18 @@ substract: sub ax, word [ebp+12] ;op2
 
 return:
 
-    pushfd;Flagregister auf Stack pushen
+    pushfd;push flags to stack
 
-    pop edx;Flagregister in edx schreiben
+    pop edx;write flags to edx
 
-    mov ebx, [ebp+20]
+    mov ebx, [ebp+20];write flag pointer address to ebx
 
-    mov [ebx], edx
+    mov [ebx], edx;write flags to pointer address
 
 
     pop edx
-    pop ecx
     pop ebx
 
     mov esp, ebp
     pop ebp
-    ret
-
-section .data
\ No newline at end of file
+    ret
\ No newline at end of file
diff --git a/src/c/a5/flagtest.c b/src/c/a5/flagtest.c
index 8ee030c..6ebf1d7 100644
--- a/src/c/a5/flagtest.c
+++ b/src/c/a5/flagtest.c
@@ -2,11 +2,10 @@
 #include <stdlib.h>
 
 /**
- *
  * @param op1 ebp+8
  * @param op2 ebp+12
  * @param what ebp+16
- * @param flags ebp+24
+ * @param flags ebp+20
  * @return
  */
 extern int addsub(int op1, int op2, char what, unsigned int *flags);
@@ -26,24 +25,44 @@ int main(int argc, char **argv) {
     int op2 = atoi(argv[3]);
     char what = *argv[2];
 
+
+    //we need the operators both as signed and unsigned
     signed short sop1 = (short) op1;
     signed short sop2 = (short) op2;
     unsigned short uop1 = (unsigned short) op1;
     unsigned short uop2 = (unsigned short) op2;
 
+
     unsigned int *flags = malloc(sizeof(unsigned int));
 
     int result = addsub(op1, op2, what, flags);
 
+    //we also need the result as signed and unsigned
     short signedRes = (short) result;
     unsigned short unsignedRes = (unsigned short) result;
 
     printf("Flags:\n");
     printf("O D I T S Z   A   P   C\n");
 
+
+    /*
+     * 0: Overflow flag
+     * 1: Direction flag
+     * 2: Interrupt enable flag
+     * 3: Trap flag
+     * 4: Signed flag
+     * 5: Zero flag
+     * 6: reserved
+     * 7: Auxiliary flag
+     * 8: reserved
+     * 9: Parity flag
+     * 10: reserved
+     * 11: Carry flag
+     */
     int flagArray[12];
 
 
+    //flags are saved as a decimal value, so we need to convert to binary
     for(int i = 0; i < 12; ++i) {
         flagArray[i] = *flags % 2;
         *flags = *flags / 2;
@@ -57,21 +76,24 @@ int main(int argc, char **argv) {
 
     printf("Ergebnis und Operanden Signed:\n");
     printf("%d %c %d = %d\t", sop1, what, sop2, signedRes);
-    if(flagArray[11] != 0)
-        printf("Ergebnis ist falsch!");
-    else
+
+    if(flagArray[0] == 0)
         printf("Ergebnis ist richtig!");
+    else
+        printf("Ergebnis ist falsch!");
 
 
     printf("\n\n");
 
+
     printf("Ergebnis und Operanden Unsigned:\n");
     printf("%u %c %u = %u\t", uop1, what, uop2, unsignedRes);
 
-    if(flagArray[0] != 0)
-        printf("Ergebnis ist falsch!");
-    else
+    if(flagArray[11] == 0)
         printf("Ergebnis ist richtig!");
+    else
+        printf("Ergebnis ist falsch!");
+
 
     printf("\n\n");
 
diff --git a/src/c/a5/run.sh b/src/c/a5/run.sh
index f4a2b1e..68ca0dd 100755
--- a/src/c/a5/run.sh
+++ b/src/c/a5/run.sh
@@ -1,4 +1,4 @@
 #!/usr/bin/env bash
 make
 ./flagtest 32769 + 2
-./flagtest 32769 - 2
+./flagtest 32769 - 2
\ No newline at end of file