From 904c398911d524da2c81dd2c871492ed89cff9ca Mon Sep 17 00:00:00 2001
From: Abdelrahman Said <said.abdelrahman89@gmail.com>
Date: Wed, 29 Mar 2023 22:47:59 +0100
Subject: [PATCH] Completed the first 8086 simulation homework

---
 8086_sim/include/reg_access.h |   2 ++
 8086_sim/reg_access.cpp       |  12 +++++++-----
 8086_sim/sim86                | Bin 31808 -> 32104 bytes
 8086_sim/sim86.cpp            |  15 +++++++++++++--
 4 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/8086_sim/include/reg_access.h b/8086_sim/include/reg_access.h
index d6a3d1a..b1c1383 100644
--- a/8086_sim/include/reg_access.h
+++ b/8086_sim/include/reg_access.h
@@ -4,6 +4,8 @@
 #include "aliases.h"
 #include "sim86_instruction.h"
 
+#define REGISTER_COUNT 13
+
 void set_register(register_access reg, u16 new_value);
 u16 get_register(register_access reg);
 const char *get_register_name(register_access reg);
diff --git a/8086_sim/reg_access.cpp b/8086_sim/reg_access.cpp
index 113953a..b5b7dfe 100644
--- a/8086_sim/reg_access.cpp
+++ b/8086_sim/reg_access.cpp
@@ -2,17 +2,17 @@
 #include "include/aliases.h"
 #include <stdio.h>
 
-#define REGISTER_COUNT 13
-
 static u16 registers[REGISTER_COUNT] = {0};
 
+#define BIT_PER_BYTE 8
+
 void set_register(register_access reg, u16 new_value) {
   if (reg.Count == 2) {
     registers[reg.Index] = new_value;
     return;
   }
 
-  u16 shift = (u16)(reg.Offset) * (u16)sizeof(u8);
+  u16 shift = (u16)(reg.Offset) * BIT_PER_BYTE;
   u16 mask = 0xff00;
 
   registers[reg.Index] &= (mask >> shift);
@@ -24,8 +24,10 @@ u16 get_register(register_access reg) {
     return registers[reg.Index];
   }
 
-  // TODO (Abdelrahman): Implement this
-  return 0;
+  u16 shift = (u16)(reg.Offset) * BIT_PER_BYTE;
+  u16 mask = 0x00ff;
+
+  return (registers[reg.Index] >> shift) & mask;
 }
 
 const char *get_register_name(register_access reg) {
diff --git a/8086_sim/sim86 b/8086_sim/sim86
index 30946de97f527f04c1168746ff0ab97d99057773..e4249f126137805112b95a19a315b87500cf3f70 100644
GIT binary patch
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diff --git a/8086_sim/sim86.cpp b/8086_sim/sim86.cpp
index 9229eec..b9e578d 100644
--- a/8086_sim/sim86.cpp
+++ b/8086_sim/sim86.cpp
@@ -42,6 +42,8 @@ int main(int argc, char *argv[]) {
 
   u32 offset = 0;
 
+  bool accessed_registers[REGISTER_COUNT] = {false};
+
   while (offset < size) {
     instruction decoded;
     Sim86_Decode8086Instruction(size - offset, buffer + offset, &decoded);
@@ -55,13 +57,22 @@ int main(int argc, char *argv[]) {
 
         if (dest.Type == Operand_Register) {
           mov_to_register(dest.Register, source);
-          printf("%s: 0x%04x\n", get_register_name(dest.Register),
-                 get_register(dest.Register));
+
+          accessed_registers[dest.Register.Index] = true;
         }
       }
     }
   }
 
+  for (u32 i = 0; i < REGISTER_COUNT; ++i) {
+    if (accessed_registers[i]) {
+      register_access reg = {i, 0, 2};
+      u16 value = get_register(reg);
+
+      printf("%s: 0x%04x (%d)\n", get_register_name(reg), value, value);
+    }
+  }
+
   return 0;
 }