Completed homework for 8086 simulator

8086_sim/.gitignore

@@ -7,3 +7,10 @@ listing_0047_challenge_flags
 listing_0048_ip_register
 listing_0049_conditional_jumps
 listing_0050_challenge_jumps
+listing_0051_memory_mov
+listing_0052_memory_add_loop
+listing_0053_add_loop_challenge
+listing_0054_draw_rectangle
+test.asm
+test
+image.data

8086_sim/listing_0051_memory_mov.asm

@@ -0,0 +1,30 @@
+; ========================================================================
+;
+; (C) Copyright 2023 by Molly Rocket, Inc., All Rights Reserved.
+;
+; This software is provided 'as-is', without any express or implied
+; warranty. In no event will the authors be held liable for any damages
+; arising from the use of this software.
+;
+; Please see https://computerenhance.com for further information
+;
+; ========================================================================
+
+; ========================================================================
+; LISTING 51
+; ========================================================================
+
+bits 16
+
+mov word [1000], 1
+mov word [1002], 2
+mov word [1004], 3
+mov word [1006], 4
+
+mov bx, 1000
+mov word [bx + 4], 10
+
+mov bx, word [1000]
+mov cx, word [1002]
+mov dx, word [1004]
+mov bp, word [1006]

8086_sim/listing_0052_memory_add_loop.asm

@@ -0,0 +1,36 @@
+; ========================================================================
+;
+; (C) Copyright 2023 by Molly Rocket, Inc., All Rights Reserved.
+;
+; This software is provided 'as-is', without any express or implied
+; warranty. In no event will the authors be held liable for any damages
+; arising from the use of this software.
+;
+; Please see https://computerenhance.com for further information
+;
+; ========================================================================
+
+; ========================================================================
+; LISTING 52
+; ========================================================================
+
+bits 16
+
+mov dx, 6
+mov bp, 1000
+
+mov si, 0
+init_loop_start:
+	mov word [bp + si], si
+	add si, 2
+	cmp si, dx
+	jnz init_loop_start
+
+mov bx, 0
+mov si, 0
+add_loop_start:
+	mov cx, word [bp + si]
+	add bx, cx
+	add si, 2
+	cmp si, dx
+	jnz add_loop_start

8086_sim/listing_0053_add_loop_challenge.asm

@@ -0,0 +1,35 @@
+; ========================================================================
+;
+; (C) Copyright 2023 by Molly Rocket, Inc., All Rights Reserved.
+;
+; This software is provided 'as-is', without any express or implied
+; warranty. In no event will the authors be held liable for any damages
+; arising from the use of this software.
+;
+; Please see https://computerenhance.com for further information
+;
+; ========================================================================
+
+; ========================================================================
+; LISTING 53
+; ========================================================================
+
+bits 16
+
+mov dx, 6
+mov bp, 1000
+
+mov si, 0
+init_loop_start:
+	mov word [bp + si], si
+	add si, 2
+	cmp si, dx
+	jnz init_loop_start
+
+mov bx, 0
+mov si, dx
+sub bp, 2
+add_loop_start:
+	add bx, word [bp + si]
+	sub si, 2
+	jnz add_loop_start

8086_sim/listing_0054_draw_rectangle.asm

@@ -0,0 +1,43 @@
+; ========================================================================
+;
+; (C) Copyright 2023 by Molly Rocket, Inc., All Rights Reserved.
+;
+; This software is provided 'as-is', without any express or implied
+; warranty. In no event will the authors be held liable for any damages
+; arising from the use of this software.
+;
+; Please see https://computerenhance.com for further information
+;
+; ========================================================================
+
+; ========================================================================
+; LISTING 54
+; ========================================================================
+
+bits 16
+
+; Start image after one row, to avoid overwriting our code!
+mov bp, 64*4
+
+mov dx, 0
+y_loop_start:
+	
+	mov cx, 0
+	x_loop_start:
+		; Fill pixel
+		mov word [bp + 0], cx ; Red
+		mov word [bp + 2], dx ; Blue
+		mov byte [bp + 3], 255 ; Alpha
+			
+		; Advance pixel location
+		add bp, 4
+			
+		; Advance X coordinate and loop
+		add cx, 1
+		cmp cx, 64
+		jnz x_loop_start
+	
+	; Advance Y coordinate and loop
+	add dx, 1
+	cmp dx, 64
+	jnz y_loop_start

8086_sim/sim86.cpp

@@ -1,22 +1,43 @@
 #include "include/aliases.h"
 #include "include/flag_access.h"
 #include "include/reg_access.h"
+#include "include/sim86_instruction.h"
 #include "include/sim86_lib.h"
 #include <bits/types/FILE.h>
 #include <stdio.h>
 #include <string.h>
 
 #define MEM_SIZE (1 << 16)
+#define BITS_PER_BYTE 8
 
 struct basic_string {
   char str[4096];
 };
 
-u16 get_operand_value(instruction_operand operand);
-basic_string get_operand_string(instruction_operand operand);
+struct membuf {
+  u8 buffer[MEM_SIZE];
+  u64 mem_start;
+};
+
+struct mem_access_result {
+  u16 value;
+  u32 error;
+};
+
+u16 get_operand_value(instruction_operand operand, bool wide);
+basic_string get_operand_string(instruction_operand operand, bool wide);
 void print_instruction(instruction inst);
 void mov_to_register(const register_access &reg,
-                     const instruction_operand &source);
+                     const instruction_operand &source, bool wide);
+void mov_to_memory(const effective_address_expression &addrexp,
+                   const instruction_operand &source, bool wide);
+mem_access_result get_mem_value(const effective_address_expression &addrexp,
+                                bool wide);
+mem_access_result set_mem_value(const effective_address_expression &addrexp,
+                                u16 value, bool wide);
+u16 get_mem_index(const effective_address_expression &addrexp);
+
+static membuf memory;
 
 int main(int argc, char *argv[]) {
   if (argc < 2) {
@@ -24,8 +45,8 @@ int main(int argc, char *argv[]) {
     return 1;
   }
 
-  u8 memory[MEM_SIZE];
-  memset((void *)memory, 0, MEM_SIZE);
+  memset((void *)memory.buffer, 0, MEM_SIZE);
+  memory.mem_start = 0;
 
   const char *filename = argv[1];
 
@@ -42,14 +63,14 @@ int main(int argc, char *argv[]) {
 
   fseek(fp, 0, SEEK_SET);
 
-  fread((void *)memory, sizeof(u8), size, fp);
+  fread((void *)memory.buffer, sizeof(u8), size, fp);
+  memory.mem_start = size + 1;
 
   fclose(fp);
 
   instruction_table table;
   Sim86_Get8086InstructionTable(&table);
 
-  u32 mem_start = size + 1;
   u32 offset = 0;
 
   bool accessed_registers[REGISTER_COUNT] = {false};
@@ -58,10 +79,12 @@ int main(int argc, char *argv[]) {
 
   while (offset < size) {
     instruction decoded;
-    Sim86_Decode8086Instruction(size - offset, memory + offset, &decoded);
+    Sim86_Decode8086Instruction(size - offset, memory.buffer + offset,
+                                &decoded);
 
     if (decoded.Op) {
       offset += decoded.Size;
+      bool wide = (decoded.Flags & Inst_Wide) == Inst_Wide;
 
       print_instruction(decoded);
 
@@ -70,11 +93,12 @@ int main(int argc, char *argv[]) {
 
       switch (decoded.Op) {
       case Op_mov: {
-
         if (dest.Type == Operand_Register) {
-          mov_to_register(dest.Register, source);
+          mov_to_register(dest.Register, source, wide);
 
           accessed_registers[dest.Register.Index] = true;
+        } else if (dest.Type == Operand_Memory) {
+          mov_to_memory(dest.Address, source, wide);
         }
 
         break;
@@ -83,7 +107,7 @@ int main(int argc, char *argv[]) {
         if (dest.Type == Operand_Register) {
           u16 value = get_register(dest.Register);
 
-          value += get_operand_value(source);
+          value += get_operand_value(source, wide);
           set_flags(value);
 
           set_register(dest.Register, value);
@@ -96,7 +120,7 @@ int main(int argc, char *argv[]) {
         if (dest.Type == Operand_Register) {
           u16 value = get_register(dest.Register);
 
-          value -= get_operand_value(source);
+          value -= get_operand_value(source, wide);
           set_flags(value);
 
           if (decoded.Op == Op_sub) {
@@ -108,7 +132,7 @@ int main(int argc, char *argv[]) {
       }
       case Op_jne: {
         if (!get_flag(FLAG_ZERO)) {
-          i16 inst_offset = get_operand_value(dest);
+          i16 inst_offset = get_operand_value(dest, wide);
 
           offset += inst_offset;
         }
@@ -136,30 +160,54 @@ int main(int argc, char *argv[]) {
   printf("\nFinal flags:\n");
   print_flags();
 
+#if 0 // Only needed (and working) for listing 0054
+#define SIZE 64
+#define BYTES SIZE * 4 * SIZE
+
+  u8 image[BYTES];
+  mempcpy(image, &(memory.buffer[memory.mem_start + (SIZE * 4)]), BYTES);
+
+  FILE *out = fopen("image.data", "wb");
+
+  fwrite(image, sizeof(u8), BYTES, out);
+
+  fclose(out);
+#endif
+
   return 0;
 }
 
-u16 get_operand_value(instruction_operand operand) {
+u16 get_operand_value(instruction_operand operand, bool wide) {
+  u16 output = 0;
+
   switch (operand.Type) {
   case Operand_Register:
-    return get_register(operand.Register);
+    output = get_register(operand.Register);
 
     break;
-  case Operand_Memory:
-    return 0;
+  case Operand_Memory: {
+    mem_access_result result = get_mem_value(operand.Address, wide);
+
+    if (result.error) {
+      break;
+    }
+
+    output = result.value;
 
     break;
+  }
   case Operand_Immediate:
-    return operand.Immediate.Value;
+    output = operand.Immediate.Value;
 
     break;
   default:
-    return 0;
     break;
   }
+
+  return output;
 }
 
-basic_string get_operand_string(instruction_operand operand) {
+basic_string get_operand_string(instruction_operand operand, bool wide) {
   basic_string output = {""};
 
   switch (operand.Type) {
@@ -167,10 +215,27 @@ basic_string get_operand_string(instruction_operand operand) {
     sprintf(output.str, "%s", get_register_name(operand.Register));
 
     break;
-  case Operand_Memory:
-    sprintf(output.str, "%s", "MEM OPERAND");
+  case Operand_Memory: {
+    char mem_string[1024] = {0};
+
+    register_access reg1 = operand.Address.Terms[0].Register;
+    if (reg1.Index != 0) {
+      sprintf(mem_string, "%s + ", get_register_name(reg1));
+    }
+
+    register_access reg2 = operand.Address.Terms[1].Register;
+    if (reg2.Index != 0) {
+      strcat(mem_string, get_register_name(reg2));
+    } else {
+      u32 length = strlen(mem_string);
+
+      sprintf(&(mem_string[length]), "%d", operand.Address.Displacement);
+    }
+
+    sprintf(output.str, "%s [%s]", wide ? "word" : "byte", mem_string);
 
     break;
+  }
   case Operand_Immediate:
     sprintf(output.str, "%d", operand.Immediate.Value);
 
@@ -183,13 +248,15 @@ basic_string get_operand_string(instruction_operand operand) {
 }
 
 void print_instruction(instruction inst) {
+  bool wide = (inst.Flags & Inst_Wide) == Inst_Wide;
+
   printf("\t%s %s, %s\n", Sim86_MnemonicFromOperationType(inst.Op),
-         get_operand_string(inst.Operands[0]).str,
-         get_operand_string(inst.Operands[1]).str);
+         get_operand_string(inst.Operands[0], wide).str,
+         get_operand_string(inst.Operands[1], wide).str);
 }
 
 void mov_to_register(const register_access &reg,
-                     const instruction_operand &source) {
+                     const instruction_operand &source, bool wide) {
   switch (source.Type) {
   case Operand_Immediate:
     set_register(reg, source.Immediate.Value);
@@ -197,7 +264,94 @@ void mov_to_register(const register_access &reg,
   case Operand_Register:
     set_register(reg, get_register(source.Register));
     break;
+  case Operand_Memory: {
+    mem_access_result result = get_mem_value(source.Address, wide);
+
+    if (!result.error) {
+      set_register(reg, result.value);
+    }
+
+    break;
+  }
   default:
     break;
   }
 }
+
+void mov_to_memory(const effective_address_expression &addrexp,
+                   const instruction_operand &source, bool wide) {
+  switch (source.Type) {
+  case Operand_Immediate:
+    set_mem_value(addrexp, source.Immediate.Value, wide);
+    break;
+  case Operand_Register:
+    set_mem_value(addrexp, get_register(source.Register), wide);
+    break;
+  case Operand_Memory: {
+    mem_access_result result = get_mem_value(source.Address, wide);
+
+    if (!result.error) {
+      set_mem_value(addrexp, result.value, wide);
+    }
+
+    break;
+  }
+  default:
+    break;
+  }
+}
+
+mem_access_result get_mem_value(const effective_address_expression &addrexp,
+                                bool wide) {
+  u16 index = get_mem_index(addrexp);
+
+  mem_access_result result = {0, 0};
+
+  if (memory.mem_start + index >= MEM_SIZE) {
+    result.error = 1;
+  } else {
+    result.value |= memory.buffer[memory.mem_start + index];
+
+    if (wide) {
+      result.value |= (memory.buffer[memory.mem_start + index + 1]
+                       << (wide ? BITS_PER_BYTE : 0));
+    }
+  }
+
+  return result;
+}
+
+mem_access_result set_mem_value(const effective_address_expression &addrexp,
+                                u16 value, bool wide) {
+  u16 index = get_mem_index(addrexp);
+
+  mem_access_result result = {0, 0};
+
+  if (memory.mem_start + index >= MEM_SIZE) {
+    result.error = 1;
+  } else {
+    memory.buffer[memory.mem_start + index] = (u8)value;
+
+    if (wide) {
+      memory.buffer[memory.mem_start + index + 1] =
+          (u8)(value >> (wide ? BITS_PER_BYTE : 0));
+    }
+
+    result.value = value;
+  }
+
+  return result;
+}
+
+u16 get_mem_index(const effective_address_expression &addrexp) {
+  u16 index = addrexp.Displacement;
+
+  const u16 term_count = 2;
+  for (u16 i = 0; i < term_count; ++i) {
+    if (addrexp.Terms[i].Register.Index != 0) {
+      index += get_register(addrexp.Terms[i].Register);
+    }
+  }
+
+  return index;
+}