Added bytecode pattern

Author: Habrador

Assets/Patterns/10. Bytecode.meta

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+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace BytecodePattern
+{
+    //Bytecode code pattern from the book "Game Programming Patterns"
+    public class GameController : MonoBehaviour
+    {
+        
+        
+        void Start()
+        {
+            //Test
+            int[] bytecode = new int[]
+            {
+                (int)Instruction.INST_LITERAL, 0, //wizard id
+                (int)Instruction.INST_LITERAL, 75, //amount
+                (int)Instruction.INST_SET_HEALTH
+            };
+
+            VM vm = new VM(gameController: this);
+
+            vm.Interpret(bytecode);
+        }
+
+
+        void Update()
+        {
+
+        }
+
+
+
+        //0 means the player's wizard and 1, 2, ... means the other wizards in the game
+        //This way we can heal our own wizard while damage other wizards with the same method
+        public void SetHealth(int wizardID, int amount)
+        {
+            Debug.Log($"Wizard {wizardID} gets health {amount}");
+        }
+
+        public void SetWizdom(int wizardID, int amount)
+        {
+            Debug.Log($"Wizard {wizardID} gets wisdom {amount}");
+        }
+
+        public void SetAgility(int wizardID, int amount)
+        {
+            Debug.Log($"Wizard {wizardID} gets agility {amount}");
+        }
+
+        public void PlaySound(int soundID)
+        {
+            Debug.Log($"Play sound {soundID}");
+        }
+
+        public void SpawnParticles(int particleType)
+        {
+            Debug.Log($"Spawn particle {particleType}");
+        }
+
+        public int GetHealth(int wizardID)
+        {
+            return 50;
+        }
+    }
+}

Assets/Patterns/10. Bytecode/Scripts.meta

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+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace BytecodePattern
+{
+    //These are the instrusctions we can choose from in our programming language
+    public enum Instruction
+    {
+        //Write stats
+        INST_SET_HEALTH,
+        INST_SET_WISDOM,
+        INST_SET_AGILITY,
+        INST_PLAY_SOUND,
+        INST_SPAWN_PARTICLES,
+        //So we can use parameters
+        INST_LITERAL,
+        //Read stats
+        INST_GET_HEALTH,
+        INST_GET_WISDOM,
+        INST_GET_AGILITY,
+        //Arithmetic
+        INST_ADD
+    }
+}

Assets/Patterns/10. Bytecode/Scripts/GameController.cs

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+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace BytecodePattern
+{
+    public class VM
+    {
+        private GameController gameController;
+
+        //Will store values for later use in the switch statement
+        private Stack<int> stackMachine = new Stack<int>();
+
+        //The max size of the stack
+        private const int MAX_STACK = 128;
+
+
+
+        public VM(GameController gameController)
+        {
+            this.gameController = gameController;
+        }
+        
+    
+
+        public void Interpret(int[] bytecode)
+        {
+            stackMachine.Clear();
+
+            //Read and execute the instructions
+            for (int i = 0; i < bytecode.Length; i++)
+            {
+                //Convert from int to enum
+                Instruction instruction = (Instruction)bytecode[i];
+
+                switch (instruction)
+                {
+                    case Instruction.INST_SET_HEALTH:
+                    {
+                        //Important to pop amount before wizard because we push wizard before amount onto the stack
+                        int amount = Pop();
+                        int wizard = Pop();
+                        
+                        gameController.SetHealth(wizard, amount);
+                        
+                        break;
+                    }
+                    case Instruction.INST_LITERAL:
+                    {
+                        //Important that this i++ is not inside bytecode[i++] or it will not jump to next i
+                        i++;
+                        
+                        int value = bytecode[i];
+                       
+                        Push(value);
+                        
+                        break;
+                    }
+                    case Instruction.INST_GET_HEALTH:
+                    {
+                        int wizard = Pop();
+
+                        Push(gameController.GetHealth(wizard));
+
+                        break;
+                    }
+                    case Instruction.INST_ADD:
+                    {
+                        int b = Pop();
+                        int a = Pop();
+                        
+                        Push(a + b);
+                        
+                        break;
+                    }
+                    default:
+                    {
+                        Debug.Log($"The VM couldn't find the instruction {instruction} :(");
+                        break;
+                    }
+                }
+            }
+        }
+
+
+
+        //Stack methods
+        private int Pop()
+        {
+            if (stackMachine.Count == 0)
+            {
+                Debug.LogError("The stack is empty :(");
+            }
+        
+            return stackMachine.Pop();
+        }
+
+        private void Push(int number)
+        {
+            //Check for stack overflow, which is useful because someone might make a mod that tries to break your game
+            if (stackMachine.Count + 1 > MAX_STACK)
+            {
+                Debug.LogError("Stack overflow is not just a place where you copy and paste code!");
+            }
+        
+            stackMachine.Push(number);
+        }
+    }
+}