Add class Instruction to simplify ExecutionEngine

src/neo-vm/ExecutionContext.cs

@@ -1,25 +1,21 @@
-using System;
-using System.IO;
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 
 namespace Neo.VM
 {
- public class ExecutionContext : IDisposable
+ public class ExecutionContext
  {
- /// <summary>
- /// Number of items to be returned
- /// </summary>
- internal readonly int RVCount;
+ private readonly Dictionary<int, Instruction> instructions = new Dictionary<int, Instruction>();
 
  /// <summary>
- /// Binary Reader of the script
+ /// Number of items to be returned
  /// </summary>
- internal readonly BinaryReader OpReader;
+ internal int RVCount { get; }
 
  /// <summary>
  /// Script
  /// </summary>
- public readonly Script Script;
+ public Script Script { get; }
 
  /// <summary>
  /// Evaluation stack
@@ -34,31 +30,24 @@ public class ExecutionContext : IDisposable
  /// <summary>
  /// Instruction pointer
  /// </summary>
- public int InstructionPointer
+ public int InstructionPointer { get; set; }
+
+ public Instruction CurrentInstruction
  {
- [MethodImpl(MethodImplOptions.AggressiveInlining)]
  get
  {
- return (int)OpReader.BaseStream.Position;
- }
- [MethodImpl(MethodImplOptions.AggressiveInlining)]
- set
- {
- OpReader.BaseStream.Seek(value, SeekOrigin.Begin);
+ return GetInstruction(InstructionPointer);
  }
  }
 
  /// <summary>
  /// Next instruction
  /// </summary>
- public OpCode NextInstruction
+ public Instruction NextInstruction
  {
- [MethodImpl(MethodImplOptions.AggressiveInlining)]
  get
  {
- var position = (int)OpReader.BaseStream.Position;
-
- return position >= Script.Length ? OpCode.RET : Script[position];
+ return GetInstruction(InstructionPointer + CurrentInstruction.Size);
  }
  }
 
@@ -83,12 +72,23 @@ internal ExecutionContext(Script script, int rvcount)
  {
  this.RVCount = rvcount;
  this.Script = script;
- this.OpReader = script.GetBinaryReader();
  }
 
- /// <summary>
- /// Free resources
- /// </summary>
- public void Dispose() => OpReader.Dispose();
+ private Instruction GetInstruction(int ip)
+ {
+ if (ip >= Script.Length) return Instruction.RET;
+ if (!instructions.TryGetValue(ip, out Instruction instruction))
+ {
+ instruction = new Instruction(Script, ip);
+ instructions.Add(ip, instruction);
+ }
+ return instruction;
+ }
+
+ internal bool MoveNext()
+ {
+ InstructionPointer += CurrentInstruction.Size;
+ return InstructionPointer < Script.Length;
+ }
  }
 }