context: //
  // MethodBody.cs
  //
  // Author:
  //   Jb Evain (jbevain@gmail.com)
  //
  // Copyright (c) 2008 - 2011 Jb Evain
  //
  // Permission is hereby granted, free of charge, to any person obtaining
  // a copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to
  // permit persons to whom the Software is furnished to do so, subject to
  // the following conditions:
  //
  // The above copyright notice and this permission notice shall be
  // included in all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  //
  
  using System;
  
  using Mono.Collections.Generic;
  
  namespace Mono.Cecil.Cil {
  
  	public sealed class MethodBody : IVariableDefinitionProvider {
  
  		readonly internal MethodDefinition method;
  
  		internal ParameterDefinition this_parameter;
  		internal int max_stack_size;
  		internal int code_size;
  		internal bool init_locals;
  		internal MetadataToken local_var_token;
  
  		internal Collection<Instruction> instructions;
  		internal Collection<ExceptionHandler> exceptions;
  		internal Collection<VariableDefinition> variables;
  		Scope scope;
  
  		public MethodDefinition Method {
  			get { return method; }
  		}
  
  		public int MaxStackSize {
  			get { return max_stack_size; }
  			set { max_stack_size = value; }
  		}
  
  		public int CodeSize {
  			get { return code_size; }
  		}
  
  		public bool InitLocals {
  			get { return init_locals; }
  			set { init_locals = value; }
  		}
  
  		public MetadataToken LocalVarToken {
  			get { return local_var_token; }
  			set { local_var_token = value; }
  		}
  
  		public Collection<Instruction> Instructions {
  			get { return instructions ?? (instructions = new InstructionCollection ()); }
  		}
  
  		public bool HasExceptionHandlers {
  			get { return !exceptions.IsNullOrEmpty (); }
  		}
  
  		public Collection<ExceptionHandler> ExceptionHandlers {
  			get { return exceptions ?? (exceptions = new Collection<ExceptionHandler> ()); }
  		}
  
  		public bool HasVariables {
  			get { return !variables.IsNullOrEmpty (); }
  		}
  
  		public Collection<VariableDefinition> Variables {
  			get { return variables ?? (variables = new VariableDefinitionCollection ()); }
  		}
  
  		public Scope Scope {
  			get { return scope; }
  			set { scope = value; }
  		}
  
  		public ParameterDefinition ThisParameter {
  			get {
  				if (method == null || method.DeclaringType == null)
  					throw new NotSupportedException ();
  
  				if (this_parameter == null) {
  					this_parameter = new ParameterDefinition (method.DeclaringType);
  					this_parameter.method = method;
  				}
  
  				return this_parameter;
  			}
  		}
  
  		public MethodBody (MethodDefinition method)
  		{
  			this.method = method;
  		}
  
  		public ILProcessor GetILProcessor ()
  		{
  			return new ILProcessor (this);
  		}
  	}
  
  	public interface IVariableDefinitionProvider {
  		bool HasVariables { get; }
  		Collection<VariableDefinition> Variables { get; }
  	}
  
  	class VariableDefinitionCollection : Collection<VariableDefinition> {
  
  		internal VariableDefinitionCollection ()
  		{
  		}
  
  		internal VariableDefinitionCollection (int capacity)
  			: base (capacity)
  		{
  		}
  
  		protected override void OnAdd (VariableDefinition item, int index)
  		{
  			item.index = index;
  		}
  
  		protected override void OnInsert (VariableDefinition item, int index)
  		{
  			item.index = index;
  
  			for (int i = index; i < size; i++)
  				items [i].index = i + 1;
  		}
  
  		protected override void OnSet (VariableDefinition item, int index)
  		{
  			item.index = index;
  		}
  
  		protected override void OnRemove (VariableDefinition item, int index)
  		{
  			item.index = -1;
  
  			for (int i = index + 1; i < size; i++)
  				items [i].index = i - 1;
  		}
  	}
  
  	class InstructionCollection : Collection<Instruction> {
  
  		internal InstructionCollection ()
  		{
  		}
  
  		internal InstructionCollection (int capacity)
  			: base (capacity)
  		{
  		}
  
  		protected override void OnAdd (Instruction item, int index)
  		{
  			if (index == 0)
  				return;
  
  			var previous = items [index - 1];
  			previous.next = item;
  			item.previous = previous;
  		}
  
  		protected override void OnInsert (Instruction item, int index)
  		{
  			if (size == 0)
  				return;
  
  			var current = items [index];
  			if (current == null) {
  				var last = items [index - 1];
  				last.next = item;
  				item.previous = last;
  				return;
  			}
  
  			var previous = current.previous;
  
gt: 			if (previous != null) {