/*  
 * PERWAPI - An API for Reading and Writing PE Files
 * 
 * Copyright (c) Diane Corney, Queensland University of Technology, 2004.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the PERWAPI Copyright as included with this
 * distribution in the file PERWAPIcopyright.rtf.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY as is explained in the copyright notice.
 *
 * The author may be contacted at d.corney@qut.edu.au
 * 
 * Version Date:  26/01/07
 */

using System;
using System.IO;
using System.Collections;
using System.Diagnostics;
using SCG = System.Collections.Generic;


namespace QUT.PERWAPI
{


    /**************************************************************************/
    // Classes to represent CIL Byte Codes
    /**************************************************************************/
    /// <summary>
    /// The IL instructions for a method
    /// </summary>
    public class CILInstructions
    {
        private static readonly uint MaxClauses = 10;
        private static readonly uint ExHeaderSize = 4;
        private static readonly uint FatExClauseSize = 24;
        private static readonly uint SmlExClauseSize = 12;
        private static readonly sbyte maxByteVal = 127;
        private static readonly sbyte minByteVal = -128;
        private static readonly byte maxUByteVal = 255;
        private static readonly int smallSize = 64;
        internal static readonly ushort TinyFormat = 0x2;
        internal static readonly ushort FatFormat = 0x03;
        internal static readonly ushort FatFormatHeader = 0x3003;
        internal static readonly ushort MoreSects = 0x8;
        internal static readonly ushort InitLocals = 0x10;
        private static readonly uint FatSize = 12;
        private static readonly uint FatWords = FatSize / 4;
        internal static readonly byte FatExceptTable = 0x41;
        internal static readonly byte SmlExceptTable = 0x01;
        internal static readonly uint EHTable = 0x1;
        internal static readonly uint SectFatFormat = 0x40;
        internal static readonly uint SectMoreSects = 0x80;

        private ArrayList exceptions, sourceLines, defaultLines;
        private SourceFile defaultSourceFile;
        private Stack blockStack;
        //private bool codeChecked = false;
        private static readonly int INITSIZE = 5;
        private CILInstruction[] buffer = new CILInstruction[INITSIZE];
        // REPLACE with ArrayList<CILInstruction> for next version of .NET
        private CILInstruction[] saveBuffer;
        private int tide = 0, saveTide = 0;
        private uint offset = 0;
        private ushort headerFlags = 0;
        private short maxStack;
        private uint paddingNeeded = 0;
        private byte exceptHeader = 0;
        private int currI = -1;
        uint localSigIx = 0;
        int numReplace = 0;
        uint codeSize = 0, exceptSize = 0;
        bool tinyFormat, fatExceptionFormat = false, inserting = false;
        MethodDef thisMeth;

        internal Scope currentScope;

        /// <summary>
        /// Shows if return statements in this code block require a value on the stack or not.
        /// </summary>
        internal bool ReturnsVoid;

        /*-------------------- Constructors ---------------------------------*/

        internal CILInstructions(MethodDef meth)
        {
            thisMeth = meth;
        }

        /*--------------------- public general editing methods ---------------------------*/
        /// <summary>
        /// The source file containing these IL instructions
        /// </summary>
        public SourceFile DefaultSourceFile
        {
            get { return defaultSourceFile; }
            set { defaultSourceFile = value; }
        }

        /// <summary>
        /// The number of instructions currently in the buffer. 
        /// </summary>
        public int NumInstructions()
        {
            if (inserting) return tide + saveTide;
            return tide;
        }

        /// <summary>
        /// Get the next instruction in the instruction buffer in sequence.  
        /// An internal index is kept to keep track of which instruction was the last
        /// retrieved by this method.  On the first call, the first instruction in 
        /// the buffer is retrieved.  The instruction index may be zeroed 
        /// using ResetInstCounter().  This method cannot be called when in "insert" mode.
        /// </summary>
        /// <returns></returns>
        public CILInstruction GetNextInstruction()
        {
            if (inserting) throw new Exception("Cannot access next instruction during insert");
            if (currI + 1 < tide)
                return buffer[++currI];
            return null;
        }

        /// <summary>
        /// Get the previous instruction in the instruction buffer in sequence.  
        /// An internal index is kept to keep track of which instruction was the last
        /// retrieved by this method. This method cannot be called when in "insert" mode.
        /// </summary>
        /// <returns></returns>
        public CILInstruction GetPrevInstruction()
        {
            if (inserting) throw new Exception("Cannot access previous instruction during insert");
            if (currI > 0)
                return buffer[--currI];
            return null;
        }

        /// <summary>
        /// Reset the counter for GetNextInstuction to the first instruction.
        /// This method cannot be called when in "insert" mode.
        /// </summary>
        public void ResetInstCounter()
        {
            if (inserting) throw new Exception("Cannot reset instruction counter during insert");
            currI = -1;
        }

        /// <summary>
        /// Reset the counter for GetNextInstuction to the first instruction.
        /// This method cannot be called when in "insert" mode.
        /// </summary>
        public void EndInstCounter()
        {
            if (inserting) throw new Exception("Cannot reset instruction counter during insert");
            currI = tide;
        }

        /// <summary>
        /// Get all the IL instructions.
        /// This method cannot be called when in "insert" mode.
        /// </summary>
        /// <returns></returns>
        public CILInstruction[] GetInstructions()
        {
            if (inserting) throw new Exception("Cannot get instructions during insert");
            return buffer;
        }

        /// <summary>
        /// Set the instruction to be the new array of instructions, this will replace
        /// any existing instructions.  This method cannot be called when in "insert" mode.
        /// </summary>
        /// <param name="insts">The new instructions</param>
        public void SetInstructions(CILInstruction[] insts)
        {
            if (inserting) throw new Exception("Cannot replace instructions during insert.");
            buffer = insts;
            tide = buffer.Length;
            for (int i = 0; i < tide; i++)
            {
                if (insts[i] == null)
                    tide = i;
                insts[i].index = (uint)i;
            }
        }

        /// <summary>
        /// This method should only be used to insert instructions into a buffer which 
        /// already contains some instructions.
        /// Start inserting instructions into the instruction buffer ie. set the buffer
        /// to "insert" mode.  The position of the insertion will be directly after 
        /// the "current instruction" as used be GetNextInstruction().  The 
        /// instructions to be inserted are any calls to the instruction specific 
        /// methods - Inst, TypeInst, MethodInst, etc.
        /// This method cannot be called if already in "insert" mode.
        /// </summary>
        public void StartInsert()
        {
            if (inserting)
                throw new Exception("Cannot insert into an instruction buffer already in insert mode");
            inserting = true;
            saveTide = tide;
            saveBuffer = buffer;
            tide = 0;
            buffer = new CILInstruction[INITSIZE];
        }

        /// <summary>
        /// Stop inserting instructions into the buffer.  Any instructions added after 
        /// this call will go at the end of the instruction buffer.  
        /// To be used with StartInsert().
        /// This method cannot be called if not in "insert" mode.
        /// </summary>
        public void EndInsert()
        {
            if (!inserting)
                throw new Exception("Cannot stop inserting if not in insert mode");
            CILInstruction[] newInsts = buffer;
            buffer = saveBuffer;
            int numNew = tide;
            tide = saveTide;
            int insPos = currI + 1;
            if (numReplace > 0) insPos--;
            InsertInstructions(insPos, newInsts, numNew);
            inserting = false;
            numReplace = 0;
        }

        /// <summary>
        /// Check if the buffer is ready for insertion of extra instructions.
        /// The buffer only needs to be in insert mode when instructions need
        /// to be added to existing instructions, not for addition of instructions
        /// to the end of the buffer.
        /// </summary>
        /// <returns></returns>
        public bool InInsertMode() { return inserting; }

        /// <summary>
        /// Remove the instruction at a specified position from the buffer.  If you 
        /// remove the "current" instruction (from GetNext or GetPrev) then the
        /// "current" instruction becomes the instruction before that in the buffer.
        /// </summary>
        /// <param name="pos">position of the instruction to be removed</param>
        public void RemoveInstruction(int pos)
        {
            if (pos < 0) return;
            for (int i = pos; i < tide - 1; i++)
            {
                buffer[i] = buffer[i + 1];
                buffer[i].index = (uint)i;
            }
            tide--;
            if (pos == currI) currI = pos - 1;
        }

        /// <summary>
        /// Remove the instructions from position "startRange" to (and including)
        /// position "endRange" from the buffer.  If the range removed contains the
        /// "current" instruction (from GetNext or GetPrev) then the "current" 
        /// instruction becomes the instruction before startRange in the buffer.
        /// </summary>
        public void RemoveInstructions(int startRange, int endRange)
        {
            if (startRange < 0) startRange = 0;
            if (endRange >= tide - 1)
            {// cut to startRange
                tide = startRange;
                return;
            }
            int offset = endRange - startRange + 1;
            for (int i = endRange + 1; i < tide; i++)
            {
                buffer[i - offset] = buffer[i];
                buffer[i - offset].index = (uint)(i - offset);
            }
            tide -= offset;
            if ((currI >= startRange) && (currI <= endRange)) currI = startRange - 1;
        }

        /// <summary>
        /// Replace a single IL instruction at position pos in the buffer 
        /// with some new instruction(s).  This removes the instruction and puts 
        /// the instruction buffer into "insert" mode at the position of the removed 
        /// instruction.  EndInsert must be called to insert the new instructions.
        /// This method cannot be called when in "insert" mode.
        /// </summary>
        /// <param name="pos">position of the instruction to be replaced</param>
        public void ReplaceInstruction(int pos)
        {
            if (inserting) throw new Exception("Cannot replace instructions during insert.");
            currI = pos;
            if ((pos > 0) || (pos < tide))
            {
                numReplace = 1;
                StartInsert();
            }
        }

        /// <summary>
        /// Replace a number of IL instructions beginning at position pos in the buffer 
        /// with some new instruction(s).  This removes the instructions and puts 
        /// the instruction buffer into "insert" mode at the position of the removed 
        /// instructions.  EndInsert must be called to insert the new instructions.
        /// The instructions from index "from" up to and including index "to" will
        /// be replaced by the new instructions entered.
        /// This method cannot be called when in "insert" mode.
        /// </summary>
        /// <param name="from">the index to start replacing instruction from</param>
        /// <param name="to">the last index of the instructions to be replaced</param>
        public void ReplaceInstruction(int from, int to)
        {
            if (inserting) throw new Exception("Cannot replace instructions during insert.");
            currI = from;
            if ((from < 0) || (from >= tide) || (to < 0))
                throw new Exception("replace index is out of range");
            if (to >= tide) to = tide - 1;
            numReplace = to - from + 1;
            StartInsert();
        }

        /*---------------- public instruction specific methods ------------------------*/

        /// <summary>
        /// Add a simple IL instruction
        /// </summary>
        /// <param name="inst">the IL instruction</param>
        public void Inst(Op inst)
        {
            AddToBuffer(new Instr(inst));
        }

        /// <summary>
        /// Add an IL instruction with an integer parameter
        /// </summary>
        /// <param name="inst">the IL instruction</param>
        /// <param name="val">the integer parameter value</param>
        public void IntInst(IntOp inst, int val)
        {
            if ((inst == IntOp.ldc_i4_s) || (inst == IntOp.ldc_i4))
            {
                if ((val < 9) && (val >= -1))
                {
                    AddToBuffer(new Instr((Op)((int)Op.ldc_i4_0 + val)));
                }
                else
                {
                    AddToBuffer(new IntInstr(inst, val));
                }
            }
            else
                AddToBuffer(new UIntInstr(inst, (uint)val));
        }

        /// <summary>
        /// Add the load long instruction
        /// </summary>
        /// <param name="cVal">the long value</param>
        public void ldc_i8(long cVal)
        {
            AddToBuffer(new LongInstr(SpecialOp.ldc_i8, cVal));
        }

        /// <summary>
        /// Add the load float32 instruction
        /// </summary>
        /// <param name="cVal">the float value</param>
        public void ldc_r4(float cVal)
        {
            AddToBuffer(new FloatInstr(SpecialOp.ldc_r4, cVal));
        }

        /// <summary>
        /// Add the load float64 instruction
        /// </summary>
        /// <param name="cVal">the float value</param>
        public void ldc_r8(double cVal)
        {
            AddToBuffer(new DoubleInstr(SpecialOp.ldc_r8, cVal));
        }

        /// <summary>
        /// Add the load string instruction
        /// </summary>
        /// <param name="str">the string value</param>
        public void ldstr(string str)
        {
            AddToBuffer(new StringInstr(SpecialOp.ldstr, str));
        }

        /// <summary>
        /// Add the calli instruction
        /// </summary>
        /// <param name="sig">the signature for the calli</param>
        public void calli(CalliSig sig)
        {
            AddToBuffer(new SigInstr(SpecialOp.calli, sig));
        }

        /// <summary>
        /// Create a new CIL label.  To place the label in the CIL instruction
        /// stream use CodeLabel.
        /// </summary>
        /// <returns>a new CIL label</returns>
        public CILLabel NewLabel()
        {
            return new CILLabel();
        }

        /// <summary>
        /// Create a new label at this position in the code buffer
        /// </summary>
        /// <returns>the label at the current position</returns>
        public CILLabel NewCodedLabel()
        {
            CILLabel lab = new CILLabel();
            lab.Buffer = this;
            AddToBuffer(lab);
            return lab;
        }

        /// <summary>
        /// Add a label to the CIL instructions
        /// </summary>
        /// <param name="lab">the label to be added</param>
        public void CodeLabel(CILLabel lab)
        {
            if (lab.Buffer == null)
            {
                lab.Buffer = this;
            }
            else if (lab.Buffer != this)
            {
                throw new DescriptorException("Cannot add a label to two different code buffers");
            }
            AddToBuffer(lab);
        }

        /// <summary>
        /// Add an instruction with a field parameter
        /// </summary>
        /// <param name="inst">the CIL instruction</param>
        /// <param name="f">the field parameter</param>
        public void FieldInst(FieldOp inst, Field f)
        {
            Debug.Assert(f != null);
            if (f is FieldDef)
                if (((FieldDef)f).GetScope() != thisMeth.GetScope())
                    throw new DescriptorException();
            AddToBuffer(new FieldInstr(inst, f));
        }

        /// <summary>
        /// Add an instruction with a method parameter
        /// </summary>
        /// <param name="inst">the CIL instruction</param>
        /// <param name="m">the method parameter</param>
        public void MethInst(MethodOp inst, Method m)
        {
            Debug.Assert(m != null);
            if (m is MethodDef)
                if (((MethodDef)m).GetScope() != thisMeth.GetScope())
                    throw new DescriptorException();
            AddToBuffer(new MethInstr(inst, m));
        }

        /// <summary>
        /// Add an instruction with a type parameter
        /// </summary>
        /// <param name="inst">the CIL instruction</param>
        /// <param name="aType">the type argument for the CIL instruction</param>
        public void TypeInst(TypeOp inst, Type aType)
        {
            Debug.Assert(aType != null);
            if (aType is ClassDef)
            {
                if (((ClassDef)aType).GetScope() != thisMeth.GetScope())
                    throw new DescriptorException();
            }
            AddToBuffer(new TypeInstr(inst, aType));
        }

        /// <summary>
        /// Add a branch instruction
        /// </summary>
        /// <param name="inst">the branch instruction</param>
        /// <param name="lab">the label that is the target of the branch</param>
        public void Branch(BranchOp inst, CILLabel lab)
        {
            Debug.Assert(lab != null);
            AddToBuffer(new BranchInstr(inst, lab));
        }

        /// <summary>
        /// Add a switch instruction
        /// </summary>
        /// <param name="labs">the target labels for the switch</param>
        public void Switch(CILLabel[] labs)
        {
            AddToBuffer(new SwitchInstr(labs));
        }

        /// <summary>
        /// Add a byte to the CIL instructions (.emitbyte)
        /// </summary>
        /// <param name="bVal"></param>
        public void emitbyte(byte bVal)
        {
            AddToBuffer(new CILByte(bVal));
        }

        /// <summary>
        /// Add an instruction which puts an integer on TOS.  This method
        /// selects the correct instruction based on the value of the integer.
        /// </summary>
        /// <param name="i">the integer value</param>
        public void PushInt(int i)
        {
            if (i == -1)
            {
                AddToBuffer(new Instr(Op.ldc_i4_m1));
            }
            else if ((i >= 0) && (i <= 8))
            {
                Op op = (Op)(Op.ldc_i4_0 + i);
                AddToBuffer(new Instr(op));
            }
            else if ((i >= minByteVal) && (i <= maxByteVal))
            {
                AddToBuffer(new IntInstr(IntOp.ldc_i4_s, i));
            }
            else
            {
                AddToBuffer(new IntInstr(IntOp.ldc_i4, i));
            }
        }

        /// <summary>
        /// Add the instruction to load a long on TOS
        /// </summary>
        /// <param name="l">the long value</param>
        public void PushLong(long l)
        {
            AddToBuffer(new LongInstr(SpecialOp.ldc_i8, l));
        }

        /// <summary>
        /// Add an instruction to push the boolean value true on TOS
        /// </summary>
        public void PushTrue()
        {
            AddToBuffer(new Instr(Op.ldc_i4_1));
        }

        /// <summary>
        ///  Add an instruction to push the boolean value false on TOS
        /// </summary>
        public void PushFalse()
        {
            AddToBuffer(new Instr(Op.ldc_i4_0));
        }

        /// <summary>
        /// Add the instruction to load an argument on TOS.  This method
        /// selects the correct instruction based on the value of argNo
        /// </summary>
        /// <param name="argNo">the number of the argument</param>
        public void LoadArg(int argNo)
        {
            if (argNo < 4)
            {
                Op op = (Op)Op.ldarg_0 + argNo;
                AddToBuffer(new Instr(op));
            }
            else if (argNo <= maxUByteVal)
            {
                AddToBuffer(new UIntInstr(IntOp.ldarg_s, (uint)argNo));
            }
            else
            {
                AddToBuffer(new UIntInstr(IntOp.ldarg, (uint)argNo));
            }
        }

        /// <summary>
        /// Add the instruction to load the address of an argument on TOS.
        /// This method selects the correct instruction based on the value
        /// of argNo.
        /// </summary>
        /// <param name="argNo">the number of the argument</param>
        public void LoadArgAdr(int argNo)
        {
            if (argNo <= maxUByteVal)
            {
                AddToBuffer(new UIntInstr(IntOp.ldarga_s, (uint)argNo));
            }
            else
            {
                AddToBuffer(new UIntInstr(IntOp.ldarga, (uint)argNo));
            }
        }

        /// <summary>
        /// Add the instruction to load a local on TOS.  This method selects
        /// the correct instruction based on the value of locNo.
        /// </summary>
        /// <param name="locNo">the number of the local to load</param>
        public void LoadLocal(int locNo)
        {
            if (locNo < 4)
            {
                Op op = (Op)Op.ldloc_0 + locNo;
                AddToBuffer(new Instr(op));
            }
            else if (locNo <= maxUByteVal)
            {
                AddToBuffer(new UIntInstr(IntOp.ldloc_s, (uint)locNo));
            }
            else
            {
                AddToBuffer(new UIntInstr(IntOp.ldloc, (uint)locNo));
            }
        }

        /// <summary>
        /// Add the instruction to load the address of a local on TOS.
        /// This method selects the correct instruction based on the 
        /// value of locNo.
        /// </summary>
        /// <param name="locNo">the number of the local</param>
        public void LoadLocalAdr(int locNo)
        {
            if (locNo <= maxUByteVal)
            {
                AddToBuffer(new UIntInstr(IntOp.ldloca_s, (uint)locNo));
            }
            else
            {
                AddToBuffer(new UIntInstr(IntOp.ldloca, (uint)locNo));
            }
        }

        /// <summary>
        /// Add the instruction to store to an argument.  This method
        /// selects the correct instruction based on the value of argNo.
        /// </summary>
        /// <param name="argNo">the argument to be stored to</param>
        public void StoreArg(int argNo)
        {
            if (argNo <= maxUByteVal)
            {
                AddToBuffer(new UIntInstr(IntOp.starg_s, (uint)argNo));
            }
            else
            {
                AddToBuffer(new UIntInstr(IntOp.starg, (uint)argNo));
            }
        }

        /// <summary>
        /// Add the instruction to store to a local.  This method selects
        /// the correct instruction based on the value of locNo.
        /// </summary>
        /// <param name="locNo">the local to be stored to</param>
        public void StoreLocal(int locNo)
        {
            if (locNo < 4)
            {
                Op op = (Op)Op.stloc_0 + locNo;
                AddToBuffer(new Instr(op));
            }
            else if (locNo <= maxUByteVal)
            {
                AddToBuffer(new UIntInstr(IntOp.stloc_s, (uint)locNo));
            }
            else
            {
                AddToBuffer(new UIntInstr(IntOp.stloc, (uint)locNo));
            }
        }

        public void IntLine(int num)
        {
            Line((uint)num, 1);
        }

        /// <summary>
        /// CLS compliant version of Line()
        /// </summary>
        /// <param name="sLin">The start line</param>
        /// <param name="sCol">The start column</param>
        /// <param name="eLin">The end line</param>
        /// <param name="eCol">The end column</param>
        public void IntLine(int sLin, int sCol, int eLin, int eCol)
        {
            Line((uint)sLin, (uint)sCol, (uint)eLin, (uint)eCol);
        }

        /// <summary>
        /// Create a new line instruction.
        /// </summary>
        /// <param name="num">The line for the given code segment.</param>
        /// <param name="startCol">The starting column for the code segment.</param>
        public void Line(uint num, uint startCol)
        {
            if (this.DefaultSourceFile == null) throw new Exception("Method can only be used if DefaultSourceFile has been set.");
            AddToBuffer(new Line(num, startCol, this.DefaultSourceFile));
        }

        /// <summary>
        /// Create a new line instruction.
        /// </summary>
        /// <param name="num">The line for the given code segment.</param>
        /// <param name="startCol">The starting column for the code segment.</param>
        /// <param name="endCol">The ending column for the code segment.</param>
        public void Line(uint num, uint startCol, uint endCol)
        {
            if (this.DefaultSourceFile == null) throw new Exception("Method can only be used if DefaultSourceFile has been set.");
            AddToBuffer(new Line(num, startCol, num, endCol, this.DefaultSourceFile));
        }

        /// <summary>
        /// Create a new line instruction.
        /// </summary>
        /// <param name="startNum">The starting line for the code segment.</param>
        /// <param name="startCol">The starting column for the code segment.</param>
        /// <param name="endNum">The ending line for the code segment.</param>
        /// <param name="endCol">The ending column for the code segment.</param>
        public void Line(uint startNum, uint startCol, uint endNum, uint endCol)
        {
            if (this.DefaultSourceFile == null) throw new Exception("Method can only be used if DefaultSourceFile has bene set.");
            AddToBuffer(new Line(startNum, startCol, endNum, endCol, this.DefaultSourceFile));
        }

        /// <summary>
        /// Create a new line instruction.
        /// </summary>
        /// <param name="startNum">The starting line for the code segment.</param>
        /// <param name="startCol">The starting column for the code segment.</param>
        /// <param name="endNum">The ending line for the code segment.</param>
        /// <param name="endCol">The ending column for the code segment.</param>
        /// <param name="sFile">The source file for the given code segment.</param>
        public void Line(uint startNum, uint startCol, uint endNum, uint endCol, SourceFile sFile)
        {
            AddToBuffer(new Line(startNum, startCol, endNum, endCol, sFile));
        }

        /// <summary>
        /// The current scope.
        /// </summary>
        public Scope CurrentScope
        {
            get { return currentScope; }
        }

        /// <summary>
        /// Open a new scope.
        /// </summary>
        public void OpenScope()
        {
            currentScope = new Scope(currentScope, thisMeth);
            AddToBuffer(new OpenScope(currentScope));
            //Console.WriteLine("Open scope on " + currentScope._thisMeth.Name());
        }

        /// <summary>
        /// Close the current scope.
        /// </summary>
        public void CloseScope()
        {
            //Console.WriteLine("Close scope on " + currentScope._thisMeth.Name());
            AddToBuffer(new CloseScope(currentScope));
            currentScope = currentScope._parent;
        }

        /// <summary>
        /// Bind a local to the CIL instructions.
        /// </summary>
        /// <param name="name">The name of the local variable..</param>
        /// <param name="index">The index of the local variable.</param>
        /// <returns>The LocalBinding object created with the given values.</returns>
        public LocalBinding BindLocal(string name, int index)
        {
            if (currentScope == null)
                throw new Exception("Scope must be opened before locals can be bound.");
            return currentScope.AddLocalBinding(name, index);
        }

        /// <summary>
        /// Bind a local to the CIL instructions.
        /// </summary>
        /// <param name="local">The local variable to load.</param>
        /// <returns>The LocalBinding object created for the given Local object.</returns>
        public LocalBinding BindLocal(Local local)
        {
            return BindLocal(local.Name, local.GetIndex());
        }

        /// <summary>
        /// Bind a constant to the CIL instructions.
        /// </summary>
        /// <param name="name">The name of the constant.</param>
        /// <param name="value">The value of the constant.</param>
        /// <param name="type">The type of the constant.</param>
        /// <returns>Return the ConstantBinding created with the given values.</returns>
        public ConstantBinding BindConstant(string name, object value, Type type)
        {
            if (currentScope == null)
                throw new Exception("Scope must be opened before constants can be bound.");
            return currentScope.AddConstantBinding(name, value, type);
        }

        /// <summary>
        /// Mark this position as the start of a new block
        /// (try, catch, filter, finally or fault)
        /// </summary>
        public void StartBlock()
        {
            if (blockStack == null) blockStack = new Stack();
            blockStack.Push(NewCodedLabel());
        }

        /// <summary>
        /// Mark this position as the end of the last started block and
        /// make it a try block.  This try block is added to the current 
        /// instructions (ie do not need to call AddTryBlock)
        /// </summary>
        /// <returns>The try block just ended</returns>
        public TryBlock EndTryBlock()
        {
            TryBlock tBlock = new TryBlock((CILLabel)blockStack.Pop(), NewCodedLabel());
            AddTryBlock(tBlock);
            return tBlock;
        }

        /// <summary>
        /// Mark this position as the end of the last started block and
        /// make it a catch block.  This catch block is associated with the
        /// specified try block.
        /// </summary>
        /// <param name="exceptType">the exception type to be caught</param>
        /// <param name="tryBlock">the try block associated with this catch block</param>
        public void EndCatchBlock(Class exceptType, TryBlock tryBlock)
        {
            Catch catchBlock = new Catch(exceptType, (CILLabel)blockStack.Pop(), NewCodedLabel());
            tryBlock.AddHandler(catchBlock);
        }

        /// <summary>
        /// Mark this position as the end of the last started block and
        /// make it a filter block.  This filter block is associated with the
        /// specified try block.  The format is:
        /// filterLab:   ...
        ///              ...
        /// filterHandler :  ...
        ///                  ...             
        /// </summary>
        /// <param name="filterLab">the label where the filter code is</param>
        /// <param name="tryBlock">the try block associated with this filter block</param>
        public void EndFilterBlock(CILLabel filterLab, TryBlock tryBlock)
        {
            Filter filBlock = new Filter(filterLab, (CILLabel)blockStack.Pop(), NewCodedLabel());
            tryBlock.AddHandler(filBlock);
        }

        /// <summary>
        /// Mark this position as the end of the last started block and
        /// make it a finally block.  This finally block is associated with the
        /// specified try block.
        /// </summary>
        /// <param name="tryBlock">the try block associated with this finally block</param>
        public void EndFinallyBlock(TryBlock tryBlock)
        {
            Finally finBlock = new Finally((CILLabel)blockStack.Pop(), NewCodedLabel());
            tryBlock.AddHandler(finBlock);
        }

        /// <summary>
        /// Mark this position as the end of the last started block and
        /// make it a fault block.  This fault block is associated with the
        /// specified try block.
        /// </summary>
        /// <param name="tryBlock">the try block associated with this fault block</param>
        public void EndFaultBlock(TryBlock tryBlock)
        {
            Fault fBlock = new Fault((CILLabel)blockStack.Pop(), NewCodedLabel());
            tryBlock.AddHandler(fBlock);
        }

        public void AddTryBlock(TryBlock tryBlock)
        {
            if (exceptions == null)
                exceptions = new ArrayList();
            else if (exceptions.Contains(tryBlock)) return;
            exceptions.Add(tryBlock);
        }

        /*------------------------- private methods ----------------------------*/

        private void AddToBuffer(CILInstruction inst)
        {
            if (tide >= buffer.Length)
            {
                CILInstruction[] tmp = buffer;
                buffer = new CILInstruction[tmp.Length * 2];
                for (int i = 0; i < tide; i++)
                {
                    buffer[i] = tmp[i];
                }
            }
            //Console.WriteLine("Adding instruction at offset " + offset + " with size " + inst.size);
            //inst.offset = offset;
            //offset += inst.size;
            inst.index = (uint)tide;
            buffer[tide++] = inst;
        }

        private void UpdateIndexesFrom(int ix)
        {
            for (int i = ix; i < tide; i++)
            {
                buffer[i].index = (uint)i;
            }
        }

        private void InsertInstructions(int ix, CILInstruction[] newInsts, int numNew)
        {
            CILInstruction[] newBuff = buffer, oldBuff = buffer;
            int newSize = tide + numNew - numReplace;
            if (buffer.Length < newSize)
            {
                newBuff = new CILInstruction[newSize];
                for (int i = 0; i < ix; i++)
                {
                    newBuff[i] = oldBuff[i];
                }
            }
            // shuffle up
            int offset = numNew - numReplace;
            int end = ix + numReplace;
            for (int i = tide - 1; i >= end; i--)
            {
                newBuff[i + offset] = oldBuff[i];
            }
            // insert new instructions
            for (int i = 0; i < numNew; i++)
            {
                newBuff[ix + i] = newInsts[i];
            }
            buffer = newBuff;
            tide += numNew - numReplace;
            UpdateIndexesFrom(ix);
        }

        internal bool IsEmpty()
        {
            return tide == 0;
        }

        internal static CILLabel GetLabel(ArrayList labs, uint targetOffset)
        {
            CILLabel lab;
            int i = 0;
            while ((i < labs.Count) && (((CILLabel)labs[i]).offset < targetOffset)) i++;
            if (i < labs.Count)
            {
                if (((CILLabel)labs[i]).offset == targetOffset) // existing label
                    lab = (CILLabel)labs[i];
                else
                {
                    lab = new CILLabel(targetOffset);
                    labs.Insert(i, lab);
                }
            }
            else
            {
                lab = new CILLabel(targetOffset);
                labs.Add(lab);
            }
            return lab;
        }

        internal void AddEHClause(EHClause ehc)
        {
            if (exceptions == null)
                exceptions = new ArrayList();
            exceptions.Add(ehc);
        }

        internal void SetAndResolveInstructions(CILInstruction[] insts)
        {
            offset = 0;
            ArrayList labels = new ArrayList();
            for (int i = 0; i < insts.Length; i++)
            {
                insts[i].offset = offset;
                offset += insts[i].size;
                if (insts[i] is BranchInstr)
                {
                    ((BranchInstr)insts[i]).MakeTargetLabel(labels);
                }
                else if (insts[i] is SwitchInstr)
                {
                    ((SwitchInstr)insts[i]).MakeTargetLabels(labels);
                }
            }
            if (exceptions != null)
            {
                for (int i = 0; i < exceptions.Count; i++)
                {
                    exceptions[i] = ((EHClause)exceptions[i]).MakeTryBlock(labels);
                }
            }
            if (labels.Count == 0) { buffer = insts; tide = buffer.Length; return; }
            buffer = new CILInstruction[insts.Length + labels.Count];
            int currentPos = 0;
            tide = 0;
            for (int i = 0; i < labels.Count; i++)
            {
                CILLabel lab = (CILLabel)labels[i];
                while ((currentPos < insts.Length) && (insts[currentPos].offset < lab.offset))
                    buffer[tide++] = insts[currentPos++];
                buffer[tide++] = lab;
            }
            while (currentPos < insts.Length)
            {
                buffer[tide++] = insts[currentPos++];
            }
        }

        internal uint GetCodeSize()
        {
            return codeSize + paddingNeeded + exceptSize;
        }

        internal void BuildTables(MetaDataOut md)
        {
            for (int i = 0; i < tide; i++)
            {
                buffer[i].BuildTables(md);
            }
            if (exceptions != null)
            {
                for (int i = 0; i < exceptions.Count; i++)
                {
                    ((TryBlock)exceptions[i]).BuildTables(md);
                }
            }
        }

        internal void BuildCILInfo(CILWriter output)
        {
            for (int i = 0; i < tide; i++)
            {
                buffer[i].BuildCILInfo(output);
            }
            if (exceptions != null)
            {
                for (int i = 0; i < exceptions.Count; i++)
                {
                    ((TryBlock)exceptions[i]).BuildCILInfo(output);
                }
            }
        }

        internal void ChangeRefsToDefs(ClassDef newType, ClassDef[] oldTypes)
        {
            for (int i = 0; i < tide; i++)
            {
                if (buffer[i] is SigInstr)
                {
                    CalliSig sig = ((SigInstr)buffer[i]).GetSig();
                    sig.ChangeRefsToDefs(newType, oldTypes);
                }
                else if (buffer[i] is TypeInstr)
                {
                    TypeInstr tinst = (TypeInstr)buffer[i];
                    if (tinst.GetTypeArg() is ClassDef)
                    {
                        ClassDef iType = (ClassDef)tinst.GetTypeArg();
                        bool changed = false;
                        for (int j = 0; (j < oldTypes.Length) && !changed; j++)
                        {
                            if (iType == oldTypes[j])
                                tinst.SetTypeArg(newType);
                        }
                    }
                }
            }
        }

        internal void AddToLines(Line line)
        {
            if ((line.sourceFile == null) || (line.sourceFile.Match(defaultSourceFile)))
            {
                if (defaultLines == null)
                {
                    if (defaultSourceFile == null)
                        throw new Exception("No Default Source File Set");
                    defaultLines = new ArrayList();
                }
                defaultLines.Add(line);
                return;
            }
            if (sourceLines == null)
            {
                sourceLines = new ArrayList();
            }
            else
            {
                for (int i = 0; i < sourceLines.Count; i++)
                {
                    ArrayList lineList = (ArrayList)sourceLines[i];
                    if (((Line)lineList[0]).sourceFile.Match(line.sourceFile))
                    {
                        lineList.Add(line);
                        return;
                    }
                }
                ArrayList newList = new ArrayList();
                newList.Add(line);
                sourceLines.Add(newList);
            }
        }

        internal void CheckCode(uint locSigIx, bool initLocals, int maxStack, MetaDataOut metaData)
        {
            if (tide == 0) return;
            offset = 0;
            for (int i = 0; i < tide; i++)
            {
                buffer[i].offset = offset;
                offset += buffer[i].size;
                if (buffer[i] is Line)
                    AddToLines((Line)buffer[i]);
            }
            bool changed = true;
            while (changed)
            {
                changed = false;
                Line prevLine = null;
                for (int i = 0; i < tide; i++)
                {
                    if (buffer[i] is Line)
                    {
                        if (prevLine != null)
                            prevLine.CalcEnd((Line)buffer[i]);
                        prevLine = (Line)buffer[i];
                    }
                    changed = buffer[i].Check(metaData) || changed;
                }
                if (prevLine != null) prevLine.Last();
                if (changed)
                {
                    for (int i = 1; i < tide; i++)
                    {
                        buffer[i].offset = buffer[i - 1].offset + buffer[i - 1].size;
                    }
                    offset = buffer[tide - 1].offset + buffer[tide - 1].size;
                }
            }
            codeSize = offset;
            if (Diag.DiagOn) Console.WriteLine("codeSize before header added = " + codeSize);
            if (maxStack == 0) this.maxStack = 8;
            else this.maxStack = (short)maxStack;
            if ((offset < smallSize) && (maxStack <= 8) && (locSigIx == 0) && (exceptions == null))
            {
                // can use tiny header
                if (Diag.DiagOn) Console.WriteLine("Tiny Header");
                tinyFormat = true;
                headerFlags = (ushort)(TinyFormat | ((ushort)codeSize << 2));
                codeSize++;
                if ((codeSize % 4) != 0) { paddingNeeded = 4 - (codeSize % 4); }
            }
            else
            {
                if (Diag.DiagOn) Console.WriteLine("Fat Header");
                tinyFormat = false;
                localSigIx = locSigIx;
                //this.maxStack = (short)maxStack;
                headerFlags = FatFormatHeader;
                if (exceptions != null)
                {
                    // Console.WriteLine("Got exceptions");
                    headerFlags |= MoreSects;
                    uint numExceptClauses = 0;
                    for (int i = 0; i < exceptions.Count; i++)
                    {
                        TryBlock tryBlock = (TryBlock)exceptions[i];
                        tryBlock.SetSize();
                        numExceptClauses += (uint)tryBlock.NumHandlers();
                        if (tryBlock.isFat()) fatExceptionFormat = true;
                    }
                    if (numExceptClauses > MaxClauses) fatExceptionFormat = true;
                    if (Diag.DiagOn) Console.WriteLine("numexceptclauses = " + numExceptClauses);
                    if (fatExceptionFormat)
                    {
                        if (Diag.DiagOn) Console.WriteLine("Fat exception format");
                        exceptHeader = FatExceptTable;
                        exceptSize = ExHeaderSize + numExceptClauses * FatExClauseSize;
                    }
                    else
                    {
                        if (Diag.DiagOn) Console.WriteLine("Tiny exception format");
                        exceptHeader = SmlExceptTable;
                        exceptSize = ExHeaderSize + numExceptClauses * SmlExClauseSize;
                    }
                    if (Diag.DiagOn) Console.WriteLine("exceptSize = " + exceptSize);
                }
                if (initLocals) headerFlags |= InitLocals;
                if ((offset % 4) != 0) { paddingNeeded = 4 - (offset % 4); }
                codeSize += FatSize;
            }
            if (Diag.DiagOn)
                Console.WriteLine("codeSize = " + codeSize + "  headerFlags = " + Hex.Short(headerFlags));
        }

        /// <summary>
        /// Returns the maximum stack depth required by these CIL instructions.
        /// </summary>
        /// <returns>The integer value of the stck depth.</returns>
        public int GetMaxStackDepthRequired()
        {
            if (tide == 0) return 0;

            // Store the code blocks we find
            SCG.List<CodeBlock> codeBlocks = new SCG.List<CodeBlock>();
            SCG.Dictionary<CILLabel, CodeBlock> cbTable = new SCG.Dictionary<CILLabel, CodeBlock>();
            SCG.List<CodeBlock> extraStartingBlocks = new SCG.List<CodeBlock>();

            // Start a default code block
            CodeBlock codeBlock = new CodeBlock(this);
            codeBlock.StartIndex = 0;

            //
            // Identify the code blocks
            //
            for (int i = 0; i < tide; i++)
            {

                /* Handling the tail instruction:
                 * The tail instruction has not been handled even though
                 * it indicates the end of a code block is coming.  The
                 * reason for this is because any valid tail instruction
                 * must be followed by a call* instruction and then a ret
                 * instruction.  Given a ret instruction must be the second
                 * next instruction anyway it has been decided to just let 
                 * the end block be caught then.
                 */

                // If we reach a branch instruction or a switch instruction 
                // then end the current code block inclusive of the instruction.
                if ((buffer[i] is BranchInstr) || (buffer[i] is SwitchInstr))
                {

                    // Close the old block
                    codeBlock.EndIndex = i;
                    if (codeBlock.EndIndex >= codeBlock.StartIndex) // Don't add empty blocks
                        codeBlocks.Add(codeBlock);

                    // Open a new block
                    codeBlock = new CodeBlock(this);
                    codeBlock.StartIndex = i + 1;

                    // If we reach a label then we need to start a new
                    // code block as the label is an entry point.
                }
                else if (buffer[i] is CILLabel)
                {

                    // Close the old block
                    codeBlock.EndIndex = i - 1;
                    if (codeBlock.EndIndex >= codeBlock.StartIndex) // Don't add empty blocks
                        codeBlocks.Add(codeBlock);

                    // Open a new block
                    codeBlock = new CodeBlock(this);
                    codeBlock.StartIndex = i;

                    // Set this label as the entry point for the code block
                    codeBlock.EntryLabel = (CILLabel)buffer[i];
                    // AND ... list in the dictionary.
                    cbTable.Add(codeBlock.EntryLabel, codeBlock);

                    // Check for the ret, throw, rethrow, or jmp instruction as they also end a block
                }
                else if (buffer[i] is Instr)
                {
                    if (
                        (((Instr)buffer[i]).GetOp() == Op.ret) ||
                        (((Instr)buffer[i]).GetOp() == Op.throwOp) ||
                        (((Instr)buffer[i]).GetOp() == Op.rethrow) ||
                        ((buffer[i] is MethInstr) && (((MethInstr)buffer[i]).GetMethodOp() == MethodOp.jmp))
                       )
                    {

                        // Close the old block
                        codeBlock.EndIndex = i;
                        if (codeBlock.EndIndex >= codeBlock.StartIndex) // Don't add empty blocks
                            codeBlocks.Add(codeBlock);

                        // Open a new block
                        // In theory this should never happen but just in case
                        // someone feels like adding dead code it is supported.
                        codeBlock = new CodeBlock(this);
                        codeBlock.StartIndex = i + 1;

                    }

                }

            }

            // Close the last block
            codeBlock.EndIndex = tide - 1;
            if (codeBlock.EndIndex >= codeBlock.StartIndex) // Don't add empty blocks
                codeBlocks.Add(codeBlock);
            codeBlock = null;

            // Check how many code blocks there are.  If an blocks return 0.
            if (codeBlocks.Count == 0) return 0;

            //
            // Loop through each code block and calculate the delta distance
            //
            for (int j = 0; j < codeBlocks.Count; j++)
            {
                CodeBlock block = codeBlocks[j];

                int maxDepth = 0;
                int currentDepth = 0;

                // Loop through each instruction to work out the max depth
                for (int i = block.StartIndex; i <= block.EndIndex; i++)
                {

                    // Get the depth after the next instruction
                    currentDepth += buffer[i].GetDeltaDistance();

                    // If the new current depth is greater then the maxDepth adjust the maxDepth to reflect
                    if (currentDepth > maxDepth)
                        maxDepth = currentDepth;

                }

                // Set the depth of the block
                block.MaxDepth = maxDepth;
                block.DeltaDistance = currentDepth;

                //
                // Link up the next blocks
                //

                // If the block ends with a branch statement set the jump and fall through.
                if (buffer[block.EndIndex] is BranchInstr)
                {
                    BranchInstr branchInst = (BranchInstr)buffer[block.EndIndex];

                    // If this is not a "br" or "br.s" then set the fall through code block
                    if ((branchInst.GetBranchOp() != BranchOp.br) &&
                        (branchInst.GetBranchOp() != BranchOp.br_s))
                        // If there is a following code block set it as the fall through
                        if (j < (codeBlocks.Count - 1))
                            block.NextBlocks.Add(codeBlocks[j + 1]);

                    // Set the code block we are jumping to
                    CodeBlock cb = null;
                    cbTable.TryGetValue(branchInst.GetDest(), out cb);
                    if (cb == null)
                        throw new Exception("Missing Branch Label");
                    block.NextBlocks.Add(cb);

                    // If the block ends in a switch instruction work out the possible next blocks
                }
                else if (buffer[block.EndIndex] is SwitchInstr)
                {
                    SwitchInstr switchInstr = (SwitchInstr)buffer[block.EndIndex];

                    // If there is a following code block set it as the fall through
                    if (j < (codeBlocks.Count - 1))
                        block.NextBlocks.Add(codeBlocks[j + 1]);

                    // Add each destination block
                    foreach (CILLabel label in switchInstr.GetDests())
                    {

                        // Check all of the code blocks to find the jump destination
                        CodeBlock cb = null;
                        cbTable.TryGetValue(label, out cb);
                        if (cb == null) throw new Exception("Missing Case Label");
                        block.NextBlocks.Add(cb);

                    }

                    // So long as the block doesn't end with a terminating instruction like ret or throw, just fall through to the next block
                }
                else if (!IsTerminatingInstruction(buffer[block.EndIndex]))
                {

                    // If there is a following code block set it as the fall through
                    if (j < (codeBlocks.Count - 1))
                        block.NextBlocks.Add(codeBlocks[j + 1]);
                }

            }

            //
            // Join up any exception blocks
            //

            if (exceptions != null)
            {
                foreach (TryBlock tryBlock in exceptions)
                {

                    // Try to find the code block where this try block starts
                    CodeBlock tryCodeBlock;
                    cbTable.TryGetValue(tryBlock.Start, out tryCodeBlock);

                    // Declare that the entry to this code block must be empty
                    tryCodeBlock.RequireEmptyEntry = true;

                    // Work with each of the handlers
                    foreach (HandlerBlock hb in tryBlock.GetHandlers())
                    {

                        // Find the code block where this handler block starts.
                        CodeBlock handlerCodeBlock;
                        cbTable.TryGetValue(hb.Start, out handlerCodeBlock);

                        // If the code block is a catch or filter block increment the delta 
                        // distance by 1. This is to factor in the exception object that will 
                        // be secretly placed on the stack by the runtime engine.
                        // However, this also means that the MaxDepth is up by one also!
                        if (hb is Catch || hb is Filter)
                        {
                            handlerCodeBlock.DeltaDistance++;
                            handlerCodeBlock.MaxDepth++;
                        }

                        // If the code block is a filter block increment the delta distance by 1
                        // This is to factor in the exception object that will be placed on the stack.
                        // if (hb is Filter) handlerCodeBlock.DeltaDistance++;

                        // Add this handler to the list of starting places
                        extraStartingBlocks.Add(handlerCodeBlock);

                    }

                }
            }


            //
            // Traverse the code blocks and get the depth
            //

            // Get the max depth at the starting entry point
            int finalMaxDepth = this.TraverseMaxDepth(codeBlocks[0]);

            // Check the additional entry points
            // If the additional points have a greater depth update the max depth
            foreach (CodeBlock cb in extraStartingBlocks)
            {
                // int tmpMaxDepth = cb.TraverseMaxDepth();
                int tmpMaxDepth = this.TraverseMaxDepth(cb);
                if (tmpMaxDepth > finalMaxDepth) finalMaxDepth = tmpMaxDepth;
            }

            // Return the max depth we have found
            return finalMaxDepth;

        }


        int TraverseMaxDepth(CodeBlock entryBlock)
        {
            int max = 0;
            SCG.Queue<CodeBlock> worklist = new SCG.Queue<CodeBlock>();
            entryBlock.Visited = true;
            entryBlock.LastVisitEntryDepth = 0;
            worklist.Enqueue(entryBlock);
            while (worklist.Count > 0)
            {
                int count = worklist.Count;
                CodeBlock unit = worklist.Dequeue();

                int maxDepth = unit.LastVisitEntryDepth + unit.MaxDepth;
                int exitDepth = unit.LastVisitEntryDepth + unit.DeltaDistance;

                if (maxDepth > max) max = maxDepth;

                foreach (CodeBlock succ in unit.NextBlocks)
                {
                    if (succ.Visited)
                    {
                        if (succ.LastVisitEntryDepth != exitDepth)
                            throw new InvalidStackDepth("inconsistent stack depth at offset " + succ.StartIndex.ToString());
                    }
                    else
                    {
                        succ.Visited = true;
                        succ.LastVisitEntryDepth = exitDepth;
                        worklist.Enqueue(succ);
                    }
                }
            }
            return max;
        }

        private bool IsTerminatingInstruction(CILInstruction cilInstr)
        {
            // Return or throw instructions are terminating instructions
            if (cilInstr is Instr)
            {
                if (((Instr)cilInstr).GetOp() == Op.ret) return true;
                if (((Instr)cilInstr).GetOp() == Op.throwOp) return true;
                if (((Instr)cilInstr).GetOp() == Op.rethrow) return true;
            }
            // jmp is a terminating instruction
            if (cilInstr is MethInstr)
            {
                if (((MethInstr)cilInstr).GetMethodOp() == MethodOp.jmp) return true;
            }
            return false;
        }

        internal void Write(PEWriter output)
        {
            if (Diag.DiagOn) Console.WriteLine("Writing header flags = " + Hex.Short(headerFlags));
            if (tinyFormat)
            {
                if (Diag.DiagOn) Console.WriteLine("Writing tiny code");
                output.Write((byte)headerFlags);
            }
            else
            {
                if (Diag.DiagOn) Console.WriteLine("Writing fat code");
                output.Write(headerFlags);
                output.Write((ushort)maxStack);
                output.Write(offset);
                output.Write(localSigIx);
            }
            if (Diag.DiagOn)
            {
                Console.WriteLine(Hex.Int(tide) + " CIL instructions");
                Console.WriteLine("starting instructions at " + output.Seek(0, SeekOrigin.Current));
            }

            // Added to enable PDB generation
            if (output.pdbWriter != null)
            {

                // Open the method
                output.pdbWriter.OpenMethod((int)thisMeth.Token());

                // Check if this is the entry point method
                if (thisMeth.HasEntryPoint()) output.pdbWriter.SetEntryPoint((int)thisMeth.Token());
            }

            // Write out each memember of the buffer
            for (int i = 0; i < tide; i++)
            {
                buffer[i].Write(output);
            }

            // Added to enable PDB generation
            if (output.pdbWriter != null && tide > 0)
            {
                output.pdbWriter.CloseMethod();
            }
            if (Diag.DiagOn) Console.WriteLine("ending instructions at " + output.Seek(0, SeekOrigin.Current));
            for (int i = 0; i < paddingNeeded; i++) { output.Write((byte)0); }
            if (exceptions != null)
            {
                // Console.WriteLine("Writing exceptions");
                // Console.WriteLine("header = " + Hex.Short(exceptHeader) + " exceptSize = " + Hex.Int(exceptSize));
                output.Write(exceptHeader);
                output.Write3Bytes((uint)exceptSize);
                for (int i = 0; i < exceptions.Count; i++)
                {
                    TryBlock tryBlock = (TryBlock)exceptions[i];
                    tryBlock.Write(output, fatExceptionFormat);
                }
            }
        }

        internal void Write(CILWriter output)
        {
            for (int i = 0; i < tide; i++)
            {
                if (!(buffer[i] is CILLabel))
                {
                    output.Write("    ");
                }
                output.Write("    ");
                buffer[i].Write(output);
            }
            if (exceptions != null)
            {
                throw new NotYetImplementedException("Exceptions not yet implemented for CIL Instructions");
                // Console.WriteLine("Writing exceptions");
                // Console.WriteLine("header = " + Hex.Short(exceptHeader) + " exceptSize = " + Hex.Int(exceptSize));
                //output.Write(exceptHeader);
                //output.Write3Bytes((uint)exceptSize);
                //for (int i = 0; i < exceptions.Count; i++) {
                //     TryBlock tryBlock = (TryBlock)exceptions[i];
                //    tryBlock.Write(output, fatExceptionFormat);
                //}
            }
        }

        /// <summary>
        /// Stores the details of a given code block
        /// </summary>
        private class CodeBlock
        {
            internal int StartIndex;
            internal int EndIndex;
            internal int DeltaDistance;
            internal int MaxDepth;
            internal CILLabel EntryLabel;
            internal ArrayList NextBlocks = new ArrayList(); // List of CodeBlock objects
            // internal int Visits;
            internal int LastVisitEntryDepth;
            internal bool RequireEmptyEntry;
            internal bool Visited = false;
            private CILInstructions cilInstr;

            /// <summary>
            /// Create a new code block definition
            /// </summary>
            /// <param name="instructions">The buffer the code block relates to</param>
            internal CodeBlock(CILInstructions instructions)
            {
                cilInstr = instructions;
            }
        }
    }
    /**************************************************************************/
    /// <summary>
    /// Descriptor for an IL instruction
    /// </summary>
    public abstract class CILInstruction
    {
        protected static readonly sbyte maxByteVal = 127;
        protected static readonly sbyte minByteVal = -128;
        protected static readonly byte leadByte = 0xFE;
        protected static readonly uint USHeapIndex = 0x70000000;
        protected static readonly uint longInstrStart = (uint)Op.arglist;
        protected static readonly string[] opcode = { 
            "nop",     "break",   "ldarg.0", "ldarg.1", "ldarg.2", "ldarg.3", "ldloc.0", "ldloc.1",
            "ldloc.2", "ldloc.3", "stloc.0", "stloc.1", "stloc.2", "stloc.3", "ldarg.s", "ldarga.s",
            "starg.s", "ldloc.s", "ldloca.s","stloc.s", "ldnull",  "ldc.i4.m1","ldc.i4.0","ldc.i4.1",
            "ldc.i4.2","ldc.i4.3","ldc.i4.4","ldc.i4.5","ldc.i4.6","ldc.i4.7","ldc.i4.8","ldc.i4.s",
            "ldc.i4",  "ldc.i8",  "ldc.r4",  "ldc.r8",  "ERROR",   "dup",     "pop",     "jmp",     
            "call",    "calli",   "ret",     "br.s",   "brfalse.s","brtrue.s","beq.s",   "bge.s",
            "bgt.s",   "ble.s",   "blt.s",   "bne.un.s","bge.un.s","bgt.un.s","ble.un.s","blt.un.s",
            "br",      "brfalse", "brtrue",  "beq",     "bge",     "bgt",     "ble",     "blt",
            "bne.un",  "bge.un",  "bgt.un",  "ble.un",  "blt.un",  "switch",  "ldind.i1","ldind.u1",
            "ldind.i2","ldind.u2","ldind.i4","ldind.u4","ldind.i8","ldind.i", "ldind.r4","ldind.r8",
            "ldind.ref","stind.ref","stind.i1","stind.i2","stind.i4","stind.i8","stind.r4","stind.r8",
            "add",     "sub",     "mul",     "div",     "div.un",  "rem",     "rem.un",  "and",
            "or",      "xor",     "shl",     "shr",     "shr.un",  "neg",     "not",     "conv.i1",
            "conv.i2", "conv.i4", "conv.i8", "conv.r4", "conv.r8", "conv.u4", "conv.u8", "callvirt",
            "cpobj",   "ldobj",   "ldstr",   "newobj", "castclass","isinst",  "conv.r.un","ERROR",
            "ERROR",   "unbox",   "throw",   "ldfld",   "ldflda",  "stfld",   "ldsfld",  "ldsflda",
            "stsfld",             "stobj",              "conv.ovf.i1.un",         "conv.ovf.i2.un",
            "conv.ovf.i4.un",   "conv.ovf.i8.un",     "conv.ovf.u1.un",         "conv.ovf.u2.un",
            "conv.ovf.u4.un",     "conv.ovf.u8.un",     "conv.ovf.i.un",          "conv.ovf.u.un",
            "box",              "newarr",             "ldlen",                  "ldelema",
            "ldelem.i1",          "ldelem.u1",          "ldelem.i2",              "ldelem.u2",
            "ldelem.i4",        "ldelem.u4",          "ldelem.i8",              "ldelem.i",
            "ldelem.r4",          "ldelem.r8",          "ldelem.ref",             "stelem.i",
            "stelem.i1",        "stelem.i2",          "stelem.i4",              "stelem.i8",
            "stelem.r4",          "stelem.r8",          "stelem.ref",             "ERROR",
            "ERROR",            "ERROR",              "ERROR",                  "ERROR",
            "ERROR",   "ERROR",   "ERROR",   "ERROR",   "ERROR",   "ERROR",   "ERROR",   "ERROR",
            "ERROR",              "ERROR",              "ERROR",                  "conv.ovf.i1",
            "conv.ovf.u1",      "conv.ovf.i2",        "conv.ovf.u2",            "conv.ovf.i4",
            "conv.ovf.u4",        "conv.ovf.i8",        "conv.ovf.u8",            "ERROR",
            "ERROR",            "ERROR",              "ERROR",                  "ERROR",
            "ERROR",   "ERROR",  "refanyval","ckfinite","ERROR",   "ERROR",   "mkrefany","ERROR",
            "ERROR",   "ERROR",   "ERROR",   "ERROR",   "ERROR",   "ERROR",   "ERROR",   "ERROR",
            "ldtoken","conv.u2","conv.u1","conv.i","conv.ovf.i","conv.ovf.u","add.ovf","add.ovf.un",
            "mul.ovf","mul.ovf.un","sub.ovf","sub.ovf.un","endfinally","leave","leave.s","stind.i",
            "conv.u"};

        protected static readonly int[] opDeltaDistance = { 
              0 /* nop */,             0 /* break */,           1 /* ldarg.0 */,         1 /* ldarg.1 */,         1 /* ldarg.2 */,   1 /* ldarg.3 */,    1 /* ldloc.0 */,     1 /* ldloc.1 */,
              1 /* ldloc.2 */,         1 /* ldloc.3 */,        -1 /* stloc.0 */,        -1 /* stloc.1 */,        -1 /* stloc.2 */,  -1 /* stloc.3 */,    1 /* ldarg.s */,     1 /* ldarga.s */,
             -1 /* starg.s */,         1 /* ldloc.s */,         1 /* ldloca.s */,       -1 /* stloc.s */,         1 /* ldnull */,    1 /* ldc.i4.m1 */,  1 /* ldc.i4.0 */,    1 /* ldc.i4.1 */,
              1 /* ldc.i4.2 */,        1 /* ldc.i4.3 */,        1 /* ldc.i4.4 */,        1 /* ldc.i4.5 */,        1 /* ldc.i4.6 */,  1 /* ldc.i4.7 */,   1 /* ldc.i4.8 */,    1 /* ldc.i4.s */,
              1 /* ldc.i4 */,          1 /* ldc.i8 */,          1 /* ldc.r4 */,          1 /* ldc.r8 */,        -99 /* ERROR */,     1 /* dup */,       -1 /* pop */,         0 /* jmp */,     
            -99 /* call */,          -99 /* calli */,           0 /* ret */,             0 /* br.s */,           -1 /* brfalse.s */,-1 /* brtrue.s */,  -2 /* beq.s */,      -2 /* bge.s */,
             -2 /* bgt.s */,          -2 /* ble.s */,          -2 /* blt.s */,          -2 /* bne.un.s */,       -2 /* bge.un.s */, -2 /* bgt.un.s */,  -2 /* ble.un.s */,   -2 /* blt.un.s */,
              0 /* br */,             -1 /* brfalse */,        -1 /* brtrue */,         -2 /* beq */,            -2 /* bge */,      -2 /* bgt */,       -2 /* ble */,        -2 /* blt */,
             -2 /* bne.un */,         -2 /* bge.un */,         -2 /* bgt.un */,         -2 /* ble.un */,         -2 /* blt.un */,   -1 /* switch */,     0 /* ldind.i1 */,    0 /* ldind.u1 */,
              0 /* ldind.i2 */,        0 /* ldind.u2 */,        0 /* ldind.i4 */,        0 /* ldind.u4 */,        0 /* ldind.i8 */,  0 /* ldind.i */,    0 /* ldind.r4 */,    0 /* ldind.r8 */,
              0 /* ldind.ref */,      -2 /* stind.ref */,      -2 /* stind.i1 */,       -2 /* stind.i2 */,       -2 /* stind.i4 */, -2 /* stind.i8 */,  -2 /* stind.r4 */,   -2 /* stind.r8 */,
             -1 /* add */,            -1 /* sub */,            -1 /* mul */,            -1 /* div */,            -1 /* div.un */,   -1 /* rem */,       -1 /* rem.un */,     -1 /* and */,
             -1 /* or */,             -1 /* xor */,            -1 /* shl */,            -1 /* shr */,            -1 /* shr.un */,    0 /* neg */,        0 /* not */,         0 /* conv.i1 */,
              0 /* conv.i2 */,         0 /* conv.i4 */,         0 /* conv.i8 */,         0 /* conv.r4 */,         0 /* conv.r8 */,   0 /* conv.u4 */,    0 /* conv.u8 */,   -99 /* callvirt */,
             -2 /* cpobj */,           0 /* ldobj */,           1 /* ldstr */,         -99 /* newobj */,          0 /* castclass */, 0 /* isinst */,     0 /* conv.r.un */, -99 /* ERROR */,
            -99 /* ERROR */,           0 /* unbox */,          -1 /* throw */,           0 /* ldfld */,           0 /* ldflda */,   -2 /* stfld */,      1 /* ldsfld */,      1 /* ldsflda */,
             -1 /* stsfld */,         -2 /* stobj */,           0 /* conv.ovf.i1.un */,  0 /* conv.ovf.i2.un */,
              0 /* conv.ovf.i4.un */,  0 /* conv.ovf.i8.un */,  0 /* conv.ovf.u1.un */,  0 /* conv.ovf.u2.un */,
              0 /* conv.ovf.u4.un */,  0 /* conv.ovf.u8.un */,  0 /* conv.ovf.i.un */,   0 /* conv.ovf.u.un */,
              0 /* box */,             0 /* newarr */,          0 /* ldlen */,          -1 /* ldelema */,
             -1 /* ldelem.i1 */,      -1 /* ldelem.u1 */,      -1 /* ldelem.i2 */,      -1 /* ldelem.u2 */,
             -1 /* ldelem.i4 */,      -1 /* ldelem.u4 */,      -1 /* ldelem.i8 */,      -1 /* ldelem.i */,
             -1 /* ldelem.r4 */,      -1 /* ldelem.r8 */,      -1 /* ldelem.ref */,     -3 /* stelem.i */,
             -3 /* stelem.i1 */,      -3 /* stelem.i2 */,      -3 /* stelem.i4 */,      -3 /* stelem.i8 */,
             -3 /* stelem.r4 */,      -3 /* stelem.r8 */,      -3 /* stelem.ref */,    -99 /* ERROR */,
            -99 /* ERROR */,         -99 /* ERROR */,         -99 /* ERROR */,         -99 /* ERROR */,
            -99 /* ERROR */,         -99 /* ERROR */,         -99 /* ERROR */,         -99 /* ERROR */,         -99 /* ERROR */,   -99 /* ERROR */,    -99 /* ERROR */,     -99 /* ERROR */,
            -99 /* ERROR */,         -99 /* ERROR */,         -99 /* ERROR */,           0 /* conv.ovf.i1 */,
              0 /* conv.ovf.u1 */,     0 /* conv.ovf.i2 */,     0 /* conv.ovf.u2 */,     0 /* conv.ovf.i4 */,
              0 /* conv.ovf.u4 */,     0 /* conv.ovf.i8 */,     0 /* conv.ovf.u8 */,   -99 /* ERROR */,
            -99 /* ERROR */,         -99 /* ERROR */,         -99 /* ERROR */,         -99 /* ERROR */,
            -99 /* ERROR */,         -99 /* ERROR */,           0 /* refanyval */,       0 /* ckfinite */,      -99 /* ERROR */,   -99 /* ERROR */,      0 /* mkrefany */,  -99 /* ERROR */,
            -99 /* ERROR */,         -99 /* ERROR */,         -99 /* ERROR */,         -99 /* ERROR */,         -99 /* ERROR */,   -99 /* ERROR */,    -99 /* ERROR */,     -99 /* ERROR */,
              1 /* ldtoken */,         0 /* conv.u2 */,         0 /* conv.u1 */,         0 /* conv.i */,          0 /* conv.ovf.i */,0 /* conv.ovf.u */,-1 /* add.ovf */,    -1 /* add.ovf.un */,
             -1 /* mul.ovf */,        -1 /* mul.ovf.un */,     -1 /* sub.ovf */,        -1 /* sub.ovf.un */,      0 /* endfinally */,0 /* leave */,      0 /* leave.s */,    -2 /* stind.i */,
              0 /* conv.u */};

        /// <summary>
        /// A list of the delta distances for the given CIL instructions.
        /// </summary>
        protected static readonly string[] FEopcode = {
            "arglist", "ceq", "cgt", "cgt.un", "clt", "clt.un", "ldftn", "ldvirtftn",
            "ERROR", "ldarg", "ldarga", "starg", "ldloc", "ldloca", "stloc", "localloc",
            "ERROR", "endfilter", "unaligned", "volatile", "tail", "initobj", "ERROR", "cpblk",
            "initblk", "ERROR", "rethrow", "ERROR", "sizeof", "refanytype", "readonly"};

        /// <summary>
        /// A list of the delta distances for the given FE CIL instructions.
        /// </summary>
        protected static readonly int[] FEopDeltaDistance = {
            1 /* arglist */, -1 /* ceq */, -1 /* cgt */, -1 /* cgt.un */, -1 /* clt */, -1 /* clt.un */, 1 /* ldftn */, 0 /* ldvirtftn */,
            -99 /* ERROR */, 1 /* ldarg */, 1 /* ldarga */, -1 /* starg */, 1 /* ldloc */, 1 /* ldloca */, -1 /* stloc */, 0 /* localloc */,
            -99 /* ERROR */, -1 /* endfilter */, 0 /* unaligned */, 0 /* volatile */, 0 /* tail */, -1 /* initobj */, -99 /* ERROR */, -3 /* cpblk */,
            -3 /* initblk */, -99 /* ERROR */, 0 /* rethrow */, -99 /* ERROR */, 1 /* sizeof */, 0 /* refanytype */, 0 /* readonly */};

        internal bool twoByteInstr = false;
        internal uint size = 1;
        internal uint offset, index;

        internal virtual bool Check(MetaDataOut md)
        {
            return false;
        }

        internal virtual void Resolve() { }

        public int GetPos() { return (int)index; }

        internal abstract string GetInstName();

        /// <summary>
        /// Get the delta distance for this instruction.
        /// </summary>
        /// <remarks>
        /// The delta distance is the resulting difference of items 
        /// left on the stack after calling this instruction.
        /// </remarks>
        /// <returns>An integer value representing the delta distance.</returns>
        internal abstract int GetDeltaDistance();

        internal virtual void BuildTables(MetaDataOut md) { }

        internal virtual void BuildCILInfo(CILWriter output) { }

        internal virtual void Write(PEWriter output) { }

        internal virtual void Write(CILWriter output) { }

    }

    /**************************************************************************/
    public class CILByte : CILInstruction
    {
        byte byteVal;

        /*-------------------- Constructors ---------------------------------*/

        internal CILByte(byte bVal)
        {
            byteVal = bVal;
        }

        public byte GetByte() { return byteVal; }

        internal override string GetInstName()
        {
            return Hex.Byte(byteVal);
        }

        /// <summary>
        /// Get the delta distance for this instruction.
        /// </summary>
        /// <remarks>
        /// The delta distance is the resulting difference of items 
        /// left on the stack after calling this instruction.
        /// </remarks>
        /// <returns>Zero, the delta distance for a CILByte</returns>
        internal override int GetDeltaDistance()
        {
            return 0;
        }

        internal override void Write(PEWriter output)
        {
            output.Write(byteVal);
        }

        internal override void Write(CILWriter output)
        {
            output.WriteLine(".emitbyte " + Hex.Byte(byteVal));  // ???? CHECK THIS ????
        }

    }

    /**************************************************************************/
    public class Instr : CILInstruction
    {
        protected uint instr;

        /*-------------------- Constructors ---------------------------------*/

        public Instr(Op inst)
        {
            instr = (uint)inst;
            if (instr >= longInstrStart)
            {
                instr -= longInstrStart;
                twoByteInstr = true;
                size++;
            }
        }

        internal Instr(uint inst)
        {
            instr = (uint)inst;
            if (instr >= longInstrStart)
            {
                instr -= longInstrStart;
                twoByteInstr = true;
                size++;
            }
        }

        public Op GetOp()
        {
            if (twoByteInstr)
                return (Op)(longInstrStart + instr);
            return (Op)instr;
        }

        internal override string GetInstName()
        {
            Op opInst = GetOp();
            return "" + opInst;
        }

        internal override void Write(PEWriter output)
        {
            //Console.WriteLine("Writing instruction " + instr + " with size " + size);
            if (twoByteInstr) output.Write(leadByte);
            output.Write((byte)instr);
        }

        internal string GetInstrString()
        {
            if (twoByteInstr)
            {
                return FEopcode[instr] + " ";
            }
            else
            {
                return opcode[instr] + " ";
            }
        }

        /// <summary>
        /// Get the delta distance for this instruction.
        /// </summary>
        /// <remarks>
        /// The delta distance is the resulting difference of items 
        /// left on the stack after calling this instruction.
        /// </remarks>
        /// <returns>An integer value representing the delta distance.</returns>
        internal override int GetDeltaDistance()
        {
            if (twoByteInstr)
            {
                return FEopDeltaDistance[instr];
            }
            else
            {
                return opDeltaDistance[instr];
            }
        }

        internal override void Write(CILWriter output)
        {
            if (twoByteInstr)
            {
                output.WriteLine(FEopcode[instr]);
            }
            else
            {
                output.WriteLine(opcode[instr]);
            }
        }

    }

    /**************************************************************************/
    public class IntInstr : Instr
    {
        int val;
        bool byteNum;

        /*-------------------- Constructors ---------------------------------*/

        public IntInstr(IntOp inst, int num)
            : base((uint)inst)
        {
            byteNum = inst == IntOp.ldc_i4_s;
            val = num;
            if (byteNum) size++;
            else size += 4;
        }

        public int GetInt() { return val; }
        public void SetInt(int num) { val = num; }

        internal sealed override void Write(PEWriter output)
        {
            base.Write(output);
            if (byteNum)
                output.Write((sbyte)val);
            else
                output.Write(val);
        }

        /// <summary>
        /// Get the delta distance for this instruction.
        /// </summary>
        /// <remarks>
        /// The delta distance is the resulting difference of items 
        /// left on the stack after calling this instruction.
        /// </remarks>
        /// <returns>An integer value representing the delta distance.</returns>
        internal override int GetDeltaDistance()
        {
            return opDeltaDistance[instr];
        }

        internal override void Write(CILWriter output)
        {
            output.WriteLine(opcode[instr] + " " + val);
        }

    }

    /**************************************************************************/
    public class UIntInstr : Instr
    {
        uint val;
        bool byteNum;

        /*-------------------- Constructors ---------------------------------*/

        public UIntInstr(IntOp inst, uint num)
            : base((uint)inst)
        {
            byteNum = (inst < IntOp.ldc_i4_s) || (inst == IntOp.unaligned);
            val = num;
            if (byteNum) size++;
            else size += 2;
        }

        public uint GetUInt() { return val; }
        public void SetUInt(uint num) { val = num; }

        /// <summary>
        /// Get the delta distance for this instruction.
        /// </summary>
        /// <remarks>
        /// The delta distance is the resulting difference of items 
        /// left on the stack after calling this instruction.
        /// </remarks>
        /// <returns>An integer value representing the delta distance.</returns>
        internal override int GetDeltaDistance()
        {
            if (twoByteInstr)
            {
                return FEopDeltaDistance[instr];
            }
            else
            {
                return opDeltaDistance[instr];
            }
        }

        internal sealed override void Write(PEWriter output)
        {
            base.Write(output);
            if (byteNum)
                output.Write((byte)val);
            else
                output.Write((ushort)val);
        }

        internal override void Write(CILWriter output)
        {
            if (twoByteInstr)
            {
                output.Write(FEopcode[instr]);
            }
            else
            {
                output.Write(opcode[instr]);
            }
            output.WriteLine(" " + val);
        }

    }

    /**************************************************************************/
    public class LongInstr : Instr
    {
        long val;

        /*-------------------- Constructors ---------------------------------*/

        public LongInstr(SpecialOp inst, long l)
            : base((uint)inst)
        {
            val = l;
            size += 8;
        }

        public long GetLong() { return val; }
        public void SetLong(long num) { val = num; }

        internal sealed override void Write(PEWriter output)
        {
            base.Write(output);
            output.Write(val);
        }

        internal override void Write(CILWriter output)
        {
            output.WriteLine("ldc.i8 " + val);
        }

    }

    /**************************************************************************/
    public class FloatInstr : Instr
    {
        float fVal;

        /*-------------------- Constructors ---------------------------------*/

        public FloatInstr(SpecialOp inst, float f)
            : base((uint)inst)
        {
            fVal = f;
            size += 4;
        }

        public float GetFloat() { return fVal; }
        public void SetFloat(float num) { fVal = num; }

        internal sealed override void Write(PEWriter output)
        {
            output.Write((byte)0x22);
            output.Write(fVal);
        }

        internal override void Write(CILWriter output)
        {
            output.WriteLine("ldc.r4 " + fVal);
        }

    }

    /**************************************************************************/
    public class DoubleInstr : Instr
    {
        double val;

        /*-------------------- Constructors ---------------------------------*/

        public DoubleInstr(SpecialOp inst, double d)
            : base((uint)inst)
        {
            val = d;
            size += 8;
        }

        public double GetDouble() { return val; }
        public void SetDouble(double num) { val = num; }

        internal sealed override void Write(PEWriter output)
        {
            base.Write(output);
            output.Write(val);
        }

        internal override void Write(CILWriter output)
        {
            output.WriteLine("ldc.r8 " + val);
        }

    }

    /**************************************************************************/
    public class StringInstr : Instr
    {
        string val;
        uint strIndex;

        /*-------------------- Constructors ---------------------------------*/

        public StringInstr(SpecialOp inst, string str)
            : base((uint)inst)
        {
            val = str;
            size += 4;
        }

        public string GetString() { return val; }
        public void SetString(string str) { val = str; }

        internal sealed override void BuildTables(MetaDataOut md)
        {
            if (Diag.DiagOn) Console.WriteLine("Adding a code string to the US heap");
            strIndex = md.AddToUSHeap(val);
        }

        internal sealed override void Write(PEWriter output)
        {
            base.Write(output);
            output.Write(USHeapIndex | strIndex);
        }

        internal override void Write(CILWriter output)
        {
            output.WriteLine("ldstr \"" + val + "\"");
        }

    }

    /**************************************************************************/
    public class CILLabel : CILInstruction
    {
        private static int labelNum = 0;
        private int num = -1;
        private CILInstructions buffer;

        /*-------------------- Constructors ---------------------------------*/

        public CILLabel()
        {
            size = 0;
        }

        internal CILLabel(uint offs)
        {
            size = 0;
            offset = offs;
        }

        internal uint GetLabelOffset()
        {
            return offset;
        }

        internal override string GetInstName()
        {
            return "Label" + num;
        }

        internal CILInstructions Buffer
        {
            get { return buffer; }
            set { buffer = value; }
        }

        internal override void BuildCILInfo(CILWriter output)
        {
            if (num == -1)
            {
                num = labelNum++;
            }
        }

        /// <summary>
        /// Get the delta distance for this instruction.
        /// </summary>
        /// <remarks>
        /// The delta distance is the resulting difference of items 
        /// left on the stack after calling this instruction.
        /// </remarks>
        /// <returns>An integer value representing the delta distance.</returns>
        internal override int GetDeltaDistance()
        {
            return 0;
        }

        internal override void Write(CILWriter output)
        {
            output.WriteLine("Label" + num + ":");
        }


    }

    /**************************************************************************/

    /// <summary>
    /// Abstract model for debug instructions.
    /// </summary>
    public abstract class DebugInst : CILInstruction { }

    /**************************************************************************/

    /// <summary>
    /// Defines a line instruction.
    /// </summary>
    public class Line : DebugInst
    {
        private static uint MaxCol = 100;
        uint startLine, startCol, endLine, endCol;
        bool hasEnd = false;
        internal SourceFile sourceFile;

        /*-------------------- Constructors ---------------------------------*/

        /// <summary>
        /// Create a new line instruction.
        /// </summary>
        /// <param name="sLine">Start of the line in the source file.</param>
        /// <param name="sCol">Starting column in the source file.</param>
        /// <param name="sFile">The filename of the souce file.</param>
        internal Line(uint sLine, uint sCol, SourceFile sFile)
        {
            startLine = sLine;
            startCol = sCol;
            sourceFile = sFile;
            size = 0;
        }

        /// <summary>
        /// Create a new line instruction.
        /// </summary>
        /// <param name="sLine">Start of the line in the source file.</param>
        /// <param name="sCol">Starting column in the source file.</param>
        /// <param name="eLine">Ending line in the source file.</param>
        /// <param name="eCol">Ending column in the source file.</param>
        /// <param name="sFile">The filename of the souce file.</param>
        internal Line(uint sLine, uint sCol, uint eLine, uint eCol, SourceFile sFile)
        {
            startLine = sLine;
            startCol = sCol;
            endLine = eLine;
            endCol = eCol;
            hasEnd = true;
            sourceFile = sFile;
            size = 0;
        }

        public int LineNum
        {
            get { return (int)startLine; }
        }

        internal void CalcEnd(Line next)
        {
            if (hasEnd) return;
            if (sourceFile != next.sourceFile)
            {
                endLine = startLine;
                endCol = MaxCol;
            }
            else
            {
                endLine = next.startLine;
                endCol = next.startCol;
                if (endCol < 0) endCol = MaxCol;
            }
            hasEnd = true;
        }

        internal void Last()
        {
            if (hasEnd) return;
            endLine = startLine;
            endCol = MaxCol;
            hasEnd = true;
        }

        /// <summary>
        /// Get the name of this instruction.
        /// </summary>
        /// <returns>A string with the value ".line".</returns>
        internal override string GetInstName()
        {
            return ".line";
        }

        /// <summary>
        /// Write this instruction to a PDB file.
        /// </summary>
        /// <param name="output">The PE writer being used to write the PE and PDB files.</param>
        internal override void Write(PEWriter output)
        {
            string sf = "";
            Guid doclang = Guid.Empty;
            Guid docvend = Guid.Empty;
            Guid doctype = Guid.Empty;
            if (sourceFile != null)
            {
                sf = sourceFile.name;
                doclang = sourceFile.language;
                docvend = sourceFile.vendor;
                doctype = sourceFile.document;

            }

            if (output.pdbWriter != null)
                output.pdbWriter.AddSequencePoint(sf, doclang, docvend, doctype, (int)offset,
                    (int)startLine, (int)startCol, (int)endLine, (int)endCol);
        }

        /// <summary>
        /// Get the delta distance for this instruction.
        /// </summary>
        /// <remarks>
        /// The delta distance is the resulting difference of items 
        /// left on the stack after calling this instruction.
        /// </remarks>
        /// <returns>An integer value representing the delta distance.</returns>
        internal override int GetDeltaDistance()
        {
            return 0;
        }

        /// <summary>
        /// Write out a line instruction to the CIL file.
        /// </summary>
        /// <param name="output">The CIL instruction writer to use to write this instruction.</param>
        internal override void Write(CILWriter output)
        {
            if (output.Debug)
            {
                string lineDetails = startLine + ", " + startCol;
                if (hasEnd)
                {
                    lineDetails += ", " + endLine + ", " + endCol;
                    if (sourceFile != null)
                    {
                        lineDetails += ", " + sourceFile.Name;
                    }
                }
                output.WriteLine(".line " + lineDetails);
            }
        }


    }

    /**************************************************************************/

    /// <summary>
    /// A local binding instruction that can be added to a list of CILInstructions.
    /// </summary>
    public class LocalBinding : DebugInst
    {
        internal int _index;
        internal string _name;
        internal DebugLocalSig _debugsig;

        /*-------------------- Constructors ---------------------------------*/

        /// <summary>
        /// Create a new local binding object.
        /// </summary>
        /// <param name="index">The index of the local in the locals tables.</param>
        /// <param name="name">The name of the local.</param>
        internal LocalBinding(int index, string name)
        {
            _index = index;
            _name = name;
        }

        /// <summary>
        /// The index of the local in the locals table.
        /// </summary>
        public int Index
        {
            get { return _index; }
        }

        /// <summary>
        /// The name of the local binding.
        /// </summary>
        public string Name
        {
            get { return _name; }
        }

        /// <summary>
        /// Get the delta distance for this instruction.
        /// </summary>
        /// <remarks>
        /// The delta distance is the resulting difference of items 
        /// left on the stack after calling this instruction.
        /// </remarks>
        /// <returns>An integer value representing the delta distance.</returns>
        internal override int GetDeltaDistance()
        {
            return 0;
        }

        /// <summary>
        /// Get the name of this instruction.
        /// </summary>
        /// <returns>A string with the name of this instruction.</returns>
        internal override string GetInstName()
        {
            return "debug - local binding";
        }

    }
    /**************************************************************************/

    /// <summary>
    /// Used to delcare constants that exist in a given scope.
    /// </summary>
    public class ConstantBinding : DebugInst
    {
        private string _name;
        private object _value;
        private Type _type;
        private uint _token;

        /*-------------------- Constructors ---------------------------------*/

        /// <summary>
        /// Create a new constant binding.
        /// </summary>
        /// <param name="name">The name of the constant.</param>
        /// <param name="value">The value of the constant.</param>
        /// <param name="type">The data type of the constant.</param>
        internal ConstantBinding(string name, object value, Type type, uint token)
        {
            _value = value;
            _name = name;
            _type = type;
            _token = token;
        }

        /// <summary>
        /// Value of the constant.
        /// </summary>
        public object Value
        {
            get { return _value; }
        }

        /// <summary>
        /// The name of the constant.
        /// </summary>
        public string Name
        {
            get { return _name; }
        }

        /// <summary>
        /// The data type of the constant.
        /// </summary>
        public Type Type
        {
            get { return _type; }
        }

        /// <summary>
        /// The token for this constant.
        /// </summary>
        public uint Token
        {
            get { return _token; }
        }

        /// <summary>
        /// Get the type signature for this constant.
        /// </summary>
        /// <returns>A byte array of the type signature.</returns>
        public byte[] GetSig()
        {
            MemoryStream str = new MemoryStream();
            _type.TypeSig(str);
            return str.ToArray();
        }

        /// <summary>
        /// Get the name of this instruction.
        /// </summary>
        /// <returns>A string with the name of this instruction.</returns>
        internal override string GetInstName()
        {
            return "debug - constant binding";
        }

        /// <summary>
        /// Get the delta distance for this instruction.
        /// </summary>
        /// <remarks>
        /// The delta distance is the resulting difference of items 
        /// left on the stack after calling this instruction.
        /// </remarks>
        /// <returns>An integer value representing the delta distance.</returns>
        internal override int GetDeltaDistance()
        {
            return 0;
        }



        }

        /**************************************************************************/
        public class SwitchInstr : Instr
        {
            CILLabel[] cases;
            uint numCases = 0;
            int[] targets;

            /*-------------------- Constructors ---------------------------------*/

            public SwitchInstr(CILLabel[] dsts)
                : base(0x45)
            {
                cases = dsts;
                if (cases != null) numCases = (uint)cases.Length;
                size += 4 + (numCases * 4);
            }

            internal SwitchInstr(int[] offsets)
                : base(0x45)
            {
                numCases = (uint)offsets.Length;
                targets = offsets;
                size += 4 + (numCases * 4);
            }

            public CILLabel[] GetDests() { return cases; }
            public void SetDests(CILLabel[] dests) { cases = dests; }

            internal override string GetInstName()
            {
                return "switch";
            }

            internal void MakeTargetLabels(ArrayList labs)
            {
                cases = new CILLabel[numCases];
                for (int i = 0; i < numCases; i++)
                {
                    cases[i] = CILInstructions.GetLabel(labs, (uint)(offset + size + targets[i]));
                }
            }

            internal sealed override void Write(PEWriter output)
            {
                base.Write(output);
                output.Write(numCases);
                for (int i = 0; i < numCases; i++)
                {
                    int target = (int)cases[i].GetLabelOffset() - (int)(offset + size);
                    output.Write(target);
                }
            }

            internal override void Write(CILWriter output)
            {
                throw new NotImplementedException("Switch instruction for CIL");
            }


        }


    public class Scope {
     private ArrayList _localBindings = new ArrayList();
     private ArrayList _constantBindings = new ArrayList();
     internal Scope _parent;
     internal MethodDef _thisMeth;

     internal Scope(MethodDef thisMeth) : this(null, thisMeth) {
     }

     internal Scope(Scope parent, MethodDef thisMeth) {
       _thisMeth = thisMeth;
       _parent = parent;
     }

       /// <summary>
       /// Add a constant to this scope.
       /// </summary>
       /// <param name="name">The name of the constant.</param>
       /// <param name="value">The value of the constant.</param>
       /// <param name="type">The type of the constant.</param>
       /// <returns>The ConstantBinding object for the new constant.</returns>
       internal ConstantBinding AddConstantBinding(string name, object value, Type type) {
           ConstantBinding binding;
           if ((binding = FindConstantBinding(name)) != null)
               return binding;

           binding = new ConstantBinding(name, value, type, _thisMeth.locToken);
           _constantBindings.Add(binding);
           return binding;
       }

       /// <summary>
       /// Find a constant in this scope.
       /// </summary>
       /// <param name="name">The name of the constant.</param>
       /// <returns>The ConstantBinding object of this constant.</returns>
       internal ConstantBinding FindConstantBinding(string name) {
           foreach (ConstantBinding binding in _constantBindings)
               if (binding.Name == name)
                   return binding;
           return null;
       }

       /// <summary>
       /// Provide a complete list of all constants bound in this scope.
       /// </summary>
       public ConstantBinding[] ConstantBindings {
           get { return (ConstantBinding[])_constantBindings.ToArray(typeof(ConstantBinding)); }
       }

     internal LocalBinding AddLocalBinding(string name, int index) {
       LocalBinding binding;
       if ((binding = FindLocalBinding(name)) != null)
         return binding;

       binding = new LocalBinding(index, name);
       _localBindings.Add(binding);
       return binding;
     }

     internal LocalBinding FindLocalBinding(string name) {
       foreach (LocalBinding binding in _localBindings)
         if (binding._name == name)
           return binding;
       return null;
     }

     internal LocalBinding FindLocalBinding(int index) {
       foreach (LocalBinding binding in _localBindings)
         if (binding._index == index)
           return binding;
       return null;
     }

     public LocalBinding[] LocalBindings {
       get { return (LocalBinding[]) _localBindings.ToArray(typeof(LocalBinding)); }
     }

     internal void BuildSignatures(MetaDataOut md) {	
       if (!md.Debug) return;
         
     try {
       Local[] locals = _thisMeth.GetLocals();
       foreach (LocalBinding binding in _localBindings) {
         if (binding._debugsig == null) {
            locals[binding._index].BuildTables(md);
            binding._debugsig = md.GetDebugSig(locals[binding._index]);
         }
         binding._debugsig.BuildMDTables(md);
       }
     } catch (Exception e) {
       throw new Exception("Exception while writing debug info for: " +
                            this._thisMeth.NameString()+"\r\n"+e.ToString());
     }
        
     }

       internal void WriteLocals(PDBWriter writer) {

         try {

             Local[] locals = _thisMeth.GetLocals();

             foreach (LocalBinding binding in _localBindings) {
                 writer.BindLocal(binding._name, binding._index, _thisMeth.locToken,0,0);
             }
         } catch (Exception e) {
             throw new Exception("Exception while writing debug info for: " +
                 this._thisMeth.NameString()+"\r\n"+e.ToString(),e);
         }

     }
       /* Constants does not work. AKB 2007-02-03
       internal void WriteConstants(PDBWriter writer) {

           try {

               // Add each constant to the current scope
               foreach (ConstantBinding binding in _constantBindings)
                   writer.BindConstant(binding);

           } catch (Exception e) {
               throw new Exception("Exception while writing debug info for: " +
                   this._thisMeth.NameString() + "\r\n" + e.ToString(), e);
           }

       }
       */
   }
   
    /*************************************************************************/ 
   
    /// <summary>
    /// A marker instruction for when a scope should be opened in the sequence of instructions.
    /// </summary>
   public class OpenScope : DebugInst {
     internal Scope _scope;
   
       /// <summary>
       /// Create a new OpenScope instruction.
       /// </summary>
       /// <param name="scope">The scope that is being opened.</param>
     public OpenScope(Scope scope) {
       size = 0;
       _scope = scope;
     }

       /// <summary>
       /// Get the name for this instruction.
       /// </summary>
       /// <returns>A string with the name of the instruction.</returns>
     internal override string GetInstName() {
       return "debug - open scope";
     }
   
       /// <summary>
       /// Build the signatures for this instruction.
       /// </summary>
       /// <param name="md">The meta data table to write the instructions to.</param>
     internal void BuildSignatures(MetaDataOut md) {
       _scope.BuildSignatures(md);
     }

       /// <summary>
       /// Get the delta distance for this instruction.
       /// </summary>
       /// <remarks>
       /// The delta distance is the resulting difference of items 
       /// left on the stack after calling this instruction.
       /// </remarks>
       /// <returns>An integer value representing the delta distance.</returns>
       /// 
       internal override int GetDeltaDistance() {
           return 0;
       }

     /// <summary>
     /// Write this instruction to the PDB file.
     /// </summary>
     /// <param name="output">The PEWriter being used to write the PE and PDB files.</param>
     internal override void Write(PEWriter output) {
       if (output.pdbWriter != null) {
         output.pdbWriter.OpenScope((int) offset);
         _scope.WriteLocals(output.pdbWriter);
         /* Constants do not work. AKB 2007-02-03
          * _scope.WriteConstants(output.pdbWriter);
          */

     }
     }
   
   }
    /************************************************************************/  
   
    /// <summary>
    /// A marker instruction for when a scope should be closed.
    /// </summary>
   public class CloseScope : DebugInst {
     internal Scope _scope;
   
       /// <summary>
       /// The constructor to build a new CloseScope instruction.
       /// </summary>
       /// <param name="scope">The scope to close.</param>
     public CloseScope(Scope scope) {
       size = 0;
       _scope = scope;
     }
   
       /// <summary>
       /// Provide access to the name of this instruction.
       /// </summary>
       /// <returns>A string containing the name of this instruction.</returns>
     internal override string GetInstName() {
       return "debug - close scope";
     }

     /// <summary>
     /// Get the delta distance for this instruction.
     /// </summary>
     /// <remarks>
     /// The delta distance is the resulting difference of items 
     /// left on the stack after calling this instruction.
     /// </remarks>
     /// <returns>An integer value representing the delta distance.</returns>
     internal override int GetDeltaDistance() {
         return 0;
     }

       /// <summary>
       /// Write this instruction.  This instruction does not get written
       /// to the PE file.  It only applys to the PDB file.
       /// </summary>
       /// <param name="output">The PEWriter that is writing the PE file.</param>
     internal override void Write(PEWriter output) {
       if (output.pdbWriter != null)
         output.pdbWriter.CloseScope((int) offset);
     }
   
   }  
    /**************************************************************************/  

    public class FieldInstr : Instr {
        Field field;

        /*-------------------- Constructors ---------------------------------*/
  
        public FieldInstr(FieldOp inst, Field f) : base((uint)inst) {
            field = f;
            size += 4;
        }

        public Field GetField() { return field; }

        public void SetField(Field fld) { field = fld; }

        internal override string GetInstName() {
            return "" + (FieldOp)instr;
        }

        internal sealed override void BuildTables(MetaDataOut md) {
            if (field == null) throw new InstructionException(IType.fieldOp,instr);
            if (field is FieldRef) field.BuildMDTables(md);
        }

        internal override void  BuildCILInfo(CILWriter output) {
            if (field == null) throw new InstructionException(IType.fieldOp,instr);
            if (field is FieldRef) field.BuildCILInfo(output);
        }

        internal sealed override void Write(PEWriter output) {
            base.Write(output);
            output.Write(field.Token());
        }

        internal override void Write(CILWriter output) {
            output.Write(GetInstrString());
            field.WriteType(output);
            output.WriteLine();
        }


    }

    /**************************************************************************/  
    public class MethInstr : Instr {
        Method meth;

        /*-------------------- Constructors ---------------------------------*/
  
        public MethInstr(MethodOp inst, Method m) : base((uint)inst) {
            meth = m;
            size += 4;
        }

        public Method GetMethod() { return meth; }

        public void SetMethod(Method mth) { meth = mth; }

        internal override string GetInstName() {
            return "" + (MethodOp)instr;
        }

        internal sealed override void BuildTables(MetaDataOut md) {
            if (meth == null) 
                throw new InstructionException(IType.methOp,instr);
            if ((meth is MethodRef) || (meth is MethodSpec)) meth.BuildMDTables(md);
        }

        internal override void BuildCILInfo(CILWriter output) {
            if (meth == null) throw new InstructionException(IType.methOp,instr);
            if ((meth is MethodRef) || (meth is MethodSpec)) meth.BuildCILInfo(output);
         }

        /// <summary>
        /// Get the MethodOp this instruction represents.
        /// </summary>
        /// <returns>The method operator from the MethodOp enum.</returns>
        public MethodOp GetMethodOp() {
            return (MethodOp)instr;
        }

        /// <summary>
        /// Get the delta distance for this instruction.
        /// </summary>
        /// <remarks>
        /// The delta distance is the resulting difference of items 
        /// left on the stack after calling this instruction.
        /// </remarks>
        /// <returns>An integer value representing the delta distance.</returns>
        internal override int GetDeltaDistance() {
            switch ((MethodOp)instr) {
                case MethodOp.callvirt:
                case MethodOp.call: {

                        // Add the parameter count to the depth
                        int depth = (int)meth.GetSig().numPars * -1;

                        // Check to see if this is an instance method
                        if (meth.GetSig().HasCallConv(CallConv.Instance)) depth--;

                        // Check to see if this method uses the optional parameters
                        if (meth.GetSig().HasCallConv(CallConv.Vararg)) depth += (int)meth.GetSig().numOptPars * -1;

                        // Check to see if this method uses the generic parameters
                        if (meth.GetSig().HasCallConv(CallConv.Generic)) depth += (int)meth.GetSig().numGenPars * -1;

                        // Check if a return value will be placed on the stack.
                        if (!meth.GetRetType().SameType(PrimitiveType.Void)) depth++;

                        return depth;
                    }
                case MethodOp.newobj: {

                        // Add the parameter count to the depth
                        int depth = (int)meth.GetSig().numPars * -1;

                        // Check to see if this method uses the optional parameters
                        if (meth.GetSig().HasCallConv(CallConv.Vararg)) depth += (int)meth.GetSig().numOptPars * -1;

                        // Check to see if this method uses the generic parameters
                        if (meth.GetSig().HasCallConv(CallConv.Generic)) depth += (int)meth.GetSig().numGenPars * -1;

                        // Add the object reference that is loaded onto the stack
                        depth++;

                        return depth;
                    }
                case MethodOp.ldtoken:
                case MethodOp.ldftn:
                    return 1;
                case MethodOp.jmp:
                case MethodOp.ldvirtfn:
                    return 0;
                default:
                    // Someone has added a new MethodOp and not added a case for it here.
                    throw new Exception("The MethodOp for this MethoInstr is not supported.");
            }
        }

         internal sealed override void Write(PEWriter output) {
            base.Write(output);
            output.Write(meth.Token());
        }

        internal override void Write(CILWriter output) {
            output.Write(GetInstrString());
            meth.WriteType(output);
            output.WriteLine();
        }

    }

    /**************************************************************************/  
    public class SigInstr : Instr {
        CalliSig signature;

        /*-------------------- Constructors ---------------------------------*/
  
        public SigInstr(SpecialOp inst, CalliSig sig) : base((uint)inst) {
            signature = sig;
            size += 4;
        }

        public CalliSig GetSig() { return signature; }

        public void SetSig(CalliSig sig) { signature = sig; }

        internal override string GetInstName() {
            return "" + (SpecialOp)instr;
        }

        /// <summary>
        /// Get the delta distance for this instruction.
        /// </summary>
        /// <remarks>
        /// The delta distance is the resulting difference of items 
        /// left on the stack after calling this instruction.
        /// </remarks>
        /// <returns>An integer value representing the delta distance.</returns>
        internal override int GetDeltaDistance() {

            // Add the parameter count to the depth
            int depth = (int)signature.NumPars * -1;

            // Check to see if this is an instance method
            if (signature.HasCallConv(CallConv.Instance)) depth--;

            // Check to see if this method uses the optional parameters
            if (signature.HasCallConv(CallConv.Vararg)) depth += (int)signature.NumOptPars * -1;

            // Check if a return value will be placed on the stack.
            if (signature.ReturnType.SameType(PrimitiveType.Void)) depth++;

            return depth;
        }

        internal sealed override void BuildTables(MetaDataOut md) {
            if (signature == null) throw new InstructionException(IType.specialOp,instr);
            signature.BuildMDTables(md);
        }

        internal override void  BuildCILInfo(CILWriter output) {
            if (signature == null) throw new InstructionException(IType.specialOp,instr);
            signature.BuildCILInfo(output);
        }

        internal sealed override void Write(PEWriter output) {
            base.Write(output);
            output.Write(signature.Token());
        }

        internal override void Write(CILWriter output) {
            output.Write(GetInstrString());
            signature.Write(output);
            output.WriteLine();
        }

    }

    /**************************************************************************/  
    public class TypeInstr : Instr {
        Type theType;

        /*-------------------- Constructors ---------------------------------*/
  
        public TypeInstr(TypeOp inst, Type aType) : base((uint)inst) {
            theType = aType;
            size += 4;
        }

        public Type GetTypeArg() { return theType; }

        public void SetTypeArg(Type ty) { theType = ty; }

        internal override string GetInstName() {
            return "" + (TypeOp)instr;
        }

        internal sealed override void BuildTables(MetaDataOut md) {
            if (theType == null) throw new InstructionException(IType.typeOp,instr);
            theType = theType.AddTypeSpec(md);
        }

        internal override void  BuildCILInfo(CILWriter output) {
            if (theType == null) throw new InstructionException(IType.typeOp,instr);
            if (!theType.isDef()) {
                theType.BuildCILInfo(output);
            }
       }

        internal sealed override void Write(PEWriter output) {
            base.Write(output);
            output.Write(theType.Token());
        }

        internal override void Write(CILWriter output) {
            output.Write(GetInstrString());
            theType.WriteName(output);
            output.WriteLine();
        }

    }

    /**************************************************************************/  
    public class BranchInstr : Instr {
        CILLabel dest;
        private bool shortVer = true;
        private static readonly byte longInstrOffset = 13;
        private int target = 0;

        /*-------------------- Constructors ---------------------------------*/
  
        public BranchInstr(BranchOp inst, CILLabel dst) : base((uint)inst) {
            dest = dst;
            shortVer = (inst < BranchOp.br) || (inst == BranchOp.leave_s);
            if (shortVer)
                size++;
            else
                size += 4;
        }

        internal BranchInstr(uint inst, int dst) : base(inst) {
            target = dst;
            shortVer = (inst < (uint)BranchOp.br) || (inst == (uint)BranchOp.leave_s);
            if (shortVer) 
                size++;
            else
                size += 4;
        }

        public CILLabel GetDest() { return dest; }

        public void SetDest(CILLabel lab) { dest = lab; }

        /// <summary>
        /// Provide access to the branch operator
        /// </summary>
        /// <returns>The branch operator from the BranchOp enum that this instruction represents.</returns>
        public BranchOp GetBranchOp() {
            return (BranchOp)instr;
        }

        internal override string GetInstName() {
            return "" + (BranchOp)instr;
        }

        internal void MakeTargetLabel(ArrayList labs) {
            uint targetOffset = (uint)(offset + size + target);
            dest = CILInstructions.GetLabel(labs,targetOffset);
        }

        internal sealed override bool Check(MetaDataOut md) {
            target = (int)dest.GetLabelOffset() - (int)(offset + size);
            if ((target < minByteVal) || (target > maxByteVal)) { // check for longver
                if (shortVer) {
                    if (instr == (uint)BranchOp.leave_s)
                        instr = (uint)BranchOp.leave;
                    else
                        instr = instr += longInstrOffset;
                    size += 3;
                    shortVer = false;
                    return true;
                }
            } else if (!shortVer) { // check for short ver
                if (instr == (uint)BranchOp.leave)
                    instr = (uint)BranchOp.leave_s;
                else
                    instr = instr -= longInstrOffset;
                size -= 3;
                shortVer = true;
                return true;
            }
            /*
            if (shortVer && ((target < minByteVal) || (target > maxByteVal))) {
              if (instr < (int)BranchOp.leave) instr += longInstrOffset;
              else instr--;
              shortVer = false;
              size += 3;
              return true;
            }
            */
            return false;
        }

        internal sealed override void Write(PEWriter output) {
            base.Write(output);
            if (shortVer)
                output.Write((sbyte)target);
            else
                output.Write(target);
        }

        internal override void Write(CILWriter output) {
            output.WriteLine(GetInstrString() + dest.GetInstName());
        }

    }
    /*************************************************************************/

}