CodecBase.cs

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//
// © Copyright Henrik Ravn 2004
//
// Use, modification and distribution are subject to the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//

using System;
using System.Runtime.InteropServices;

namespace DotZLib
{
    public abstract class CodecBase : Codec, IDisposable
    {

        #region Data members

        internal ZStream _ztream = new ZStream();

        protected bool _isDisposed = false;

        protected const int kBufferSize = 16384;

        private byte[] _outBuffer = new byte[kBufferSize];
        private byte[] _inBuffer = new byte[kBufferSize];

        private GCHandle _hInput;
        private GCHandle _hOutput;

        private uint _checksum = 0;

        #endregion

        public CodecBase()
        {
            try
            {
                _hInput = GCHandle.Alloc(_inBuffer, GCHandleType.Pinned);
                _hOutput = GCHandle.Alloc(_outBuffer, GCHandleType.Pinned);
            }
            catch (Exception)
            {
                CleanUp(false);
                throw;
            }
        }


        #region Codec Members

        public event DataAvailableHandler DataAvailable;

        protected void OnDataAvailable()
        {
            if (_ztream.total_out > 0)
            {
                if (DataAvailable != null)
                    DataAvailable( _outBuffer, 0, (int)_ztream.total_out);
                resetOutput();
            }
        }

        public void Add(byte[] data)
        {
            Add(data,0,data.Length);
        }

        public abstract void Add(byte[] data, int offset, int count);

        public abstract void Finish();

        public uint Checksum { get { return _checksum; } }

        #endregion

        #region Destructor & IDisposable stuff

        ~CodecBase()
        {
            CleanUp(false);
        }

        public void Dispose()
        {
            CleanUp(true);
        }

        protected abstract void CleanUp();

        // performs the release of the handles and calls the dereived CleanUp()
        private void CleanUp(bool isDisposing)
        {
            if (!_isDisposed)
            {
                CleanUp();
                if (_hInput.IsAllocated)
                    _hInput.Free();
                if (_hOutput.IsAllocated)
                    _hOutput.Free();

                _isDisposed = true;
            }
        }


        #endregion

        #region Helper methods

        protected void copyInput(byte[] data, int startIndex, int count)
        {
            Array.Copy(data, startIndex, _inBuffer,0, count);
            _ztream.next_in = _hInput.AddrOfPinnedObject();
            _ztream.total_in = 0;
            _ztream.avail_in = (uint)count;

        }

        protected void resetOutput()
        {
            _ztream.total_out = 0;
            _ztream.avail_out = kBufferSize;
            _ztream.next_out = _hOutput.AddrOfPinnedObject();
        }

        protected void setChecksum(uint newSum)
        {
            _checksum = newSum;
        }
        #endregion

    }
}