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using System;
using System.IO;
using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
namespace ByteFX.Data.MySqlClient
{
/// <summary>
/// Summary description for CompressedStream.
/// </summary>
internal class CompressedStream : Stream
{
private Stream srcStream;
private byte[] buffer;
private int index;
public CompressedStream( Stream src )
{
srcStream = src;
index = 0;
buffer = new byte[0];
}
#region Properties
public override bool CanRead
{
get { return srcStream.CanRead; }
}
public override bool CanWrite
{
get { return srcStream.CanWrite; }
}
public override bool CanSeek
{
get { return srcStream.CanSeek; }
}
public override long Length
{
get { return srcStream.Length; }
}
public override long Position
{
get { return srcStream.Position; }
set { srcStream.Position = value; }
}
#endregion
public override void Close()
{
srcStream.Close();
base.Close ();
}
public override void Flush()
{
srcStream.Flush();
}
public override void SetLength(long value)
{
srcStream.SetLength( value );
}
public override int ReadByte()
{
EnsureData(1);
return (int)buffer[index++];
}
public override int Read(byte[] buffer, int offset, int count)
{
if (buffer == null)
throw new ArgumentNullException( "buffer", "Buffer must not be null" );
if (offset < 0 || offset >= buffer.Length)
throw new ArgumentOutOfRangeException( "Offset must be a valid position in buffer" );
if ((offset + count) > buffer.Length)
throw new ArgumentException( "Buffer is not large enough to complete operation" );
EnsureData( count );
for (int i=0; i < count; i++)
buffer[offset+i] = this.buffer[index++];
return count;
}
public override void Write(byte[] buffer, int offset, int count)
{
srcStream.Write( buffer, offset, count );
}
public override long Seek(long offset, SeekOrigin origin)
{
return srcStream.Seek( offset, origin );
}
private void ReadBuffer( Stream s, byte[] buf, int offset, int length )
{
while (length > 0)
{
int amountRead = s.Read( buf, offset, length );
if (amountRead == 0)
throw new MySqlException("Unexpected end of data encountered");
length -= amountRead;
offset += amountRead;
}
}
private void ReadNextPacket()
{
// read off the uncompressed and compressed lengths
int compressedLen = srcStream.ReadByte() + (srcStream.ReadByte() << 8) +
(srcStream.ReadByte() << 16);
byte seq = (byte)srcStream.ReadByte();
int unCompressedLen = srcStream.ReadByte() + (srcStream.ReadByte() << 8) +
(srcStream.ReadByte() << 16);
// if the data is in fact compressed, then uncompress it
byte[] unCompressedBuffer = null;
if (unCompressedLen > 0)
{
unCompressedBuffer = new byte[ unCompressedLen ];
InflaterInputStream iis = new InflaterInputStream( srcStream );
ReadBuffer( iis, unCompressedBuffer, 0, unCompressedLen );
}
else
{
unCompressedBuffer = new byte[ compressedLen ];
ReadBuffer( srcStream, unCompressedBuffer, 0, compressedLen );
}
// now join this buffer to our existing one
int left = buffer.Length - index;
byte[] newBuffer = new byte[ left + unCompressedBuffer.Length ];
int newIndex = 0;
// first copy in the rest of the original
for (int i=index; i < buffer.Length; i++)
newBuffer[newIndex++] = buffer[i];
unCompressedBuffer.CopyTo( newBuffer, newIndex );
buffer = newBuffer;
index = 0;
}
private void EnsureData( int size )
{
while ((buffer.Length - index) < size)
ReadNextPacket();
}
}
}
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