/// <summary>
/// Compress the entirety of the MemoryStream to the destination Stream, or if compressing increases the size, just copy the original data over
/// </summary>
/// <param name="uncompressedSource">A MemoryStream that will have its full contents compressed</param>
/// <param name="compressedDestination">Output Stream to write results to</param>
/// <param name="compressionKind">Compression Type</param>
/// <param name="compressionStrategy">The balance of speed vs size for the compressor</param>
public static void CompressCopyTo(MemoryStream uncompressedSource, IOStream compressedDestination, CompressionKind compressionKind, CompressionStrategy compressionStrategy)
{
uncompressedSource.Seek(0, SeekOrigin.Begin);
if (compressionKind == CompressionKind.None)
{
uncompressedSource.CopyTo(compressedDestination);
}
else
{
var temporaryStream = new MemoryStream(); //How can we avoid this?? We need to know the length of the compressed stream to write the header before we can write the stream itself...
using (var compressingStream = CompressionFactory.CreateCompressorStream(compressionKind, compressionStrategy, temporaryStream))
uncompressedSource.CopyTo(compressingStream);
if (temporaryStream.Length >= uncompressedSource.Length)
{
//Write the original data rather than the compressed data
uncompressedSource.Seek(0, SeekOrigin.Begin);
WriteBlockHeader(compressedDestination, (int)uncompressedSource.Length, false);
uncompressedSource.CopyTo(compressedDestination);
}
else
{
temporaryStream.Seek(0, SeekOrigin.Begin);
WriteBlockHeader(compressedDestination, (int)temporaryStream.Length, true);
temporaryStream.CopyTo(compressedDestination);
}
}
}
/// <summary>
/// Provides a Stream that when read from, reads consecutive blocks of compressed data from an ORC Stream.
/// All data in the <paramref name="inputStream"/> will be consumed.
/// </summary>
public static IOStream GetDecompressingStream(IOStream inputStream, CompressionKind compressionKind)
{
if (compressionKind == CompressionKind.None)
{
return(inputStream);
}
else
{
return(new ConcatenatingStream(() =>
{
int blockLength;
bool isCompressed;
bool headerAvailable = ReadBlockHeader(inputStream, out blockLength, out isCompressed);
if (!headerAvailable)
{
return null;
}
var streamSegment = new StreamSegment(inputStream, blockLength, true);
if (!isCompressed)
{
return streamSegment;
}
else
{
return CompressionFactory.CreateDecompressorStream(compressionKind, streamSegment);
}
}, false));
}
}
