/// <summary>
/// Retrieve the compression level of the stream
///
/// RFC 1950
/// 0 1
/// +---+---+
/// |CMF|FLG| (more-->)
/// +---+---+
///
/// FLG (FLaGs)
/// This flag byte is divided as follows:
///
/// bits 0 to 4 FCHECK (check bits for CMF and FLG)
/// bit 5 FDICT (preset dictionary)
/// bits 6 to 7 FLEVEL (compression level)
///
/// FLEVEL (Compression level)
/// These flags are available for use by specific compression
/// methods. The "deflate" method (CM = 8) sets these flags as
/// follows:
///
/// 0 - compressor used fastest algorithm
/// 1 - compressor used fast algorithm
/// 2 - compressor used default algorithm
/// 3 - compressor used maximum compression, slowest algorithm
///
/// ZLib enumeration
/// public enum CompressLevel
/// {
/// Default = -1,
/// None,
/// Best = 9,
/// Fastest = 1
/// }
///
/// http://code.activestate.com/lists/python-list/204644/
/// Two bytes, that's not really a lot of known plaintext, but every little bit might be a liability, I guess.
/// </summary>
private static CompressLevel RetrieveCompressionLevel()
{
byte cmf = ZLibWrapper.ReadBytes(1, ZLibBufferType.InputBuffer)[0];
int flg = ZLibWrapper.ReadBytes(1, ZLibBufferType.InputBuffer)[0];
CompressLevel fLevel;
flg = (flg & 0xC0); // Mask : 11000000 = 192 = 0xC0
flg = flg >> 6;
switch (flg)
{
case 0:
fLevel = CompressLevel.None;
break;
case 1:
fLevel = CompressLevel.Fastest;
break;
case 2:
fLevel = CompressLevel.Default;
break;
case 3:
fLevel = CompressLevel.Best;
break;
default:
fLevel = CompressLevel.Best;
break;
}
return(fLevel);
}
/// <summary>
/// Compress a stream with ZLib
/// </summary>
/// <param name="snipStreamWrapper">A stream wrapper object</param>
/// <param name="compressLevel">Compression level of stream.</param>
public static void Compress(SnipStreamWrapper snipStreamWrapper, CompressLevel compressLevel)
{
var numBytesAddressing = snipStreamWrapper.OutputBufferLength;
ZLibWrapper.CopyByteArrayToInputBuffer(snipStreamWrapper.OutputBuffer, 0,
snipStreamWrapper.OutputBufferLength);
if (_deflaterBest == null)
{
_deflaterBest = new Deflater(CompressLevel.Best);
_deflaterBest.DataAvailable += ZLibWrapper.WriteInOutputBuffer;
}
if (_deflaterNone == null)
{
_deflaterNone = new Deflater(CompressLevel.None);
_deflaterNone.DataAvailable += ZLibWrapper.WriteInOutputBuffer;
}
if (_deflaterFastest == null)
{
_deflaterFastest = new Deflater(CompressLevel.Fastest);
_deflaterFastest.DataAvailable += ZLibWrapper.WriteInOutputBuffer;
}
if (_deflaterDefault == null)
{
_deflaterDefault = new Deflater(CompressLevel.Default);
_deflaterDefault.DataAvailable += ZLibWrapper.WriteInOutputBuffer;
}
try
{
while (numBytesAddressing > 0u)
{
uint numBytes = Math.Min(numBytesAddressing, 8192u); //8192u); 65536u
if (compressLevel == CompressLevel.None)
{
_deflaterNone.Add(ZLibWrapper.ReadBytes((int)numBytes, ZLibBufferType.InputBuffer));
}
if (compressLevel == CompressLevel.Best)
{
_deflaterBest.Add(ZLibWrapper.ReadBytes((int)numBytes, ZLibBufferType.InputBuffer));
}
if (compressLevel == CompressLevel.Default)
{
_deflaterDefault.Add(ZLibWrapper.ReadBytes((int)numBytes, ZLibBufferType.InputBuffer));
}
if (compressLevel == CompressLevel.Fastest)
{
_deflaterFastest.Add(ZLibWrapper.ReadBytes((int)numBytes, ZLibBufferType.InputBuffer));
}
numBytesAddressing -= numBytes;
}
string deflateErrorMsg = string.Empty;
if (compressLevel == CompressLevel.None)
{
deflateErrorMsg = _deflaterNone._ztream.msg;
}
if (compressLevel == CompressLevel.Best)
{
deflateErrorMsg = _deflaterBest._ztream.msg;
}
if (compressLevel == CompressLevel.Default)
{
deflateErrorMsg = _deflaterDefault._ztream.msg;
}
if (compressLevel == CompressLevel.Fastest)
{
deflateErrorMsg = _deflaterFastest._ztream.msg;
}
if (!string.IsNullOrWhiteSpace(deflateErrorMsg))
{
MessageBox.Show(string.Format("ZLib.Compress: {0}", deflateErrorMsg),
TranslateUI.TranslateUiGlobalization.ResManager.GetString("ZLib_Error"),
MessageBoxButtons.OK,
MessageBoxIcon.Error);
}
if (compressLevel == CompressLevel.None)
{
_deflaterNone.Finish(); // flush zlib buffer
}
if (compressLevel == CompressLevel.Best)
{
_deflaterBest.Finish(); // flush zlib buffer
}
if (compressLevel == CompressLevel.Default)
{
_deflaterDefault.Finish(); // flush zlib buffer
}
if (compressLevel == CompressLevel.Fastest)
{
_deflaterFastest.Finish(); // flush zlib buffer
}
ZLibWrapper.Position(0, ZLibBufferType.OutputBuffer);
}
catch (Exception ex)
{
MessageBox.Show(
string.Format(TranslateUI.TranslateUiGlobalization.ResManager.GetString(name: "MSG_ErrorWithNewLine"), arg0: ex),
TranslateUI.TranslateUiGlobalization.ResManager.GetString(name: "ZLib_Compress"),
MessageBoxButtons.OK,
MessageBoxIcon.Error);
}
finally
{
if (ZLibWrapper.OutputBufferLength == 0)
{
MessageBox.Show(
TranslateUI.TranslateUiGlobalization.ResManager.GetString(name: "ZLib_OutputBufferEmpty"),
TranslateUI.TranslateUiGlobalization.ResManager.GetString(name: "ZLib_Compress"),
MessageBoxButtons.OK,
MessageBoxIcon.Error);
}
}
}
/// <summary>
/// Decompress a stream with ZLib
/// </summary>
/// <param name="compressLevel">Compression level of stream</param>
/// <param name="expectedSize">Expected size</param>
public static void Decompress(out CompressLevel compressLevel, int expectedSize = 0)
{
uint numBytesAddressing = ZLibWrapper.InputBufferLength;
compressLevel = CompressLevel.None;
try
{
ZLibWrapper.Position(0, ZLibBufferType.InputBuffer);
compressLevel = RetrieveCompressionLevel();
ZLibWrapper.Position(0, ZLibBufferType.InputBuffer);
if (expectedSize == 0)
{
// no decompression. copy input buffer in output buffer
ZLibWrapper.CopyInputBufferToOutputBuffer(8);
compressLevel = CompressLevel.None; // for compression
}
else
{
if (_inflater == null)
{
_inflater = new Inflater();
_inflater.DataAvailable += ZLibWrapper.WriteInOutputBuffer;
}
while (numBytesAddressing > 0u)
{
uint numBytes = Math.Min(numBytesAddressing, 8192u); //8192u); 65536u
_inflater.Add(ZLibWrapper.ReadBytes((int)numBytes, ZLibBufferType.InputBuffer));
numBytesAddressing -= numBytes;
}
string inflateErrorMsg = _inflater._ztream.msg;
if (!string.IsNullOrWhiteSpace(inflateErrorMsg))
{
MessageBox.Show(string.Format("ZLib.Decompress: {0}", inflateErrorMsg),
TranslateUI.TranslateUiGlobalization.ResManager.GetString("ZLib_Error"),
MessageBoxButtons.OK,
MessageBoxIcon.Error);
}
_inflater.Finish(); //flush zlib buffer
}
ZLibWrapper.Position(0, ZLibBufferType.OutputBuffer);
}
catch (Exception ex)
{
MessageBox.Show(
string.Format(TranslateUI.TranslateUiGlobalization.ResManager.GetString(name: "MSG_ErrorWithNewLine"), ex),
TranslateUI.TranslateUiGlobalization.ResManager.GetString(name: "ZLib_Decompress"),
MessageBoxButtons.OK, MessageBoxIcon.Error);
}
finally
{
if (ZLibWrapper.OutputBufferLength == 0)
{
MessageBox.Show(
TranslateUI.TranslateUiGlobalization.ResManager.GetString(name: "ZLib_OutputBufferEmpty"),
TranslateUI.TranslateUiGlobalization.ResManager.GetString(name: "ZLib_Decompress"),
MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
}