/// <summary>
/// Helper function
/// </summary>
/// <param name="initialDictionary">Part of the MS-OXRTFCP spec. </param>
/// <param name="streamReader">BinaryReader which is pointing at the input data. </param>
/// <param name="writeOffset">Write offset</param>
/// <returns> CompressionPositions class containing DictionaryOffset, LongestMatchLength, WriteOffset</returns>
static internal CompressionPositions FindLongestMatch(byte[] initialDictionary, BinaryReader streamReader, int writeOffset)
{
var chardict = Encoding.UTF8.GetString(initialDictionary).ToCharArray();
var readCharacter = streamReader.Read();
var positionData = new CompressionPositions()
{
WriteOffset = writeOffset
};
if (readCharacter == -1)
{
return(positionData);
}
var previousWriteOffset = writeOffset;
var matchLength = 0;
var dictionaryIndex = 0;
while (true)
{
if (initialDictionary[dictionaryIndex % MAX_DICT_SIZE] == readCharacter)
{
if (++matchLength <= 17 && matchLength > positionData.LongestMatchLength)
{
positionData.DictionaryOffset = dictionaryIndex - matchLength + 1;
initialDictionary[positionData.WriteOffset] = Convert.ToByte(readCharacter);
positionData.WriteOffset = (positionData.WriteOffset + 1) % MAX_DICT_SIZE;
positionData.LongestMatchLength = matchLength;
}
if ((readCharacter = streamReader.Read()) == -1)
{
streamReader.BaseStream.Seek(streamReader.BaseStream.Position - matchLength, SeekOrigin.Begin);
return(positionData);
}
}
else
{
streamReader.BaseStream.Seek(streamReader.BaseStream.Position - matchLength - 1, SeekOrigin.Begin);
matchLength = 0;
if ((readCharacter = streamReader.Read()) == -1)
{
break;
}
}
if (++dictionaryIndex >= previousWriteOffset + positionData.LongestMatchLength)
{
break;
}
}
streamReader.BaseStream.Seek(streamReader.BaseStream.Position - matchLength - 1, 0);
return(positionData);
}
/// <summary>
/// Takes in data, compresses it using LZFu. Returns the data as a byte array.
/// </summary>
/// <param name="data">Byte array containing data to be compressed.</param>
/// <returns>Byte array containing the data that is compressed.</returns>
internal byte[] Compress(byte[] data)
{
using (var inStream = new MemoryStream(data))
using (var binaryReader = new BinaryReader(inStream))
{
var positionData = new CompressionPositions {
WriteOffset = InitDictSize
};
var controlByte = 0;
var controlBit = 1;
var tokenOffset = 0;
using (var outStream = new MemoryStream())
using (var tokenStream = new MemoryStream())
{
while (true)
{
int dictReference;
positionData = FindLongestMatch(_initialDictionary, binaryReader, positionData.WriteOffset);
if (binaryReader.PeekChar() < 0)
{
controlByte |= 1 << controlBit - 1;
tokenOffset += 2;
dictReference = (positionData.WriteOffset & 0xFFF) << 4;
var bytes = BitConverter.GetBytes((ushort)dictReference);
Array.Reverse(bytes);
tokenStream.Write(bytes, 0, 2);
outStream.WriteByte((byte)controlByte);
outStream.Write(tokenStream.ToArray(), 0, tokenOffset);
break;
}
var readChar = binaryReader.ReadBytes(positionData.LongestMatchLength > 1
? positionData.LongestMatchLength
: 1);
if (positionData.LongestMatchLength > 1)
{
controlByte |= 1 << controlBit - 1;
controlBit++;
tokenOffset += 2;
dictReference = (positionData.DictionaryOffset & 0xFFF) << 4 |
(positionData.LongestMatchLength - 2) & 0xf;
var bytes = BitConverter.GetBytes((ushort)dictReference);
Array.Reverse(bytes);
tokenStream.Write(bytes, 0, 2);
}
else
{
if (positionData.LongestMatchLength == 0)
{
_initialDictionary[positionData.WriteOffset] = Convert.ToByte(readChar[0]);
positionData.WriteOffset = (positionData.WriteOffset + 1) % MaxDictSize;
}
controlByte |= 0 << controlBit - 1;
controlBit++;
tokenOffset++;
tokenStream.Write(readChar, 0, readChar.Length);
}
positionData.LongestMatchLength = 0;
if (controlBit > 8)
{
outStream.WriteByte((byte)controlByte);
outStream.Write(tokenStream.ToArray(), 0, tokenOffset);
controlByte = 0;
controlBit = 1;
tokenOffset = 0;
tokenStream.SetLength(0);
}
}
var compSize = (uint)outStream.Length + 12;
var rawSize = (uint)data.Length;
var crcValue = Crc32Calculator.CalculateCrc32(outStream.ToArray());
using (var resultStream = new MemoryStream())
{
resultStream.Write(BitConverter.GetBytes(compSize), 0, BitConverter.GetBytes(compSize).Length);
resultStream.Write(BitConverter.GetBytes(rawSize), 0, BitConverter.GetBytes(rawSize).Length);
resultStream.Write(Encoding.UTF8.GetBytes(CompType), 0,
Encoding.UTF8.GetBytes(CompType).Length);
resultStream.Write(BitConverter.GetBytes(crcValue), 0, BitConverter.GetBytes(crcValue).Length);
resultStream.Write(outStream.ToArray(), 0, outStream.ToArray().Length);
return(resultStream.ToArray());
}
}
}
}
/// <summary>
/// Takes in data, compresses it using LZFu. Returns the data as a byte array.
/// </summary>
/// <param name="data">Byte array containing data to be compressed.</param>
/// <returns>Byte array containing the data that is compressed.</returns>
static internal byte[] Compress(byte[] data)
{
var builder = new StringBuilder();
builder.Append(@"{\rtf1\ansi\mac\deff0\deftab720{\fonttbl;}");
builder.Append(@"{\f0\fnil \froman \fswiss \fmodern \fscript ");
builder.Append(@"\fdecor MS Sans SerifSymbolArialTimes New RomanCourier{\colortbl\red0\green0\blue0");
builder.Append("\r\n");
builder.Append(@"\par \pard\plain\f0\fs20\b\i\u\tab\tx");
InitialDictionary = Encoding.UTF8.GetBytes(builder.ToString());
Array.Resize(ref InitialDictionary, MAX_DICT_SIZE);
var positionData = new CompressionPositions()
{
WriteOffset = INIT_DICT_SIZE
};
var inStream = new MemoryStream(data);
var binaryReader = new BinaryReader(inStream);
var controlByte = 0;
var controlBit = 1;
var tokenOffset = 0;
using (MemoryStream outStream = new MemoryStream())
using (MemoryStream tokenStream = new MemoryStream())
{
while (true)
{
var dictReference = 0;
positionData = FindLongestMatch(InitialDictionary, binaryReader, positionData.WriteOffset);
byte[] readChar;
if (binaryReader.PeekChar() < 0)
{
controlByte |= 1 << controlBit - 1;
controlBit++;
tokenOffset += 2;
dictReference = (positionData.WriteOffset & 0xFFF) << 4;
var bytes = BitConverter.GetBytes((ushort)dictReference);
Array.Reverse(bytes);
tokenStream.Write(bytes, 0, 2);
outStream.WriteByte((byte)controlByte);
outStream.Write(tokenStream.ToArray(), 0, tokenOffset);
break;
}
readChar = binaryReader.ReadBytes(positionData.LongestMatchLength > 1 ? positionData.LongestMatchLength : 1);
if (positionData.LongestMatchLength > 1)
{
controlByte |= 1 << controlBit - 1;
controlBit++;
tokenOffset += 2;
dictReference = (positionData.DictionaryOffset & 0xFFF) << 4 | (positionData.LongestMatchLength - 2) & 0xf;
var bytes = BitConverter.GetBytes((ushort)dictReference);
Array.Reverse(bytes);
tokenStream.Write(bytes, 0, 2);
}
else
{
if (positionData.LongestMatchLength == 0)
{
InitialDictionary[positionData.WriteOffset] = Convert.ToByte(readChar[0]);
positionData.WriteOffset = (positionData.WriteOffset + 1) % MAX_DICT_SIZE;
}
controlByte |= 0 << controlBit - 1;
controlBit++;
tokenOffset++;
tokenStream.Write(readChar, 0, readChar.Length);
}
positionData.LongestMatchLength = 0;
if (controlBit > 8)
{
outStream.WriteByte((byte)controlByte);
outStream.Write(tokenStream.ToArray(), 0, tokenOffset);
controlByte = 0;
controlBit = 1;
tokenOffset = 0;
tokenStream.SetLength(0);
}
}
var compSize = (uint)outStream.Length + 12;
var rawSize = (uint)data.Length;
var crcValue = Crc32Calculator.CalculateCrc32(outStream.ToArray());
using (var resultStream = new MemoryStream())
{
resultStream.Write(BitConverter.GetBytes(compSize), 0, BitConverter.GetBytes(compSize).Length);
resultStream.Write(BitConverter.GetBytes(rawSize), 0, BitConverter.GetBytes(rawSize).Length);
resultStream.Write(Encoding.UTF8.GetBytes(COMP_TYPE), 0, Encoding.UTF8.GetBytes(COMP_TYPE).Length);
resultStream.Write(BitConverter.GetBytes(crcValue), 0, BitConverter.GetBytes(crcValue).Length);
resultStream.Write(outStream.ToArray(), 0, outStream.ToArray().Length);
return(resultStream.ToArray());
}
}
}
