/// <summary>
/// Decodes the data in the stream with the LZW decoder
/// </summary>
/// <param name="compressedInput">Stream of compressed data</param>
/// <param name="output">Stream of decompressed data</param>
public static void Decode(Stream compressedInput, Stream output)
{
NBitStream input = new NBitStream(compressedInput);
//int bitsInChunk = MIN_CHUNK_SIZE; // Min size
byte firstByte = 0;
long nextCommand = 0;
input.BitsInChunk = MIN_CHUNK_SIZE;
var dic = new LzwDictionary(DICTIONARY_SIZE);
while ((nextCommand = input.Read()) != EOD)
{
if (nextCommand < 0)
{
break;
}
// Do our reset
if (nextCommand == CLEAR_TABLE)
{
input.BitsInChunk = MIN_CHUNK_SIZE;
dic = new LzwDictionary(DICTIONARY_SIZE);
}
else
{
byte[] data = dic.GetData(nextCommand);
if (data == null)
{
dic.Visit(firstByte);
data = dic.GetData(nextCommand);
dic.Clearbuffer(); // clear buffer
}
if (data != null)
{
dic.Visit(data);
if (dic.GetNextCode() >= 2047)
{
input.BitsInChunk = 12;
}
else if (dic.GetNextCode() >= 1023)
{
input.BitsInChunk = 11;
}
else if (dic.GetNextCode() >= 511)
{
input.BitsInChunk = 10;
}
else
{
input.BitsInChunk = 9;
}
firstByte = data[0];
output.Write(data, 0, data.Length);
}
else
{
//throw new Exception("Error: data is null");
}
}
output.Flush();
}
}
/// <summary>
/// Decodes the data in the stream with the LZW decoder
/// </summary>
/// <param name="compressedInput">Stream of compressed data</param>
/// <param name="output">Stream of decompressed data</param>
public static void Decode(Stream compressedInput, Stream output)
{
NBitStream input = new NBitStream(compressedInput);
//byte firstByte = 0;
long nextCommand = 0;
long lastCommand = -1; // CLEAR_TABLE;
int earlyChange = 1;
LzwTable table = new LzwTable(TABLE_SIZE);
// The input needs the bits in chunk set properly to read the data
input.BitsInChunk = MIN_CHUNK_SIZE;
while ((nextCommand = input.Read()) != EOD)
{
if (nextCommand < 0)
{
break; // EOF?
}
// Do our reset
if (nextCommand == CLEAR_TABLE)
{
input.BitsInChunk = MIN_CHUNK_SIZE;
table = new LzwTable(TABLE_SIZE);
lastCommand = -1;
}
else
{
//if (table[lastCommand] == null)
//{
// throw new Exception(String.Format("Corrupted LZW: code {0} (table size: {1})", lastCommand, table.Length));
//}
// Check if the command is already in the table
// We could use a dictionary here, but I don't think we need the extra overhead of a hash
if (nextCommand < table.Count)
{
table[(int)nextCommand].writeTo(output);
if (lastCommand != -1)
{
table.Add(table[(int)lastCommand].concatenate(table[(int)nextCommand].firstChar));
}
}
else
{
LZWString outString = table[(int)lastCommand].concatenate(table[(int)lastCommand].firstChar);
outString.writeTo(output);
table.Add(outString);
}
// The input needs the bits in chunk set properly to read the data
if (table.GetNextCode() >= 4096 - earlyChange)
{
input.BitsInChunk = 13;
}
else
if (table.GetNextCode() >= 2048 - earlyChange)
{
input.BitsInChunk = 12;
}
else if (table.GetNextCode() >= 1024 - earlyChange)
{
input.BitsInChunk = 11;
}
else if (table.GetNextCode() >= 512 - earlyChange)
{
input.BitsInChunk = 10;
}
else
{
input.BitsInChunk = 9;
}
lastCommand = nextCommand;
}
} // while end
output.Flush();
}
