/// <summary>Decompress the LZW-compressed <see cref="Stream"/> <paramref name="source"/> into the <paramref name="output"/>, returning the number of bytes decompressed.</summary>
/// <param name="source">The <see cref="Stream"/> to decompress from.</param>
/// <param name="output">The byte array to write into.</param>
/// <param name="start">The first byte offset in <paramref name="output"/> to write into.</param>
/// <param name="count">The number of bytes in <paramref name="source"/> to write to at a maximum.</param>
/// <returns>The number of bytes written.</returns>
public static int Decompress(Stream source, byte[] output, int start, int count)
{
var bits = new BitStream(source);
int offset = start, end = start + count;
int tokenBits = 9; // Number of bits in a token.
int endToken = 0x1FF; // Last token to cause an increase in the bits.
int currentToken = 0x0102; // First undefined token.
int[] tokenOffsets = new int[4096]; // Indexes into output for each token.
int[] tokenLengths = new int[4096]; // Byte length of each token.
while (offset < end) {
int token = bits.ReadLSB(tokenBits);
if (token == 0x101) {
break;
} else if (token == 0x100) {
tokenBits = 9;
endToken = 0x1FF;
currentToken = 0x0102;
} else {
int tokenLength; // Size of the token in bytes.
if (token > 0xFF) {
if (token >= currentToken)
throw new InvalidDataException("LZW decompression encountered out-of-range token.");
tokenLength = tokenLengths[token] + 1;
int writeLength = tokenLength;
int tokenOffset = tokenOffsets[token];
if (end - offset < writeLength)
writeLength = end - offset;
for (int index = 0; index < writeLength; index++)
output[offset++] = output[tokenOffset++];
} else {
tokenLength = 1;
output[offset++] = (byte)token;
}
if (currentToken > endToken && tokenBits < 12) {
tokenBits++;
endToken = (endToken << 1) + 1;
}
if (currentToken <= endToken) {
tokenOffsets[currentToken] = offset - tokenLength;
tokenLengths[currentToken] = tokenLength;
currentToken++;
}
}
}
return offset - start;
}
/// <summary>Decompress the LZW-compressed <see cref="Stream"/> <paramref name="source"/> into the <paramref name="output"/>, returning the number of bytes decompressed.</summary>
/// <param name="source">The <see cref="Stream"/> to decompress from.</param>
/// <param name="output">The byte array to write into.</param>
/// <param name="start">The first byte offset in <paramref name="output"/> to write into.</param>
/// <param name="count">The number of bytes in <paramref name="source"/> to write to at a maximum.</param>
/// <returns>The number of bytes written.</returns>
public static int Decompress(Stream source, byte[] output, int start, int count)
{
var bits = new BitStream(source);
int offset = start, end = start + count;
int tokenBits = 9; // Number of bits in a token.
int endToken = 0x1FF; // Last token to cause an increase in the bits.
int currentToken = 0x0102; // First undefined token.
int[] tokenOffsets = new int[4096]; // Indexes into output for each token.
int[] tokenLengths = new int[4096]; // Byte length of each token.
while (offset < end)
{
int token = bits.ReadLSB(tokenBits);
if (token == 0x101)
{
break;
}
else if (token == 0x100)
{
tokenBits = 9;
endToken = 0x1FF;
currentToken = 0x0102;
}
else
{
int tokenLength; // Size of the token in bytes.
if (token > 0xFF)
{
if (token >= currentToken)
{
throw new InvalidDataException("LZW decompression encountered out-of-range token.");
}
tokenLength = tokenLengths[token] + 1;
int writeLength = tokenLength;
int tokenOffset = tokenOffsets[token];
if (end - offset < writeLength)
{
writeLength = end - offset;
}
for (int index = 0; index < writeLength; index++)
{
output[offset++] = output[tokenOffset++];
}
}
else
{
tokenLength = 1;
output[offset++] = (byte)token;
}
if (currentToken > endToken && tokenBits < 12)
{
tokenBits++;
endToken = (endToken << 1) + 1;
}
if (currentToken <= endToken)
{
tokenOffsets[currentToken] = offset - tokenLength;
tokenLengths[currentToken] = tokenLength;
currentToken++;
}
}
}
return(offset - start);
}