private static int DecodeValue(ref BitBuffer bitBuffer, Node node)
{
// This cannot cause an infinite loop if the tables are correct.
while (node.Value == -1)
{
node = node[bitBuffer.GetBit()];
}
return(node.Value);
}
private static int DecodeValue(ref BitBuffer bitBuffer, Node node)
{
// This cannot cause an infinite loop if the tables are correct.
while (node.Value == -1) node = node[bitBuffer.GetBit()];
return node.Value;
}
// 'explode' decompression
public static int DecompressBlock(byte[] inBuffer, int index, int count, byte[] outBuffer)
{
bool ascii;
byte b;
b = inBuffer[index++];
// Check the ASCII encoding flag
if (b == 0) ascii = false; // Don't use ASCII encoding
else if (b == 1) ascii = true; // Use ASCII encoding
else throw new InvalidDataException();
b = inBuffer[index++];
if (b < 4 || b > 6) throw new InvalidDataException();
int dictSize = 0x40 << b; // Calculate dictionnary size
int lowOffsetSize = b;
var bitBuffer = new BitBuffer(inBuffer, index, count - 2);
try
{
int i = 0;
while (i < outBuffer.Length && !bitBuffer.Eof)
{
int t = bitBuffer.GetBit();
if (t == 0) // Litteral
{
// Depending on the compression mode, this can either be a raw byte or a coded ASCII character
t = ascii ? DecodeValue(ref bitBuffer, asciiTree) : bitBuffer.GetByte();
outBuffer[i++] = (byte)t;
}
else // Length/Offset Pair
{
// Get the length
int length = DecodeValue(ref bitBuffer, lengthTree);
if (length == 519) break; // Length 519 means end of stream
// Get the offset
int offsetHigh = DecodeValue(ref bitBuffer, offsetTree);
int offset = length == 2 ?
i - ((offsetHigh << 2) | bitBuffer.GetBits(2)) - 1 :
i - ((offsetHigh << lowOffsetSize) | bitBuffer.GetBits(lowOffsetSize)) - 1;
if (offset < 0) throw new InvalidDataException();
// Copy
while (length-- != 0) outBuffer[i++] = outBuffer[offset++];
}
}
return i;
}
finally { bitBuffer.Dispose(); }
}
// 'explode' decompression
public static int DecompressBlock(byte[] inBuffer, int index, int count, byte[] outBuffer)
{
bool ascii;
byte b;
b = inBuffer[index++];
// Check the ASCII encoding flag
if (b == 0)
{
ascii = false; // Don't use ASCII encoding
}
else if (b == 1)
{
ascii = true; // Use ASCII encoding
}
else
{
throw new InvalidDataException();
}
b = inBuffer[index++];
if (b < 4 || b > 6)
{
throw new InvalidDataException();
}
int dictSize = 0x40 << b; // Calculate dictionnary size
int lowOffsetSize = b;
var bitBuffer = new BitBuffer(inBuffer, index, count - 2);
try
{
int i = 0;
while (i < outBuffer.Length && !bitBuffer.Eof)
{
int t = bitBuffer.GetBit();
if (t == 0) // Litteral
{
// Depending on the compression mode, this can either be a raw byte or a coded ASCII character
t = ascii ? DecodeValue(ref bitBuffer, asciiTree) : bitBuffer.GetByte();
outBuffer[i++] = (byte)t;
}
else // Length/Offset Pair
{
// Get the length
int length = DecodeValue(ref bitBuffer, lengthTree);
if (length == 519)
{
break; // Length 519 means end of stream
}
// Get the offset
int offsetHigh = DecodeValue(ref bitBuffer, offsetTree);
int offset = length == 2 ?
i - ((offsetHigh << 2) | bitBuffer.GetBits(2)) - 1 :
i - ((offsetHigh << lowOffsetSize) | bitBuffer.GetBits(lowOffsetSize)) - 1;
if (offset < 0)
{
throw new InvalidDataException();
}
// Copy
while (length-- != 0)
{
outBuffer[i++] = outBuffer[offset++];
}
}
}
return(i);
}
finally { bitBuffer.Dispose(); }
}
