public HuffTreeNode(HUFF_STREAM stream, bool isData, long relOffset, long maxStreamPos)
{
if (stream.p >= maxStreamPos)
{
return;
}
int readData = stream.ReadByte();
this.data = (byte)readData;
this.isData = isData;
if (!this.isData)
{
int offset = this.data & 0x3F;
bool zeroIsData = (this.data & 0x80) > 0;
bool oneIsData = (this.data & 0x40) > 0;
long zeroRelOffset = (relOffset ^ (relOffset & 1)) + (offset * 2) + 2;
int currStreamPos = stream.p;
stream.p += (int)(zeroRelOffset - relOffset) - 1;
this.child0 = new HuffTreeNode(stream, zeroIsData, zeroRelOffset, maxStreamPos);
this.child1 = new HuffTreeNode(stream, oneIsData, zeroRelOffset + 1, maxStreamPos);
stream.p = currStreamPos;
}
}
public static byte[] Huffman_Decompress(byte[] b, byte atype)
{
HUFF_STREAM instream = new HUFF_STREAM(b);
long ReadBytes = 0;
byte type = (byte)instream.ReadByte();
type = atype;
if (type != 0x28 && type != 0x24)
{
return(b);
}
int decompressedSize = instream.readThree();
ReadBytes += 4;
if (decompressedSize == 0)
{
instream.p -= 3;
decompressedSize = instream.ReadInt32();
ReadBytes += 4;
}
List <byte> o = new List <byte>();
int treeSize = instream.ReadByte(); ReadBytes++;
treeSize = (treeSize + 1) * 2;
long treeEnd = (instream.p - 1) + treeSize;
// the relative offset may be 4 more (when the initial decompressed size is 0), but
// since it's relative that doesn't matter, especially when it only matters if
// the given value is odd or even.
HuffTreeNode rootNode = new HuffTreeNode(instream, false, 5, treeEnd);
ReadBytes += treeSize;
// re-position the stream after the tree (the stream is currently positioned after the root
// node, which is located at the start of the tree definition)
instream.p = (int)treeEnd;
// the current u32 we are reading bits from.
int data = 0;
// the amount of bits left to read from <data>
byte bitsLeft = 0;
// a cache used for writing when the block size is four bits
int cachedByte = -1;
// the current output size
HuffTreeNode currentNode = rootNode;
while (instream.hasBytes())
{
while (!currentNode.isData)
{
// if there are no bits left to read in the data, get a new byte from the input
if (bitsLeft == 0)
{
ReadBytes += 4;
data = instream.ReadInt32();
bitsLeft = 32;
}
// get the next bit
bitsLeft--;
bool nextIsOne = (data & (1 << bitsLeft)) != 0;
// go to the next node, the direction of the child depending on the value of the current/next bit
currentNode = nextIsOne ? currentNode.child1 : currentNode.child0;
}
switch (type)
{
case 0x28:
{
// just copy the data if the block size is a full byte
// outstream.WriteByte(currentNode.Data);
o.Add(currentNode.data);
break;
}
case 0x24:
{
// cache the first half of the data if the block size is a half byte
if (cachedByte < 0)
{
cachedByte = currentNode.data;
}
else
{
cachedByte |= currentNode.data << 4;
o.Add((byte)cachedByte);
cachedByte = -1;
}
break;
}
}
currentNode = rootNode;
}
if (ReadBytes % 4 != 0)
{
ReadBytes += 4 - (ReadBytes % 4);
}
return(o.ToArray());
}
