/// <summary>
/// Reads the next symbol from input. The symbol is encoded using the
/// huffman tree.
/// </summary>
/// <param name="input">
/// input the input source.
/// </param>
/// <returns>
/// the next symbol, or -1 if not enough input is available.
/// </returns>
public int GetSymbol(StreamManipulator input)
{
int lookahead, symbol;
if ((lookahead = input.PeekBits(9)) >= 0)
{
if ((symbol = tree[lookahead]) >= 0)
{
input.DropBits(symbol & 15);
return symbol >> 4;
}
int subtree = -(symbol >> 4);
int bitlen = symbol & 15;
if ((lookahead = input.PeekBits(bitlen)) >= 0)
{
symbol = tree[subtree | (lookahead >> 9)];
input.DropBits(symbol & 15);
return symbol >> 4;
}
else
{
int bits = input.AvailableBits;
lookahead = input.PeekBits(bits);
symbol = tree[subtree | (lookahead >> 9)];
if ((symbol & 15) <= bits)
{
input.DropBits(symbol & 15);
return symbol >> 4;
}
else
{
return -1;
}
}
}
else
{
int bits = input.AvailableBits;
lookahead = input.PeekBits(bits);
symbol = tree[lookahead];
if (symbol >= 0 && (symbol & 15) <= bits)
{
input.DropBits(symbol & 15);
return symbol >> 4;
}
else
{
return -1;
}
}
}
public bool Decode(StreamManipulator input)
{
decode_loop:
for (; ; )
{
switch (mode)
{
case LNUM:
lnum = input.PeekBits(5);
if (lnum < 0)
{
return false;
}
lnum += 257;
input.DropBits(5);
// System.err.println("LNUM: "+lnum);
mode = DNUM;
goto case DNUM; // fall through
case DNUM:
dnum = input.PeekBits(5);
if (dnum < 0)
{
return false;
}
dnum++;
input.DropBits(5);
// System.err.println("DNUM: "+dnum);
num = lnum + dnum;
litdistLens = new byte[num];
mode = BLNUM;
goto case BLNUM; // fall through
case BLNUM:
blnum = input.PeekBits(4);
if (blnum < 0)
{
return false;
}
blnum += 4;
input.DropBits(4);
blLens = new byte[19];
ptr = 0;
// System.err.println("BLNUM: "+blnum);
mode = BLLENS;
goto case BLLENS; // fall through
case BLLENS:
while (ptr < blnum)
{
int len = input.PeekBits(3);
if (len < 0)
{
return false;
}
input.DropBits(3);
// System.err.println("blLens["+BL_ORDER[ptr]+"]: "+len);
blLens[BL_ORDER[ptr]] = (byte)len;
ptr++;
}
blTree = new InflaterHuffmanTree(blLens);
blLens = null;
ptr = 0;
mode = LENS;
goto case LENS; // fall through
case LENS:
{
int symbol;
while (((symbol = blTree.GetSymbol(input)) & ~15) == 0)
{
/* Normal case: symbol in [0..15] */
// System.err.println("litdistLens["+ptr+"]: "+symbol);
litdistLens[ptr++] = lastLen = (byte)symbol;
if (ptr == num)
{
/* Finished */
return true;
}
}
/* need more input ? */
if (symbol < 0)
{
return false;
}
/* otherwise repeat code */
if (symbol >= 17)
{
/* repeat zero */
// System.err.println("repeating zero");
lastLen = 0;
}
else
{
if (ptr == 0)
{
throw new PiaException();
}
}
repSymbol = symbol - 16;
}
mode = REPS;
goto case REPS; // fall through
case REPS:
{
int bits = repBits[repSymbol];
int count = input.PeekBits(bits);
if (count < 0)
{
return false;
}
input.DropBits(bits);
count += repMin[repSymbol];
// System.err.println("litdistLens repeated: "+count);
if (ptr + count > num)
{
throw new PiaException();
}
while (count-- > 0)
{
litdistLens[ptr++] = lastLen;
}
if (ptr == num)
{
/* Finished */
return true;
}
}
mode = LENS;
goto decode_loop;
}
}
}