public GetSymbol ( |
||
input | /// input the input source. /// | |
return | int |
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); mode = DNUM; goto case DNUM; case DNUM: dnum = input.PeekBits(5); if (dnum < 0) { return false; } dnum++; input.DropBits(5); num = lnum+dnum; litdistLens = new byte[num]; mode = BLNUM; goto case BLNUM; case BLNUM: blnum = input.PeekBits(4); if (blnum < 0) { return false; } blnum += 4; input.DropBits(4); blLens = new byte[19]; ptr = 0; mode = BLLENS; goto case BLLENS; case BLLENS: while (ptr < blnum) { int len = input.PeekBits(3); if (len < 0) { return false; } input.DropBits(3); blLens[BL_ORDER[ptr]] = (byte) len; ptr++; } blTree = new InflaterHuffmanTree(blLens); blLens = null; ptr = 0; mode = LENS; goto case LENS; case LENS: { int symbol; while (((symbol = blTree.GetSymbol(input)) & ~15) == 0) { litdistLens[ptr++] = lastLen = (byte)symbol; if (ptr == num) { return true; } } if (symbol < 0) { return false; } if (symbol >= 17) { lastLen = 0; } else { if (ptr == 0) { throw new SharpZipBaseException(); } } repSymbol = symbol-16; } mode = REPS; goto case REPS; case REPS: { int bits = repBits[repSymbol]; int count = input.PeekBits(bits); if (count < 0) { return false; } input.DropBits(bits); count += repMin[repSymbol]; if (ptr + count > num) { throw new SharpZipBaseException(); } while (count-- > 0) { litdistLens[ptr++] = lastLen; } if (ptr == num) { return true; } } mode = LENS; goto decode_loop; } } }