int getNextValue(PngDecodingDataStream stream) throws IOException {
int code = stream.getNextIdatBit();
int codelength = 0;
// Here we are taking advantage of the fact that 1 bits are used as
// a prefix to the longer codeValues.
while (codelength < MAX_CODE_LENGTH && code > codeLengthInfo[codelength].max) {
code = ((code << 1) | stream.getNextIdatBit());
codelength++;
}
if (codelength >= MAX_CODE_LENGTH) stream.error();
// Now we have a Huffman code of length (codelength + 1) that
// is somewhere in the range
// minCodesByLength[codelength]..maxCodesByLength[codelength].
// This code is the (offset + 1)'th code of (codelength + 1);
int offset = code - codeLengthInfo[codelength].min;
// indexesByLength[codelength] is the first code of length (codelength + 1)
// so now we can look up the value for the Huffman code in the table.
int index = codeLengthInfo[codelength].baseIndex + offset;
return codeValues[index];
}
