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]; }