Class Nibbler

runtime/Packer.h:331–404

* This class takes in a data stream of pack() Nibbles followed by pack()'ed * values as produced by the compressor and unpack()'s them one by one. */

 * values as produced by the compressor and unpack()'s them one by one.
 */
class Nibbler {
PRIVATE:
    // Position in the nibble stream
    const TwoNibbles *nibblePosition;

    // Indicates whether whether to use the first nibble or second
    bool onFirstNibble;

    // Number of nibbles in this stream
    int numNibbles;

    // Position in the stream marking the next packed value
    const char *currPackedValue;

    // End of the last valid packed value
    const char *endOfValues;

public:
    /**
     * Nibbler Constructor
     *
     * \param nibbleStart
     *      Data stream consisting of the Nibbles followed by pack()ed values.
     * \param numNibbles
     *      Number of nibbles in the data stream
     */
    Nibbler(const char *nibbleStart, int numNibbles)
        : nibblePosition(reinterpret_cast<const TwoNibbles*>(nibbleStart))
        , onFirstNibble(true)
        , numNibbles(numNibbles)
        , currPackedValue(nibbleStart + (numNibbles + 1)/2)
        , endOfValues(nullptr)
    {
        endOfValues = nibbleStart
                             + (numNibbles + 1)/2
                             + getSizeOfPackedValues(nibblePosition, numNibbles);
    }

    /**
     * Returns the next pack()-ed value in the stream
     *
     * \tparam T
     *      Type of the value in the stream
     * \return
     *      Next pack()-ed value in the stream
     */
    template<typename T>
    T getNext() {
        assert(currPackedValue < endOfValues);

        uint8_t nibble = (onFirstNibble) ? nibblePosition->first
                                         : nibblePosition->second;

        T ret = unpack<T>(&currPackedValue, nibble);

        if (!onFirstNibble)
            ++nibblePosition;