Function pack

runtime/Packer.h:93–127

 */
template<typename T>
inline typename std::enable_if<std::is_integral<T>::value &&
                                !std::is_signed<T>::value, int>::type
pack(char **buffer, T val) {
    // Binary search for the smallest container. It is also worth noting that
    // with -O3, the compiler will strip out extraneous if-statements based on T
    // For example, if T is uint16_t, it would only leave the t < 1U<<8 check

    //TODO(syang0) Is this too costly vs. a simple for loop?
    int numBytes;
    if (val < (1UL << 8)) {
            numBytes = 1;
    } else if (val < (1UL << 16)) {
        numBytes = 2;
    } else if (val < (1UL << 24)) {
        numBytes = 3;
    } else if (val < (1UL << 32)) {
        numBytes = 4;
    } else if (val < (1UL << 40)) {
        numBytes = 5;
    } else if (val < (1UL << 48)) {
        numBytes = 6;
    } else if (val < (1UL << 56)) {
        numBytes = 7;
    } else {
        numBytes = 8;
    }

    // Although we store the entire value here, we take advantage of the fact
    // that x86-64 is little-endian (storing the least significant bits first)
    // and lop off the rest by only partially incrementing the buffer pointer
    *reinterpret_cast<T*>(*buffer) = val;
    *buffer += numBytes;

    return numBytes;
}

/**
 * Below are a series of pack functions that take in a signed integer,