A bunch of bit ops where you need some "magic numbers" now logged in my gists for posterity.

BitOps.cpp

bool PowerOf2(unsigned long value)
{
    return (value != 0) && !(value & (value-1));
}

int BitCount(unsigned long value)
{
    value = (value & 0x55555555) + ((value & 0xAAAAAAAA) >> 1);
    value = (value & 0x33333333) + ((value & 0xCCCCCCCC) >> 2);
    value = (value & 0x0F0F0F0F) + ((value & 0xF0F0F0F0) >> 4);
    value = (value & 0x00FF00FF) + ((value & 0xFF00FF00) >> 8);
    value = (value & 0x0000FFFF) + ((value & 0xFFFF0000) >> 16);
    return value;
}

unsigned long BitReverse(unsigned long value)
{
    value = ((value & 0x55555555) << 1) | ((value & 0xAAAAAAAA) >> 1);
    value = ((value & 0x33333333) << 2) | ((value & 0xCCCCCCCC) >> 2);
    value = ((value & 0x0F0F0F0F) << 4) | ((value & 0xF0F0F0F0) >> 4);
    value = ((value & 0x00FF00FF) << 8) | ((value & 0xFF00FF00) >> 8);
    value = ((value & 0x0000FFFF) << 16) | ((value & 0xFFFF0000) >> 16);
    return value;
}