What does this bit-manipulating function do?

unsigned long ccNextPOT(unsigned long x){

    x = x - 1;
    x = x | (x >> 1);
    x = x | (x >> 2);
    x = x | (x >> 4);
    x = x | (x >> 8);
    x = x | (x >>16);
    return x + 1;
}

bit-manipulation

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The OR and SHIFT statements fills with ones all bits of x to the right of most significant bit (up to 32 bits). Together with the pre-decrement and post-increment statements, this computes (as the function name suggets) the next power-of-two number, equal or greater than the given number (if x is greater than 0 and less than 2^32)

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This function rounds x up to the next highest power of 2. It‘s exactly the code in here

unsigned int v; // compute the next highest power of 2 of 32-bit v

v--;
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
v++;