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Postings from February 2014
sv_grow has this comment:
* If the new size is a big power of two, don't bother: we assume the
* caller wanted a nice 2^N sized block and will be annoyed at getting
* 2^N+1 */
if (newlen & 0xff)
newlen++;
But 'newlen & 0xff' checks that it is not a multiple of 256, not that
it is not a power of 2, so the chances of skipping COW are greater
than they ought to be. Is there any easy and efficient way to check
for powers of 2 in C? The only way I can think of offhand is to loop
and shift, checking whether 'foo>>n == 1 && foo>>n<<n == foo'. Is it
worth that?
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