ilog2(3) - NetBSD Manual Pages

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ILOG2(3)                NetBSD Library Functions Manual               ILOG2(3)

ilog2 -- integer base-2 logarithm
#include <sys/bitops.h> int ilog2(size x);
For positive x, the ilog2() macro returns the integer part of the base-2 logarithm of x; that is, floor(log_2(x) ). If n = ilog2(x), then n is the largest integer such that 2**n <= x; in other words, ilog2() returns the largest integer to which 2 can be raised to obtain a value at most x. The type of the input parameter must be unsigned. If x is a constant expression, then so is ilog2(x).
ilog2() returns -1 when x is zero.
bitops(3), ffs(3), ilogb(3), log2(3), imax(9), powerof2(9)
The ilog2() macro first appeared in NetBSD 5.0. NetBSD 10.99 November 5, 2021 NetBSD 10.99
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