ILOG2(3)

✨ ILOG2(3) — ilog2, the integer base-2 logarithm ✨

okay bestie, welcome to ILOG2(3) 💖 this one is short, iconic, and lowkey doing math at the club. it's the ilog2 manual page, and we're gonna get through it together, no cap.

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🎀 NAME 🎀

ilog2 — integer base-2 logarithm 💅

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🌸 SYNOPSIS 🌸

#include <sys/bitops.h>

int
ilog2(size x);

literally the whole vibe right there, bestie 🫶

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🦋 DESCRIPTION 🦋

okay so for positive x, the ilog2() macro returns the integer part of the base-2 logarithm of x — that is, floor(log_2(x) ). slay. 🔥

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. that's the whole plot, and it ate 💅

the type of the input parameter must be unsigned. not me being strict, that's just the rule, bestie 🙈

if x is a constant expression, then so is ilog2(x). constant-expression main character energy, periodt ✨

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💀 ERRORS 💀

ilog2() returns -1 when x is zero. yes, zero gets the -1, no cap 😭

bestie please notice this: zero does not get a cute little logarithm moment. it gets -1. that's the error behavior and we respect it 💖

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🌈 SEE ALSO 🌈

• bitops(3)
• ffs(3)
• ilogb(3)
• log2(3)
• imax(9)
• powerof2(9)

go read those too, iykyk 🧚💜

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👑 HISTORY 👑

the ilog2() macro first appeared in NetBSD 5.0. vintage-ish, but make it fashion 💅⭐

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and that's the page, bestie 🎀 this cutie is from Debian, dated November 5, 2021 — mwah 💋🫶