====== (This is the legacy documentation for stable SDL2, the current stable version; [https://wiki.libsdl.org/SDL3/ SDL3] is the current development version.) ======
= SDL_MostSignificantBitIndex32 =

Use this function to get the index of the most significant (set) bit in a

== Header File ==

Defined in [SDL_bits.h](https://github.com/libsdl-org/SDL/blob/SDL2/include/SDL_bits.h)

== Syntax ==

<syntaxhighlight lang='c'>
SDL_FORCE_INLINE int SDL_MostSignificantBitIndex32(Uint32 x);</syntaxhighlight>

== Function Parameters ==

{|
|'''x'''
|the number to find the MSB of
|}

== Return Value ==

Returns the index of the most significant bit of x, or -1 if x is 0.

== Code Examples ==

<syntaxhighlight lang='c'>

#include "SDL.h"
#include "SDL_bits.h"

int main(int argc, char *argv[]) {
  if (argc != 2) {
    SDL_Log("Usage: %s <number", argv[0]);
    return 1;
  }
  int bitmask = SDL_atoi(argv[1]);
  if (bitmask < 0) {
    SDL_Log("Number must be positive");
    return 1;
  }
  int index = SDL_MostSignificantBitIndex32(bitmask);
  SDL_Log("MSB index is %d", index);
  return 0;
}
</syntaxhighlight>

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[[CategoryAPI]], [[CategoryAPIFunction]], [[CategoryBits]]