STDC_LEADING_ONES(3)   FreeBSD Library Functions Manual   STDC_LEADING_ONES(3)

NAME

     stdc_leading_ones - find the number of leading ones in an integer

SYNOPSIS

     /* -lc */
     #include <stdbit.h>

     unsigned int
     stdc_leading_ones_uc(unsigned char value);

     unsigned int
     stdc_leading_ones_us(unsigned short value);

     unsigned int
     stdc_leading_ones_ui(unsigned int value);

     unsigned int
     stdc_leading_ones_ul(unsigned long value);

     unsigned int
     stdc_leading_ones_ull(unsigned long long value);

     unsigned int
     stdc_leading_ones(value);

DESCRIPTION

     The stdc_leading_ones_type() family of functions returns the number of
     leading ones in value, where value is of type unsigned char, unsigned
     short, unsigned int, unsigned long, or unsigned long long for type being
     uc, us, ui, ul, or ull respectively.  The stdc_leading_ones(value) type-
     generic macro picks the appropriate stdc_leading_ones_type() function
     based on the type of value.

RETURN VALUES

     Returns the number of leading ones in value.  If value is all ones, the
     total number of bits in the type of value is returned.

SEE ALSO

     stdbit(3), stdc_leading_zeros(3), stdc_trailing_ones(3),
     stdc_first_leading_zero(3)

STANDARDS

     The stdc_leading_ones_type() family of functions and the
     stdc_leading_ones() type-generic macro conform to ISO/IEC 9899:2024
     ("ISO C23").

HISTORY

     The stdc_leading_ones_type() family of functions and the
     stdc_leading_ones() type-generic macro were added in FreeBSD 15.1.

AUTHOR

     Robert Clausecker <fuz@FreeBSD.org>

FreeBSD 15.1-STABLE-HBSD       November 9, 2025           STDC_LEADING_ONES(3)