1.\" 2.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org> 3.\" 4.\" SPDX-License-Identifier: BSD-2-Clause 5.\" 6.Dd November 9, 2025 7.Dt STDC_LEADING_ONES 3 8.Os 9.Sh NAME 10.Nm stdc_leading_ones 11.Nd find the number of leading ones in an integer 12.Sh SYNOPSIS 13.Lb libc 14.In stdbit.h 15.Ft unsigned int 16.Fn stdc_leading_ones_uc "unsigned char value" 17.Ft unsigned int 18.Fn stdc_leading_ones_us "unsigned short value" 19.Ft unsigned int 20.Fn stdc_leading_ones_ui "unsigned int value" 21.Ft unsigned int 22.Fn stdc_leading_ones_ul "unsigned long value" 23.Ft unsigned int 24.Fn stdc_leading_ones_ull "unsigned long long value" 25.Ft unsigned int 26.Fn stdc_leading_ones "value" 27.Sh DESCRIPTION 28The 29.Nm stdc_leading_ones_ Ns Em type Ns () 30family of functions returns the number of leading ones in 31.Fa value , 32where 33.Fa value 34is of type 35.Va unsigned char , 36.Va unsigned short , 37.Va unsigned int , 38.Va unsigned long , 39or 40.Va unsigned long long 41for 42.Em type 43being 44.Sy uc , 45.Sy us , 46.Sy ui , 47.Sy ul , 48or 49.Sy ull 50respectively. 51The 52.Fn stdc_leading_ones "value" 53type-generic macro picks the appropriate 54.Nm stdc_leading_ones_ Ns Em type Ns () 55function based on the type of 56.Fa value . 57.Sh RETURN VALUES 58Returns the number of leading ones in 59.Fa value . 60If 61.Fa value 62is all ones, 63the total number of bits in the type of 64.Fa value 65is returned. 66.Sh SEE ALSO 67.Xr stdbit 3 , 68.Xr stdc_leading_zeros 3 , 69.Xr stdc_trailing_ones 3 , 70.Xr stdc_first_leading_zero 3 71.Sh STANDARDS 72The 73.Nm stdc_leading_ones_ Ns Em type Ns () 74family of functions and the 75.Fn stdc_leading_ones 76type-generic macro conform to 77.St -isoC-2023 . 78.Sh HISTORY 79The 80.Nm stdc_leading_ones_ Ns Em type Ns () 81family of functions and the 82.Fn stdc_leading_ones 83type-generic macro were added in 84.Fx 15.1. 85.Sh AUTHOR 86.An Robert Clausecker Aq Mt fuz@FreeBSD.org 87