1*d790b16bSRobert Clausecker.\" 2*d790b16bSRobert Clausecker.\" Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org> 3*d790b16bSRobert Clausecker.\" 4*d790b16bSRobert Clausecker.\" SPDX-License-Identifier: BSD-2-Clause 5*d790b16bSRobert Clausecker.\" 6*d790b16bSRobert Clausecker.Dd November 9, 2025 7*d790b16bSRobert Clausecker.Dt STDC_COUNT_ONES 3 8*d790b16bSRobert Clausecker.Os 9*d790b16bSRobert Clausecker.Sh NAME 10*d790b16bSRobert Clausecker.Nm stdc_count_ones 11*d790b16bSRobert Clausecker.Nd count the ones in an integer 12*d790b16bSRobert Clausecker.Sh SYNOPSIS 13*d790b16bSRobert Clausecker.Lb libc 14*d790b16bSRobert Clausecker.In stdbit.h 15*d790b16bSRobert Clausecker.Ft unsigned int 16*d790b16bSRobert Clausecker.Fn stdc_count_ones_uc "unsigned char value" 17*d790b16bSRobert Clausecker.Ft unsigned int 18*d790b16bSRobert Clausecker.Fn stdc_count_ones_us "unsigned short value" 19*d790b16bSRobert Clausecker.Ft unsigned int 20*d790b16bSRobert Clausecker.Fn stdc_count_ones_ui "unsigned int value" 21*d790b16bSRobert Clausecker.Ft unsigned int 22*d790b16bSRobert Clausecker.Fn stdc_count_ones_ul "unsigned long value" 23*d790b16bSRobert Clausecker.Ft unsigned int 24*d790b16bSRobert Clausecker.Fn stdc_count_ones_ull "unsigned long long value" 25*d790b16bSRobert Clausecker.Ft unsigned int 26*d790b16bSRobert Clausecker.Fn stdc_count_ones "value" 27*d790b16bSRobert Clausecker.Sh DESCRIPTION 28*d790b16bSRobert ClauseckerThe 29*d790b16bSRobert Clausecker.Nm stdc_count_ones_ Ns Em type Ns () 30*d790b16bSRobert Clauseckerfamily of functions returns the number of bits set to\~1 in 31*d790b16bSRobert Clausecker.Fa value , 32*d790b16bSRobert Clauseckerwhere 33*d790b16bSRobert Clausecker.Fa value 34*d790b16bSRobert Clauseckeris of type 35*d790b16bSRobert Clausecker.Va unsigned char , 36*d790b16bSRobert Clausecker.Va unsigned short , 37*d790b16bSRobert Clausecker.Va unsigned int , 38*d790b16bSRobert Clausecker.Va unsigned long , 39*d790b16bSRobert Clauseckeror 40*d790b16bSRobert Clausecker.Va unsigned long long 41*d790b16bSRobert Clauseckerfor 42*d790b16bSRobert Clausecker.Em type 43*d790b16bSRobert Clauseckerbeing 44*d790b16bSRobert Clausecker.Sy uc , 45*d790b16bSRobert Clausecker.Sy us , 46*d790b16bSRobert Clausecker.Sy ui , 47*d790b16bSRobert Clausecker.Sy ul , 48*d790b16bSRobert Clauseckeror 49*d790b16bSRobert Clausecker.Sy ull 50*d790b16bSRobert Clauseckerrespectively. 51*d790b16bSRobert ClauseckerThis is also known as the 52*d790b16bSRobert Clausecker.Dq population count 53*d790b16bSRobert Clausecker(popcount) or 54*d790b16bSRobert Clausecker.Dq Hamming weight 55*d790b16bSRobert Clauseckeroperation. 56*d790b16bSRobert ClauseckerThe 57*d790b16bSRobert Clausecker.Fn stdc_count_ones "value" 58*d790b16bSRobert Clauseckertype-generic macro picks the appropriate 59*d790b16bSRobert Clausecker.Nm stdc_count_ones_ Ns Em type Ns () 60*d790b16bSRobert Clauseckerfunction based on the type of 61*d790b16bSRobert Clausecker.Fa value . 62*d790b16bSRobert Clausecker.Sh RETURN VALUES 63*d790b16bSRobert ClauseckerReturns the number of bits set to\~1 in 64*d790b16bSRobert Clausecker.Fa value . 65*d790b16bSRobert Clausecker.Sh SEE ALSO 66*d790b16bSRobert Clausecker.Xr bit_count 3 , 67*d790b16bSRobert Clausecker.Xr stdbit 3 , 68*d790b16bSRobert Clausecker.Xr stdc_count_zeros 3 , 69*d790b16bSRobert Clausecker.Xr stdc_has_single_bit 3 70*d790b16bSRobert Clausecker.Sh STANDARDS 71*d790b16bSRobert ClauseckerThe 72*d790b16bSRobert Clausecker.Nm stdc_count_ones_ Ns Em type Ns () 73*d790b16bSRobert Clauseckerfamily of functions and the 74*d790b16bSRobert Clausecker.Fn stdc_count_ones 75*d790b16bSRobert Clauseckertype-generic macro conform to 76*d790b16bSRobert Clausecker.St -isoC-2023 . 77*d790b16bSRobert Clausecker.Sh HISTORY 78*d790b16bSRobert ClauseckerThe 79*d790b16bSRobert Clausecker.Nm stdc_count_ones_ Ns Em type Ns () 80*d790b16bSRobert Clauseckerfamily of functions and the 81*d790b16bSRobert Clausecker.Fn stdc_count_ones 82*d790b16bSRobert Clauseckertype-generic macro were added in 83*d790b16bSRobert Clausecker.Fx 15.1. 84*d790b16bSRobert Clausecker.Sh AUTHOR 85*d790b16bSRobert Clausecker.An Robert Clausecker Aq Mt fuz@FreeBSD.org 86