.\" .\" Copyright (c) 2025 Robert Clausecker <[email protected]> .\" .\" SPDX-License-Identifier: BSD-2-Clause .\" .Dd November 9, 2025 .Dt STDC_BIT_WIDTH 3 .Os .Sh NAME .Nm stdc_bit_width .Nd find the first trailing one in an intege .Sh SYNOPSIS .Lb libc .In stdbit.h .Ft unsigned int .Fn stdc_bit_width_uc "unsigned char value" .Ft unsigned int .Fn stdc_bit_width_us "unsigned short value" .Ft unsigned int .Fn stdc_bit_width_ui "unsigned int value" .Ft unsigned int .Fn stdc_bit_width_ul "unsigned long value" .Ft unsigned int .Fn stdc_bit_width_ull "unsigned long long value" .Ft unsigned int .Fn stdc_bit_width "value" .Sh DESCRIPTION The .Nm stdc_bit_width_ Ns Em type Ns () family of functions returns the number of bits needed to represent .Fa value , where .Fa value is of type .Va unsigned char , .Va unsigned short , .Va unsigned int , .Va unsigned long , or .Va unsigned long long for .Em type being .Sy uc , .Sy us , .Sy ui , .Sy ul , or .Sy ull respectively. The .Fn stdc_bit_width "value" type-generic macro picks the appropriate .Nm stdc_bit_width_ Ns Em type Ns () function based on the type of .Fa value . .Pp Functions .Fn stdc_bit_width_ui , .Fn stdc_bit_width_ul , and .Fn stdc_bit_width_ull are identical to .Bx 4.3 functions .Xr fls 3 , .Xr flsl 3 , and .Xr flsll 3 respectively, except for operating on unsigned instead of signed values. .Sh RETURN VALUES Returns the least number of bits needed to represent .Fa value . If .Fa value is zero, the return value is zero. Otherwise it is .EQ 1 + \(lf log sub 2 italic value \(rf . .EN .Sh SEE ALSO .Xr bit_fls 3 , .Xr fls 3 , .Xr flsl 3 , .Xr flsll 3 , .Xr stdbit 3 , .Xr stdc_count_leading_zeros 3 , .Xr stdc_first_leading_one 3 .Sh STANDARDS The .Nm stdc_bit_width_ Ns Em type Ns () family of functions and the .Fn stdc_bit_width type-generic macro conform to .St -isoC-2023 . .Sh HISTORY The .Nm stdc_bit_width_ Ns Em type Ns () family of functions and the .Fn stdc_bit_width type-generic macro were added in .Fx 15.1. .Sh AUTHOR .An Robert Clausecker Aq Mt [email protected]
