1.\" 2.\" This file and its contents are supplied under the terms of the 3.\" Common Development and Distribution License ("CDDL"), version 1.0. 4.\" You may only use this file in accordance with the terms of version 5.\" 1.0 of the CDDL. 6.\" 7.\" A full copy of the text of the CDDL should have accompanied this 8.\" source. A copy of the CDDL is also available via the Internet at 9.\" http://www.illumos.org/license/CDDL. 10.\" 11.\" 12.\" Copyright 2024 Oxide Computer Company 13.\" 14.Dd October 27, 2024 15.Dt STDC_BIT_CEIL 9F 16.Os 17.Sh NAME 18.Nm stdc_bit_ceil , 19.Nm stdc_bit_ceil_uc , 20.Nm stdc_bit_ceil_us , 21.Nm stdc_bit_ceil_ui , 22.Nm stdc_bit_ceil_ul , 23.Nm stdc_bit_ceil_ull 24.Nd find smallest power of 2 not less than value 25.Sh SYNOPSIS 26.In sys/stdbit.h 27.Ft generic_value_type 28.Fo stdc_bit_ceil 29.Fa "generic_value_type value" 30.Fc 31.Ft "unsigned char" 32.Fo stdc_bit_ceil_uc 33.Fa "unsigned char value" 34.Fc 35.Ft "unsigned short" 36.Fo stdc_bit_ceil_us 37.Fa "unsigned short value" 38.Fc 39.Ft "unsigned int" 40.Fo stdc_bit_ceil_ui 41.Fa "unsigned int value" 42.Fc 43.Ft "unsigned long" 44.Fo stdc_bit_ceil_ul 45.Fa "unsigned long value" 46.Fc 47.Ft "unsigned long long" 48.Fo stdc_bit_ceil_ull 49.Fa "unsigned long long value" 50.Fc 51.Sh DESCRIPTION 52The 53.Fn stdc_bit_ceil 54family of functions finds the smallest power of 2 that is not less than 55.Fa value . 56If the resulting value would not fit in the type, then 0 is returned. 57For example, if one were to use UINT8_MAX with 58.Fn stdc_bit_ceil_uc 59the next power of two would be 0x100, which is larger than would fit in 60an 8-bit unsigned char, resulting in 0. 61.Pp 62The 63.Fn stdc_bit_ceil 64function is generic and will operate on all 8, 16, 32, and 64-bit 65unsigned integers; however, it is only available in C23. 66The other functions all operate on a specific integer type, but 67otherwise behave the same and are available regardless of the C language 68version. 69.Sh CONTEXT 70These functions may be called from 71.Sy user , 72.Sy kernel , 73or 74.Sy interrupt 75context. 76.Sh RETURN VALUES 77The functions in the 78.Fn stdc_bit_ceil 79family returns the smallest power of 2 that is not less than 80.Fa value . 81These functions cannot fail. 82.Sh INTERFACE STABILITY 83.Sy Committed 84.Sh SEE ALSO 85.Xr stdc_bit_ceil 3C , 86.Xr stdc_bit_floor 9F , 87.Xr stdc_bit_width 9F , 88.Xr stdc_count_ones 9F , 89.Xr stdc_count_zero 9F , 90.Xr stdc_first_leading_one 9F , 91.Xr stdc_first_leading_zero 9F , 92.Xr stdc_first_trailing_one 9F , 93.Xr stdc_first_trailing_zero 9F , 94.Xr stdc_has_single_bit 9F , 95.Xr stdc_leading_ones 9F , 96.Xr stdc_leading_zeros 9F , 97.Xr stdc_trailing_ones 9F , 98.Xr stdc_trailing_zeros 9F 99