1*aaceae98SRobert Mustacchi.\" 2*aaceae98SRobert Mustacchi.\" This file and its contents are supplied under the terms of the 3*aaceae98SRobert Mustacchi.\" Common Development and Distribution License ("CDDL"), version 1.0. 4*aaceae98SRobert Mustacchi.\" You may only use this file in accordance with the terms of version 5*aaceae98SRobert Mustacchi.\" 1.0 of the CDDL. 6*aaceae98SRobert Mustacchi.\" 7*aaceae98SRobert Mustacchi.\" A full copy of the text of the CDDL should have accompanied this 8*aaceae98SRobert Mustacchi.\" source. A copy of the CDDL is also available via the Internet at 9*aaceae98SRobert Mustacchi.\" http://www.illumos.org/license/CDDL. 10*aaceae98SRobert Mustacchi.\" 11*aaceae98SRobert Mustacchi.\" 12*aaceae98SRobert Mustacchi.\" Copyright 2024 Oxide Computer Company 13*aaceae98SRobert Mustacchi.\" 14*aaceae98SRobert Mustacchi.Dd October 27, 2024 15*aaceae98SRobert Mustacchi.Dt STDC_LEADING_ONES 3C 16*aaceae98SRobert Mustacchi.Os 17*aaceae98SRobert Mustacchi.Sh NAME 18*aaceae98SRobert Mustacchi.Nm stdc_leading_ones , 19*aaceae98SRobert Mustacchi.Nm stdc_leading_ones_uc , 20*aaceae98SRobert Mustacchi.Nm stdc_leading_ones_us , 21*aaceae98SRobert Mustacchi.Nm stdc_leading_ones_ui , 22*aaceae98SRobert Mustacchi.Nm stdc_leading_ones_ul , 23*aaceae98SRobert Mustacchi.Nm stdc_leading_ones_ull 24*aaceae98SRobert Mustacchi.Nd count consecutive leading one bits 25*aaceae98SRobert Mustacchi.Sh LIBRARY 26*aaceae98SRobert Mustacchi.Lb libc 27*aaceae98SRobert Mustacchi.Sh SYNOPSIS 28*aaceae98SRobert Mustacchi.In stdbit.h 29*aaceae98SRobert Mustacchi.Ft "unsigned int" 30*aaceae98SRobert Mustacchi.Fo stdc_leading_ones 31*aaceae98SRobert Mustacchi.Fa "generic_value_type value" 32*aaceae98SRobert Mustacchi.Fc 33*aaceae98SRobert Mustacchi.Ft "unsigned int" 34*aaceae98SRobert Mustacchi.Fo stdc_leading_ones_uc 35*aaceae98SRobert Mustacchi.Fa "unsigned char value" 36*aaceae98SRobert Mustacchi.Fc 37*aaceae98SRobert Mustacchi.Ft "unsigned int" 38*aaceae98SRobert Mustacchi.Fo stdc_leading_ones_us 39*aaceae98SRobert Mustacchi.Fa "unsigned short value" 40*aaceae98SRobert Mustacchi.Fc 41*aaceae98SRobert Mustacchi.Ft "unsigned int" 42*aaceae98SRobert Mustacchi.Fo stdc_leading_ones_ui 43*aaceae98SRobert Mustacchi.Fa "unsigned int value" 44*aaceae98SRobert Mustacchi.Fc 45*aaceae98SRobert Mustacchi.Ft "unsigned int" 46*aaceae98SRobert Mustacchi.Fo stdc_leading_ones_ul 47*aaceae98SRobert Mustacchi.Fa "unsigned long value" 48*aaceae98SRobert Mustacchi.Fc 49*aaceae98SRobert Mustacchi.Ft "unsigned int" 50*aaceae98SRobert Mustacchi.Fo stdc_leading_ones_ull 51*aaceae98SRobert Mustacchi.Fa "unsigned long long value" 52*aaceae98SRobert Mustacchi.Fc 53*aaceae98SRobert Mustacchi.Sh DESCRIPTION 54*aaceae98SRobert MustacchiThe 55*aaceae98SRobert Mustacchi.Fn stdc_leading_ones 56*aaceae98SRobert Mustacchifamily of functions counts the number of consecutive one bits present in 57*aaceae98SRobert Mustacchi.Fa value 58*aaceae98SRobert Mustacchistarting at the most significant bit. 59*aaceae98SRobert Mustacchi.Pp 60*aaceae98SRobert MustacchiThe 61*aaceae98SRobert Mustacchi.Fn stdc_leading_ones 62*aaceae98SRobert Mustacchifunction is generic and will operate on all 8, 16, 32, and 64-bit 63*aaceae98SRobert Mustacchiunsigned integers; however, it is only available in C23. 64*aaceae98SRobert MustacchiThe other functions all operate on a specific integer type, but 65*aaceae98SRobert Mustacchiotherwise behave the same and are available regardless of the C language 66*aaceae98SRobert Mustacchiversion. 67*aaceae98SRobert Mustacchi.Sh RETURN VALUES 68*aaceae98SRobert MustacchiThe functions in the 69*aaceae98SRobert Mustacchi.Fn stdc_leading_ones 70*aaceae98SRobert Mustacchifamily always return the number of leading ones found in 71*aaceae98SRobert Mustacchi.Fa value . 72*aaceae98SRobert MustacchiThese functions cannot fail. 73*aaceae98SRobert Mustacchi.Sh EXAMPLES 74*aaceae98SRobert Mustacchi.Sy Example 1 75*aaceae98SRobert MustacchiPrinting the number of leading zeros. 76*aaceae98SRobert Mustacchi.Bd -literal 77*aaceae98SRobert Mustacchi#include <stdbit.h> 78*aaceae98SRobert Mustacchi#include <stdio.h> 79*aaceae98SRobert Mustacchi#include <limits.h> 80*aaceae98SRobert Mustacchi 81*aaceae98SRobert Mustacchiint 82*aaceae98SRobert Mustacchimain(void) 83*aaceae98SRobert Mustacchi{ 84*aaceae98SRobert Mustacchi printf("0x%x 0x%x 0x%x 0x%x\en", stdc_leading_ones_uc(0xf6), 85*aaceae98SRobert Mustacchi stdc_leading_ones_us(0x9009), stdc_leading_ones_ui(UINT32_MAX), 86*aaceae98SRobert Mustacchi stdc_leading_ones_ull(0)); 87*aaceae98SRobert Mustacchi return (0); 88*aaceae98SRobert Mustacchi} 89*aaceae98SRobert Mustacchi.Ed 90*aaceae98SRobert Mustacchi.Pp 91*aaceae98SRobert MustacchiWhen compiled and run, this produces: 92*aaceae98SRobert Mustacchi.Bd -literal -offset indent 93*aaceae98SRobert Mustacchi$ ./a.out 94*aaceae98SRobert Mustacchi0x4 0x1 0x20 0x0 95*aaceae98SRobert Mustacchi.Ed 96*aaceae98SRobert Mustacchi.Sh INTERFACE STABILITY 97*aaceae98SRobert Mustacchi.Sy Committed 98*aaceae98SRobert Mustacchi.Sh MT-LEVEL 99*aaceae98SRobert Mustacchi.Sy Async-Signal-Safe 100*aaceae98SRobert Mustacchi.Sh SEE ALSO 101*aaceae98SRobert Mustacchi.Xr stdc_bit_ceil 3C , 102*aaceae98SRobert Mustacchi.Xr stdc_bit_floor 3C , 103*aaceae98SRobert Mustacchi.Xr stdc_bit_width 3C , 104*aaceae98SRobert Mustacchi.Xr stdc_count_ones 3C , 105*aaceae98SRobert Mustacchi.Xr stdc_count_zeros 3C , 106*aaceae98SRobert Mustacchi.Xr stdc_first_leading_one 3C , 107*aaceae98SRobert Mustacchi.Xr stdc_first_leading_zero 3C , 108*aaceae98SRobert Mustacchi.Xr stdc_first_trailing_one 3C , 109*aaceae98SRobert Mustacchi.Xr stdc_first_trailing_zero 3C , 110*aaceae98SRobert Mustacchi.Xr stdc_has_single_bit 3C , 111*aaceae98SRobert Mustacchi.Xr stdc_leading_zeros 3C , 112*aaceae98SRobert Mustacchi.Xr stdc_trailing_ones 3C , 113*aaceae98SRobert Mustacchi.Xr stdc_trailing_zeros 3C , 114*aaceae98SRobert Mustacchi.Xr stdbit.h 3HEAD 115