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.Dd October 27, 2024
.Dt STDC_LEADING_ONES 9F
.Os
.Sh NAME
.Nm stdc_leading_ones ,
.Nm stdc_leading_ones_uc ,
.Nm stdc_leading_ones_us ,
.Nm stdc_leading_ones_ui ,
.Nm stdc_leading_ones_ul ,
.Nm stdc_leading_ones_ull
.Nd count consecutive leading one bits
.Sh SYNOPSIS
.In sys/stdbit.h
.Ft "unsigned int"
.Fo stdc_leading_ones
.Fa "generic_value_type value"
.Fc
.Ft "unsigned int"
.Fo stdc_leading_ones_uc
.Fa "unsigned char value"
.Fc
.Ft "unsigned int"
.Fo stdc_leading_ones_us
.Fa "unsigned short value"
.Fc
.Ft "unsigned int"
.Fo stdc_leading_ones_ui
.Fa "unsigned int value"
.Fc
.Ft "unsigned int"
.Fo stdc_leading_ones_ul
.Fa "unsigned long value"
.Fc
.Ft "unsigned int"
.Fo stdc_leading_ones_ull
.Fa "unsigned long long value"
.Fc
.Sh DESCRIPTION
The
.Fn stdc_leading_ones
family of functions counts the number of consecutive one bits present in
.Fa value
starting at the most significant bit.
.Pp
The
.Fn stdc_leading_ones
function is generic and will operate on all 8, 16, 32, and 64-bit
unsigned integers; however, it is only available in C23.
The other functions all operate on a specific integer type, but
otherwise behave the same and are available regardless of the C language
version.
.Sh CONTEXT
These functions may be called from
.Sy user ,
.Sy kernel ,
or
.Sy interrupt
context.
.Sh RETURN VALUES
The functions in the
.Fn stdc_leading_ones
family always return the number of leading ones found in
.Fa value .
These functions cannot fail.
.Sh INTERFACE STABILITY
.Sy Committed
.Sh SEE ALSO
.Xr stdc_first_leading_one 3C ,
.Xr stdc_bit_ceil 9F ,
.Xr stdc_bit_floor 9F ,
.Xr stdc_bit_width 9F ,
.Xr stdc_count_ones 9F ,
.Xr stdc_count_zeros 9F ,
.Xr stdc_first_leading_one 9F ,
.Xr stdc_first_leading_zero 9F ,
.Xr stdc_first_trailing_one 9F ,
.Xr stdc_first_trailing_zero 9F ,
.Xr stdc_has_single_bit 9F ,
.Xr stdc_leading_zeros 9F ,
.Xr stdc_trailing_ones 9F ,
.Xr stdc_trailing_zeros 9F