NAME
stdc_first_leading_zero – find the first leading zero in an integer
SYNOPSIS
Standard C Library (libc, -lc)
#include <stdbit.h>
unsigned int
stdc_first_leading_zero_uc(unsigned char value);
unsigned int
stdc_first_leading_zero_us(unsigned short value);
unsigned int
stdc_first_leading_zero_ui(unsigned int value);
unsigned int
stdc_first_leading_zero_ul(unsigned long value);
unsigned int
stdc_first_leading_zero_ull(unsigned long long value);
unsigned int
stdc_first_leading_zero(value);
DESCRIPTION
The stdc_first_leading_zero_type() family of functions returns the index of the most significant clear bit in value, where value is of type unsigned char, unsigned short, unsigned int, unsigned long, or unsigned long long for type being uc, us, ui, ul, or ull respectively. The stdc_first_leading_zero(value) type-generic macro picks the appropriate stdc_first_leading_zero_type() function based on the type of value.
RETURN VALUES
Returns the index of the most significant clear bit in value. The bits are numbered such that the most significant bit has number 1, and the least significant bit has number w where w is the number of bits in the type of value. If no bits are clear in value (i.e. value is the bitwise complement of zero), zero is returned.
SEE ALSO
stdbit(3), stdc_first_leading_ones(3), stdc_first_trailing_zero(3), stdc_leading_ones(3)
STANDARDS
The stdc_first_leading_zero_type() family of functions and the stdc_first_leading_zero() type-generic macro conform to ISO/IEC 9899:2024 (“ISO C23”).
HISTORY
The stdc_first_leading_zero_type() family of functions and the stdc_first_leading_zero() type-generic macro were added in FreeBSD 15.1.
AUTHORS
Robert Clausecker ⟨[email protected]⟩