BITX64(9F) Kernel Functions for Drivers BITX64(9F)

NAME

bitx8, bitx16, bitx32, bitx64 - extract bits from an integer

SYNOPSIS

#include <sys/bitext.h>

uint8_t
bitx8(uint8_t value, uint_t high, uint_t low);

uint16_t
bitx16(uint16_t value, uint_t high, uint_t low);

uint32_t
bitx32(uint32_t value, uint_t high, uint_t low);

uint64_t
bitx64(uint64_t value, uint_t high, uint_t low);

INTERFACE LEVEL

Volatile - This interface is still evolving in illumos. API and ABI
stability is not guaranteed.

PARAMETERS

value An integer to extract a value from.

high The high end, inclusive, of the bit range to extract from
value.

low The low end, inclusive, of the bit range to extract from
value.

DESCRIPTION

The bitx8(), bitx16(), bitx32(), and bitx64() functions are used to extract
a range of bits from on an 8, 16, 32, and 64-bit value respectively. These
functions are all implementations of a classical application of a bitwise-
AND of a mask and a logical right shift. More specifically, the arguments
high and low describe an inclusive range of bits ([low, high]) to extract
from value. The extracted bits are all shifted right such that the
resulting value starts at bit 0 (that is, shifted over by low).

Each of the variants here operates on a specifically sized integer. high
and low must fit within the bit range that the integer implies. For
example, the valid range for bitx32 is from 0 to 31. high must not be less
than low.

CONTEXT

These functions may be called in all contexts, user, kernel, and interrupt.

RETURN VALUES

Upon successful completion, the bitx8(), bitx16(), bitx32(), and bitx64()
functions all return the indicated portion of val.

SEE ALSO

bitdel64(9F), bitset64(9F)

illumos April 12, 2022 illumos