xref: /netbsd-src/share/man/man3/bitmap.3 (revision f55f5e634e99d4f328f3725a3bb4a7bfe0206f95)

.\"	$NetBSD: bitmap.3,v 1.12 2018/03/08 06:47:30 wiz Exp $
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Christos Zoulas.
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.Dd March 8, 2018
.Dt BITMAP 3
.Os
.Sh NAME
.Nm __BITMAP_CLR ,
.Nm __BITMAP_ISSET ,
.Nm __BITMAP_SET ,
.Nm __BITMAP_SIZE ,
.Nm __BITMAP_TYPE ,
.Nm __BITMAP_ZERO
.Nd bitmap manipulation macros
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/bitops.h
.Fn __BITMAP_CLR "int bit" "type *bitmap"
.Fn __BITMAP_ISSET "int bit" "type *bitmap"
.Fn __BITMAP_SET "int bit" "type *bitmap"
.Fn __BITMAP_SIZE "type" "int nbits"
.Fn __BITMAP_TYPE "name" "type" "int nbits"
.Fn __BITMAP_ZERO "type *bitmap"
.Sh DESCRIPTION
The supplied macros are similar to the
.Xr select 2
.Fn FD_SET
family, to the
.Xr setbit 9 ,
macros and the
.Xr bitstring 3
library.
They are different from
.Fn FD_SET
because they are designed to handle multiple sized bitmaps at the same time,
and they can be of any integral type.
They are different from
.Xr setbit 9
because they can operate on different integral types, not just on bytes.
They are different from
.Xr bitstring 3
because they are just macros, they don't allocate memory or use code,
and they can be used in both kernel and userland.
.Pp
The following macros are provided for manipulating creating and manipulating
bitmaps:
.Pp
.Fn __BITMAP_CLR bit bitmap
removes the given
.Fa bit
from the
.Fa bitmap .
.Pp
.Fn __BITMAP_ISSET bit bitmap
is non-zero if
.Fa bit
is a member of
.Fa bitmap ,
zero otherwise.
.Pp
.Fn __BITMAP_SET bit bitmap
Sets the given
.Fa bit
in the
.Fa bitmap .
.Pp
.Fn __BITMAP_SIZE type nbits
Returns the number of elements would be required of the given
.Fa type
to hold
.Fa nbits .
.Pp
.Fn __BITMAP_TYPE name type nbits
Declares the properly sized bitmap structure
of the given
.Fa type
that holds
.Fa nbits
and is named
.Fa name .
.Pp
.Fn __BITMAP_ZERO bitmap
initializes a descriptor set pointed to by
.Fa bitmap
to the null set.
.Pp
The behavior of these macros is undefined for negative
bit values or ones greater than the number of bits the bitmap can hold.
.Sh EXAMPLES
.Bd -literal
#include <sys/bitops.h>

int
main(int argc, char **argv)
{
	__BITMAP_TYPE(, uint32_t, 5000) bitmap;

	/* Initialize the read set to null */
	__BITMAP_ZERO(&bitmap);

	/* Set bit 1 */
	__BITMAP_SET(1, &bitmap);

	for (size_t i = 0; i < 5000; i++) {
		if (__BITMAP_ISSET(i, &bitmap)) {
			/* Should just print 1 */
			printf("Bit %zu is set\en", i);
			__BITMAP_CLR(i, &bitmap);
		}
		break;
	}
	return 0;
}
.Ed
.Sh SEE ALSO
.Xr select 2 ,
.Xr bitops 3 ,
.Xr bitstring 3 ,
.Xr setbit 9
.Sh HISTORY
The
.Fn __BITMAP_*
macros appeared in
.Nx 7.0 .