BITSTRING(3)

BITSTRING(3) | Library Functions Manual | BITSTRING(3)

# NAME

`bit_alloc`, `bit_clear`, `bit_decl`, `bit_ffc`, `bit_ffs`, `bit_nclear`, `bit_nset`, `bit_set`, `bitstr_size`, `bit_test` —
bit-string manipulation macros

# SYNOPSIS

`#include <sys/types.h>`
`#include <bitstring.h>`

bitstr_t *
`bit_decl`(bitstr_t *name, size_t nbits);

bitstr_t *
`bit_alloc`(size_t nbits);

`bit_clear`(bitstr_t *name, size_t bit);

`bit_ffc`(const bitstr_t *name, size_t nbits, int *value);

`bit_ffs`(const bitstr_t *name, size_t nbits, int *value);

`bit_nclear`(bitstr_t *name, size_t start, size_t stop);

`bit_nset`(bitstr_t *name, size_t start, size_t stop);

`bit_set`(bitstr_t *name, size_t bit);

`bitstr_size`(size_t nbits);

`bit_test`(const bitstr_t *name, size_t bit);

# DESCRIPTION

These macros operate on strings of bits.

The macro `bit_alloc`() returns a pointer of type “bitstr_t” to sufficient space to store nbits bits, or `NULL` if no space is available.

The macro `bit_decl`() allocates sufficient space to store nbits bits on the stack.

The macro `bitstr_size`() returns the number of elements of type bitstr_t necessary to store nbits bits. This is useful for copying bit strings.

The macros `bit_clear`() and `bit_set`() clear or set the zero-based numbered bit bit, in the bit string name.

The `bit_nset`() and `bit_nclear`() macros set or clear the zero-based numbered bits from start to stop in the bit string name.

The `bit_test`() macro evaluates to non-zero if the zero-based numbered bit bit of bit string name is set, and zero otherwise.

The `bit_ffs`() macro stores in the location referenced by value the zero-based number of the first bit set in the array of nbits bits referenced by name. If no bits are set, the location referenced by value is set to -1.

The macro `bit_ffc`() stores in the location referenced by value the zero-based number of the first bit not set in the array of nbits bits referenced by name. If all bits are set, the location referenced by value is set to -1.

The arguments to these macros are evaluated only once and may safely have side effects.

# EXAMPLES

    #include <limits.h>
    #include <bitstring.h>

    ...
    #define	LPR_BUSY_BIT		0
    #define	LPR_FORMAT_BIT		1
    #define	LPR_DOWNLOAD_BIT	2
    ...
    #define	LPR_AVAILABLE_BIT	9
    #define	LPR_MAX_BITS		10

    void
    make_lpr_available(void)
    {
    	bitstr_t bit_decl(bitlist, LPR_MAX_BITS);
    	...
    	bit_nclear(bitlist, 0, LPR_MAX_BITS - 1);
    	...
    	if (!bit_test(bitlist, LPR_BUSY_BIT)) {
    		bit_clear(bitlist, LPR_FORMAT_BIT);
    		bit_clear(bitlist, LPR_DOWNLOAD_BIT);
    		bit_set(bitlist, LPR_AVAILABLE_BIT);
    	}
    }

# SEE ALSO

bitmap(3), calloc(3), setbit(9)

# HISTORY

The `bitstring` functions first appeared in 4.4BSD.

December 29, 2016 | NetBSD 9.0