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 8.0