BIT_ALLOC(3) | Library Functions Manual | BIT_ALLOC(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 <bitstring.h>`

bitstr_t *
`bit_alloc`(int nbits);

`bit_clear`(bit_str name, int bit);

`bit_decl`(bit_str name, int nbits);

`bit_ffc`(bit_str name, int nbits, int *value);

`bit_ffs`(bit_str name, int nbits, int *value);

`bit_nclear`(bit_str name, int start, int stop);

`bit_nset`(bit_str name, int start, int stop);

`bit_set`(bit_str name, int bit);

`bitstr_size`(int nbits);

`bit_test`(bit_str name, int bit);

# DESCRIPTION

These macros operate on strings of bits.

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

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

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

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

The `bit_nclear`() and `bit_nset`() macros clear or set 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 `bit_ffc`() macro 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

    make_lpr_available()
    {
    	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

malloc(3)

# HISTORY

These functions first appeared in 4.3BSD-Reno.

September 11, 2022 | Debian