Other Alias
bit_clear, bit_decl, bit_ffs, bit_nclear, bit_nset, bit_set, bitstr_size, bit_testSYNOPSIS
In bsd/bitstring.h Ft bitstr_t * Fn bit_alloc int nbits Ft void Fn bit_decl bitstr_t *name int nbits Ft void Fn bit_clear bitstr_t *name int bit Ft void Fn bit_ffc bitstr_t *name int nbits int *value Ft void Fn bit_ffs bitstr_t *name int nbits int *value Ft void Fn bit_nclear bitstr_t *name int start int stop Ft void Fn bit_nset bitstr_t *name int start int stop Ft void Fn bit_set bitstr_t *name int bit Ft int Fn bitstr_size int nbits Ft int Fn bit_test bitstr_t *name int bitDESCRIPTION
These macros operate on strings of bits.The macro Fn bit_alloc returns a pointer of type ``Fa bitstr_t * '' to sufficient space to store Fa nbits bits, or NULL if no space is available.
The macro Fn bit_decl allocates sufficient space to store Fa nbits bits on the stack.
The macro Fn bitstr_size returns the number of elements of type Fa bitstr_t necessary to store Fa nbits bits. This is useful for copying bit strings.
The macros Fn bit_clear and Fn bit_set clear or set the zero-based numbered bit Fa bit , in the bit string name
The Fn bit_nset and Fn bit_nclear macros set or clear the zero-based numbered bits from Fa start through Fa stop in the bit string name
The Fn bit_test macro evaluates to non-zero if the zero-based numbered bit Fa bit of bit string Fa name is set, and zero otherwise.
The Fn bit_ffs macro stores in the location referenced by Fa value the zero-based number of the first bit set in the array of Fa nbits bits referenced by Fa name . If no bits are set, the location referenced by Fa value is set to -1.
The macro Fn bit_ffc stores in the location referenced by Fa value the zero-based number of the first bit not set in the array of Fa nbits bits referenced by Fa name . If all bits are set, the location referenced by Fa 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 <bsd/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); } }
HISTORY
The bitstring functions first appeared in BSD 4.4