bitstring(3) - NetBSD Manual Pages

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BITSTRING(3)            NetBSD 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 <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 macro bit_alloc() returns a pointer of type ``bitstr_t *'' to suffi- cient 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 num- bered 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 refer- enced 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
The bitstring functions first appeared in 4.4BSD. NetBSD 6.0 July 19, 1993 NetBSD 6.0
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