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@(#)bitstring.3 8.1 (Berkeley) 7/19/93
.Dd July 19, 1993 .Dt BITSTRING 3 .Os BSD 4 .Sh NAME .Nm bit_alloc , .Nm bit_clear , .Nm bit_decl , .Nm bit_ffs , .Nm bit_nclear , .Nm bit_nset, .Nm bit_set , .Nm bitstr_size , .Nm bit_test .Nd bit-string manipulation macros .Sh SYNOPSIS .Fd #include <bitstring.h> .Ft bitstr_t * .Fn bit_alloc "int nbits" .Fn bit_decl "bitstr_t *name" "int nbits" .Fn bit_clear "bitstr_t *name" "int bit" .Fn bit_ffc "bitstr_t *name" "int nbits" "int *value" .Fn bit_ffs "bitstr_t *name" "int nbits" "int *value" .Fn bit_nclear "bitstr_t *name" "int start" "int stop" .Fn bit_nset "bitstr_t *name" "int start" "int stop" .Fn bit_set "bitstr_t *name" "int bit" .Ft int .Fn bitstr_size "int nbits" .Ft int .Fn bit_test "bitstr_t *name" "int bit" .Sh DESCRIPTION These macros operate on strings of bits.
p The macro .Fn bit_alloc returns a pointer of type .Dq Fa "bitstr_t *" to sufficient space to store .Fa nbits bits, or .Dv NULL if no space is available.
p The macro .Fn bit_decl allocates sufficient space to store .Fa nbits bits on the stack.
p 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.
p The macros .Fn bit_clear and .Fn bit_set clear or set the zero-based numbered bit .Fa bit , in the bit string .Ar name .
p The .Fn bit_nset and .Fn bit_nclear macros set or clear the zero-based numbered bits from .Fa start to .Fa stop in the bit string .Ar name .
p 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.
p 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.
p 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.
p The macros .Fn bit_clear , .Fn bit_set and .Fn bit_test will evaluate the .Fa bit argument more than once, so avoid using pre- or post-, increment or decrement. The arguments to the other macros are evaluated only once and may safely have side effects. .Sh EXAMPLE d -literal -offset indent #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); } } .Ed .Sh SEE ALSO .Xr malloc 3 .Sh HISTORY The .Nm bitstring functions first appeared in 4.4BSD.