xref: /dragonfly/share/man/man3/bitstring.3 (revision 2c603719) 
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34.\"     @(#)bitstring.3	8.1 (Berkeley) 7/19/93
35.\" $FreeBSD: src/share/man/man3/bitstring.3,v 1.6.2.5 2001/12/17 11:30:11 ru Exp $
36.\" $DragonFly: src/share/man/man3/bitstring.3,v 1.2 2003/06/17 04:36:58 dillon Exp $
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38.Dd July 19, 1993
39.Dt BITSTRING 3
40.Os
41.Sh NAME
42.Nm bit_alloc ,
43.Nm bit_clear ,
44.Nm bit_decl ,
45.Nm bit_ffs ,
46.Nm bit_nclear ,
47.Nm bit_nset ,
48.Nm bit_set ,
49.Nm bitstr_size ,
50.Nm bit_test
51.Nd bit-string manipulation macros
52.Sh SYNOPSIS
53.In bitstring.h
54.Ft bitstr_t *
55.Fn bit_alloc "int nbits"
56.Ft void
57.Fn bit_decl "bitstr_t *name" "int nbits"
58.Ft void
59.Fn bit_clear "bitstr_t *name" "int bit"
60.Ft void
61.Fn bit_ffc "bitstr_t *name" "int nbits" "int *value"
62.Ft void
63.Fn bit_ffs "bitstr_t *name" "int nbits" "int *value"
64.Ft void
65.Fn bit_nclear "bitstr_t *name" "int start" "int stop"
66.Ft void
67.Fn bit_nset "bitstr_t *name" "int start" "int stop"
68.Ft void
69.Fn bit_set "bitstr_t *name" "int bit"
70.Ft int
71.Fn bitstr_size "int nbits"
72.Ft int
73.Fn bit_test "bitstr_t *name" "int bit"
74.Sh DESCRIPTION
75These macros operate on strings of bits.
76.Pp
77The macro
78.Fn bit_alloc
79returns a pointer of type
80.Dq Fa "bitstr_t *"
81to sufficient space to store
82.Fa nbits
83bits, or
84.Dv NULL
85if no space is available.
86.Pp
87The macro
88.Fn bit_decl
89allocates sufficient space to store
90.Fa nbits
91bits on the stack.
92.Pp
93The macro
94.Fn bitstr_size
95returns the number of elements of type
96.Fa bitstr_t
97necessary to store
98.Fa nbits
99bits.
100This is useful for copying bit strings.
101.Pp
102The macros
103.Fn bit_clear
104and
105.Fn bit_set
106clear or set the zero-based numbered bit
107.Fa bit ,
108in the bit string
109.Ar name .
110.Pp
111The
112.Fn bit_nset
113and
114.Fn bit_nclear
115macros
116set or clear the zero-based numbered bits from
117.Fa start
118through
119.Fa stop
120in the bit string
121.Ar name .
122.Pp
123The
124.Fn bit_test
125macro
126evaluates to non-zero if the zero-based numbered bit
127.Fa bit
128of bit string
129.Fa name
130is set, and zero otherwise.
131.Pp
132The
133.Fn bit_ffs
134macro
135stores in the location referenced by
136.Fa value
137the zero-based number of the first bit set in the array of
138.Fa nbits
139bits referenced by
140.Fa name .
141If no bits are set, the location referenced by
142.Fa value
143is set to \-1.
144.Pp
145The macro
146.Fn bit_ffc
147stores in the location referenced by
148.Fa value
149the zero-based number of the first bit not set in the array of
150.Fa nbits
151bits referenced by
152.Fa name .
153If all bits are set, the location referenced by
154.Fa value
155is set to \-1.
156.Pp
157The arguments to these macros are evaluated only once and may safely
158have side effects.
159.Sh EXAMPLES
160.Bd -literal -offset indent
161#include <limits.h>
162#include <bitstring.h>
163
164\&...
165#define	LPR_BUSY_BIT		0
166#define	LPR_FORMAT_BIT		1
167#define	LPR_DOWNLOAD_BIT	2
168\&...
169#define	LPR_AVAILABLE_BIT	9
170#define	LPR_MAX_BITS		10
171
172make_lpr_available()
173{
174	bitstr_t bit_decl(bitlist, LPR_MAX_BITS);
175	...
176	bit_nclear(bitlist, 0, LPR_MAX_BITS - 1);
177	...
178	if (!bit_test(bitlist, LPR_BUSY_BIT)) {
179		bit_clear(bitlist, LPR_FORMAT_BIT);
180		bit_clear(bitlist, LPR_DOWNLOAD_BIT);
181		bit_set(bitlist, LPR_AVAILABLE_BIT);
182	}
183}
184.Ed
185.Sh SEE ALSO
186.Xr malloc 3
187.Sh HISTORY
188The
189.Nm bitstring
190functions first appeared in
191.Bx 4.4 .
192