1Judy::1(3)            User Contributed Perl Documentation           Judy::1(3)
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NAME

6       Judy::1 - Efficient integer to bit map
7

SYNOPSIS

9         use Judy::1 qw( Set Get Unset Count MemUsed First );
10
11         my $judy;
12         print Set( $judy, 123456 )
13             ? "ok - bit successfully set at 123456\n"
14             : "not ok - bit already set at 123456\n";
15
16         print Get( $judy, 654321 )
17             ? "not ok - set bit at 654321\n"
18             : "ok - bit not set at 654321\n";
19
20         my ( $count ) = Count( $judy, 0, -1 );
21         print "$count bits set in Judy::1 array\n";
22
23         my ( $key ) = First( $judy, 0 );
24         if ( defined $key ) {
25             print "ok - first bit set is at $key\n";
26         }
27         else {
28             print "not ok - no bits set in array\n";
29         }
30
31         printf "$count Keys used %d bytes of memory\n", MemUsed( $judy );
32
33         print Unset( $judy, 123456 )
34             ? "ok - bit successfully unset at 123456\n"
35             : "not ok - bit was not unset at 123456\n";
36

EXPORT

38       All functions are exportable by Sub::Exporter.
39

DESCRIPTION

41       Judy::1 is the equivalent of a bit array or bit map. A bit is addressed
42       by an $Key. The array may be sparse, and the $Key may be any native
43       integer. If a key is present, it represents a set bit. If a key is
44       absent, it represents an unset bit.
45
46       Nothing special is required to allocate a Judy::1 array. Just start
47       using it.
48
49         my $judy;
50         if ( Get( $judy, 10 ) ) {
51             ...
52         }
53
54       Memory to support the array is allocated as bits are set, and released
55       as bits are unset. If the Judy::1 pointer ($Judy) is 0 or undef, all
56       bits are unset (and the Judy::1 array requires no memory).
57
58       As with an ordinary array, a Judy::1 array contains no duplicate keys.
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DATA TYPES

61   $Judy - Judy::1 array
62   $Key - integer
63   bool - boolean
64   count - integer

BASIC FUNCTIONS

66   bool = Set( $Judy, $Key )
67       Insert/set $Key's bit in the Judy::1 array $Judy. Return true if the
68       bit was previously unset, false otherwise.
69
70   bool = Unset( $Judy, $Key )
71       Unset $Key's bit in the Judy::1 array $Judy; that is, remove $Key from
72       the Judy::1 array. Return true if the bit was previously set, false
73       otherwise.
74
75   bool = Delete( $Judy, $Key )
76       Alias for "Unset()".
77
78   bool = Test( $Judy, $Key )
79       Test if $Key's bit is set in the Judy::1 array $Judy. Return true if
80       the bit is set, false otherwise.
81
82   bool = Get( $Judy, $Key )
83       Alias for "Test()".
84
85   count = Count( $Judy, $Key1, $Key2 )
86       Count the number of set bits between $Key1 and $Key2 (inclusive). To
87       count all set bits in a Judy::1 bit array, use:
88
89           $count = Count( $judy, 0, -1 );
90
91       Note: The -1 promotes to the maximum integer, that is, all ones.
92
93   $Key = Nth( $Judy, $Nth )
94       Locate the c<$Nth> key that is present in the Judy::1 array $Judy
95       ("$Nth = 1" returns the first key present). To refer to the last key in
96       a fully populated array (all keys present, which is rare), use "$Nth =
97       0".
98
99       Returns nothing if there is not an nth key.
100
101   bytes = Free( $Judy )
102       Free the entire Judy::1 array $Judy (much faster than using a Next(),
103       Unset() loop). Returns the number of bytes freed. $Judy is set to 0.
104
105   bytes = MemUsed( $Judy )
106       Returns the number of bytes of memory currently in use by Judy::1 array
107       $Judy. This is a very fast routine, and may be used after a Set() or
108       Unset() call with little performance impact.
109

Search Functions

111       The Judy::1 search functions allow you to search for set or unset bits
112       in the array. You may search inclusively or exclusively, in either
113       forward or reverse directions.
114
115   $Key = First( $Judy, $Key )
116       Search (inclusive) for the first set $Key that is equal to or greater
117       than the passed $Key. (Start with $Key = 0 to find the first key in the
118       array.) First() is typically used to begin a sorted-order scan of the
119       keys present in a Judy::1 array.
120
121   $Key = Next( $Judy, $Key )
122       Search (exclusive) for the next key present that is greater than the
123       passed $Key. Next() is typically used to continue a sorted-order scan
124       of the keys present in a Judy::1 array, or to locate a "neighbor" of a
125       given key.
126
127   $Key = Last( $Judy, $Key )
128       Search (inclusive) for the last key present that is equal to or less
129       than the passed $Key. (Start with $Key = -1, that is, all ones, to find
130       the last key in the array.) Last() is typically used to begin a
131       reverse-sorted-order scan of the keys present in a Judy::1 array.
132
133   $Key = Prev( $Judy, $Key )
134       Search (exclusive) for the previous key present that is less than the
135       passed $Key. Prev() is typically used to continue a reverse-sorted-
136       order scan of the keys present in a Judy::1 array, or to locate a
137       "neighbor" of a given key.
138
139   $Key = FirstEmpty( $Judy, $Key )
140       Search (inclusive) for the first absent key that is equal to or greater
141       than the passed $Key. (Start with $Key = 0 to find the first key absent
142       in the array.)
143
144   $Key = NextEmpty( $Judy, $Key )
145       Search (exclusive) for the next absent key that is greater than the
146       passed $Key.
147
148   $Key = LastEmpty( $Judy, $Key )
149       Search (inclusive) for the last absent key that is equal to or less
150       than the passed $Key. (Start with $Key = -1 to find the last key absent
151       in the array.)
152
153   $Key = PrevEmpty( $Judy, $Key )
154       Search (exclusive) for the previous absent key that is less than the
155       passed $Key.
156

MULTIDIMENSIONAL Judy::L

158       See Judy.
159

ERRORS & WARNINGS

161       See Judy.
162

AUTHOR

164       See Judy.
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168perl v5.32.1                      2021-01-27                        Judy::1(3)
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