2 Scalar::Vec::Util - Utility routines for vec strings.
8 use Scalar::Vec::Util qw/vfill vcopy veq/;
11 vfill $s, 0, 100, 1; # Fill with 100 bits 1 starting at 0.
13 vcopy $s, 20, $t, 10, 30; # Copy 30 bits from $s, starting at 20,
14 # to $t, starting at 10.
15 vcopy $t, 10, $t, 20, 30; # Overalapping areas DWIM.
16 if (veq $t, 10, $t, 20, 30) { ... } # Yes, they are equal now.
19 A set of utilities to manipulate bits in vec strings. Highly optimized
20 XS routines are used when available, but straightforward pure perl
21 replacements are also provided for platforms without a C compiler.
23 This module doesn't reimplement bit vectors. It can be used on the very
24 same scalars that "vec" builds, or actually on any Perl string
29 True when pure perl fallbacks are used instead of XS functions.
32 Size in bits of the unit used for moves. The higher this value is, the
33 faster the XS functions are. It's usually "CHAR_BIT *
34 $Config{alignbytes}", except on non-little-endian architectures where it
35 currently falls back to "CHAR_BIT" (e.g. SPARC).
38 "vfill $vec, $start, $length, $bit"
39 Starting at $start in $vec, fills $length bits with $bit. Grows $vec if
42 "vcopy $from => $from_start, $to => $to_start, $length"
43 Copies $length bits starting at $from_start in $from to $to_start in
44 $to. If "$from_start + $length" is too long for $from, zeros are copied
45 past $length. Grows $to if necessary.
47 "veq $v1 => $v1_start, $v2 => $v2_start, $length"
48 Returns true if the $length bits starting at $v1_start in $v1 and
49 $v2_start in $v2 are equal, and false otherwise. If needed, $length is
50 decreased to fit inside $v1 and $v2 boundaries.
53 The functions "vfill", "vcopy" and "veq" are only exported on request.
54 All of them are exported by the tags ':funcs' and ':all'.
56 The constants "SVU_PP" and "SVU_SIZE" are also only exported on request.
57 They are all exported by the tags ':consts' and ':all'.
60 The following timings were obtained by running the "samples/bench.pl"
61 script. The "_pp" entries are the pure Perl versions, while "_bv" are
64 This is for perl 5.8.8 on a Core 2 Duo 2.66GHz machine (unit is 64
66 Filling bits at a given position :
67 Rate vfill_pp vfill_bv vfill
68 vfill_pp 80.3/s -- -100% -100%
69 vfill_bv 1053399/s 1312401% -- -11%
70 vfill 1180792/s 1471129% 12% --
72 Copying bits from a bit vector to a different one :
73 Rate vcopy_pp vcopy_bv vcopy
74 vcopy_pp 112/s -- -100% -100%
75 vcopy_bv 62599/s 55622% -- -89%
76 vcopy 558491/s 497036% 792% --
78 Moving bits in the same bit vector from a given position to a different one :
79 Rate vmove_pp vmove_bv vmove
80 vmove_pp 64.8/s -- -100% -100%
81 vmove_bv 64742/s 99751% -- -88%
82 vmove 547980/s 845043% 746% --
84 Testing bit equality from different positions of different bit vectors :
85 Rate veq_pp veq_bv veq
86 veq_pp 92.7/s -- -100% -100%
87 veq_bv 32777/s 35241% -- -94%
88 veq 505828/s 545300% 1443% --
90 This is for perl 5.10.0 on a Pentium 4 3.0GHz (unit is 32 bits).
91 Rate vfill_pp vfill_bv vfill
92 vfill_pp 185/s -- -100% -100%
93 vfill_bv 407979/s 220068% -- -16%
94 vfill 486022/s 262184% 19% --
96 Rate vcopy_pp vcopy_bv vcopy
97 vcopy_pp 61.5/s -- -100% -100%
98 vcopy_bv 32548/s 52853% -- -83%
99 vcopy 187360/s 304724% 476% --
101 Rate vmove_pp vmove_bv vmove
102 vmove_pp 63.1/s -- -100% -100%
103 vmove_bv 32829/s 51933% -- -83%
104 vmove 188572/s 298787% 474% --
106 Rate veq_pp veq_bv veq
107 veq_pp 34.2/s -- -100% -100%
108 veq_bv 17518/s 51190% -- -91%
109 veq 192181/s 562591% 997% --
111 This is for perl 5.10.0 on an UltraSPARC-IIi (unit is 8 bits).
112 Rate vfill_pp vfill vfill_bv
113 vfill_pp 4.23/s -- -100% -100%
114 vfill 30039/s 709283% -- -17%
115 vfill_bv 36022/s 850568% 20% --
117 Rate vcopy_pp vcopy_bv vcopy
118 vcopy_pp 2.74/s -- -100% -100%
119 vcopy_bv 8146/s 297694% -- -60%
120 vcopy 20266/s 740740% 149% --
122 Rate vmove_pp vmove_bv vmove
123 vmove_pp 2.66/s -- -100% -100%
124 vmove_bv 8274/s 311196% -- -59%
125 vmove 20287/s 763190% 145% --
127 Rate veq_pp veq_bv veq
128 veq_pp 7.33/s -- -100% -100%
129 veq_bv 2499/s 33978% -- -87%
130 veq 19675/s 268193% 687% --
133 Please report architectures where we can't use the alignment as the move
134 unit. I'll add exceptions for them.
137 Carp, Exporter (core modules since perl 5), XSLoader (since perl 5.006).
140 Bit::Vector gives a complete reimplementation of bit vectors.
143 Vincent Pit, "<perl at profvince.com>", <http://www.profvince.com>.
145 You can contact me by mail or on #perl @ FreeNode (vincent or
149 Please report any bugs or feature requests to "bug-scalar-vec-util at
150 rt.cpan.org", or through the web interface at
151 <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Scalar-Vec-Util>. I will
152 be notified, and then you'll automatically be notified of progress on
153 your bug as I make changes.
156 You can find documentation for this module with the perldoc command.
158 perldoc Scalar::Vec::Util
160 Tests code coverage report is available at
161 <http://www.profvince.com/perl/cover/Scalar-Vec-Util>.
164 Copyright 2008 Vincent Pit, all rights reserved.
166 This program is free software; you can redistribute it and/or modify it
167 under the same terms as Perl itself.