NAME Scalar::Vec::Util - Utility routines for vec strings. VERSION Version 0.03 SYNOPSIS use Scalar::Vec::Util qw/vfill vcopy veq/; my $s; vfill $s, 0, 100, 1; # Fill with 100 bits 1 starting at 0. my $t; vcopy $s, 20, $t, 10, 30; # Copy 30 bits from $s, starting at 20, # to $t, starting at 10. vcopy $t, 10, $t, 20, 30; # Overalapping areas DWIM. if (veq $t, 10, $t, 20, 30) { ... } # Yes, they are equal now. DESCRIPTION A set of utilities to manipulate bits in vec strings. Highly optimized XS routines are used when available, but straightforward pure perl replacements are also provided for platforms without a C compiler. This module doesn't reimplement bit vectors. It can be used on the very same scalars that "vec" builds, or actually on any Perl string ("SVt_PV"). CONSTANTS "SVU_PP" True when pure perl fallbacks are used instead of XS functions. "SVU_SIZE" Size in bits of the unit used for moves. The higher this value is, the faster the XS functions are. It's usually "CHAR_BIT * $Config{alignbytes}", except on non-little-endian architectures where it currently falls back to "CHAR_BIT" (e.g. SPARC). FUNCTIONS "vfill $vec, $start, $length, $bit" Starting at $start in $vec, fills $length bits with $bit. Grows $vec if necessary. "vcopy $from => $from_start, $to => $to_start, $length" Copies $length bits starting at $from_start in $from to $to_start in $to. If "$from_start + $length" is too long for $from, zeros are copied past $length. Grows $to if necessary. "veq $v1 => $v1_start, $v2 => $v2_start, $length" Returns true if the $length bits starting at $v1_start in $v1 and $v2_start in $v2 are equal, and false otherwise. If needed, $length is decreased to fit inside $v1 and $v2 boundaries. EXPORT The functions "vfill", "vcopy" and "veq" are only exported on request. All of them are exported by the tags ':funcs' and ':all'. The constants "SVU_PP" and "SVU_SIZE" are also only exported on request. They are all exported by the tags ':consts' and ':all'. BENCHMARKS The following timings were obtained by running the "samples/bench.pl" script with perl 5.8.8 on a Core 2 Duo 2.66GHz machine. The "_pp" entries are the pure Perl versions, while "_bv" are Bit::Vector versions. Filling bits at a given position : Rate vfill_pp vfill_bv vfill vfill_pp 80.3/s -- -100% -100% vfill_bv 1053399/s 1312401% -- -11% vfill 1180792/s 1471129% 12% -- Copying bits from a bit vector to a different one : Rate vcopy_pp vcopy_bv vcopy vcopy_pp 112/s -- -100% -100% vcopy_bv 62599/s 55622% -- -89% vcopy 558491/s 497036% 792% -- Moving bits in the same bit vector from a given position to a different one : Rate vmove_pp vmove_bv vmove vmove_pp 64.8/s -- -100% -100% vmove_bv 64742/s 99751% -- -88% vmove 547980/s 845043% 746% -- Testing bit equality from different positions of different bit vectors : Rate veq_pp veq_bv veq veq_pp 92.7/s -- -100% -100% veq_bv 32777/s 35241% -- -94% veq 505828/s 545300% 1443% -- CAVEATS Please report architectures where we can't use the alignment as the move unit. I'll add exceptions for them. DEPENDENCIES Carp, Exporter (core modules since perl 5), XSLoader (since perl 5.006). SEE ALSO Bit::Vector gives a complete reimplementation of bit vectors. AUTHOR Vincent Pit, "", . You can contact me by mail or on #perl @ FreeNode (vincent or Prof_Vince). BUGS Please report any bugs or feature requests to "bug-scalar-vec-util at rt.cpan.org", or through the web interface at . I will be notified, and then you'll automatically be notified of progress on your bug as I make changes. SUPPORT You can find documentation for this module with the perldoc command. perldoc Scalar::Vec::Util Tests code coverage report is available at . COPYRIGHT & LICENSE Copyright 2008 Vincent Pit, all rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.