From: Vincent Pit Date: Tue, 23 Oct 2012 14:06:17 +0000 (-0200) Subject: POD overhaul X-Git-Tag: v0.08~15 X-Git-Url: http://git.vpit.fr/?a=commitdiff_plain;h=2a9dee79e2745ec96ce0955559ba2d8116b74526;p=perl%2Fmodules%2FScalar-Vec-Util.git POD overhaul --- diff --git a/lib/Scalar/Vec/Util.pm b/lib/Scalar/Vec/Util.pm index 802f1c3..a370396 100644 --- a/lib/Scalar/Vec/Util.pm +++ b/lib/Scalar/Vec/Util.pm @@ -40,35 +40,38 @@ BEGIN { 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. + vcopy $t, 10, $t, 20, 30; # Overlapping areas DWIM. if (veq $t, 10, $t, 20, 30) { ... } # Yes, they are equal now. =head1 DESCRIPTION -A set of utilities to manipulate bits in vec strings. -Highly optimized XS routines are used when available, but straightforward pure perl replacements are also provided for platforms without a C compiler. +This module provides a set of utility routines that efficiently manipulate bits in vec strings. +Highly optimized XS functions are used whenever possible, but straightforward pure Perl replacements are also available for platforms without a C compiler. -This module doesn't reimplement bit vectors. -It can be used on the very same scalars that C builds, or actually on any Perl string (C). +Note that this module does not aim at reimplementing bit vectors : all its functions can be used on any Perl string, just like L. =head1 CONSTANTS =head2 C -True when pure perl fallbacks are used instead of XS functions. +True when pure Perl fallbacks are used instead of XS functions. =head2 C -Size in bits of the unit used for moves. +The size (in bits) of the unit used for bit operations. The higher this value is, the faster the XS functions are. -It's usually C, except on non-little-endian architectures where it currently falls back to C (e.g. SPARC). +It is usually C, except on non-little-endian architectures where it currently falls back to C (e.g. SPARC). =head1 FUNCTIONS -=head2 C +=head2 C -Starting at C<$start> in C<$vec>, fills C<$length> bits with C<$bit>. -Grows C<$vec> if necessary. + vfill $vec, $start, $length, $bit; + +Starting at C<$start> in C<$vec>, fills C<$length> bits with ones if C<$bit> is true and with zeros if C<$bit> is false. + +C<$vec> is upgraded to a string and extended if necessary. +Bits that are outside of the specified area are left untouched. =cut @@ -90,12 +93,21 @@ sub vfill_pp ($$$$) { } } -=head2 C<< vcopy $from => $from_start, $to => $to_start, $length >> +=head2 C + + vcopy $from => $from_start, $to => $to_start, $length; Copies C<$length> bits starting at C<$from_start> in C<$from> to C<$to_start> in C<$to>. -If C<$from_start + $length> is too long for C<$from>, zeros are copied past C<$length>. -Grows C<$to> if necessary. -Doesn't need to allocate any extra memory. + +C<$from> and C<$to> are allowed to be the same scalar, and the given areas can rightfully overlap. + +C<$from> is upgraded to a string if it isn't one already. +If C<$from_start + $length> goes out of the bounds of C<$from>, then the extra bits are treated as zeros. +C<$to> is upgraded to a string and extended if necessary. +The content of C<$from> is not modified, except when it is equal to C<$to>. +Bits that are outside of the specified area are left untouched. + +This function does not need to allocate any extra memory. =cut @@ -112,12 +124,19 @@ sub vcopy_pp ($$$$$) { } } -=head2 C<< vshift $v, $start, $length => $bits [, $insert ] >> +=head2 C + + vshift $v, $start, $length => $bits, $insert; In the area starting at C<$start> and of length C<$length> in C<$v>, shift bits C positions left if C<< $bits > 0 >> and right otherwise. -If C<$insert> is defined, also fills the resulting gap with ones if C<$insert> is true and zeros if it's false. -Bits outside of the specified area are left untouched. -Doesn't need to allocate any extra memory. + +When C<$insert> is defined, the resulting gap is also filled with ones if C<$insert> is true and with zeros if C<$insert> is false. + +C<$v> is upgraded to a string if it isn't one already. +If C<$start + $length> goes out of the bounds of C<$v>, then the extra bits are treated as zeros. +Bits that are outside of the specified area are left untouched. + +This function does not need to allocate any extra memory. =cut @@ -145,11 +164,17 @@ sub vshift ($$$$;$) { } } -=head2 C<< vrot $v, $start, $length, $bits >> +=head2 C + + vrot $v, $start, $length, $bits; In the area starting at C<$start> and of length C<$length> in C<$v>, rotates bits C positions left if C<< $bits > 0 >> and right otherwise. -Bits outside of the specified area are left untouched. -Currently allocates an extra buffer of size C. + +C<$v> is upgraded to a string if it isn't one already. +If C<$start + $length> goes out of the bounds of C<$v>, then the extra bits are treated as zeros. +Bits that are outside of the specified area are left untouched. + +This function currently allocates an extra buffer of size C. =cut @@ -178,10 +203,16 @@ sub vrot ($$$$) { } } -=head2 C<< veq $v1 => $v1_start, $v2 => $v2_start, $length >> +=head2 C + + veq $v1 => $v1_start, $v2 => $v2_start, $length; Returns true if the C<$length> bits starting at C<$v1_start> in C<$v1> and C<$v2_start> in C<$v2> are equal, and false otherwise. -If needed, C<$length> is decreased to fit inside C<$v1> and C<$v2> boundaries. + +C<$v1> and C<$v2> are upgraded to strings if they aren't already, but their contents are never modified. +If C<$v1_start + $length> (respectively C<$v2_start + $length>) goes out of the bounds of C<$v1> (respectively C<$v2>), then the extra bits are treated as zeros. + +This function does not need to allocate any extra memory. =cut