Initial Commit

database/perl/lib/bytes.pm

@@ -0,0 +1,124 @@
+package bytes;
+
+our $VERSION = '1.07';
+
+$bytes::hint_bits = 0x00000008;
+
+sub import {
+    $^H |= $bytes::hint_bits;
+}
+
+sub unimport {
+    $^H &= ~$bytes::hint_bits;
+}
+
+sub AUTOLOAD {
+    require "bytes_heavy.pl";
+    goto &$AUTOLOAD if defined &$AUTOLOAD;
+    require Carp;
+    Carp::croak("Undefined subroutine $AUTOLOAD called");
+}
+
+sub length (_);
+sub chr (_);
+sub ord (_);
+sub substr ($$;$$);
+sub index ($$;$);
+sub rindex ($$;$);
+
+1;
+__END__
+
+=head1 NAME
+
+bytes - Perl pragma to expose the individual bytes of characters
+
+=head1 NOTICE
+
+Because the bytes pragma breaks encapsulation (i.e. it exposes the innards of
+how the perl executable currently happens to store a string), the byte values
+that result are in an unspecified encoding.
+
+B<Use of this module for anything other than debugging purposes is
+strongly discouraged.>  If you feel that the functions here within
+might be useful for your application, this possibly indicates a
+mismatch between your mental model of Perl Unicode and the current
+reality. In that case, you may wish to read some of the perl Unicode
+documentation: L<perluniintro>, L<perlunitut>, L<perlunifaq> and
+L<perlunicode>.
+
+=head1 SYNOPSIS
+
+    use bytes;
+    ... chr(...);       # or bytes::chr
+    ... index(...);     # or bytes::index
+    ... length(...);    # or bytes::length
+    ... ord(...);       # or bytes::ord
+    ... rindex(...);    # or bytes::rindex
+    ... substr(...);    # or bytes::substr
+    no bytes;
+
+
+=head1 DESCRIPTION
+
+Perl's characters are stored internally as sequences of one or more bytes.
+This pragma allows for the examination of the individual bytes that together
+comprise a character.
+
+Originally the pragma was designed for the loftier goal of helping incorporate
+Unicode into Perl, but the approach that used it was found to be defective,
+and the one remaining legitimate use is for debugging when you need to
+non-destructively examine characters' individual bytes.  Just insert this
+pragma temporarily, and remove it after the debugging is finished.
+
+The original usage can be accomplished by explicit (rather than this pragma's
+implicit) encoding using the L<Encode> module:
+
+    use Encode qw/encode/;
+
+    my $utf8_byte_string   = encode "UTF8",   $string;
+    my $latin1_byte_string = encode "Latin1", $string;
+
+Or, if performance is needed and you are only interested in the UTF-8
+representation:
+
+    utf8::encode(my $utf8_byte_string = $string);
+
+C<no bytes> can be used to reverse the effect of C<use bytes> within the
+current lexical scope.
+
+As an example, when Perl sees C<$x = chr(400)>, it encodes the character
+in UTF-8 and stores it in C<$x>. Then it is marked as character data, so,
+for instance, C<length $x> returns C<1>. However, in the scope of the
+C<bytes> pragma, C<$x> is treated as a series of bytes - the bytes that make
+up the UTF8 encoding - and C<length $x> returns C<2>:
+
+ $x = chr(400);
+ print "Length is ", length $x, "\n";     # "Length is 1"
+ printf "Contents are %vd\n", $x;         # "Contents are 400"
+ {
+     use bytes; # or "require bytes; bytes::length()"
+     print "Length is ", length $x, "\n"; # "Length is 2"
+     printf "Contents are %vd\n", $x;     # "Contents are 198.144 (on
+                                          # ASCII platforms)"
+ }
+
+C<chr()>, C<ord()>, C<substr()>, C<index()> and C<rindex()> behave similarly.
+
+For more on the implications, see L<perluniintro> and L<perlunicode>.
+
+C<bytes::length()> is admittedly handy if you need to know the
+B<byte length> of a Perl scalar.  But a more modern way is:
+
+   use Encode 'encode';
+   length(encode('UTF-8', $scalar))
+
+=head1 LIMITATIONS
+
+C<bytes::substr()> does not work as an I<lvalue()>.
+
+=head1 SEE ALSO
+
+L<perluniintro>, L<perlunicode>, L<utf8>, L<Encode>
+
+=cut