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                <textarea name="file_content" style="width:100%; height:400px; font-family:monospace;">package ExtUtils::Constant::Base;

use strict;
use vars qw($VERSION);
use Carp;
use Text::Wrap;
use ExtUtils::Constant::Utils qw(C_stringify perl_stringify);
$VERSION = &#039;0.05&#039;;

use constant is_perl56 =&gt; ($] &lt; 5.007 &amp;&amp; $] &gt; 5.005_50);


=head1 NAME

ExtUtils::Constant::Base - base class for ExtUtils::Constant objects

=head1 SYNOPSIS

    require ExtUtils::Constant::Base;
    @ISA = &#039;ExtUtils::Constant::Base&#039;;

=head1 DESCRIPTION

ExtUtils::Constant::Base provides a base implementation of methods to
generate C code to give fast constant value lookup by named string. Currently
it&#039;s mostly used ExtUtils::Constant::XS, which generates the lookup code
for the constant() subroutine found in many XS modules.

=head1 USAGE

ExtUtils::Constant::Base exports no subroutines. The following methods are
available

=over 4

=cut

sub valid_type {
  # Default to assuming that you don&#039;t need different types of return data.
  1;
}
sub default_type {
  &#039;&#039;;
}

=item header

A method returning a scalar containing definitions needed, typically for a
C header file.

=cut

sub header {
  &#039;&#039;
}

# This might actually be a return statement. Note that you are responsible
# for any space you might need before your value, as it lets to perform
# &quot;tricks&quot; such as &quot;return KEY_&quot; and have strings appended.
sub assignment_clause_for_type;
# In which case this might be an empty string
sub return_statement_for_type {undef};
sub return_statement_for_notdef;
sub return_statement_for_notfound;

# &quot;#if 1&quot; is true to a C pre-processor
sub macro_from_name {
  1;
}

sub macro_from_item {
  1;
}

sub macro_to_ifdef {
    my ($self, $macro) = @_;
    if (ref $macro) {
	return $macro-&gt;[0];
    }
    if (defined $macro &amp;&amp; $macro ne &quot;&quot; &amp;&amp; $macro ne &quot;1&quot;) {
	return $macro ? &quot;#ifdef $macro\n&quot; : &quot;#if 0\n&quot;;
    }
    return &quot;&quot;;
}

sub macro_to_ifndef {
    my ($self, $macro) = @_;
    if (ref $macro) {
	# Can&#039;t invert these stylishly, so &quot;bodge it&quot;
	return &quot;$macro-&gt;[0]#else\n&quot;;
    }
    if (defined $macro &amp;&amp; $macro ne &quot;&quot; &amp;&amp; $macro ne &quot;1&quot;) {
	return $macro ? &quot;#ifndef $macro\n&quot; : &quot;#if 1\n&quot;;
    }
    croak &quot;Can&#039;t generate an ifndef for unconditional code&quot;;
}

sub macro_to_endif {
    my ($self, $macro) = @_;

    if (ref $macro) {
	return $macro-&gt;[1];
    }
    if (defined $macro &amp;&amp; $macro ne &quot;&quot; &amp;&amp; $macro ne &quot;1&quot;) {
	return &quot;#endif\n&quot;;
    }
    return &quot;&quot;;
}

sub name_param {
  &#039;name&#039;;
}

# This is possibly buggy, in that it&#039;s not mandatory (below, in the main
# C_constant parameters, but is expected to exist here, if it&#039;s needed)
# Buggy because if you&#039;re definitely pure 8 bit only, and will never be
# presented with your constants in utf8, the default form of C_constant can&#039;t
# be told not to do the utf8 version.

sub is_utf8_param {
  &#039;utf8&#039;;
}

sub memEQ {
  &quot;!memcmp&quot;;
}

=item memEQ_clause args_hashref

A method to return a suitable C C&lt;if&gt; statement to check whether I&lt;name&gt;
is equal to the C variable C&lt;name&gt;. If I&lt;checked_at&gt; is defined, then it
is used to avoid C&lt;memEQ&gt; for short names, or to generate a comment to
highlight the position of the character in the C&lt;switch&gt; statement.

If i&lt;checked_at&gt; is a reference to a scalar, then instead it gives
the characters pre-checked at the beginning, (and the number of chars by
which the C variable name has been advanced. These need to be chopped from
the front of I&lt;name&gt;).

=cut

sub memEQ_clause {
#    if (memEQ(name, &quot;thingy&quot;, 6)) {
  # Which could actually be a character comparison or even &quot;&quot;
  my ($self, $args) = @_;
  my ($name, $checked_at, $indent) = @{$args}{qw(name checked_at indent)};
  $indent = &#039; &#039; x ($indent || 4);
  my $front_chop;
  if (ref $checked_at) {
    # regexp won&#039;t work on 5.6.1 without use utf8; in turn that won&#039;t work
    # on 5.005_03.
    substr ($name, 0, length $$checked_at,) = &#039;&#039;;
    $front_chop = C_stringify ($$checked_at);
    undef $checked_at;
  }
  my $len = length $name;

  if ($len &lt; 2) {
    return $indent . &quot;{\n&quot;
	if (defined $checked_at and $checked_at == 0) or $len == 0;
    # We didn&#039;t switch, drop through to the code for the 2 character string
    $checked_at = 1;
  }

  my $name_param = $self-&gt;name_param;

  if ($len &lt; 3 and defined $checked_at) {
    my $check;
    if ($checked_at == 1) {
      $check = 0;
    } elsif ($checked_at == 0) {
      $check = 1;
    }
    if (defined $check) {
      my $char = C_stringify (substr $name, $check, 1);
      # Placate 5.005 with a break in the string. I can&#039;t see a good way of
      # getting it to not take [ as introducing an array lookup, even with
      # ${name_param}[$check]
      return $indent . &quot;if ($name_param&quot; . &quot;[$check] == &#039;$char&#039;) {\n&quot;;
    }
  }
  if (($len == 2 and !defined $checked_at)
     or ($len == 3 and defined ($checked_at) and $checked_at == 2)) {
    my $char1 = C_stringify (substr $name, 0, 1);
    my $char2 = C_stringify (substr $name, 1, 1);
    return $indent .
      &quot;if ($name_param&quot; . &quot;[0] == &#039;$char1&#039; &amp;&amp; $name_param&quot; . &quot;[1] == &#039;$char2&#039;) {\n&quot;;
  }
  if (($len == 3 and defined ($checked_at) and $checked_at == 1)) {
    my $char1 = C_stringify (substr $name, 0, 1);
    my $char2 = C_stringify (substr $name, 2, 1);
    return $indent .
      &quot;if ($name_param&quot; . &quot;[0] == &#039;$char1&#039; &amp;&amp; $name_param&quot; . &quot;[2] == &#039;$char2&#039;) {\n&quot;;
  }

  my $pointer = &#039;^&#039;;
  my $have_checked_last = defined ($checked_at) &amp;&amp; $len == $checked_at + 1;
  if ($have_checked_last) {
    # Checked at the last character, so no need to memEQ it.
    $pointer = C_stringify (chop $name);
    $len--;
  }

  $name = C_stringify ($name);
  my $memEQ = $self-&gt;memEQ();
  my $body = $indent . &quot;if ($memEQ($name_param, \&quot;$name\&quot;, $len)) {\n&quot;;
  # Put a little ^ under the letter we checked at
  # Screws up for non printable and non-7 bit stuff, but that&#039;s too hard to
  # get right.
  if (defined $checked_at) {
    $body .= $indent . &quot;/*      &quot; . (&#039; &#039; x length $memEQ)
      . (&#039; &#039; x length $name_param)
      . (&#039; &#039; x $checked_at) . $pointer
      . (&#039; &#039; x ($len - $checked_at + length $len)) . &quot;    */\n&quot;;
  } elsif (defined $front_chop) {
    $body .= $indent . &quot;/*                $front_chop&quot;
      . (&#039; &#039; x ($len + 1 + length $len)) . &quot;    */\n&quot;;
  }
  return $body;
}

=item dump_names arg_hashref, ITEM...

An internal function to generate the embedded perl code that will regenerate
the constant subroutines.  I&lt;default_type&gt;, I&lt;types&gt; and I&lt;ITEM&gt;s are the
same as for C_constant.  I&lt;indent&gt; is treated as number of spaces to indent
by.  If C&lt;declare_types&gt; is true a C&lt;$types&gt; is always declared in the perl
code generated, if defined and false never declared, and if undefined C&lt;$types&gt;
is only declared if the values in I&lt;types&gt; as passed in cannot be inferred from
I&lt;default_types&gt; and the I&lt;ITEM&gt;s.

=cut

sub dump_names {
  my ($self, $args, @items) = @_;
  my ($default_type, $what, $indent, $declare_types)
    = @{$args}{qw(default_type what indent declare_types)};
  $indent = &#039; &#039; x ($indent || 0);

  my $result;
  my (@simple, @complex, %used_types);
  foreach (@items) {
    my $type;
    if (ref $_) {
      $type = $_-&gt;{type} || $default_type;
      if ($_-&gt;{utf8}) {
        # For simplicity always skip the bytes case, and reconstitute this entry
        # from its utf8 twin.
        next if $_-&gt;{utf8} eq &#039;no&#039;;
        # Copy the hashref, as we don&#039;t want to mess with the caller&#039;s hashref.
        $_ = {%$_};
        unless (is_perl56) {
          utf8::decode ($_-&gt;{name});
        } else {
          $_-&gt;{name} = pack &#039;U*&#039;, unpack &#039;U0U*&#039;, $_-&gt;{name};
        }
        delete $_-&gt;{utf8};
      }
    } else {
      $_ = {name=&gt;$_};
      $type = $default_type;
    }
    $used_types{$type}++;
    if ($type eq $default_type
        # grr 5.6.1
        and length $_-&gt;{name}
        and length $_-&gt;{name} == ($_-&gt;{name} =~ tr/A-Za-z0-9_//)
        and !defined ($_-&gt;{macro}) and !defined ($_-&gt;{value})
        and !defined ($_-&gt;{default}) and !defined ($_-&gt;{pre})
        and !defined ($_-&gt;{post}) and !defined ($_-&gt;{def_pre})
        and !defined ($_-&gt;{def_post}) and !defined ($_-&gt;{weight})) {
      # It&#039;s the default type, and the name consists only of A-Za-z0-9_
      push @simple, $_-&gt;{name};
    } else {
      push @complex, $_;
    }
  }

  if (!defined $declare_types) {
    # Do they pass in any types we weren&#039;t already using?
    foreach (keys %$what) {
      next if $used_types{$_};
      $declare_types++; # Found one in $what that wasn&#039;t used.
      last; # And one is enough to terminate this loop
    }
  }
  if ($declare_types) {
    $result = $indent . &#039;my $types = {map {($_, 1)} qw(&#039;
      . join (&quot; &quot;, sort keys %$what) . &quot;)};\n&quot;;
  }
  local $Text::Wrap::huge = &#039;overflow&#039;;
  local $Text::Wrap::columns = 80;
  $result .= wrap ($indent . &quot;my \@names = (qw(&quot;,
		   $indent . &quot;               &quot;, join (&quot; &quot;, sort @simple) . &quot;)&quot;);
  if (@complex) {
    foreach my $item (sort {$a-&gt;{name} cmp $b-&gt;{name}} @complex) {
      my $name = perl_stringify $item-&gt;{name};
      my $line = &quot;,\n$indent            {name=&gt;\&quot;$name\&quot;&quot;;
      $line .= &quot;, type=&gt;\&quot;$item-&gt;{type}\&quot;&quot; if defined $item-&gt;{type};
      foreach my $thing (qw (macro value default pre post def_pre def_post)) {
        my $value = $item-&gt;{$thing};
        if (defined $value) {
          if (ref $value) {
            $line .= &quot;, $thing=&gt;[\&quot;&quot;
              . join (&#039;&quot;, &quot;&#039;, map {perl_stringify $_} @$value) . &#039;&quot;]&#039;;
          } else {
            $line .= &quot;, $thing=&gt;\&quot;&quot; . perl_stringify($value) . &quot;\&quot;&quot;;
          }
        }
      }
      $line .= &quot;}&quot;;
      # Ensure that the enclosing C comment doesn&#039;t end
      # by turning */  into *&quot; . &quot;/
      $line =~ s!\*\/!\*&quot; . &quot;/!gs;
      # gcc -Wall doesn&#039;t like finding /* inside a comment
      $line =~ s!\/\*!/&quot; . &quot;\*!gs;
      $result .= $line;
    }
  }
  $result .= &quot;);\n&quot;;

  $result;
}

=item assign arg_hashref, VALUE...

A method to return a suitable assignment clause. If I&lt;type&gt; is aggregate
(eg I&lt;PVN&gt; expects both pointer and length) then there should be multiple
I&lt;VALUE&gt;s for the components. I&lt;pre&gt; and I&lt;post&gt; if defined give snippets
of C code to proceed and follow the assignment. I&lt;pre&gt; will be at the start
of a block, so variables may be defined in it.

=cut
# Hmm. value undef to to NOTDEF? value () to do NOTFOUND?

sub assign {
  my $self = shift;
  my $args = shift;
  my ($indent, $type, $pre, $post, $item)
      = @{$args}{qw(indent type pre post item)};
  $post ||= &#039;&#039;;
  my $clause;
  my $close;
  if ($pre) {
    chomp $pre;
    $close = &quot;$indent}\n&quot;;
    $clause = $indent . &quot;{\n&quot;;
    $indent .= &quot;  &quot;;
    $clause .= &quot;$indent$pre&quot;;
    $clause .= &quot;;&quot; unless $pre =~ /;$/;
    $clause .= &quot;\n&quot;;
  }
  confess &quot;undef \$type&quot; unless defined $type;
  confess &quot;Can&#039;t generate code for type $type&quot;
    unless $self-&gt;valid_type($type);

  $clause .= join &#039;&#039;, map {&quot;$indent$_\n&quot;}
    $self-&gt;assignment_clause_for_type({type=&gt;$type,item=&gt;$item}, @_);
  chomp $post;
  if (length $post) {
    $clause .= &quot;$post&quot;;
    $clause .= &quot;;&quot; unless $post =~ /;$/;
    $clause .= &quot;\n&quot;;
  }
  my $return = $self-&gt;return_statement_for_type($type);
  $clause .= &quot;$indent$return\n&quot; if defined $return;
  $clause .= $close if $close;
  return $clause;
}

=item return_clause arg_hashref, ITEM

A method to return a suitable C&lt;#ifdef&gt; clause. I&lt;ITEM&gt; is a hashref
(as passed to C&lt;C_constant&gt; and C&lt;match_clause&gt;. I&lt;indent&gt; is the number
of spaces to indent, defaulting to 6.

=cut

sub return_clause {

##ifdef thingy
#      *iv_return = thingy;
#      return PERL_constant_ISIV;
##else
#      return PERL_constant_NOTDEF;
##endif
  my ($self, $args, $item) = @_;
  my $indent = $args-&gt;{indent};

  my ($name, $value, $default, $pre, $post, $def_pre, $def_post, $type)
    = @$item{qw (name value default pre post def_pre def_post type)};
  $value = $name unless defined $value;
  my $macro = $self-&gt;macro_from_item($item);
  $indent = &#039; &#039; x ($indent || 6);
  unless (defined $type) {
    # use Data::Dumper; print STDERR Dumper ($item);
    confess &quot;undef \$type&quot;;
  }

  ##ifdef thingy
  my $clause = $self-&gt;macro_to_ifdef($macro);

  #      *iv_return = thingy;
  #      return PERL_constant_ISIV;
  $clause
    .= $self-&gt;assign ({indent=&gt;$indent, type=&gt;$type, pre=&gt;$pre, post=&gt;$post,
		       item=&gt;$item}, ref $value ? @$value : $value);

  if (defined $macro &amp;&amp; $macro ne &quot;&quot; &amp;&amp; $macro ne &quot;1&quot;) {
    ##else
    $clause .= &quot;#else\n&quot;;

    #      return PERL_constant_NOTDEF;
    if (!defined $default) {
      my $notdef = $self-&gt;return_statement_for_notdef();
      $clause .= &quot;$indent$notdef\n&quot; if defined $notdef;
    } else {
      my @default = ref $default ? @$default : $default;
      $type = shift @default;
      $clause .= $self-&gt;assign ({indent=&gt;$indent, type=&gt;$type, pre=&gt;$pre,
				 post=&gt;$post, item=&gt;$item}, @default);
    }
  }
  ##endif
  $clause .= $self-&gt;macro_to_endif($macro);

  return $clause;
}

sub match_clause {
  # $offset defined if we have checked an offset.
  my ($self, $args, $item) = @_;
  my ($offset, $indent) = @{$args}{qw(checked_at indent)};
  $indent = &#039; &#039; x ($indent || 4);
  my $body = &#039;&#039;;
  my ($no, $yes, $either, $name, $inner_indent);
  if (ref $item eq &#039;ARRAY&#039;) {
    ($yes, $no) = @$item;
    $either = $yes || $no;
    confess &quot;$item is $either expecting hashref in [0] || [1]&quot;
      unless ref $either eq &#039;HASH&#039;;
    $name = $either-&gt;{name};
  } else {
    confess &quot;$item-&gt;{name} has utf8 flag &#039;$item-&gt;{utf8}&#039;, should be false&quot;
      if $item-&gt;{utf8};
    $name = $item-&gt;{name};
    $inner_indent = $indent;
  }

  $body .= $self-&gt;memEQ_clause ({name =&gt; $name, checked_at =&gt; $offset,
				 indent =&gt; length $indent});
  # If we&#039;ve been presented with an arrayref for $item, then the user string
  # contains in the range 128-255, and we need to check whether it was utf8
  # (or not).
  # In the worst case we have two named constants, where one&#039;s name happens
  # encoded in UTF8 happens to be the same byte sequence as the second&#039;s
  # encoded in (say) ISO-8859-1.
  # In this case, $yes and $no both have item hashrefs.
  if ($yes) {
    $body .= $indent . &quot;  if (&quot; . $self-&gt;is_utf8_param . &quot;) {\n&quot;;
  } elsif ($no) {
    $body .= $indent . &quot;  if (!&quot; . $self-&gt;is_utf8_param . &quot;) {\n&quot;;
  }
  if ($either) {
    $body .= $self-&gt;return_clause ({indent=&gt;4 + length $indent}, $either);
    if ($yes and $no) {
      $body .= $indent . &quot;  } else {\n&quot;;
      $body .= $self-&gt;return_clause ({indent=&gt;4 + length $indent}, $no);
    }
    $body .= $indent . &quot;  }\n&quot;;
  } else {
    $body .= $self-&gt;return_clause ({indent=&gt;2 + length $indent}, $item);
  }
  $body .= $indent . &quot;}\n&quot;;
}


=item switch_clause arg_hashref, NAMELEN, ITEMHASH, ITEM...

An internal method to generate a suitable C&lt;switch&gt; clause, called by
C&lt;C_constant&gt; I&lt;ITEM&gt;s are in the hash ref format as given in the description
of C&lt;C_constant&gt;, and must all have the names of the same length, given by
I&lt;NAMELEN&gt;.  I&lt;ITEMHASH&gt; is a reference to a hash, keyed by name, values being
the hashrefs in the I&lt;ITEM&gt; list.  (No parameters are modified, and there can
be keys in the I&lt;ITEMHASH&gt; that are not in the list of I&lt;ITEM&gt;s without
causing problems - the hash is passed in to save generating it afresh for
each call).

=cut

sub switch_clause {
  my ($self, $args, $namelen, $items, @items) = @_;
  my ($indent, $comment) = @{$args}{qw(indent comment)};
  $indent = &#039; &#039; x ($indent || 2);

  local $Text::Wrap::huge = &#039;overflow&#039;;
  local $Text::Wrap::columns = 80;

  my @names = sort map {$_-&gt;{name}} @items;
  my $leader = $indent . &#039;/* &#039;;
  my $follower = &#039; &#039; x length $leader;
  my $body = $indent . &quot;/* Names all of length $namelen.  */\n&quot;;
  if (defined $comment) {
    $body = wrap ($leader, $follower, $comment) . &quot;\n&quot;;
    $leader = $follower;
  }
  my @safe_names = @names;
  foreach (@safe_names) {
    confess sprintf &quot;Name &#039;$_&#039; is length %d, not $namelen&quot;, length
      unless length == $namelen;
    # Argh. 5.6.1
    # next unless tr/A-Za-z0-9_//c;
    next if tr/A-Za-z0-9_// == length;
    $_ = &#039;&quot;&#039; . perl_stringify ($_) . &#039;&quot;&#039;;
    # Ensure that the enclosing C comment doesn&#039;t end
    # by turning */  into *&quot; . &quot;/
    s!\*\/!\*&quot;.&quot;/!gs;
    # gcc -Wall doesn&#039;t like finding /* inside a comment
    s!\/\*!/&quot;.&quot;\*!gs;
  }
  $body .= wrap ($leader, $follower, join (&quot; &quot;, @safe_names) . &quot; */&quot;) . &quot;\n&quot;;
  # Figure out what to switch on.
  # (RMS, Spread of jump table, Position, Hashref)
  my @best = (1e38, ~0);
  # Prefer the last character over the others. (As it lets us shorten the
  # memEQ clause at no cost).
  foreach my $i ($namelen - 1, 0 .. ($namelen - 2)) {
    my ($min, $max) = (~0, 0);
    my %spread;
    if (is_perl56) {
      # Need proper Unicode preserving hash keys for bytes in range 128-255
      # here too, for some reason. grr 5.6.1 yet again.
      tie %spread, &#039;ExtUtils::Constant::Aaargh56Hash&#039;;
    }
    foreach (@names) {
      my $char = substr $_, $i, 1;
      my $ord = ord $char;
      confess &quot;char $ord is out of range&quot; if $ord &gt; 255;
      $max = $ord if $ord &gt; $max;
      $min = $ord if $ord &lt; $min;
      push @{$spread{$char}}, $_;
      # warn &quot;$_ $char&quot;;
    }
    # I&#039;m going to pick the character to split on that minimises the root
    # mean square of the number of names in each case. Normally this should
    # be the one with the most keys, but it may pick a 7 where the 8 has
    # one long linear search. I&#039;m not sure if RMS or just sum of squares is
    # actually better.
    # $max and $min are for the tie-breaker if the root mean squares match.
    # Assuming that the compiler may be building a jump table for the
    # switch() then try to minimise the size of that jump table.
    # Finally use &lt; not &lt;= so that if it still ties the earliest part of
    # the string wins. Because if that passes but the memEQ fails, it may
    # only need the start of the string to bin the choice.
    # I think. But I&#039;m micro-optimising. :-)
    # OK. Trump that. Now favour the last character of the string, before the
    # rest.
    my $ss;
    $ss += @$_ * @$_ foreach values %spread;
    my $rms = sqrt ($ss / keys %spread);
    if ($rms &lt; $best[0] || ($rms == $best[0] &amp;&amp; ($max - $min) &lt; $best[1])) {
      @best = ($rms, $max - $min, $i, \%spread);
    }
  }
  confess &quot;Internal error. Failed to pick a switch point for @names&quot;
    unless defined $best[2];
  # use Data::Dumper; print Dumper (@best);
  my ($offset, $best) = @best[2,3];
  $body .= $indent . &quot;/* Offset $offset gives the best switch position.  */\n&quot;;

  my $do_front_chop = $offset == 0 &amp;&amp; $namelen &gt; 2;
  if ($do_front_chop) {
    $body .= $indent . &quot;switch (*&quot; . $self-&gt;name_param() . &quot;++) {\n&quot;;
  } else {
    $body .= $indent . &quot;switch (&quot; . $self-&gt;name_param() . &quot;[$offset]) {\n&quot;;
  }
  foreach my $char (sort keys %$best) {
    confess sprintf &quot;&#039;$char&#039; is %d bytes long, not 1&quot;, length $char
      if length ($char) != 1;
    confess sprintf &quot;char %#X is out of range&quot;, ord $char if ord ($char) &gt; 255;
    $body .= $indent . &quot;case &#039;&quot; . C_stringify ($char) . &quot;&#039;:\n&quot;;
    foreach my $thisone (sort {
	# Deal with the case of an item actually being an array ref to 1 or 2
	# hashrefs. Don&#039;t assign to $a or $b, as they&#039;re aliases to the orignal
	my $l = ref $a eq &#039;ARRAY&#039; ? ($a-&gt;[0] || $-&gt;[1]) : $a;
	my $r = ref $b eq &#039;ARRAY&#039; ? ($b-&gt;[0] || $-&gt;[1]) : $b;
	# Sort by weight first
	($r-&gt;{weight} || 0) &lt;=&gt; ($l-&gt;{weight} || 0)
	    # Sort equal weights by name
	    or $l-&gt;{name} cmp $r-&gt;{name}}
			 # If this looks evil, maybe it is.  $items is a
			 # hashref, and we&#039;re doing a hash slice on it
			 @{$items}{@{$best-&gt;{$char}}}) {
      # warn &quot;You are here&quot;;
      if ($do_front_chop) {
        $body .= $self-&gt;match_clause ({indent =&gt; 2 + length $indent,
				       checked_at =&gt; \$char}, $thisone);
      } else {
        $body .= $self-&gt;match_clause ({indent =&gt; 2 + length $indent,
				       checked_at =&gt; $offset}, $thisone);
      }
    }
    $body .= $indent . &quot;  break;\n&quot;;
  }
  $body .= $indent . &quot;}\n&quot;;
  return $body;
}

sub C_constant_return_type {
  &quot;static int&quot;;
}

sub C_constant_prefix_param {
  &#039;&#039;;
}

sub C_constant_prefix_param_defintion {
  &#039;&#039;;
}

sub name_param_definition {
  &quot;const char *&quot; . $_[0]-&gt;name_param;
}

sub namelen_param {
  &#039;len&#039;;
}

sub namelen_param_definition {
  &#039;size_t &#039; . $_[0]-&gt;namelen_param;
}

sub C_constant_other_params {
  &#039;&#039;;
}

sub C_constant_other_params_defintion {
  &#039;&#039;;
}

=item params WHAT

An &quot;internal&quot; method, subject to change, currently called to allow an
overriding class to cache information that will then be passed into all
the C&lt;*param*&gt; calls. (Yes, having to read the source to make sense of this is
considered a known bug). I&lt;WHAT&gt; is be a hashref of types the constant
function will return. In ExtUtils::Constant::XS this method is used to
returns a hashref keyed IV NV PV SV to show which combination of pointers will
be needed in the C argument list generated by
C_constant_other_params_definition and C_constant_other_params

=cut

sub params {
  &#039;&#039;;
}


=item dogfood arg_hashref, ITEM...

An internal function to generate the embedded perl code that will regenerate
the constant subroutines.  Parameters are the same as for C_constant.

Currently the base class does nothing and returns an empty string.

=cut

sub dogfood {
  &#039;&#039;
}

=item normalise_items args, default_type, seen_types, seen_items, ITEM...

Convert the items to a normalised form. For 8 bit and Unicode values converts
the item to an array of 1 or 2 items, both 8 bit and UTF-8 encoded.

=cut

sub normalise_items
{
    my $self = shift;
    my $args = shift;
    my $default_type = shift;
    my $what = shift;
    my $items = shift;
    my @new_items;
    foreach my $orig (@_) {
	my ($name, $item);
      if (ref $orig) {
        # Make a copy which is a normalised version of the ref passed in.
        $name = $orig-&gt;{name};
        my ($type, $macro, $value) = @$orig{qw (type macro value)};
        $type ||= $default_type;
        $what-&gt;{$type} = 1;
        $item = {name=&gt;$name, type=&gt;$type};

        undef $macro if defined $macro and $macro eq $name;
        $item-&gt;{macro} = $macro if defined $macro;
        undef $value if defined $value and $value eq $name;
        $item-&gt;{value} = $value if defined $value;
        foreach my $key (qw(default pre post def_pre def_post weight
			    not_constant)) {
          my $value = $orig-&gt;{$key};
          $item-&gt;{$key} = $value if defined $value;
          # warn &quot;$key $value&quot;;
        }
      } else {
        $name = $orig;
        $item = {name=&gt;$name, type=&gt;$default_type};
        $what-&gt;{$default_type} = 1;
      }
      warn +(ref ($self) || $self)
	. &quot;doesn&#039;t know how to handle values of type $_ used in macro $name&quot;
	  unless $self-&gt;valid_type ($item-&gt;{type});
      # tr///c is broken on 5.6.1 for utf8, so my original tr/\0-\177//c
      # doesn&#039;t work. Upgrade to 5.8
      # if ($name !~ tr/\0-\177//c || $] &lt; 5.005_50) {
      if ($name =~ tr/\0-\177// == length $name || $] &lt; 5.005_50
	 || $args-&gt;{disable_utf8_duplication}) {
        # No characters outside 7 bit ASCII.
        if (exists $items-&gt;{$name}) {
          die &quot;Multiple definitions for macro $name&quot;;
        }
        $items-&gt;{$name} = $item;
      } else {
        # No characters outside 8 bit. This is hardest.
        if (exists $items-&gt;{$name} and ref $items-&gt;{$name} ne &#039;ARRAY&#039;) {
          confess &quot;Unexpected ASCII definition for macro $name&quot;;
        }
        # Again, 5.6.1 tr broken, so s/5\.6.*/5\.8\.0/;
        # if ($name !~ tr/\0-\377//c) {
        if ($name =~ tr/\0-\377// == length $name) {
#          if ($] &lt; 5.007) {
#            $name = pack &quot;C*&quot;, unpack &quot;U*&quot;, $name;
#          }
          $item-&gt;{utf8} = &#039;no&#039;;
          $items-&gt;{$name}[1] = $item;
          push @new_items, $item;
          # Copy item, to create the utf8 variant.
          $item = {%$item};
        }
        # Encode the name as utf8 bytes.
        unless (is_perl56) {
          utf8::encode($name);
        } else {
#          warn &quot;Was &gt;$name&lt; &quot; . length ${name};
          $name = pack &#039;C*&#039;, unpack &#039;C*&#039;, $name . pack &#039;U*&#039;;
#          warn &quot;Now &#039;${name}&#039; &quot; . length ${name};
        }
        if ($items-&gt;{$name}[0]) {
          die &quot;Multiple definitions for macro $name&quot;;
        }
        $item-&gt;{utf8} = &#039;yes&#039;;
        $item-&gt;{name} = $name;
        $items-&gt;{$name}[0] = $item;
        # We have need for the utf8 flag.
        $what-&gt;{&#039;&#039;} = 1;
      }
      push @new_items, $item;
    }
    @new_items;
}

=item C_constant arg_hashref, ITEM...

A function that returns a B&lt;list&gt; of C subroutine definitions that return
the value and type of constants when passed the name by the XS wrapper.
I&lt;ITEM...&gt; gives a list of constant names. Each can either be a string,
which is taken as a C macro name, or a reference to a hash with the following
keys

=over 8

=item name

The name of the constant, as seen by the perl code.

=item type

The type of the constant (I&lt;IV&gt;, I&lt;NV&gt; etc)

=item value

A C expression for the value of the constant, or a list of C expressions if
the type is aggregate. This defaults to the I&lt;name&gt; if not given.

=item macro

The C pre-processor macro to use in the C&lt;#ifdef&gt;. This defaults to the
I&lt;name&gt;, and is mainly used if I&lt;value&gt; is an C&lt;enum&gt;. If a reference an
array is passed then the first element is used in place of the C&lt;#ifdef&gt;
line, and the second element in place of the C&lt;#endif&gt;. This allows
pre-processor constructions such as

    #if defined (foo)
    #if !defined (bar)
    ...
    #endif
    #endif

to be used to determine if a constant is to be defined.

A &quot;macro&quot; 1 signals that the constant is always defined, so the C&lt;#if&gt;/C&lt;#endif&gt;
test is omitted.

=item default

Default value to use (instead of C&lt;croak&gt;ing with &quot;your vendor has not
defined...&quot;) to return if the macro isn&#039;t defined. Specify a reference to
an array with type followed by value(s).

=item pre

C code to use before the assignment of the value of the constant. This allows
you to use temporary variables to extract a value from part of a C&lt;struct&gt;
and return this as I&lt;value&gt;. This C code is places at the start of a block,
so you can declare variables in it.

=item post

C code to place between the assignment of value (to a temporary) and the
return from the function. This allows you to clear up anything in I&lt;pre&gt;.
Rarely needed.

=item def_pre

=item def_post

Equivalents of I&lt;pre&gt; and I&lt;post&gt; for the default value.

=item utf8

Generated internally. Is zero or undefined if name is 7 bit ASCII,
&quot;no&quot; if the name is 8 bit (and so should only match if SvUTF8() is false),
&quot;yes&quot; if the name is utf8 encoded.

The internals automatically clone any name with characters 128-255 but none
256+ (ie one that could be either in bytes or utf8) into a second entry
which is utf8 encoded.

=item weight

Optional sorting weight for names, to determine the order of
linear testing when multiple names fall in the same case of a switch clause.
Higher comes earlier, undefined defaults to zero.

=back

In the argument hashref, I&lt;package&gt; is the name of the package, and is only
used in comments inside the generated C code. I&lt;subname&gt; defaults to
C&lt;constant&gt; if undefined.

I&lt;default_type&gt; is the type returned by C&lt;ITEM&gt;s that don&#039;t specify their
type. It defaults to the value of C&lt;default_type()&gt;. I&lt;types&gt; should be given
either as a comma separated list of types that the C subroutine I&lt;subname&gt;
will generate or as a reference to a hash. I&lt;default_type&gt; will be added to
the list if not present, as will any types given in the list of I&lt;ITEM&gt;s. The
resultant list should be the same list of types that C&lt;XS_constant&gt; is
given. [Otherwise C&lt;XS_constant&gt; and C&lt;C_constant&gt; may differ in the number of
parameters to the constant function. I&lt;indent&gt; is currently unused and
ignored. In future it may be used to pass in information used to change the C
indentation style used.]  The best way to maintain consistency is to pass in a
hash reference and let this function update it.

I&lt;breakout&gt; governs when child functions of I&lt;subname&gt; are generated.  If there
are I&lt;breakout&gt; or more I&lt;ITEM&gt;s with the same length of name, then the code
to switch between them is placed into a function named I&lt;subname&gt;_I&lt;len&gt;, for
example C&lt;constant_5&gt; for names 5 characters long.  The default I&lt;breakout&gt; is
3.  A single C&lt;ITEM&gt; is always inlined.

=cut

# The parameter now BREAKOUT was previously documented as:
#
# I&lt;NAMELEN&gt; if defined signals that all the I&lt;name&gt;s of the I&lt;ITEM&gt;s are of
# this length, and that the constant name passed in by perl is checked and
# also of this length. It is used during recursion, and should be C&lt;undef&gt;
# unless the caller has checked all the lengths during code generation, and
# the generated subroutine is only to be called with a name of this length.
#
# As you can see it now performs this function during recursion by being a
# scalar reference.

sub C_constant {
  my ($self, $args, @items) = @_;
  my ($package, $subname, $default_type, $what, $indent, $breakout) =
    @{$args}{qw(package subname default_type types indent breakout)};
  $package ||= &#039;Foo&#039;;
  $subname ||= &#039;constant&#039;;
  # I&#039;m not using this. But a hashref could be used for full formatting without
  # breaking this API
  # $indent ||= 0;

  my ($namelen, $items);
  if (ref $breakout) {
    # We are called recursively. We trust @items to be normalised, $what to
    # be a hashref, and pinch %$items from our parent to save recalculation.
    ($namelen, $items) = @$breakout;
  } else {
    $items = {};
    if (is_perl56) {
      # Need proper Unicode preserving hash keys.
      require ExtUtils::Constant::Aaargh56Hash;
      tie %$items, &#039;ExtUtils::Constant::Aaargh56Hash&#039;;
    }
    $breakout ||= 3;
    $default_type ||= $self-&gt;default_type();
    if (!ref $what) {
      # Convert line of the form IV,UV,NV to hash
      $what = {map {$_ =&gt; 1} split /,\s*/, ($what || &#039;&#039;)};
      # Figure out what types we&#039;re dealing with, and assign all unknowns to the
      # default type
    }
    @items = $self-&gt;normalise_items ({}, $default_type, $what, $items, @items);
    # use Data::Dumper; print Dumper @items;
  }
  my $params = $self-&gt;params ($what);

  # Probably &quot;static int&quot;
  my ($body, @subs);
  $body = $self-&gt;C_constant_return_type($params) . &quot;\n$subname (&quot;
    # Eg &quot;pTHX_ &quot;
    . $self-&gt;C_constant_prefix_param_defintion($params)
      # Probably &quot;const char *name&quot;
      . $self-&gt;name_param_definition($params);
  # Something like &quot;, STRLEN len&quot;
  $body .= &quot;, &quot; . $self-&gt;namelen_param_definition($params)
    unless defined $namelen;
  $body .= $self-&gt;C_constant_other_params_defintion($params);
  $body .= &quot;) {\n&quot;;

  if (defined $namelen) {
    # We are a child subroutine. Print the simple description
    my $comment = &#039;When generated this function returned values for the list&#039;
      . &#039; of names given here.  However, subsequent manual editing may have&#039;
        . &#039; added or removed some.&#039;;
    $body .= $self-&gt;switch_clause ({indent=&gt;2, comment=&gt;$comment},
				   $namelen, $items, @items);
  } else {
    # We are the top level.
    $body .= &quot;  /* Initially switch on the length of the name.  */\n&quot;;
    $body .= $self-&gt;dogfood ({package =&gt; $package, subname =&gt; $subname,
			      default_type =&gt; $default_type, what =&gt; $what,
			      indent =&gt; $indent, breakout =&gt; $breakout},
			     @items);
    $body .= &#039;  switch (&#039;.$self-&gt;namelen_param().&quot;) {\n&quot;;
    # Need to group names of the same length
    my @by_length;
    foreach (@items) {
      push @{$by_length[length $_-&gt;{name}]}, $_;
    }
    foreach my $i (0 .. $#by_length) {
      next unless $by_length[$i];	# None of this length
      $body .= &quot;  case $i:\n&quot;;
      if (@{$by_length[$i]} == 1) {
        my $only_thing = $by_length[$i]-&gt;[0];
        if ($only_thing-&gt;{utf8}) {
          if ($only_thing-&gt;{utf8} eq &#039;yes&#039;) {
            # With utf8 on flag item is passed in element 0
            $body .= $self-&gt;match_clause (undef, [$only_thing]);
          } else {
            # With utf8 off flag item is passed in element 1
            $body .= $self-&gt;match_clause (undef, [undef, $only_thing]);
          }
        } else {
          $body .= $self-&gt;match_clause (undef, $only_thing);
        }
      } elsif (@{$by_length[$i]} &lt; $breakout) {
        $body .= $self-&gt;switch_clause ({indent=&gt;4},
				       $i, $items, @{$by_length[$i]});
      } else {
        # Only use the minimal set of parameters actually needed by the types
        # of the names of this length.
        my $what = {};
        foreach (@{$by_length[$i]}) {
          $what-&gt;{$_-&gt;{type}} = 1;
          $what-&gt;{&#039;&#039;} = 1 if $_-&gt;{utf8};
        }
        $params = $self-&gt;params ($what);
        push @subs, $self-&gt;C_constant ({package=&gt;$package,
					subname=&gt;&quot;${subname}_$i&quot;,
					default_type =&gt; $default_type,
					types =&gt; $what, indent =&gt; $indent,
					breakout =&gt; [$i, $items]},
				       @{$by_length[$i]});
        $body .= &quot;    return ${subname}_$i (&quot;
	  # Eg &quot;aTHX_ &quot;
	  . $self-&gt;C_constant_prefix_param($params)
	    # Probably &quot;name&quot;
	    . $self-&gt;name_param($params);
	$body .= $self-&gt;C_constant_other_params($params);
        $body .= &quot;);\n&quot;;
      }
      $body .= &quot;    break;\n&quot;;
    }
    $body .= &quot;  }\n&quot;;
  }
  my $notfound = $self-&gt;return_statement_for_notfound();
  $body .= &quot;  $notfound\n&quot; if $notfound;
  $body .= &quot;}\n&quot;;
  return (@subs, $body);
}

1;
__END__

=back

=head1 BUGS

Not everything is documented yet.

Probably others.

=head1 AUTHOR

Nicholas Clark &lt;nick@ccl4.org&gt; based on the code in C&lt;h2xs&gt; by Larry Wall and
others
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