package ExtUtils::Constant;
$VERSION = 0.17;

=head1 NAME

ExtUtils::Constant - generate XS code to import C header constants


    use ExtUtils::Constant qw (WriteConstants);
        NAME => 'Foo',
        NAMES => [qw(FOO BAR BAZ)],
    # Generates wrapper code to make the values of the constants FOO BAR BAZ
    #  available to perl


ExtUtils::Constant facilitates generating C and XS wrapper code to allow
perl modules to AUTOLOAD constants defined in C library header files.
It is principally used by the C<h2xs> utility, on which this code is based.
It doesn't contain the routines to scan header files to extract these

=head1 USAGE

Generally one only needs to call the C<WriteConstants> function, and then

    #include ""

in the C section of C<Foo.xs>


in the XS section of C<Foo.xs>.

For greater flexibility use C<constant_types()>, C<C_constant> and
C<XS_constant>, with which C<WriteConstants> is implemented.

Currently this module understands the following types. h2xs may only know
a subset. The sizes of the numeric types are chosen by the C<Configure>
script at compile time.

=over 4

=item IV

signed integer, at least 32 bits.

=item UV

unsigned integer, the same size as I<IV>

=item NV

floating point type, probably C<double>, possibly C<long double>

=item PV

NUL terminated string, length will be determined with C<strlen>

=item PVN

A fixed length thing, given as a [pointer, length] pair. If you know the
length of a string at compile time you may use this instead of I<PV>

=item SV

A B<mortal> SV.

=item YES

Truth.  (C<PL_sv_yes>)  The value is not needed (and ignored).

=item NO

Defined Falsehood.  (C<PL_sv_no>)  The value is not needed (and ignored).

=item UNDEF

C<undef>.  The value of the macro is not needed.



=over 4


if ($] >= 5.006) {
  eval "use warnings; 1" or die $@;
use strict;
use Carp qw(croak cluck);

use Exporter;
use ExtUtils::Constant::Utils qw(C_stringify);
use ExtUtils::Constant::XS qw(%XS_Constant %XS_TypeSet);

@ISA = 'Exporter';

%EXPORT_TAGS = ( 'all' => [ qw(
	XS_constant constant_types return_clause memEQ_clause C_stringify
	C_constant autoload WriteConstants WriteMakefileSnippet
) ] );

@EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } );

=item constant_types

A function returning a single scalar with C<#define> definitions for the
constants used internally between the generated C and XS functions.


sub constant_types {

sub memEQ_clause {
  cluck "ExtUtils::Constant::memEQ_clause is deprecated";
  ExtUtils::Constant::XS->memEQ_clause({name=>$_[0], checked_at=>$_[1],

sub return_clause ($$) {
  cluck "ExtUtils::Constant::return_clause is deprecated";
  my $indent = shift;
  ExtUtils::Constant::XS->return_clause({indent=>$indent}, @_);

sub switch_clause {
  cluck "ExtUtils::Constant::switch_clause is deprecated";
  my $indent = shift;
  my $comment = shift;
  ExtUtils::Constant::XS->switch_clause({indent=>$indent, comment=>$comment},

sub C_constant {
  my ($package, $subname, $default_type, $what, $indent, $breakout, @items)
    = @_;
  ExtUtils::Constant::XS->C_constant({package => $package, subname => $subname,
				      default_type => $default_type,
				      types => $what, indent => $indent,
				      breakout => $breakout}, @items);


A function to generate the XS code to implement the perl subroutine
I<PACKAGE>::constant used by I<PACKAGE>::AUTOLOAD to load constants.
This XS code is a wrapper around a C subroutine usually generated by
C<C_constant>, and usually named C<constant>.

I<TYPES> should be given either as a comma separated list of types that the
C subroutine C<constant> will generate or as a reference to a hash. It should
be the same list of types as C<C_constant> was given.
[Otherwise C<XS_constant> and C<C_constant> may have different ideas about
the number of parameters passed to the C function C<constant>]

You can call the perl visible subroutine something other than C<constant> if
you give the parameter I<SUBNAME>. The C subroutine it calls defaults to
the name of the perl visible subroutine, unless you give the parameter


sub XS_constant {
  my $package = shift;
  my $what = shift;
  my $subname = shift;
  my $C_subname = shift;
  $subname ||= 'constant';
  $C_subname ||= $subname;

  if (!ref $what) {
    # Convert line of the form IV,UV,NV to hash
    $what = {map {$_ => 1} split /,\s*/, ($what)};
  my $params = ExtUtils::Constant::XS->params ($what);
  my $type;

  my $xs = <<"EOT";
#ifdef dXSTARG
	dXSTARG; /* Faster if we have it.  */
	STRLEN		len;
        int		type;

  if ($params->{IV}) {
    $xs .= "	IV		iv;\n";
  } else {
    $xs .= "	/* IV\t\tiv;\tUncomment this if you need to return IVs */\n";
  if ($params->{NV}) {
    $xs .= "	NV		nv;\n";
  } else {
    $xs .= "	/* NV\t\tnv;\tUncomment this if you need to return NVs */\n";
  if ($params->{PV}) {
    $xs .= "	const char	*pv;\n";
  } else {
    $xs .=
      "	/* const char\t*pv;\tUncomment this if you need to return PVs */\n";

  $xs .= << 'EOT';
	SV *		sv;
        const char *	s = SvPV(sv, len);
  if ($params->{''}) {
  $xs .= << 'EOT';
	int		utf8 = SvUTF8(sv);
  $xs .= << 'EOT';

  if ($params->{IV} xor $params->{NV}) {
    $xs .= << "EOT";
        /* Change this to $C_subname(aTHX_ s, len, &iv, &nv);
           if you need to return both NVs and IVs */
  $xs .= "	type = $C_subname(aTHX_ s, len";
  $xs .= ', utf8' if $params->{''};
  $xs .= ', &iv' if $params->{IV};
  $xs .= ', &nv' if $params->{NV};
  $xs .= ', &pv' if $params->{PV};
  $xs .= ', &sv' if $params->{SV};
  $xs .= ");\n";

  $xs .= << "EOT";
      /* Return 1 or 2 items. First is error message, or undef if no error.
           Second, if present, is found value */
        switch (type) {
        case PERL_constant_NOTFOUND:
          sv = sv_2mortal(newSVpvf("%s is not a valid $package macro", s));
        case PERL_constant_NOTDEF:
          sv = sv_2mortal(newSVpvf(
	    "Your vendor has not defined $package macro %s, used", s));

  foreach $type (sort keys %XS_Constant) {
    # '' marks utf8 flag needed.
    next if $type eq '';
    $xs .= "\t/* Uncomment this if you need to return ${type}s\n"
      unless $what->{$type};
    $xs .= "        case PERL_constant_IS$type:\n";
    if (length $XS_Constant{$type}) {
      $xs .= << "EOT";
          EXTEND(SP, 1);
    } else {
      # Do nothing. return (), which will be correctly interpreted as
      # (undef, undef)
    $xs .= "          break;\n";
    unless ($what->{$type}) {
      chop $xs; # Yes, another need for chop not chomp.
      $xs .= " */\n";
  $xs .= << "EOT";
          sv = sv_2mortal(newSVpvf(
	    "Unexpected return type %d while processing $package macro %s, used",
               type, s));

  return $xs;


A function to generate the AUTOLOAD subroutine for the module I<PACKAGE>
I<VERSION> is the perl version the code should be backwards compatible with.
It defaults to the version of perl running the subroutine.  If I<AUTOLOADER>
is true, the AUTOLOAD subroutine falls back on AutoLoader::AUTOLOAD for all
names that the constant() routine doesn't recognise.


# ' # Grr. syntax highlighters that don't grok pod.

sub autoload {
  my ($module, $compat_version, $autoloader) = @_;
  $compat_version ||= $];
  croak "Can't maintain compatibility back as far as version $compat_version"
    if $compat_version < 5;
  my $func = "sub AUTOLOAD {\n"
  . "    # This AUTOLOAD is used to 'autoload' constants from the constant()\n"
  . "    # XS function.";
  $func .= "  If a constant is not found then control is passed\n"
  . "    # to the AUTOLOAD in AutoLoader." if $autoloader;

  $func .= "\n\n"
  . "    my \$constname;\n";
  $func .=
    "    our \$AUTOLOAD;\n"  if ($compat_version >= 5.006);

  $func .= <<"EOT";
    (\$constname = \$AUTOLOAD) =~ s/.*:://;
    croak "&${module}::constant not defined" if \$constname eq 'constant';
    my (\$error, \$val) = constant(\$constname);

  if ($autoloader) {
    $func .= <<'EOT';
    if ($error) {
	if ($error =~  /is not a valid/) {
	    $AutoLoader::AUTOLOAD = $AUTOLOAD;
	    goto &AutoLoader::AUTOLOAD;
	} else {
	    croak $error;
  } else {
    $func .=
      "    if (\$error) { croak \$error; }\n";

  $func .= <<'END';
	no strict 'refs';
	# Fixed between 5.005_53 and 5.005_61
#XXX	if ($] >= 5.00561) {
#XXX	    *$AUTOLOAD = sub () { $val };
#XXX	}
#XXX	else {
	    *$AUTOLOAD = sub { $val };
#XXX	}
    goto &$AUTOLOAD;


  return $func;

=item WriteMakefileSnippet

WriteMakefileSnippet ATTRIBUTE =E<gt> VALUE [, ...] 

A function to generate perl code for Makefile.PL that will regenerate
the constant subroutines.  Parameters are named as passed to C<WriteConstants>,
with the addition of C<INDENT> to specify the number of leading spaces
(default 2).

Currently only C<INDENT>, C<NAME>, C<DEFAULT_TYPE>, C<NAMES>, C<C_FILE> and
C<XS_FILE> are recognised.


sub WriteMakefileSnippet {
  my %args = @_;
  my $indent = $args{INDENT} || 2;

  my $result = <<"EOT";
                                   NAME         => '$args{NAME}',
                                   NAMES        => \\\@names,
                                   DEFAULT_TYPE => '$args{DEFAULT_TYPE}',
  foreach (qw (C_FILE XS_FILE)) {
    next unless exists $args{$_};
    $result .= sprintf "                                   %-12s => '%s',\n",
      $_, $args{$_};
  $result .= <<'EOT';

  $result =~ s/^/' 'x$indent/gem;
  return ExtUtils::Constant::XS->dump_names({default_type=>$args{DEFAULT_TYPE},
    . $result;

=item WriteConstants ATTRIBUTE =E<gt> VALUE [, ...]

Writes a file of C code and a file of XS code which you should C<#include>
and C<INCLUDE> in the C and XS sections respectively of your module's XS
code.  You probably want to do this in your C<Makefile.PL>, so that you can
easily edit the list of constants without touching the rest of your module.
The attributes supported are

=over 4

=item NAME

Name of the module.  This must be specified


The default type for the constants.  If not specified C<IV> is assumed.


The names of the constants are grouped by length.  Generate child subroutines
for each group with this number or more names in.

=item NAMES

An array of constants' names, either scalars containing names, or hashrefs
as detailed in L<"C_constant">.

=item C_FILE

The name of the file to write containing the C code.  The default is
C<>.  The C<-> in the name ensures that the file can't be
mistaken for anything related to a legitimate perl package name, and
not naming the file C<.c> avoids having to override Makefile.PL's
C<.xs> to C<.c> rules.

=item XS_FILE

The name of the file to write containing the XS code.  The default is


The perl visible name of the XS subroutine generated which will return the
constants. The default is C<constant>.


The name of the C subroutine generated which will return the constants.
The default is I<SUBNAME>.  Child subroutines have C<_> and the name
length appended, so constants with 10 character names would be in
C<constant_10> with the default I<XS_SUBNAME>.



sub WriteConstants {
  my %ARGS =
    ( # defaults
     C_FILE =>       '',
     XS_FILE =>      '',
     SUBNAME =>      'constant',
     DEFAULT_TYPE => 'IV',

  $ARGS{C_SUBNAME} ||= $ARGS{SUBNAME}; # No-one sane will have C_SUBNAME eq '0'

  croak "Module name not specified" unless length $ARGS{NAME};

  my ($c_fh, $xs_fh);
  if ($] <= 5.008) {
      # We need these little games, rather than doing things unconditionally,
      # because we're used in core Makefile.PLs before IO is available (needed
      # by filehandle), but also we want to work on older perls where undefined
      # scalars do not automatically turn into anonymous file handles.
      require FileHandle;
      $c_fh = FileHandle->new();
      $xs_fh = FileHandle->new();
  open $c_fh, ">$ARGS{C_FILE}" or die "Can't open $ARGS{C_FILE}: $!";
  open $xs_fh, ">$ARGS{XS_FILE}" or die "Can't open $ARGS{XS_FILE}: $!";

  # As this subroutine is intended to make code that isn't edited, there's no
  # need for the user to specify any types that aren't found in the list of
  # names.
  my $types = {};

  print $c_fh constant_types(); # macro defs
  print $c_fh "\n";

  # indent is still undef. Until anyone implements indent style rules with it.
  foreach (ExtUtils::Constant::XS->C_constant({package => $ARGS{NAME},
					       subname => $ARGS{C_SUBNAME},
					       default_type =>
					       types => $types,
					       breakout => $ARGS{BREAKOUT_AT}},
					       @{$ARGS{NAMES}})) {
    print $c_fh $_, "\n"; # C constant subs
  print $xs_fh XS_constant ($ARGS{NAME}, $types, $ARGS{XS_SUBNAME},

  close $c_fh or warn "Error closing $ARGS{C_FILE}: $!";
  close $xs_fh or warn "Error closing $ARGS{XS_FILE}: $!";



=head1 AUTHOR

Nicholas Clark <> based on the code in C<h2xs> by Larry Wall and