lib/ExtUtils/Constant.pm

package ExtUtils::Constant;
use vars qw (@ISA $VERSION @EXPORT_OK %EXPORT_TAGS);
$VERSION = 0.16;

=head1 NAME

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

=head1 SYNOPSIS

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

=head1 DESCRIPTION

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
constants.

=head1 USAGE

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

    #include "const-c.inc"

in the C section of C<Foo.xs>

    INCLUDE: const-xs.inc

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.

=back

=head1 FUNCTIONS

=over 4

=cut

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.

=cut

sub constant_types {
  ExtUtils::Constant::XS->header();
}

sub memEQ_clause {
  cluck "ExtUtils::Constant::memEQ_clause is deprecated";
  ExtUtils::Constant::XS->memEQ_clause({name=>$_[0], checked_at=>$_[1],
                                        indent=>$_[2]});
}

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);
}

=item XS_constant PACKAGE, TYPES, SUBNAME, C_SUBNAME

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
I<C_SUBNAME>.

=cut

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";
void
$subname(sv)
    PREINIT:
#ifdef dXSTARG
        dXSTARG; /* Faster if we have it.  */
#else
        dTARGET;
#endif
        STRLEN          len;
        int             type;
EOT

  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";
  }

  $xs .= << 'EOT';
    INPUT:
        SV *            sv;
        const char *    s = SvPV(sv, len);
EOT
  if ($params->{''}) {
  $xs .= << 'EOT';
    INPUT:
        int             utf8 = SvUTF8(sv);
EOT
  }
  $xs .= << 'EOT';
    PPCODE:
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 */
EOT
  }
  $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));
          PUSHs(sv);
          break;
        case PERL_constant_NOTDEF:
          sv = sv_2mortal(newSVpvf(
            "Your vendor has not defined $package macro %s, used", s));
          PUSHs(sv);
          break;
EOT

  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);
          PUSHs(&PL_sv_undef);
          $XS_Constant{$type};
EOT
    } 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";
        default:
          sv = sv_2mortal(newSVpvf(
            "Unexpected return type %d while processing $package macro %s, used",
               type, s));
          PUSHs(sv);
        }
EOT

  return $xs;
}


=item autoload PACKAGE, VERSION, AUTOLOADER

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.

=cut

# ' # 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);
EOT

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

END

  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.

=cut

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

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

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

=item DEFAULT_TYPE

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

=item BREAKOUT_AT

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<const-c.inc>.  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
C<const-xs.inc>.

=item SUBNAME

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

=item C_SUBNAME

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>.

=back

=cut

sub WriteConstants {
  my %ARGS =
    ( # defaults
     C_FILE =>       'const-c.inc',
     XS_FILE =>      'const-xs.inc',
     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};

  open my $c_fh, ">$ARGS{C_FILE}" or die "Can't open $ARGS{C_FILE}: $!";
  open my $xs_fh, ">$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 =>
                                               $ARGS{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},
                            $ARGS{C_SUBNAME});

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

1;
__END__

=back

=head1 AUTHOR

Nicholas Clark <nick@ccl4.org> based on the code in C<h2xs> by Larry Wall and
others

=cut
Revision:	1.1
Committed:	Thu Jun 30 14:27:10 2005 UTC (21 years, 4 months ago) by root
Branch:	MAIN
CVS Tags:	PERL-5-8-7, HEAD
Branch point for:	PERL
Log Message:	* empty log message *
#	Content
1	package ExtUtils::Constant;
2	use vars qw (@ISA $VERSION @EXPORT_OK %EXPORT_TAGS);
3	$VERSION = 0.16;
4
5	=head1 NAME
6
7	ExtUtils::Constant - generate XS code to import C header constants
8
9	=head1 SYNOPSIS
10
11	use ExtUtils::Constant qw (WriteConstants);
12	WriteConstants(
13	NAME => 'Foo',
14	NAMES => [qw(FOO BAR BAZ)],
15	);
16	# Generates wrapper code to make the values of the constants FOO BAR BAZ
17	# available to perl
18
19	=head1 DESCRIPTION
20
21	ExtUtils::Constant facilitates generating C and XS wrapper code to allow
22	perl modules to AUTOLOAD constants defined in C library header files.
23	It is principally used by the C<h2xs> utility, on which this code is based.
24	It doesn't contain the routines to scan header files to extract these
25	constants.
26
27	=head1 USAGE
28
29	Generally one only needs to call the C<WriteConstants> function, and then
30
31	#include "const-c.inc"
32
33	in the C section of C<Foo.xs>
34
35	INCLUDE: const-xs.inc
36
37	in the XS section of C<Foo.xs>.
38
39	For greater flexibility use C<constant_types()>, C<C_constant> and
40	C<XS_constant>, with which C<WriteConstants> is implemented.
41
42	Currently this module understands the following types. h2xs may only know
43	a subset. The sizes of the numeric types are chosen by the C<Configure>
44	script at compile time.
45
46	=over 4
47
48	=item IV
49
50	signed integer, at least 32 bits.
51
52	=item UV
53
54	unsigned integer, the same size as I<IV>
55
56	=item NV
57
58	floating point type, probably C<double>, possibly C<long double>
59
60	=item PV
61
62	NUL terminated string, length will be determined with C<strlen>
63
64	=item PVN
65
66	A fixed length thing, given as a [pointer, length] pair. If you know the
67	length of a string at compile time you may use this instead of I<PV>
68
69	=item SV
70
71	A B<mortal> SV.
72
73	=item YES
74
75	Truth. (C<PL_sv_yes>) The value is not needed (and ignored).
76
77	=item NO
78
79	Defined Falsehood. (C<PL_sv_no>) The value is not needed (and ignored).
80
81	=item UNDEF
82
83	C<undef>. The value of the macro is not needed.
84
85	=back
86
87	=head1 FUNCTIONS
88
89	=over 4
90
91	=cut
92
93	if ($] >= 5.006) {
94	eval "use warnings; 1" or die $@;
95	}
96	use strict;
97	use Carp qw(croak cluck);
98
99	use Exporter;
100	use ExtUtils::Constant::Utils qw(C_stringify);
101	use ExtUtils::Constant::XS qw(%XS_Constant %XS_TypeSet);
102
103	@ISA = 'Exporter';
104
105	%EXPORT_TAGS = ( 'all' => [ qw(
106	XS_constant constant_types return_clause memEQ_clause C_stringify
107	C_constant autoload WriteConstants WriteMakefileSnippet
108	) ] );
109
110	@EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } );
111
112	=item constant_types
113
114	A function returning a single scalar with C<#define> definitions for the
115	constants used internally between the generated C and XS functions.
116
117	=cut
118
119	sub constant_types {
120	ExtUtils::Constant::XS->header();
121	}
122
123	sub memEQ_clause {
124	cluck "ExtUtils::Constant::memEQ_clause is deprecated";
125	ExtUtils::Constant::XS->memEQ_clause({name=>$_[0], checked_at=>$_[1],
126	indent=>$_[2]});
127	}
128
129	sub return_clause ($$) {
130	cluck "ExtUtils::Constant::return_clause is deprecated";
131	my $indent = shift;
132	ExtUtils::Constant::XS->return_clause({indent=>$indent}, @_);
133	}
134
135	sub switch_clause {
136	cluck "ExtUtils::Constant::switch_clause is deprecated";
137	my $indent = shift;
138	my $comment = shift;
139	ExtUtils::Constant::XS->switch_clause({indent=>$indent, comment=>$comment},
140	@_);
141	}
142
143	sub C_constant {
144	my ($package, $subname, $default_type, $what, $indent, $breakout, @items)
145	= @_;
146	ExtUtils::Constant::XS->C_constant({package => $package, subname => $subname,
147	default_type => $default_type,
148	types => $what, indent => $indent,
149	breakout => $breakout}, @items);
150	}
151
152	=item XS_constant PACKAGE, TYPES, SUBNAME, C_SUBNAME
153
154	A function to generate the XS code to implement the perl subroutine
155	I<PACKAGE>::constant used by I<PACKAGE>::AUTOLOAD to load constants.
156	This XS code is a wrapper around a C subroutine usually generated by
157	C<C_constant>, and usually named C<constant>.
158
159	I<TYPES> should be given either as a comma separated list of types that the
160	C subroutine C<constant> will generate or as a reference to a hash. It should
161	be the same list of types as C<C_constant> was given.
162	[Otherwise C<XS_constant> and C<C_constant> may have different ideas about
163	the number of parameters passed to the C function C<constant>]
164
165	You can call the perl visible subroutine something other than C<constant> if
166	you give the parameter I<SUBNAME>. The C subroutine it calls defaults to
167	the name of the perl visible subroutine, unless you give the parameter
168	I<C_SUBNAME>.
169
170	=cut
171
172	sub XS_constant {
173	my $package = shift;
174	my $what = shift;
175	my $subname = shift;
176	my $C_subname = shift;
177	$subname \|\|= 'constant';
178	$C_subname \|\|= $subname;
179
180	if (!ref $what) {
181	# Convert line of the form IV,UV,NV to hash
182	$what = {map {$_ => 1} split /,\s*/, ($what)};
183	}
184	my $params = ExtUtils::Constant::XS->params ($what);
185	my $type;
186
187	my $xs = <<"EOT";
188	void
189	$subname(sv)
190	PREINIT:
191	#ifdef dXSTARG
192	dXSTARG; /* Faster if we have it. */
193	#else
194	dTARGET;
195	#endif
196	STRLEN len;
197	int type;
198	EOT
199
200	if ($params->{IV}) {
201	$xs .= " IV iv;\n";
202	} else {
203	$xs .= " /* IV\t\tiv;\tUncomment this if you need to return IVs */\n";
204	}
205	if ($params->{NV}) {
206	$xs .= " NV nv;\n";
207	} else {
208	$xs .= " /* NV\t\tnv;\tUncomment this if you need to return NVs */\n";
209	}
210	if ($params->{PV}) {
211	$xs .= " const char *pv;\n";
212	} else {
213	$xs .=
214	" /* const char\tpv;\tUncomment this if you need to return PVs /\n";
215	}
216
217	$xs .= << 'EOT';
218	INPUT:
219	SV * sv;
220	const char * s = SvPV(sv, len);
221	EOT
222	if ($params->{''}) {
223	$xs .= << 'EOT';
224	INPUT:
225	int utf8 = SvUTF8(sv);
226	EOT
227	}
228	$xs .= << 'EOT';
229	PPCODE:
230	EOT
231
232	if ($params->{IV} xor $params->{NV}) {
233	$xs .= << "EOT";
234	/* Change this to $C_subname(aTHX_ s, len, &iv, &nv);
235	if you need to return both NVs and IVs */
236	EOT
237	}
238	$xs .= " type = $C_subname(aTHX_ s, len";
239	$xs .= ', utf8' if $params->{''};
240	$xs .= ', &iv' if $params->{IV};
241	$xs .= ', &nv' if $params->{NV};
242	$xs .= ', &pv' if $params->{PV};
243	$xs .= ', &sv' if $params->{SV};
244	$xs .= ");\n";
245
246	$xs .= << "EOT";
247	/* Return 1 or 2 items. First is error message, or undef if no error.
248	Second, if present, is found value */
249	switch (type) {
250	case PERL_constant_NOTFOUND:
251	sv = sv_2mortal(newSVpvf("%s is not a valid $package macro", s));
252	PUSHs(sv);
253	break;
254	case PERL_constant_NOTDEF:
255	sv = sv_2mortal(newSVpvf(
256	"Your vendor has not defined $package macro %s, used", s));
257	PUSHs(sv);
258	break;
259	EOT
260
261	foreach $type (sort keys %XS_Constant) {
262	# '' marks utf8 flag needed.
263	next if $type eq '';
264	$xs .= "\t/* Uncomment this if you need to return ${type}s\n"
265	unless $what->{$type};
266	$xs .= " case PERL_constant_IS$type:\n";
267	if (length $XS_Constant{$type}) {
268	$xs .= << "EOT";
269	EXTEND(SP, 1);
270	PUSHs(&PL_sv_undef);
271	$XS_Constant{$type};
272	EOT
273	} else {
274	# Do nothing. return (), which will be correctly interpreted as
275	# (undef, undef)
276	}
277	$xs .= " break;\n";
278	unless ($what->{$type}) {
279	chop $xs; # Yes, another need for chop not chomp.
280	$xs .= " */\n";
281	}
282	}
283	$xs .= << "EOT";
284	default:
285	sv = sv_2mortal(newSVpvf(
286	"Unexpected return type %d while processing $package macro %s, used",
287	type, s));
288	PUSHs(sv);
289	}
290	EOT
291
292	return $xs;
293	}
294
295
296	=item autoload PACKAGE, VERSION, AUTOLOADER
297
298	A function to generate the AUTOLOAD subroutine for the module I<PACKAGE>
299	I<VERSION> is the perl version the code should be backwards compatible with.
300	It defaults to the version of perl running the subroutine. If I<AUTOLOADER>
301	is true, the AUTOLOAD subroutine falls back on AutoLoader::AUTOLOAD for all
302	names that the constant() routine doesn't recognise.
303
304	=cut
305
306	# ' # Grr. syntax highlighters that don't grok pod.
307
308	sub autoload {
309	my ($module, $compat_version, $autoloader) = @_;
310	$compat_version \|\|= $];
311	croak "Can't maintain compatibility back as far as version $compat_version"
312	if $compat_version < 5;
313	my $func = "sub AUTOLOAD {\n"
314	. " # This AUTOLOAD is used to 'autoload' constants from the constant()\n"
315	. " # XS function.";
316	$func .= " If a constant is not found then control is passed\n"
317	. " # to the AUTOLOAD in AutoLoader." if $autoloader;
318
319
320	$func .= "\n\n"
321	. " my \$constname;\n";
322	$func .=
323	" our \$AUTOLOAD;\n" if ($compat_version >= 5.006);
324
325	$func .= <<"EOT";
326	(\$constname = \$AUTOLOAD) =~ s/.*:://;
327	croak "&${module}::constant not defined" if \$constname eq 'constant';
328	my (\$error, \$val) = constant(\$constname);
329	EOT
330
331	if ($autoloader) {
332	$func .= <<'EOT';
333	if ($error) {
334	if ($error =~ /is not a valid/) {
335	$AutoLoader::AUTOLOAD = $AUTOLOAD;
336	goto &AutoLoader::AUTOLOAD;
337	} else {
338	croak $error;
339	}
340	}
341	EOT
342	} else {
343	$func .=
344	" if (\$error) { croak \$error; }\n";
345	}
346
347	$func .= <<'END';
348	{
349	no strict 'refs';
350	# Fixed between 5.005_53 and 5.005_61
351	#XXX if ($] >= 5.00561) {
352	#XXX *$AUTOLOAD = sub () { $val };
353	#XXX }
354	#XXX else {
355	*$AUTOLOAD = sub { $val };
356	#XXX }
357	}
358	goto &$AUTOLOAD;
359	}
360
361	END
362
363	return $func;
364	}
365
366
367	=item WriteMakefileSnippet
368
369	WriteMakefileSnippet ATTRIBUTE =E<gt> VALUE [, ...]
370
371	A function to generate perl code for Makefile.PL that will regenerate
372	the constant subroutines. Parameters are named as passed to C<WriteConstants>,
373	with the addition of C<INDENT> to specify the number of leading spaces
374	(default 2).
375
376	Currently only C<INDENT>, C<NAME>, C<DEFAULT_TYPE>, C<NAMES>, C<C_FILE> and
377	C<XS_FILE> are recognised.
378
379	=cut
380
381	sub WriteMakefileSnippet {
382	my %args = @_;
383	my $indent = $args{INDENT} \|\| 2;
384
385	my $result = <<"EOT";
386	ExtUtils::Constant::WriteConstants(
387	NAME => '$args{NAME}',
388	NAMES => \\\@names,
389	DEFAULT_TYPE => '$args{DEFAULT_TYPE}',
390	EOT
391	foreach (qw (C_FILE XS_FILE)) {
392	next unless exists $args{$_};
393	$result .= sprintf " %-12s => '%s',\n",
394	$_, $args{$_};
395	}
396	$result .= <<'EOT';
397	);
398	EOT
399
400	$result =~ s/^/' 'x$indent/gem;
401	return ExtUtils::Constant::XS->dump_names({default_type=>$args{DEFAULT_TYPE},
402	indent=>$indent,},
403	@{$args{NAMES}})
404	. $result;
405	}
406
407	=item WriteConstants ATTRIBUTE =E<gt> VALUE [, ...]
408
409	Writes a file of C code and a file of XS code which you should C<#include>
410	and C<INCLUDE> in the C and XS sections respectively of your module's XS
411	code. You probably want to do this in your C<Makefile.PL>, so that you can
412	easily edit the list of constants without touching the rest of your module.
413	The attributes supported are
414
415	=over 4
416
417	=item NAME
418
419	Name of the module. This must be specified
420
421	=item DEFAULT_TYPE
422
423	The default type for the constants. If not specified C<IV> is assumed.
424
425	=item BREAKOUT_AT
426
427	The names of the constants are grouped by length. Generate child subroutines
428	for each group with this number or more names in.
429
430	=item NAMES
431
432	An array of constants' names, either scalars containing names, or hashrefs
433	as detailed in L<"C_constant">.
434
435	=item C_FILE
436
437	The name of the file to write containing the C code. The default is
438	C<const-c.inc>. The C<-> in the name ensures that the file can't be
439	mistaken for anything related to a legitimate perl package name, and
440	not naming the file C<.c> avoids having to override Makefile.PL's
441	C<.xs> to C<.c> rules.
442
443	=item XS_FILE
444
445	The name of the file to write containing the XS code. The default is
446	C<const-xs.inc>.
447
448	=item SUBNAME
449
450	The perl visible name of the XS subroutine generated which will return the
451	constants. The default is C<constant>.
452
453	=item C_SUBNAME
454
455	The name of the C subroutine generated which will return the constants.
456	The default is I<SUBNAME>. Child subroutines have C<_> and the name
457	length appended, so constants with 10 character names would be in
458	C<constant_10> with the default I<XS_SUBNAME>.
459
460	=back
461
462	=cut
463
464	sub WriteConstants {
465	my %ARGS =
466	( # defaults
467	C_FILE => 'const-c.inc',
468	XS_FILE => 'const-xs.inc',
469	SUBNAME => 'constant',
470	DEFAULT_TYPE => 'IV',
471	@_);
472
473	$ARGS{C_SUBNAME} \|\|= $ARGS{SUBNAME}; # No-one sane will have C_SUBNAME eq '0'
474
475	croak "Module name not specified" unless length $ARGS{NAME};
476
477	open my $c_fh, ">$ARGS{C_FILE}" or die "Can't open $ARGS{C_FILE}: $!";
478	open my $xs_fh, ">$ARGS{XS_FILE}" or die "Can't open $ARGS{XS_FILE}: $!";
479
480	# As this subroutine is intended to make code that isn't edited, there's no
481	# need for the user to specify any types that aren't found in the list of
482	# names.
483	my $types = {};
484
485	print $c_fh constant_types(); # macro defs
486	print $c_fh "\n";
487
488	# indent is still undef. Until anyone implements indent style rules with it.
489	foreach (ExtUtils::Constant::XS->C_constant({package => $ARGS{NAME},
490	subname => $ARGS{C_SUBNAME},
491	default_type =>
492	$ARGS{DEFAULT_TYPE},
493	types => $types,
494	breakout => $ARGS{BREAKOUT_AT}},
495	@{$ARGS{NAMES}})) {
496	print $c_fh $_, "\n"; # C constant subs
497	}
498	print $xs_fh XS_constant ($ARGS{NAME}, $types, $ARGS{XS_SUBNAME},
499	$ARGS{C_SUBNAME});
500
501	close $c_fh or warn "Error closing $ARGS{C_FILE}: $!";
502	close $xs_fh or warn "Error closing $ARGS{XS_FILE}: $!";
503	}
504
505	1;
506	__END__
507
508	=back
509
510	=head1 AUTHOR
511
512	Nicholas Clark <nick@ccl4.org> based on the code in C<h2xs> by Larry Wall and
513	others
514
515	=cut