share/automake-1.11/Automake/Struct.pm - toolchains/kvm - Git at Google

 # autoconf -- create `configure' using m4 macros
 # Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc.

 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation; either version 2, or (at your option)
 # any later version.

 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.

 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.

 # This file is basically Perl 5.6's Class::Struct, but made compatible
 # with Perl 5.5.  If someday this has to be updated, be sure to rename
 # all the occurrences of Class::Struct into Automake::Struct, otherwise
 # if we `use' a Perl module (e.g., File::stat) that uses Class::Struct,
 # we would have two packages defining the same symbols.  Boom.

 ###############################################################
 # The main copy of this file is in Automake's CVS repository. #
 # Updates should be sent to automake-patches@gnu.org.         #
 ###############################################################

 package Automake::Struct;

 ## See POD after __END__

 use 5.005_03;

 use strict;
 use vars qw(@ISA @EXPORT $VERSION);

 use Carp;

 require Exporter;
 @ISA = qw(Exporter);
 @EXPORT = qw(struct);

 $VERSION = '0.58';

 ## Tested on 5.002 and 5.003 without class membership tests:
 my $CHECK_CLASS_MEMBERSHIP = ($] >= 5.003_95);

 my $print = 0;
 sub printem {
     if (@_) { $print = shift }
     else    { $print++ }
 }

 {
     package Automake::Struct::Tie_ISA;

     sub TIEARRAY {
         my $class = shift;
         return bless [], $class;
     }

     sub STORE {
         my ($self, $index, $value) = @_;
         Automake::Struct::_subclass_error();
     }

     sub FETCH {
         my ($self, $index) = @_;
         $self->[$index];
     }

     sub FETCHSIZE {
         my $self = shift;
         return scalar(@$self);
     }

     sub DESTROY { }
 }

 sub struct {

     # Determine parameter list structure, one of:
     #   struct( class => [ element-list ])
     #   struct( class => { element-list })
     #   struct( element-list )
     # Latter form assumes current package name as struct name.

     my ($class, @decls);
     my $base_type = ref $_[1];
     if ( $base_type eq 'HASH' ) {
         $class = shift;
         @decls = %{shift()};
         _usage_error() if @_;
     }
     elsif ( $base_type eq 'ARRAY' ) {
         $class = shift;
         @decls = @{shift()};
         _usage_error() if @_;
     }
     else {
         $base_type = 'ARRAY';
         $class = (caller())[0];
         @decls = @_;
     }
     _usage_error() if @decls % 2 == 1;

     # Ensure we are not, and will not be, a subclass.

     my $isa = do {
         no strict 'refs';
         \@{$class . '::ISA'};
     };
     _subclass_error() if @$isa;
     tie @$isa, 'Automake::Struct::Tie_ISA';

     # Create constructor.

     croak "function 'new' already defined in package $class"
         if do { no strict 'refs'; defined &{$class . "::new"} };

     my @methods = ();
     my %refs = ();
     my %arrays = ();
     my %hashes = ();
     my %classes = ();
     my $got_class = 0;
     my $out = '';

     $out = "{\n  package $class;\n  use Carp;\n  sub new {\n";
     $out .= "    my (\$class, \%init) = \@_;\n";
     $out .= "    \$class = __PACKAGE__ unless \@_;\n";

     my $cnt = 0;
     my $idx = 0;
     my( $cmt, $name, $type, $elem );

     if( $base_type eq 'HASH' ){
         $out .= "    my(\$r) = {};\n";
         $cmt = '';
     }
     elsif( $base_type eq 'ARRAY' ){
         $out .= "    my(\$r) = [];\n";
     }
     while( $idx < @decls ){
         $name = $decls[$idx];
         $type = $decls[$idx+1];
         push( @methods, $name );
         if( $base_type eq 'HASH' ){
             $elem = "{'${class}::$name'}";
         }
         elsif( $base_type eq 'ARRAY' ){
             $elem = "[$cnt]";
             ++$cnt;
             $cmt = " # $name";
         }
         if( $type =~ /^\*(.)/ ){
             $refs{$name}++;
             $type = $1;
         }
         my $init = "defined(\$init{'$name'}) ? \$init{'$name'} :";
         if( $type eq '@' ){
             $out .= "    croak 'Initializer for $name must be array reference'\n";
             $out .= "        if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'ARRAY';\n";
             $out .= "    \$r->$elem = $init [];$cmt\n";
             $arrays{$name}++;
         }
         elsif( $type eq '%' ){
             $out .= "    croak 'Initializer for $name must be hash reference'\n";
             $out .= "        if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n";
             $out .= "    \$r->$elem = $init {};$cmt\n";
             $hashes{$name}++;
         }
         elsif ( $type eq '$') {
             $out .= "    \$r->$elem = $init undef;$cmt\n";
         }
         elsif( $type =~ /^\w+(?:::\w+)*$/ ){
             $init = "defined(\$init{'$name'}) ? \%{\$init{'$name'}} : ()";
             $out .= "    croak 'Initializer for $name must be hash reference'\n";
             $out .= "        if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n";
             $out .= "    \$r->$elem = '${type}'->new($init);$cmt\n";
             $classes{$name} = $type;
             $got_class = 1;
         }
         else{
             croak "'$type' is not a valid struct element type";
         }
         $idx += 2;
     }
     $out .= "    bless \$r, \$class;\n  }\n";

     # Create accessor methods.

     my( $pre, $pst, $sel );
     $cnt = 0;
     foreach $name (@methods){
         if ( do { no strict 'refs'; defined &{$class . "::$name"} } ) {
             carp "function '$name' already defined, overrides struct accessor method";
         }
         else {
             $pre = $pst = $cmt = $sel = '';
             if( defined $refs{$name} ){
                 $pre = "\\(";
                 $pst = ")";
                 $cmt = " # returns ref";
             }
             $out .= "  sub $name {$cmt\n    my \$r = shift;\n";
             if( $base_type eq 'ARRAY' ){
                 $elem = "[$cnt]";
                 ++$cnt;
             }
             elsif( $base_type eq 'HASH' ){
                 $elem = "{'${class}::$name'}";
             }
             if( defined $arrays{$name} ){
                 $out .= "    my \$i;\n";
                 $out .= "    \@_ ? (\$i = shift) : return \$r->$elem;\n";
                 $sel = "->[\$i]";
             }
             elsif( defined $hashes{$name} ){
                 $out .= "    my \$i;\n";
                 $out .= "    \@_ ? (\$i = shift) : return \$r->$elem;\n";
                 $sel = "->{\$i}";
             }
             elsif( defined $classes{$name} ){
                 if ( $CHECK_CLASS_MEMBERSHIP ) {
                     $out .= "    croak '$name argument is wrong class' if \@_ && ! UNIVERSAL::isa(\$_[0], '$classes{$name}');\n";
                 }
             }
             $out .= "    croak 'Too many args to $name' if \@_ > 1;\n";
             $out .= "    \@_ ? ($pre\$r->$elem$sel = shift$pst) : $pre\$r->$elem$sel$pst;\n";
             $out .= "  }\n";
         }
     }
     $out .= "}\n1;\n";

     print $out if $print;
     my $result = eval $out;
     carp $@ if $@;
 }

 sub _usage_error {
     confess "struct usage error";
 }

 sub _subclass_error {
     croak 'struct class cannot be a subclass (@ISA not allowed)';
 }

 1; # for require


 __END__

 =head1 NAME

 Automake::Struct - declare struct-like datatypes as Perl classes

 =head1 SYNOPSIS

     use Automake::Struct;
             # declare struct, based on array:
     struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]);
             # declare struct, based on hash:
     struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... });

     package CLASS_NAME;
     use Automake::Struct;
             # declare struct, based on array, implicit class name:
     struct( ELEMENT_NAME => ELEMENT_TYPE, ... );


     package Myobj;
     use Automake::Struct;
             # declare struct with four types of elements:
     struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' );

     $obj = new Myobj;               # constructor

                                     # scalar type accessor:
     $element_value = $obj->s;           # element value
     $obj->s('new value');               # assign to element

                                     # array type accessor:
     $ary_ref = $obj->a;                 # reference to whole array
     $ary_element_value = $obj->a(2);    # array element value
     $obj->a(2, 'new value');            # assign to array element

                                     # hash type accessor:
     $hash_ref = $obj->h;                # reference to whole hash
     $hash_element_value = $obj->h('x'); # hash element value
     $obj->h('x', 'new value');        # assign to hash element

                                     # class type accessor:
     $element_value = $obj->c;           # object reference
     $obj->c->method(...);               # call method of object
     $obj->c(new My_Other_Class);        # assign a new object


 =head1 DESCRIPTION

 C<Automake::Struct> exports a single function, C<struct>.
 Given a list of element names and types, and optionally
 a class name, C<struct> creates a Perl 5 class that implements
 a "struct-like" data structure.

 The new class is given a constructor method, C<new>, for creating
 struct objects.

 Each element in the struct data has an accessor method, which is
 used to assign to the element and to fetch its value.  The
 default accessor can be overridden by declaring a C<sub> of the
 same name in the package.  (See Example 2.)

 Each element's type can be scalar, array, hash, or class.


 =head2 The C<struct()> function

 The C<struct> function has three forms of parameter-list.

     struct( CLASS_NAME => [ ELEMENT_LIST ]);
     struct( CLASS_NAME => { ELEMENT_LIST });
     struct( ELEMENT_LIST );

 The first and second forms explicitly identify the name of the
 class being created.  The third form assumes the current package
 name as the class name.

 An object of a class created by the first and third forms is
 based on an array, whereas an object of a class created by the
 second form is based on a hash. The array-based forms will be
 somewhat faster and smaller; the hash-based forms are more
 flexible.

 The class created by C<struct> must not be a subclass of another
 class other than C<UNIVERSAL>.

 It can, however, be used as a superclass for other classes. To facilitate
 this, the generated constructor method uses a two-argument blessing.
 Furthermore, if the class is hash-based, the key of each element is
 prefixed with the class name (see I<Perl Cookbook>, Recipe 13.12).

 A function named C<new> must not be explicitly defined in a class
 created by C<struct>.

 The I<ELEMENT_LIST> has the form

     NAME => TYPE, ...

 Each name-type pair declares one element of the struct. Each
 element name will be defined as an accessor method unless a
 method by that name is explicitly defined; in the latter case, a
 warning is issued if the warning flag (B<-w>) is set.


 =head2 Element Types and Accessor Methods

 The four element types -- scalar, array, hash, and class -- are
 represented by strings -- C<'$'>, C<'@'>, C<'%'>, and a class name --
 optionally preceded by a C<'*'>.

 The accessor method provided by C<struct> for an element depends
 on the declared type of the element.

 =over

 =item Scalar (C<'$'> or C<'*$'>)

 The element is a scalar, and by default is initialized to C<undef>
 (but see L<Initializing with new>).

 The accessor's argument, if any, is assigned to the element.

 If the element type is C<'$'>, the value of the element (after
 assignment) is returned. If the element type is C<'*$'>, a reference
 to the element is returned.

 =item Array (C<'@'> or C<'*@'>)

 The element is an array, initialized by default to C<()>.

 With no argument, the accessor returns a reference to the
 element's whole array (whether or not the element was
 specified as C<'@'> or C<'*@'>).

 With one or two arguments, the first argument is an index
 specifying one element of the array; the second argument, if
 present, is assigned to the array element.  If the element type
 is C<'@'>, the accessor returns the array element value.  If the
 element type is C<'*@'>, a reference to the array element is
 returned.

 =item Hash (C<'%'> or C<'*%'>)

 The element is a hash, initialized by default to C<()>.

 With no argument, the accessor returns a reference to the
 element's whole hash (whether or not the element was
 specified as C<'%'> or C<'*%'>).

 With one or two arguments, the first argument is a key specifying
 one element of the hash; the second argument, if present, is
 assigned to the hash element.  If the element type is C<'%'>, the
 accessor returns the hash element value.  If the element type is
 C<'*%'>, a reference to the hash element is returned.

 =item Class (C<'Class_Name'> or C<'*Class_Name'>)

 The element's value must be a reference blessed to the named
 class or to one of its subclasses. The element is initialized to
 the result of calling the C<new> constructor of the named class.

 The accessor's argument, if any, is assigned to the element. The
 accessor will C<croak> if this is not an appropriate object
 reference.

 If the element type does not start with a C<'*'>, the accessor
 returns the element value (after assignment). If the element type
 starts with a C<'*'>, a reference to the element itself is returned.

 =back

 =head2 Initializing with C<new>

 C<struct> always creates a constructor called C<new>. That constructor
 may take a list of initializers for the various elements of the new
 struct.

 Each initializer is a pair of values: I<element name>C< =E<gt> >I<value>.
 The initializer value for a scalar element is just a scalar value. The
 initializer for an array element is an array reference. The initializer
 for a hash is a hash reference.

 The initializer for a class element is also a hash reference, and the
 contents of that hash are passed to the element's own constructor.

 See Example 3 below for an example of initialization.


 =head1 EXAMPLES

 =over

 =item Example 1

 Giving a struct element a class type that is also a struct is how
 structs are nested.  Here, C<timeval> represents a time (seconds and
 microseconds), and C<rusage> has two elements, each of which is of
 type C<timeval>.

     use Automake::Struct;

     struct( rusage => {
         ru_utime => timeval,  # seconds
         ru_stime => timeval,  # microseconds
     });

     struct( timeval => [
         tv_secs  => '$',
         tv_usecs => '$',
     ]);

         # create an object:
     my $t = new rusage;

         # $t->ru_utime and $t->ru_stime are objects of type timeval.
         # set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec.
     $t->ru_utime->tv_secs(100);
     $t->ru_utime->tv_usecs(0);
     $t->ru_stime->tv_secs(5);
     $t->ru_stime->tv_usecs(0);


 =item Example 2

 An accessor function can be redefined in order to provide
 additional checking of values, etc.  Here, we want the C<count>
 element always to be nonnegative, so we redefine the C<count>
 accessor accordingly.

     package MyObj;
     use Automake::Struct;

     # declare the struct
     struct ( 'MyObj', { count => '$', stuff => '%' } );

     # override the default accessor method for 'count'
     sub count {
         my $self = shift;
         if ( @_ ) {
             die 'count must be nonnegative' if $_[0] < 0;
             $self->{'count'} = shift;
             warn "Too many args to count" if @_;
         }
         return $self->{'count'};
     }

     package main;
     $x = new MyObj;
     print "\$x->count(5) = ", $x->count(5), "\n";
                             # prints '$x->count(5) = 5'

     print "\$x->count = ", $x->count, "\n";
                             # prints '$x->count = 5'

     print "\$x->count(-5) = ", $x->count(-5), "\n";
                             # dies due to negative argument!

 =item Example 3

 The constructor of a generated class can be passed a list
 of I<element>=>I<value> pairs, with which to initialize the struct.
 If no initializer is specified for a particular element, its default
 initialization is performed instead. Initializers for non-existent
 elements are silently ignored.

 Note that the initializer for a nested struct is specified
 as an anonymous hash of initializers, which is passed on to the nested
 struct's constructor.


     use Automake::Struct;

     struct Breed =>
     {
         name  => '$',
         cross => '$',
     };

     struct Cat =>
     [
         name     => '$',
         kittens  => '@',
         markings => '%',
         breed    => 'Breed',
     ];


     my $cat = Cat->new( name     => 'Socks',
                         kittens  => ['Monica', 'Kenneth'],
                         markings => { socks=>1, blaze=>"white" },
                         breed    => { name=>'short-hair', cross=>1 },
                       );

     print "Once a cat called ", $cat->name, "\n";
     print "(which was a ", $cat->breed->name, ")\n";
     print "had two kittens: ", join(' and ', @{$cat->kittens}), "\n";

 =back

 =head1 Author and Modification History

 Modified by Akim Demaille, 2001-08-03

     Rename as Automake::Struct to avoid name clashes with
     Class::Struct.

     Make it compatible with Perl 5.5.

 Modified by Damian Conway, 1999-03-05, v0.58.

     Added handling of hash-like arg list to class ctor.

     Changed to two-argument blessing in ctor to support
     derivation from created classes.

     Added classname prefixes to keys in hash-based classes
     (refer to "Perl Cookbook", Recipe 13.12 for rationale).

     Corrected behavior of accessors for '*@' and '*%' struct
     elements.  Package now implements documented behavior when
     returning a reference to an entire hash or array element.
     Previously these were returned as a reference to a reference
     to the element.


 Renamed to C<Class::Struct> and modified by Jim Miner, 1997-04-02.

     members() function removed.
     Documentation corrected and extended.
     Use of struct() in a subclass prohibited.
     User definition of accessor allowed.
     Treatment of '*' in element types corrected.
     Treatment of classes as element types corrected.
     Class name to struct() made optional.
     Diagnostic checks added.


 Originally C<Class::Template> by Dean Roehrich.

     # Template.pm   --- struct/member template builder
     #   12mar95
     #   Dean Roehrich
     #
     # changes/bugs fixed since 28nov94 version:
     #  - podified
     # changes/bugs fixed since 21nov94 version:
     #  - Fixed examples.
     # changes/bugs fixed since 02sep94 version:
     #  - Moved to Class::Template.
     # changes/bugs fixed since 20feb94 version:
     #  - Updated to be a more proper module.
     #  - Added "use strict".
     #  - Bug in build_methods, was using @var when @$var needed.
     #  - Now using my() rather than local().
     #
     # Uses perl5 classes to create nested data types.
     # This is offered as one implementation of Tom Christiansen's "structs.pl"
     # idea.

 =cut

 ### Setup "GNU" style for perl-mode and cperl-mode.
 ## Local Variables:
 ## perl-indent-level: 2
 ## perl-continued-statement-offset: 2
 ## perl-continued-brace-offset: 0
 ## perl-brace-offset: 0
 ## perl-brace-imaginary-offset: 0
 ## perl-label-offset: -2
 ## cperl-indent-level: 2
 ## cperl-brace-offset: 0
 ## cperl-continued-brace-offset: 0
 ## cperl-label-offset: -2
 ## cperl-extra-newline-before-brace: t
 ## cperl-merge-trailing-else: nil
 ## cperl-continued-statement-offset: 2
 ## End:
	# autoconf -- create `configure' using m4 macros
	# Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc.

	# This program is free software; you can redistribute it and/or modify
	# it under the terms of the GNU General Public License as published by
	# the Free Software Foundation; either version 2, or (at your option)
	# any later version.

	# This program is distributed in the hope that it will be useful,
	# but WITHOUT ANY WARRANTY; without even the implied warranty of
	# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	# GNU General Public License for more details.

	# You should have received a copy of the GNU General Public License
	# along with this program. If not, see <http://www.gnu.org/licenses/>.

	# This file is basically Perl 5.6's Class::Struct, but made compatible
	# with Perl 5.5. If someday this has to be updated, be sure to rename
	# all the occurrences of Class::Struct into Automake::Struct, otherwise
	# if we `use' a Perl module (e.g., File::stat) that uses Class::Struct,
	# we would have two packages defining the same symbols. Boom.

	###############################################################
	# The main copy of this file is in Automake's CVS repository. #
	# Updates should be sent to automake-patches@gnu.org. #
	###############################################################

	package Automake::Struct;

	## See POD after __END__

	use 5.005_03;

	use strict;
	use vars qw(@ISA @EXPORT $VERSION);

	use Carp;

	require Exporter;
	@ISA = qw(Exporter);
	@EXPORT = qw(struct);

	$VERSION = '0.58';

	## Tested on 5.002 and 5.003 without class membership tests:
	my $CHECK_CLASS_MEMBERSHIP = ($] >= 5.003_95);

	my $print = 0;
	sub printem {
	if (@_) { $print = shift }
	else { $print++ }
	}

	{
	package Automake::Struct::Tie_ISA;

	sub TIEARRAY {
	my $class = shift;
	return bless [], $class;
	}

	sub STORE {
	my ($self, $index, $value) = @_;
	Automake::Struct::_subclass_error();
	}

	sub FETCH {
	my ($self, $index) = @_;
	$self->[$index];
	}

	sub FETCHSIZE {
	my $self = shift;
	return scalar(@$self);
	}

	sub DESTROY { }
	}

	sub struct {

	# Determine parameter list structure, one of:
	# struct( class => [ element-list ])
	# struct( class => { element-list })
	# struct( element-list )
	# Latter form assumes current package name as struct name.

	my ($class, @decls);
	my $base_type = ref $_[1];
	if ( $base_type eq 'HASH' ) {
	$class = shift;
	@decls = %{shift()};
	_usage_error() if @_;
	}
	elsif ( $base_type eq 'ARRAY' ) {
	$class = shift;
	@decls = @{shift()};
	_usage_error() if @_;
	}
	else {
	$base_type = 'ARRAY';
	$class = (caller())[0];
	@decls = @_;
	}
	_usage_error() if @decls % 2 == 1;

	# Ensure we are not, and will not be, a subclass.

	my $isa = do {
	no strict 'refs';
	\@{$class . '::ISA'};
	};
	_subclass_error() if @$isa;
	tie @$isa, 'Automake::Struct::Tie_ISA';

	# Create constructor.

	croak "function 'new' already defined in package $class"
	if do { no strict 'refs'; defined &{$class . "::new"} };

	my @methods = ();
	my %refs = ();
	my %arrays = ();
	my %hashes = ();
	my %classes = ();
	my $got_class = 0;
	my $out = '';

	$out = "{\n package $class;\n use Carp;\n sub new {\n";
	$out .= " my (\$class, \%init) = \@_;\n";
	$out .= " \$class = __PACKAGE__ unless \@_;\n";

	my $cnt = 0;
	my $idx = 0;
	my( $cmt, $name, $type, $elem );

	if( $base_type eq 'HASH' ){
	$out .= " my(\$r) = {};\n";
	$cmt = '';
	}
	elsif( $base_type eq 'ARRAY' ){
	$out .= " my(\$r) = [];\n";
	}
	while( $idx < @decls ){
	$name = $decls[$idx];
	$type = $decls[$idx+1];
	push( @methods, $name );
	if( $base_type eq 'HASH' ){
	$elem = "{'${class}::$name'}";
	}
	elsif( $base_type eq 'ARRAY' ){
	$elem = "[$cnt]";
	++$cnt;
	$cmt = " # $name";
	}
	if( $type =~ /^\*(.)/ ){
	$refs{$name}++;
	$type = $1;
	}
	my $init = "defined(\$init{'$name'}) ? \$init{'$name'} :";
	if( $type eq '@' ){
	$out .= " croak 'Initializer for $name must be array reference'\n";
	$out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'ARRAY';\n";
	$out .= " \$r->$elem = $init [];$cmt\n";
	$arrays{$name}++;
	}
	elsif( $type eq '%' ){
	$out .= " croak 'Initializer for $name must be hash reference'\n";
	$out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n";
	$out .= " \$r->$elem = $init {};$cmt\n";
	$hashes{$name}++;
	}
	elsif ( $type eq '$') {
	$out .= " \$r->$elem = $init undef;$cmt\n";
	}
	elsif( $type =~ /^\w+(?:::\w+)*$/ ){
	$init = "defined(\$init{'$name'}) ? \%{\$init{'$name'}} : ()";
	$out .= " croak 'Initializer for $name must be hash reference'\n";
	$out .= " if defined(\$init{'$name'}) && ref(\$init{'$name'}) ne 'HASH';\n";
	$out .= " \$r->$elem = '${type}'->new($init);$cmt\n";
	$classes{$name} = $type;
	$got_class = 1;
	}
	else{
	croak "'$type' is not a valid struct element type";
	}
	$idx += 2;
	}
	$out .= " bless \$r, \$class;\n }\n";

	# Create accessor methods.

	my( $pre, $pst, $sel );
	$cnt = 0;
	foreach $name (@methods){
	if ( do { no strict 'refs'; defined &{$class . "::$name"} } ) {
	carp "function '$name' already defined, overrides struct accessor method";
	}
	else {
	$pre = $pst = $cmt = $sel = '';
	if( defined $refs{$name} ){
	$pre = "\\(";
	$pst = ")";
	$cmt = " # returns ref";
	}
	$out .= " sub $name {$cmt\n my \$r = shift;\n";
	if( $base_type eq 'ARRAY' ){
	$elem = "[$cnt]";
	++$cnt;
	}
	elsif( $base_type eq 'HASH' ){
	$elem = "{'${class}::$name'}";
	}
	if( defined $arrays{$name} ){
	$out .= " my \$i;\n";
	$out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
	$sel = "->[\$i]";
	}
	elsif( defined $hashes{$name} ){
	$out .= " my \$i;\n";
	$out .= " \@_ ? (\$i = shift) : return \$r->$elem;\n";
	$sel = "->{\$i}";
	}
	elsif( defined $classes{$name} ){
	if ( $CHECK_CLASS_MEMBERSHIP ) {
	$out .= " croak '$name argument is wrong class' if \@_ && ! UNIVERSAL::isa(\$_[0], '$classes{$name}');\n";
	}
	}
	$out .= " croak 'Too many args to $name' if \@_ > 1;\n";
	$out .= " \@_ ? ($pre\$r->$elem$sel = shift$pst) : $pre\$r->$elem$sel$pst;\n";
	$out .= " }\n";
	}
	}
	$out .= "}\n1;\n";

	print $out if $print;
	my $result = eval $out;
	carp $@ if $@;
	}

	sub _usage_error {
	confess "struct usage error";
	}

	sub _subclass_error {
	croak 'struct class cannot be a subclass (@ISA not allowed)';
	}

	1; # for require


	__END__

	=head1 NAME

	Automake::Struct - declare struct-like datatypes as Perl classes

	=head1 SYNOPSIS

	use Automake::Struct;
	# declare struct, based on array:
	struct( CLASS_NAME => [ ELEMENT_NAME => ELEMENT_TYPE, ... ]);
	# declare struct, based on hash:
	struct( CLASS_NAME => { ELEMENT_NAME => ELEMENT_TYPE, ... });

	package CLASS_NAME;
	use Automake::Struct;
	# declare struct, based on array, implicit class name:
	struct( ELEMENT_NAME => ELEMENT_TYPE, ... );


	package Myobj;
	use Automake::Struct;
	# declare struct with four types of elements:
	struct( s => '$', a => '@', h => '%', c => 'My_Other_Class' );

	$obj = new Myobj; # constructor

	# scalar type accessor:
	$element_value = $obj->s; # element value
	$obj->s('new value'); # assign to element

	# array type accessor:
	$ary_ref = $obj->a; # reference to whole array
	$ary_element_value = $obj->a(2); # array element value
	$obj->a(2, 'new value'); # assign to array element

	# hash type accessor:
	$hash_ref = $obj->h; # reference to whole hash
	$hash_element_value = $obj->h('x'); # hash element value
	$obj->h('x', 'new value'); # assign to hash element

	# class type accessor:
	$element_value = $obj->c; # object reference
	$obj->c->method(...); # call method of object
	$obj->c(new My_Other_Class); # assign a new object


	=head1 DESCRIPTION

	C<Automake::Struct> exports a single function, C<struct>.
	Given a list of element names and types, and optionally
	a class name, C<struct> creates a Perl 5 class that implements
	a "struct-like" data structure.

	The new class is given a constructor method, C<new>, for creating
	struct objects.

	Each element in the struct data has an accessor method, which is
	used to assign to the element and to fetch its value. The
	default accessor can be overridden by declaring a C<sub> of the
	same name in the package. (See Example 2.)

	Each element's type can be scalar, array, hash, or class.


	=head2 The C<struct()> function

	The C<struct> function has three forms of parameter-list.

	struct( CLASS_NAME => [ ELEMENT_LIST ]);
	struct( CLASS_NAME => { ELEMENT_LIST });
	struct( ELEMENT_LIST );

	The first and second forms explicitly identify the name of the
	class being created. The third form assumes the current package
	name as the class name.

	An object of a class created by the first and third forms is
	based on an array, whereas an object of a class created by the
	second form is based on a hash. The array-based forms will be
	somewhat faster and smaller; the hash-based forms are more
	flexible.

	The class created by C<struct> must not be a subclass of another
	class other than C<UNIVERSAL>.

	It can, however, be used as a superclass for other classes. To facilitate
	this, the generated constructor method uses a two-argument blessing.
	Furthermore, if the class is hash-based, the key of each element is
	prefixed with the class name (see I<Perl Cookbook>, Recipe 13.12).

	A function named C<new> must not be explicitly defined in a class
	created by C<struct>.

	The I<ELEMENT_LIST> has the form

	NAME => TYPE, ...

	Each name-type pair declares one element of the struct. Each
	element name will be defined as an accessor method unless a
	method by that name is explicitly defined; in the latter case, a
	warning is issued if the warning flag (B<-w>) is set.


	=head2 Element Types and Accessor Methods

	The four element types -- scalar, array, hash, and class -- are
	represented by strings -- C<'$'>, C<'@'>, C<'%'>, and a class name --
	optionally preceded by a C<'*'>.

	The accessor method provided by C<struct> for an element depends
	on the declared type of the element.

	=over

	=item Scalar (C<'$'> or C<'*$'>)

	The element is a scalar, and by default is initialized to C<undef>
	(but see L<Initializing with new>).

	The accessor's argument, if any, is assigned to the element.

	If the element type is C<'$'>, the value of the element (after
	assignment) is returned. If the element type is C<'*$'>, a reference
	to the element is returned.

	=item Array (C<'@'> or C<'*@'>)

	The element is an array, initialized by default to C<()>.

	With no argument, the accessor returns a reference to the
	element's whole array (whether or not the element was
	specified as C<'@'> or C<'*@'>).

	With one or two arguments, the first argument is an index
	specifying one element of the array; the second argument, if
	present, is assigned to the array element. If the element type
	is C<'@'>, the accessor returns the array element value. If the
	element type is C<'*@'>, a reference to the array element is
	returned.

	=item Hash (C<'%'> or C<'*%'>)

	The element is a hash, initialized by default to C<()>.

	With no argument, the accessor returns a reference to the
	element's whole hash (whether or not the element was
	specified as C<'%'> or C<'*%'>).

	With one or two arguments, the first argument is a key specifying
	one element of the hash; the second argument, if present, is
	assigned to the hash element. If the element type is C<'%'>, the
	accessor returns the hash element value. If the element type is
	C<'*%'>, a reference to the hash element is returned.

	=item Class (C<'Class_Name'> or C<'*Class_Name'>)

	The element's value must be a reference blessed to the named
	class or to one of its subclasses. The element is initialized to
	the result of calling the C<new> constructor of the named class.

	The accessor's argument, if any, is assigned to the element. The
	accessor will C<croak> if this is not an appropriate object
	reference.

	If the element type does not start with a C<'*'>, the accessor
	returns the element value (after assignment). If the element type
	starts with a C<'*'>, a reference to the element itself is returned.

	=back

	=head2 Initializing with C<new>

	C<struct> always creates a constructor called C<new>. That constructor
	may take a list of initializers for the various elements of the new
	struct.

	Each initializer is a pair of values: I<element name>C< =E<gt> >I<value>.
	The initializer value for a scalar element is just a scalar value. The
	initializer for an array element is an array reference. The initializer
	for a hash is a hash reference.

	The initializer for a class element is also a hash reference, and the
	contents of that hash are passed to the element's own constructor.

	See Example 3 below for an example of initialization.


	=head1 EXAMPLES

	=over

	=item Example 1

	Giving a struct element a class type that is also a struct is how
	structs are nested. Here, C<timeval> represents a time (seconds and
	microseconds), and C<rusage> has two elements, each of which is of
	type C<timeval>.

	use Automake::Struct;

	struct( rusage => {
	ru_utime => timeval, # seconds
	ru_stime => timeval, # microseconds
	});

	struct( timeval => [
	tv_secs => '$',
	tv_usecs => '$',
	]);

	# create an object:
	my $t = new rusage;

	# $t->ru_utime and $t->ru_stime are objects of type timeval.
	# set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec.
	$t->ru_utime->tv_secs(100);
	$t->ru_utime->tv_usecs(0);
	$t->ru_stime->tv_secs(5);
	$t->ru_stime->tv_usecs(0);


	=item Example 2

	An accessor function can be redefined in order to provide
	additional checking of values, etc. Here, we want the C<count>
	element always to be nonnegative, so we redefine the C<count>
	accessor accordingly.

	package MyObj;
	use Automake::Struct;

	# declare the struct
	struct ( 'MyObj', { count => '$', stuff => '%' } );

	# override the default accessor method for 'count'
	sub count {
	my $self = shift;
	if ( @_ ) {
	die 'count must be nonnegative' if $_[0] < 0;
	$self->{'count'} = shift;
	warn "Too many args to count" if @_;
	}
	return $self->{'count'};
	}

	package main;
	$x = new MyObj;
	print "\$x->count(5) = ", $x->count(5), "\n";
	# prints '$x->count(5) = 5'

	print "\$x->count = ", $x->count, "\n";
	# prints '$x->count = 5'

	print "\$x->count(-5) = ", $x->count(-5), "\n";
	# dies due to negative argument!

	=item Example 3

	The constructor of a generated class can be passed a list
	of I<element>=>I<value> pairs, with which to initialize the struct.
	If no initializer is specified for a particular element, its default
	initialization is performed instead. Initializers for non-existent
	elements are silently ignored.

	Note that the initializer for a nested struct is specified
	as an anonymous hash of initializers, which is passed on to the nested
	struct's constructor.


	use Automake::Struct;

	struct Breed =>
	{
	name => '$',
	cross => '$',
	};

	struct Cat =>
	[
	name => '$',
	kittens => '@',
	markings => '%',
	breed => 'Breed',
	];


	my $cat = Cat->new( name => 'Socks',
	kittens => ['Monica', 'Kenneth'],
	markings => { socks=>1, blaze=>"white" },
	breed => { name=>'short-hair', cross=>1 },
	);

	print "Once a cat called ", $cat->name, "\n";
	print "(which was a ", $cat->breed->name, ")\n";
	print "had two kittens: ", join(' and ', @{$cat->kittens}), "\n";

	=back

	=head1 Author and Modification History

	Modified by Akim Demaille, 2001-08-03

	Rename as Automake::Struct to avoid name clashes with
	Class::Struct.

	Make it compatible with Perl 5.5.

	Modified by Damian Conway, 1999-03-05, v0.58.

	Added handling of hash-like arg list to class ctor.

	Changed to two-argument blessing in ctor to support
	derivation from created classes.

	Added classname prefixes to keys in hash-based classes
	(refer to "Perl Cookbook", Recipe 13.12 for rationale).

	Corrected behavior of accessors for '@' and '%' struct
	elements. Package now implements documented behavior when
	returning a reference to an entire hash or array element.
	Previously these were returned as a reference to a reference
	to the element.


	Renamed to C<Class::Struct> and modified by Jim Miner, 1997-04-02.

	members() function removed.
	Documentation corrected and extended.
	Use of struct() in a subclass prohibited.
	User definition of accessor allowed.
	Treatment of '*' in element types corrected.
	Treatment of classes as element types corrected.
	Class name to struct() made optional.
	Diagnostic checks added.


	Originally C<Class::Template> by Dean Roehrich.

	# Template.pm --- struct/member template builder
	# 12mar95
	# Dean Roehrich
	#
	# changes/bugs fixed since 28nov94 version:
	# - podified
	# changes/bugs fixed since 21nov94 version:
	# - Fixed examples.
	# changes/bugs fixed since 02sep94 version:
	# - Moved to Class::Template.
	# changes/bugs fixed since 20feb94 version:
	# - Updated to be a more proper module.
	# - Added "use strict".
	# - Bug in build_methods, was using @var when @$var needed.
	# - Now using my() rather than local().
	#
	# Uses perl5 classes to create nested data types.
	# This is offered as one implementation of Tom Christiansen's "structs.pl"
	# idea.

	=cut

	### Setup "GNU" style for perl-mode and cperl-mode.
	## Local Variables:
	## perl-indent-level: 2
	## perl-continued-statement-offset: 2
	## perl-continued-brace-offset: 0
	## perl-brace-offset: 0
	## perl-brace-imaginary-offset: 0
	## perl-label-offset: -2
	## cperl-indent-level: 2
	## cperl-brace-offset: 0
	## cperl-continued-brace-offset: 0
	## cperl-label-offset: -2
	## cperl-extra-newline-before-brace: t
	## cperl-merge-trailing-else: nil
	## cperl-continued-statement-offset: 2
	## End: