NAME

       FFI::Platypus::Record - FFI support for structured records data

VERSION

       version 0.47

SYNOPSIS

       C:

        struct my_person {
          int         age;
          const char  title[3];
          const char *name
        };

        void process_person(struct my_person *person)
        {
          /* ... */
        }

       Perl:

        package MyPerson;

        use FFI::Platypus::Record;

        record_layout(qw(
          int       age
          string(3) title
          string_rw name
        );

        package main;

        use FFI::Platypus;

        my $ffi = FFI::Platypus->new;
        $ffi->lib("myperson.so");
        $ffi->type("record(MyPerson)" => 'MyPerson');

        my $person = MyPerson->new(
          age   => 40,
          title => "Mr.",
          name  => "John Smith",
        );

        $ffi->attach( process_person => [ 'MyPerson' ] => 'void' );

        process_person($person);

        $person->age($person->age + 1); # another year older

        process_person($person);

DESCRIPTION

       [version 0.21]

       This module provides a mechanism for building classes that can be used to mange structured
       data records (known as C as "structs" and in some languages as "records").  A structured
       record is a series of bytes that have structure understood by the C or other foreign
       language library that you are interfacing with.  It is designed for use with FFI and
       FFI::Platypus, though it may have other applications.

FUNCTIONS

   record_layout
        record_layout($ffi, $type => $name, ... );
        record_layout($type => $name, ... );

       Define the layout of the record.  You may optionally provide an instance of FFI::Platypus
       as the first argument in order to use its type aliases.  Then you provide members as
       type/name pairs.

       For each member you declare, "record_layout" will create an accessor which can be used to
       read and write its value. For example imagine a class "Foo":

        package Foo;

        use FFI::Platypus::Record;

        record_layout(
          int          => 'bar',  #  int bar;
          'string(10)' => 'baz',  #  char baz[10];
        );

       You can get and set its fields with like named "bar" and "baz" accessors:

        my $foo = Foo->new;

        $foo->bar(22);
        my $value = $foo->bar;

        $foo->baz("grimlock\0\0"); # should be 10 characters long
        my $string_value = $foo->baz; # includes the trailing \0\0

       You can also pass initial values in to the constructor, either passing as a list of key
       value pairs or by passing a hash reference:

        $foo = Foo->new(
          bar => 22,
          baz => "grimlock\0\0",
        );

        # same as:

        $foo = Foo->new( {
          bar => 22,
          baz => "grimlock\0\0",
        } );

       If there are members of a record that you need to account for in terms of size and
       alignment, but do not want to have an accessor for, you can use ":" as a place holder for
       its name:

        record_layout(
          'int'        => ':',
          'string(10)' => 'baz',
        );

       strings

       So far I've shown fixed length strings.  These are declared with the word "string"
       followed by the length of the string in parentheticals.  Fixed length strings are included
       inside the record itself and do not need to be allocated or deallocated separately from
       the record.  Variable length strings must be allocated on the heap, and thus require a
       sense of "ownership", that is whomever allocates variable length strings should be
       responsible for also free'ing them.  To handle this, you can add a "ro" or "rw" trait to a
       string field.  The default is "ro", means that you can get, but not set its value:

        package Foo;

        record_layout(
          'string ro' => 'bar',  # same type as 'string' and 'string_ro'
        );

        package main;

        my $foo = Foo->new;

        my $string = $foo->bar;  # GOOD
        $foo->bar("starscream"); # BAD

       If you specify a field is "rw", then you can set its value:

        package Foo;

        record_layout(
          'string rw' => 'bar',  # same type as 'string_rw'
        );

        package main;

        my $foo = Foo->new;

        my $string = $foo->bar;  # GOOD
        $foo->bar("starscream"); # GOOD

       Any string value that is pointed to by the record will be free'd when it falls out of
       scope, so you must be very careful that any "string rw" fields are not set or modified by
       C code.  You should also take care not to copy any record that has a "rw" string in it
       because its values will be free'd twice!

        use Clone qw( clone );

        my $foo2 = clone $foo;  # BAD  bar will be free'd twice

       arrays

       Arrays of integer, floating points and opaque pointers are supported.

        package Foo;

        record_layout(
          'int[10]' => 'bar',
        );

        my $foo = Foo->new;

        $foo->bar([1,2,3,4,5,6,7,8,9,10]); # sets the values for the array
        my $list = $foo->bar;  # returns a list reference

        $foo->bar(5, -6); # sets the 5th element in the array to -6
        my $item = $foo->bar(5); gets the 5th element in the array

TODO

       These useful features (and probably more) are missing:

       Unions
       Nested records

SEE ALSO

       FFI::Platypus
           The main platypus documentation.

       FFI::Platypus::Record::TieArray
           Tied array interface for record array members.

       Convert::Binary::C
           Another method for constructing and dissecting structured data records.

       pack and unpack
           Built-in Perl functions for constructing and dissecting structured data records.

AUTHOR

       Author: Graham Ollis <plicease@cpan.org>

       Contributors:

       Bakkiaraj Murugesan (bakkiaraj)

       Dylan Cali (calid)

       pipcet

       Zaki Mughal (zmughal)

       Fitz Elliott (felliott)

       Vickenty Fesunov (vyf)

       Gregor Herrmann (gregoa)

COPYRIGHT AND LICENSE

       This software is copyright (c) 2015 by Graham Ollis.

       This is free software; you can redistribute it and/or modify it under the same terms as
       the Perl 5 programming language system itself.