NAME

    FFI::Platypus::Declare - (discouraged) Declarative interface to
    FFI::Platypus

VERSION

    version 1.34

SYNOPSIS

     use FFI::Platypus::Declare 'string', 'int';
     
     lib undef; # use libc
     attach puts => [string] => int;
     
     puts("hello world");

DESCRIPTION

    This module is officially discouraged. The idea was to provide a
    simpler declarative interface without the need of (directly) creating
    an FFI::Platypus instance. In practice it is almost as complicated and
    makes it difficult to upgrade to the proper OO interface if the need
    arises. I have stopped using it mainly for this reason. It will remain
    as part of the Platypus core distribution to keep old code working, but
    you are encouraged to write new code using the OO interface.
    Alternatively, you can try the Perl 6 inspired NativeCall, which
    provides most of the goals this module was intended for (that is a
    simple interface at the cost of some power), without much of the
    complexity. The remainder of this document describes the interface.

    This module provides a declarative interface to FFI::Platypus. It
    provides a more concise interface at the cost of a little less power,
    and a little more namespace pollution.

    Any strings passed into the use line will be declared as types and
    exported as constants into your namespace, so that you can use them
    without quotation marks.

    Aliases can be declared using a list reference:

     use FFI::Platypus [ 'int[48]' => 'my_integer_array' ];

    Custom types can also be declared as a list reference (the type name
    must include a ::):

     use FFI::Platypus [ '::StringPointer' => 'my_string_pointer' ];
     # short for FFI::Platypus::Type::StringPointer

FUNCTIONS

    All functions are exported into your namespace. If you do not want
    that, then use the OO interface (see FFI::Platypus).

 lib

     lib $libpath;

    Specify one or more dynamic libraries to search for symbols. If you are
    unsure of the location / version of the library then you can use
    FFI::CheckLib#find_lib.

 type

     type $type;
     type $type = $alias;

    Declare the given type.

    Examples:

     type 'uint8'; # only really checks that uint8 is a valid type
     type 'uint8' => 'my_unsigned_int_8';

 custom_type

     custom_type $alias => \%args;

    Declare the given custom type. See FFI::Platypus::Type#Custom-Types for
    details.

 load_custom_type

     load_custom_type $name => $alias, @type_args;

    Load the custom type defined in the module $name, and make an alias
    with the name $alias. If the custom type requires any arguments, they
    may be passed in as @type_args. See FFI::Platypus::Type#Custom-Types
    for details.

    If $name contains :: then it will be assumed to be a fully qualified
    package name. If not, then FFI::Platypus::Type:: will be prepended to
    it.

 type_meta

     my $meta = type_meta $type;

    Get the type meta data for the given type.

    Example:

     my $meta = type_meta 'int';

 attach

     attach $name => \@argument_types => $return_type;
     attach [$c_name => $perl_name] => \@argument_types => $return_type;
     attach [$address => $perl_name] => \@argument_types => $return_type;

    Find and attach a C function as a Perl function as a real live xsub.

    If just one $name is given, then the function will be attached in Perl
    with the same name as it has in C. The second form allows you to give
    the Perl function a different name. You can also provide a memory
    address (the third form) of a function to attach.

    Examples:

     attach 'my_function', ['uint8'] => 'string';
     attach ['my_c_function_name' => 'my_perl_function_name'], ['uint8'] => 'string';
     my $string1 = my_function($int);
     my $string2 = my_perl_function_name($int);

 closure

     my $closure = closure $codeblock;

    Create a closure that can be passed into a C function. For details on
    closures, see FFI::Platypus::Type#Closures.

    Example:

     my $closure1 = closure { return $_[0] * 2 };
     my $closure2 = closure sub { return $_[0] * 4 };

 sticky

     my $closure = sticky closure $codeblock;

    Keyword to indicate the closure should not be deallocated for the life
    of the current process.

    If you pass a closure into a C function without saving a reference to
    it like this:

     foo(closure { ... });         # BAD

    Perl will not see any references to it and try to free it immediately.
    (this has to do with the way Perl and C handle responsibilities for
    memory allocation differently). One fix for this is to make sure the
    closure remains in scope using either my or our. If you know the
    closure will need to remain in existence for the life of the process
    (or if you do not care about leaking memory), then you can add the
    sticky keyword to tell FFI::Platypus to keep the thing in memory.

     foo(sticky closure { ... });  # OKAY

 cast

     my $converted_value = cast $original_type, $converted_type, $original_value;

    The cast function converts an existing $original_value of type
    $original_type into one of type $converted_type. Not all types are
    supported, so care must be taken. For example, to get the address of a
    string, you can do this:

     my $address = cast 'string' => 'opaque', $string_value;

 attach_cast

     attach_cast "cast_name", $original_type, $converted_type;
     my $converted_value = cast_name($original_value);

    This function creates a subroutine which can be used to convert
    variables just like the cast function above. The above synopsis is
    roughly equivalent to this:

     sub cast_name { cast($original_type, $converted_type, $_[0]) }
     my $converted_value = cast_name($original_value);

    Except that the attach_cast variant will be much faster if called
    multiple times since the cast does not need to be dynamically allocated
    on each instance.

 sizeof

     my $size = sizeof $type;

    Returns the total size of the given type. For example to get the size
    of an integer:

     my $intsize = sizeof 'int'; # usually 4 or 8 depending on platform

    You can also get the size of arrays

     my $intarraysize = sizeof 'int[64]';

    Keep in mind that "pointer" types will always be the pointer / word
    size for the platform that you are using. This includes strings, opaque
    and pointers to other types.

    This function is not very fast, so you might want to save this value as
    a constant, particularly if you need the size in a loop with many
    iterations.

 lang

     lang $language;

    Specifies the foreign language that you will be interfacing with. The
    default is C. The foreign language specified with this attribute
    changes the default native types (for example, if you specify Rust, you
    will get i32 as an alias for sint32 instead of int as you do with C).

    In the future this may attribute may offer hints when doing demangling
    of languages that require it like C++.

 abi

     abi $abi;

    Set the ABI or calling convention for use in subsequent calls to
    "attach". May be either a string name or integer value from
    FFI::Platypus#abis.

SEE ALSO

    FFI::Platypus

      Object oriented interface to Platypus.

    FFI::Platypus::Type

      Type definitions for Platypus.

    FFI::Platypus::API

      Custom types API for Platypus.

    FFI::Platypus::Memory

      memory functions for FFI.

    FFI::CheckLib

      Find dynamic libraries in a portable way.

    FFI::TinyCC

      JIT compiler for FFI.

AUTHOR

    Author: Graham Ollis <plicease@cpan.org>

    Contributors:

    Carlos D. Álvaro (cdalvaro)

COPYRIGHT AND LICENSE

    This software is copyright (c) 2020 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.

