---
name: "FFI::C::UnionDef"
section: "3pm"
platform: "linux"
package: "libffi-c-perl"
version: "0.15-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/FFI::C::UnionDef"
---

# FFI::C::UnionDef(3pm)

Union data definition for FFI

## NAME

FFI::C::UnionDef - Union data definition for FFI

## VERSION

version 0.15

## SYNOPSIS

In your C code:

```
 #include <stdint.h>
 #include <stdio.h>

 typedef union {
   uint8_t  u8;
   uint16_t u16;
   uint32_t u32;
 } anyint_t;

 void
 print_anyint_as_u32(anyint_t *any)
 {
   printf("0x%x\n", any->u32);
 }
```

In your Perl code:

```
 use FFI::Platypus 1.00;
 use FFI::C::UnionDef;

 my $ffi = FFI::Platypus->new( api => 1 );
 # See FFI::Platypus::Bundle for how bundle works.
 $ffi->bundle;

 my $def = FFI::C::UnionDef->new(
   $ffi,
   name => 'anyint_t',
   class => 'AnyInt',
   members => [
     u8  => 'uint8',
     u16 => 'uint16',
     u32 => 'uint32',
   ],
 );

 $ffi->attach( print_anyint_as_u32 => ['anyint_t'] );

 my $int = AnyInt->new({ u8 => 42 });
 print_anyint_as_u32($int);  # 0x2a on Intel,
```

## DESCRIPTION

This class creates a def for a C `"union"`.

## CONSTRUCTOR

### new

```
 my $def = FFI::C::UnionDef->new(%opts);
 my $def = FFI::C::UnionDef->new($ffi, %opts);
```

For standard def options, see FFI::C::Def.

- members

  This should be an array reference containing name, type pairs. For a union, the order doesn't matter.

## METHODS

### create

```
 my $instance = $def->create;
 my $instance = $def->class->new;          # if class was specified
 my $instance = $def->create(\%init);
 my $instance = $def->class->new(\%init);  # if class was specified
```

This creates an instance of the `"union"`, returns a FFI::C::Union.

You can optionally initialize member values using `%init`.

## SEE ALSO

- FFI::C

  - FFI::C::Array

  - FFI::C::ArrayDef

  - FFI::C::Def

  - FFI::C::File

  - FFI::C::PosixFile

  - FFI::C::Struct

  - FFI::C::StructDef

  - FFI::C::Union

  - FFI::C::UnionDef

  - FFI::C::Util

  - FFI::Platypus::Record

  ## AUTHOR

Graham Ollis \<plicease@cpan.org\>

## COPYRIGHT AND LICENSE

This software is copyright (c) 2020-2022 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.