NAME

FFI::C - C data types for FFI

VERSION

version 0.10

SYNOPSIS

In C:

 #include <stdint.h>
 
 typedef struct {
   uint8_t red;
   uint8_t green;
   uint8_t blue;
 } color_value_t;
 
 typedef struct {
   char name[22];
   color_value_t value;
 } named_color_t;
 
 typedef named_color_t array_named_color_t[4];
 
 typedef union {
   uint8_t  u8;
   uint16_t u16;
   uint32_t u32;
   uint64_t u64;
 } anyint_t;

In Perl:

 use FFI::C;
 
 package ColorValue {
   FFI::C->struct([
     red   => 'uint8',
     green => 'uint8',
     blue  => 'uint8',
   ]);
 }
 
 package NamedColor {
   FFI::C->struct([
     name  => 'string(22)',
     value => 'color_value_t',
   ]);
 }
 
 package ArrayNamedColor {
   FFI::C->array(['named_color_t' => 4]);
 };
 
 my $array = ArrayNamedColor->new([
   { name => "red",    value => { red   => 255 } },
   { name => "green",  value => { green => 255 } },
   { name => "blue",   value => { blue  => 255 } },
   { name => "purple", value => { red   => 255,
                                  blue  => 255 } },
 ]);
 
 # dim each color by 1/2
 foreach my $color (@$array)
 {
   $color->value->red  ( $color->value->red   / 2 );
   $color->value->green( $color->value->green / 2 );
   $color->value->blue ( $color->value->blue  / 2 );
 }
 
 # print out the colors
 foreach my $color (@$array)
 {
   printf "%s [%02x %02x %02x]\n",
     $color->name,
     $color->value->red,
     $color->value->green,
     $color->value->blue;
 }
 
 package AnyInt {
   FFI::C->union([
     u8  => 'uint8',
     u16 => 'uint16',
     u32 => 'uint32',
     u64 => 'uint64',
   ]);
 }
 
 my $int = AnyInt->new({ u8 => 42 });
 print $int->u32;

DESCRIPTION

This distribution provides tools for building classes to interface for common C data types. Arrays, struct, union and nested types based on those are supported.

To work with C APIs that work with C file pointers you can use FFI::C::File and FFI::C::PosixFile.

METHODS

ffi

 FFI::C->ffi($ffi);
 my $ffi = FFI::C->ffi;

Get or set the FFI::Platypus instance used for the current Perl file (.pl or .pm).

By default a new Platypus instance is created the on the first call to ffi, or when a new type is created with struct, union or array below, so if you want to use your own Platypus instance make sure that you set it as soon as possible.

The Platypus instance is file scoped because scoping on just one package doesn't make sense if you are defining multiple types in one file since each type must be in its own package. It also doesn't make sense to make the Platypus instance global, because different distributions would conflict.

struct

 FFI::C->struct($name, \@members);
 FFI::C->struct(\@members);

Generate a new FFI::C::Struct class with the given @members into the calling package. (@members should be a list of name/type pairs). You may optionally give a $name which will be used for the FFI::Platypus type name for the generated class. If you do not specify a $name, a C style name will be generated from the last segment in the calling package name by converting to snake case and appending a _t to the end.

As an example, given:

 package MyLibrary::FooBar {
   FFI::C->struct([
     a => 'uint8',
     b => 'float',
   ]);
 };

You can use MyLibrary::FooBar via the file scoped FFI::Platypus instance using the type foo_bar_t.

 my $foobar = MyLibrary::FooBar->new({ a => 1, b => 3.14 });
 $ffi->function( my_library_func => [ 'foo_bar_t' ] => 'void' )->call($foobar);

union

 FFI::C->union($name, \@members);
 FFI::C->union(\@members);

This works exactly like the struct method above, except a FFI::C::Union class is generated instead.

array

 FFI::C->array($name, [$type, $count]);
 FFI::C->array($name, [$type]);
 FFI::C->array([$type, $count]);
 FFI::C->array([$type]);

This is similar to struct and union above, except FFI::C::Array is generated. For an array you give it the member type and the element count. The element count is optional for variable length arrays, but keep in mind that when you create such an array you do need to provide a size.

enum

 FFI::C->enum($name, \@values, \%config);
 FFI::C->enum(\@values, \%config);
 FFI::C->enum(\@values, \%config);
 FFI::C->enum(\@values);

Defines an enum. The @values and %config are passed to FFI::Platypus::Type::Enum, except the constants are exported to the calling package by default.

EXAMPLES

unix time struct

 use FFI::Platypus 1.00;
 use FFI::C;
 
 my $ffi = FFI::Platypus->new(
   api => 1,
   lib => [undef],
 );
 FFI::C->ffi($ffi);
 
 package Unix::TimeStruct {
 
   FFI::C->struct(tm => [
     tm_sec    => 'int',
     tm_min    => 'int',
     tm_hour   => 'int',
     tm_mday   => 'int',
     tm_mon    => 'int',
     tm_year   => 'int',
     tm_wday   => 'int',
     tm_yday   => 'int',
     tm_isdst  => 'int',
     tm_gmtoff => 'long',
     _tm_zone  => 'opaque',
   ]);
 
   # For now 'string' is unsupported by FFI::C, but we
   # can cast the time zone from an opaque pointer to
   # string.
   sub tm_zone {
     my $self = shift;
     $ffi->cast('opaque', 'string', $self->_tm_zone);
   }
 
   # attach the C localtime function
   $ffi->attach( localtime => ['time_t*'] => 'tm', sub {
     my($inner, $class, $time) = @_;
     $time = time unless defined $time;
     $inner->(\$time);
   });
 }
 
 # now we can actually use our My::UnixTime class
 my $time = Unix::TimeStruct->localtime;
 printf "time is %d:%d:%d %s\n",
   $time->tm_hour,
   $time->tm_min,
   $time->tm_sec,
   $time->tm_zone;

CAVEATS

FFI::C objects must be passed into C via FFI::Platypus by pointers. So-called "pass-by-value" is not and will not be supported. For "pass-by-value" record types, you should instead use FFI::Platypus::Record.

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 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.