Ubuntu Manpage: FFI::C - C data types for FFI

NAME

       FFI::C - C data types for FFI

VERSION

       version 0.15

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.

       Core FFI::Platypus also provides FFI::Platypus::Record for manipulating and passing
       structured data.  Typically you want to use FFI::C instead, the main exception is when you
       need to pass structured data by value instead of by reference.

       To work with C APIs that work with C file pointers you can use FFI::C::File and
       FFI::C::PosixFile.  For C APIs that expose the POSIX "stat" structure use FFI::C::Stat.

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.

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.

NAME

VERSION

SYNOPSIS

DESCRIPTION

METHODS

EXAMPLES

CAVEATS

SEE ALSO

AUTHOR

COPYRIGHT AND LICENSE