CODEWITHSUNDEEP
rubydllshared-librariesfiddle
Ríša Werner
Ríša Werner

Reputation: 501

Nested structures in Ruby Fiddle

It is kind of a desperate question since I've searched through the documentation and Fiddle's code and found no clue about nested structs (although the FFI library was able to do that apparently and Fiddle should be a wrapper for FFI).

Upvotes: 38

Views: 1342

Answers (1)

bliof
bliof

Reputation: 2987

How about:

data.c

#include <stdio.h>

struct A
{
    int a_id;
};

struct B
{
    int b_id;
    struct A a_nested;
};

void dump_b(struct B* b) {
    printf("B.b_id: %d\n", b->b_id);
    printf("B.a_nested.a_id: %d\n", b->a_nested.a_id);
}

fiddle.rb

# frozen_string_literal: true

require 'fiddle'
require 'fiddle/import'

module Test
  extend Fiddle::Importer

  dlload './data.dylib'

  B = struct [
    "int id",
    "int a_id"
  ]

  extern 'void dump_b(struct B*)'
end

b = Test::B.malloc

b.id = 123
b.a_id = 13

puts b.id
puts b.a_id

Test.dump_b(b)

or ffi.rb

require 'ffi'

module Test
  extend FFI::Library

  ffi_lib 'data.dylib'

  class A < FFI::Struct
    layout :id,  :int
  end

  class B < FFI::Struct
    layout :id,  :int,
           :a_nested, A
  end

  attach_function :dump_b, [:pointer], :void
end

a = Test::A.new

a[:id] = 3000

b = Test::B.new

b[:id] = 1000
b[:a_nested] = a

puts b[:id]
puts b[:a_nested][:id]

Test.dump_b(b)

Result

$ gcc -c data.c
$ gcc -dynamiclib data.o -o data.dylib
$ ruby fiddle.rb
123
13
B.b_id: 123
B.a_nested.a_id: 13
$ ruby ffi.rb
1000
3000
B.b_id: 1000
B.a_nested.a_id: 3000

Upvotes: 1

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