Class: FFI::ManagedStruct

Inherits:
Struct
  • Object
show all
Defined in:
lib/ffi/managedstruct.rb

Overview

FFI::ManagedStruct allows custom garbage-collection of your FFI::Structs.

The typical use case would be when interacting with a library that has a nontrivial memory management design, such as a linked list or a binary tree.

When the Struct instance is garbage collected, FFI::ManagedStruct will invoke the class’s release() method during object finalization.

Examples:

Example usage:

module MyLibrary
  ffi_lib "libmylibrary"
  attach_function :new_dlist, [], :pointer
  attach_function :destroy_dlist, [:pointer], :void
end

class DoublyLinkedList < FFI::ManagedStruct
  @@@
  struct do |s|
    s.name 'struct dlist'
    s.include 'dlist.h'
    s.field :head, :pointer
    s.field :tail, :pointer
  end
  @@@

  def self.release ptr
    MyLibrary.destroy_dlist(ptr)
  end
end

begin
  ptr = DoublyLinkedList.new(MyLibrary.new_dlist)
  #  do something with the list
end
# struct is out of scope, and will be GC'd using DoublyLinkedList#release

Instance Method Summary collapse

Methods inherited from Struct

#align, #alignment, alignment, auto_ptr, by_ref, by_value, #clear, in, layout, #members, members, offset_of, #offset_of, offsets, #offsets, out, ptr, size, #size, size=, #to_ptr, val, #values

Constructor Details

#initialize(pointer) ⇒ ManagedStruct #initialize ⇒ ManagedStruct

A new instance of FFI::ManagedStruct.

Overloads:

  • #initialize(pointer) ⇒ ManagedStruct

    Create a new ManagedStruct which will invoke the class method #release on

    Parameters:

Raises:

  • (NoMethodError) 


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# File 'lib/ffi/managedstruct.rb', line 77

def initialize(pointer=nil)
  raise NoMethodError, "release() not implemented for class #{self}" unless self.class.respond_to?(:release, true)
  raise ArgumentError, "Must supply a pointer to memory for the Struct" unless pointer
  super AutoPointer.new(pointer, self.class.method(:release))
end