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.
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
When passed a pointer, create a new ManagedStruct which will invoke the class method release() on
# File lib/ffi/managedstruct.rb, line 48 def initialize(pointer=nil) raise NoMethodError, "release() not implemented for class #{self}" unless self.class.respond_to? :release raise ArgumentError, "Must supply a pointer to memory for the Struct" unless pointer super AutoPointer.new(pointer, self.class.method(:release)) end
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