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#
# Copyright (C) 2008 Mike Dalessio <mike.dalessio@gmail.com>
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# * Redistributions of source code must retain the above copyright notice, this
# list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above copyright notice
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
# * Neither the name of the Evan Phoenix nor the names of its contributors
# may be used to endorse or promote products derived from this software
# without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
module FFI
#
# 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
#
#
class ManagedStruct < FFI::Struct
# call-seq:
# ManagedStruct.new(pointer)
# ManagedStruct.new
#
# When passed a pointer, create a new ManagedStruct which will invoke the class method release() on
def initialize(pointer=nil)
raise NoMethodError, "release() not implemented for class #{self.class}" unless self.class.respond_to? :release
raise ArgumentError, "Must supply a pointer to memory for the Struct" unless pointer
super FFI::AutoPointer.new(pointer, self.class.method(:release))
end
end
end
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