note
	description: "Read/Write synchronization object, allows multiple reader threads to have access to a resource, and only one writer thread."
	legal: "See notice at end of class."
	status: "See notice at end of class."
	date: "$Date: 2017-05-25 15:02:28 +0000 (Thu, 25 May 2017) $"
	revision: "$Revision: 100436 $"

class 
	READ_WRITE_LOCK

inherit
	DISPOSABLE

create 
	make

feature {NONE} -- Initialization

	make
			-- Create read/write lock.
		do
			item := eif_thr_rwl_create
		ensure
			item_set: is_set
		end
	
feature -- Access

	is_set: BOOLEAN
			-- Is read/write lock initialized?
		do
			Result := item /= default_pointer or else not {PLATFORM}.is_thread_capable
		end
	
feature -- Status setting

	acquire_read_lock
			-- Lock current on a read.
		require
			is_set: is_set
		do
			eif_thr_rwl_rdlock (item)
		end

	acquire_write_lock
			-- Lock current on a write.
		require
			is_set: is_set
		do
			eif_thr_rwl_wrlock (item)
		end

	release_read_lock
			-- Unlock Reader lock.
		require
			is_set: is_set
		do
			eif_thr_rwl_unlock (item)
		end

	release_write_lock
			-- Unlock Writer lock.
		require
			is_set: is_set
		do
			eif_thr_rwl_unlock (item)
		end

	destroy
			-- Destroy read/write lock.
		require
			is_set: is_set
		do
			eif_thr_rwl_destroy (item)
			item := default_pointer
		ensure
			not_set: not is_set
		end
	
feature -- Obsolete

	release_reader_lock
		obsolete "Use `release_read_lock' or `release_write_lock'. [2017-05-31]"
			-- Unlock Reader or Writer lock.
			-- Was declared in READ_WRITE_LOCK as synonym of release_writer_lock.
		require
			is_set: is_set
		do
			eif_thr_rwl_unlock (item)
		end

	release_writer_lock
		obsolete "Use `release_read_lock' or `release_write_lock'. [2017-05-31]"
			-- Unlock Reader or Writer lock.
			-- Was declared in READ_WRITE_LOCK as synonym of release_reader_lock.
		require
			is_set: is_set
		do
			eif_thr_rwl_unlock (item)
		end
	
feature {NONE} -- Implementation

	item: POINTER
			-- C reference to the read/write lock.
	
feature -- Removal

	dispose
			-- Called by the garbage collector when the read/write lock is
			-- collected.
		do
			if is_set then
				destroy
			end
		end
	
feature {NONE} -- Externals

	eif_thr_rwl_create: POINTER
		external
			"C use %"eif_threads.h%""
		end

	eif_thr_rwl_rdlock (an_item: POINTER)
		external
			"C blocking use %"eif_threads.h%""
		end

	eif_thr_rwl_unlock (an_item: POINTER)
		external
			"C use %"eif_threads.h%""
		end

	eif_thr_rwl_wrlock (an_item: POINTER)
		external
			"C blocking use %"eif_threads.h%""
		end

	eif_thr_rwl_destroy (an_item: POINTER)
		external
			"C use %"eif_threads.h%""
		end
	
note
	copyright: "Copyright (c) 1984-2017, Eiffel Software and others"
	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
	source: "[
		Eiffel Software
		5949 Hollister Ave., Goleta, CA 93117 USA
		Telephone 805-685-1006, Fax 805-685-6869
		Website http://www.eiffel.com
		Customer support http://support.eiffel.com
	]"

end -- class READ_WRITE_LOCK

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