note
	description: "[
		Facilities for tuning up the garbage collection mechanism.
		This class may be used as ancestor by classes needing its facilities.
	]"
	library: "Free implementation of ELKS library"
	status: "See notice at end of class."
	legal: "See notice at end of class."
	date: "$Date: 2018-04-28 20:47:46 +0000 (Sat, 28 Apr 2018) $"
	revision: "$Revision: 101696 $"

class 
	MEMORY

inherit
	DISPOSABLE

	MEM_CONST

create 
	default_create

feature -- Measurement

	memory_statistics (memory_type: INTEGER_32): MEM_INFO
			-- Memory usage information for memory_type
		require
			type_ok: memory_type = Total_memory or memory_type = Eiffel_memory or memory_type = C_memory
		do
			create Result.make (memory_type)
		ensure
			instance_free: class
		end

	gc_statistics (collector_type: INTEGER_32): GC_INFO
			-- Garbage collection information for collector_type.
		require
			type_ok: collector_type = Full_collector or collector_type = Incremental_collector
		do
			create Result.make (collector_type)
		ensure
			instance_free: class
		end
	
feature -- Status report

	memory_threshold: INTEGER_32
			-- Minimum amount of bytes to be allocated before
			-- starting an automatic garbage collection.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_mem_tget"
		ensure
			instance_free: class
		end

	collection_period: INTEGER_32
			-- Period of full collection.
			-- If the environment variable EIF_FULL_COLLECTION_PERIOD
			-- is defined, it is set to the closest reasonable
			-- value from it.
			-- If null, no full collection is launched.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_mem_pget"
		ensure
			instance_free: class
		end

	coalesce_period: INTEGER_32
			-- Period of full coalesce (in number of collections)
			-- If the environment variable EIF_FULL_COALESCE_PERIOD
			-- is defined, it is set to the closest reasonable
			-- value from it.
			-- If null, no full coalescing is launched.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_coalesce_period"
		ensure
			instance_free: class
		end

	collecting: BOOLEAN
			-- Is garbage collection enabled?
		external
			"C use %"eif_memory.h%""
		alias
			"eif_gc_ison"
		ensure
			instance_free: class
		end

	largest_coalesced_block: INTEGER_32
			-- Size of largest coalesced block since last call to
			-- largest_coalesced; 0 if none.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_mem_largest"
		ensure
			instance_free: class
		end

	max_mem: INTEGER_32
			-- Maximum amount of bytes the run-time can allocate.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_get_max_mem"
		ensure
			instance_free: class
		end

	chunk_size: INTEGER_32
			-- Minimal size of a memory chunk. The run-time always
			-- allocates a multiple of this size.
			-- If the environment variable EIF_MEMORY_CHUNK
			-- is defined, it is set to the closest reasonable
			-- value from it.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_get_chunk_size"
		ensure
			instance_free: class
		end

	tenure: INTEGER_32
			-- Maximum age of object before being considered
			-- as old (old objects are not scanned during
			-- partial collection).
			-- If the environment variable EIF_TENURE_MAX
			-- is defined, it is set to the closest reasonable
			-- value from it.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_tenure"
		ensure
			instance_free: class
		end

	generation_object_limit: INTEGER_32
			-- Maximum size of object in generational scavenge zone.
			-- If the environment variable EIF_GS_LIMIT
			-- is defined, it is set to the closest reasonable
			-- value from it.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_generation_object_limit"
		ensure
			instance_free: class
		end

	scavenge_zone_size: INTEGER_32
			-- Size of generational scavenge zone.
			-- If the environment variable EIF_MEMORY_SCAVENGE
			-- is defined, it is set to the closest reasonable
			-- value from it.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_scavenge_zone_size"
		ensure
			instance_free: class
		end

	referers (an_object: ANY): SPECIAL [ANY]
			-- Objects that refer to an_object.
		do
			Result := find_referers (an_object, Special_any_dynamic_type)
		ensure
			instance_free: class
		end

	objects_instance_of (an_object: ANY): SPECIAL [ANY]
			-- Objects that have same dynamic type as an_object.
		do
			Result := objects_instance_of_type (an_object.generating_type.type_id)
		ensure
			instance_free: class
		end

	objects_instance_of_type (a_type_id: INTEGER_32): SPECIAL [ANY]
			-- Objects that have same dynamic type as an_object.
		do
			Result := find_instance_of (a_type_id, Special_any_dynamic_type)
		ensure
			instance_free: class
		end

	memory_map: HASH_TABLE [ARRAYED_LIST [ANY], INTEGER_32]
			-- Retrieves all object in system as a table indexed by dynamic type
			-- where elements are all instances of a given data type.
		local
			i, nb, dtype: INTEGER_32
			l_spec: SPECIAL [ANY]
			l_item: ANY
			l_list: detachable ARRAYED_LIST [ANY]
			l_memory_count_map: HASH_TABLE [INTEGER_32, INTEGER_32]
		do
			l_spec := find_all_instances (Special_any_dynamic_type)
			create l_memory_count_map.make (100)
			from
				i := 0
				nb := l_spec.count
			until
				i >= nb
			loop
				l_item := l_spec.item (i)
				if l_item /= Void then
					dtype := l_item.generating_type.type_id
					l_memory_count_map.force (l_memory_count_map.item (dtype) + 1, dtype)
				end
				i := i + 1
			end
			create Result.make (100)
			from
				i := 0
				nb := l_spec.count
			until
				i >= nb
			loop
				l_item := l_spec.item (i)
				if l_item /= Void then
					dtype := l_item.generating_type.type_id
					Result.search (dtype)
					if Result.found and then attached Result.found_item as l_found_item then
						l_list := l_found_item
					else
						create l_list.make (l_memory_count_map.item (dtype))
						Result.put (l_list, dtype)
					end
					l_list.extend (l_item)
				end
				i := i + 1
			end
		ensure
			instance_free: class
		end

	memory_count_map: HASH_TABLE [INTEGER_32, INTEGER_32]
			-- Number of instances per dynamic type present in system.
			-- Same as memory_map except that no references on the objects themselves
			-- is kept.
		local
			i, nb, dtype: INTEGER_32
			l_spec: SPECIAL [ANY]
			l_item: ANY
		do
			l_spec := find_all_instances (Special_any_dynamic_type)
			create Result.make (100)
			from
				i := 0
				nb := l_spec.count
			until
				i >= nb
			loop
				l_item := l_spec.item (i)
				if l_item /= Void then
					dtype := l_item.generating_type.type_id
					Result.search (dtype)
					if Result.found then
						Result.force (Result.found_item + 1, dtype)
					else
						Result.put (1, dtype)
					end
				end
				i := i + 1
			end
		ensure
			instance_free: class
		end
	
feature -- Status setting

	execute_without_collection (a_action: PROCEDURE)
			-- Execute a_action with the garbage collector disabled.
			-- If a_action modifies the status of collecting, we restore
			-- it no matter what at the end.
		require
			a_action_not_void: a_action /= Void
		local
			l_is_collecting: like collecting
			retried: BOOLEAN
		do
			if not retried then
				l_is_collecting := collecting
				if l_is_collecting then
					collection_off
					a_action.call (Void)
					collection_on
				else
					a_action.call (Void)
					collection_off
				end
			else
				if l_is_collecting then
					collection_on
				else
					collection_off
				end
			end
		ensure
			instance_free: class
			collection_status_preserved: collecting = old collecting
		rescue
			retried := True
			retry
		end

	collection_off
			-- Disable garbage collection.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_gc_stop"
		ensure
			instance_free: class
		end

	collection_on
			-- Enable garbage collection.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_gc_run"
		ensure
			instance_free: class
		end

	allocate_fast
			-- Enter speed mode: will optimize speed of memory
			-- allocation rather than memory usage.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_mem_speed"
		ensure
			instance_free: class
		end

	allocate_compact
			-- Enter memory mode: will try to compact memory
			-- before requesting more from the operating system.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_mem_slow"
		ensure
			instance_free: class
		end

	allocate_tiny
			-- Enter tiny mode: will enter memory mode
			-- after having freed as much memory as possible.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_mem_tiny"
		ensure
			instance_free: class
		end

	enable_time_accounting
			-- Enable GC time accouting, accessible in gc_statistics.
		do
			gc_monitoring (True)
		ensure
			instance_free: class
		end

	disable_time_accounting
			-- Disable GC time accounting (default).
		do
			gc_monitoring (False)
		ensure
			instance_free: class
		end

	set_memory_threshold (value: INTEGER_32)
			-- Set a new memory_threshold in bytes. Whenever the memory
			-- allocated for Eiffel reaches this value, an automatic
			-- collection is performed.
		require
			positive_value: value > 0
		external
			"C use %"eif_memory.h%""
		alias
			"eif_mem_tset"
		ensure
			instance_free: class
		end

	set_collection_period (value: INTEGER_32)
			-- Set collection_period. Every value collection,
			-- the Garbage collector will perform a collection
			-- on the whole memory (full collection), otherwise
			-- a simple partial collection is done.
		require
			positive_value: value >= 0
		external
			"C use %"eif_memory.h%""
		alias
			"eif_mem_pset"
		ensure
			instance_free: class
		end

	set_coalesce_period (value: INTEGER_32)
			-- Set coalesce_period. Every value collection,
			-- the Garbage Collector will coalesce
			-- the whole memory.
		require
			positive_value: value >= 0
		external
			"C use %"eif_memory.h%""
		alias
			"eif_set_coalesce_period"
		ensure
			instance_free: class
		end

	set_max_mem (value: INTEGER_32)
			-- Set the maximum amount of memory the run-time can allocate.
		require
			positive_value: value > 0
		external
			"C use %"eif_memory.h%""
		alias
			"eif_set_max_mem"
		ensure
			instance_free: class
		end
	
feature -- Removal

	dispose
			-- Action to be executed just before garbage collection
			-- reclaims an object.
			-- Default version does nothing; redefine in descendants
			-- to perform specific dispose actions. Those actions
			-- should only take care of freeing external resources;
			-- they should not perform remote calls on other objects
			-- since these may also be dead and reclaimed.
		do
		end

	free (object: ANY)
			-- Free object, by-passing garbage collection.
			-- Erratic behavior will result if the object is still
			-- referenced.
		external
			"built_in static"
		ensure
			instance_free: class
		end

	full_coalesce
			-- Coalesce the whole memory: merge adjacent free
			-- blocks to reduce fragmentation. Useful, when
			-- a lot of memory is allocated with garbage collector off.
		external
			"C use %"eif_memory.h%""
		alias
			"eif_mem_coalesc"
		ensure
			instance_free: class
		end

	collect
			-- Force a partial collection cycle if garbage
			-- collection is enabled; do nothing otherwise.
		external
			"C use %"eif_memory.h%""
		ensure
			instance_free: class
		end

	full_collect
			-- Force a full collection cycle if garbage
			-- collection is enabled; do nothing otherwise.
		external
			"C use %"eif_memory.h%""
		alias
			"plsc"
		ensure
			instance_free: class
		end
	
feature {NONE} -- Implementation

	gc_monitoring (flag: BOOLEAN)
			-- Set up GC monitoring according to flag
		external
			"C use %"eif_memory.h%""
		alias
			"eif_gc_mon"
		ensure
			instance_free: class
		end

	find_referers (target: ANY; result_type: INTEGER_32): SPECIAL [ANY]
		external
			"built_in static"
		ensure
			instance_free: class
		end

	find_instance_of (dtype, result_type: INTEGER_32): SPECIAL [ANY]
		external
			"C signature (EIF_INTEGER, EIF_INTEGER): EIF_REFERENCE use %"eif_traverse.h%""
		ensure
			instance_free: class
		end

	find_all_instances (result_type: INTEGER_32): SPECIAL [ANY]
		external
			"C signature (EIF_INTEGER): EIF_REFERENCE use %"eif_traverse.h%""
		ensure
			instance_free: class
		end

	Special_any_dynamic_type: INTEGER_32
			-- Dynamic type ID of an instance of SPECIAL [ANY]
		once
			Result := ({SPECIAL [ANY]}).type_id
		ensure
			instance_free: class
		end
	
note
	copyright: "Copyright (c) 1984-2018, 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 MEMORY

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