note
	description: "[
		Encoding of arbitrary objects graphs within a session of a same program.
		
		Some routines are explicitely frozen, not because we do not want them to be redefined
		but if they are frozen, it saves us having to look at all possible descendants whenever
		we do a change.
	]"
	legal: "See notice at end of class."
	status: "See notice at end of class."
	date: "$Date: 2017-03-28 12:36:24 +0000 (Tue, 28 Mar 2017) $"
	revision: "$Revision: 100064 $"

class interface
	SED_SESSION_SERIALIZER

create 
	make (a_serializer: SED_READER_WRITER)
			-- Initialize current instance
		require
			a_serializer_not_void: a_serializer /= Void
			a_serializer_ready: a_serializer.is_ready_for_writing
		ensure
			serializer_set: serializer = a_serializer

feature -- Access

	generating_type: TYPE [detachable SED_SESSION_SERIALIZER]
			-- Type of current object
			-- (type of which it is a direct instance)
			-- (from ANY)
		ensure -- from ANY
			generating_type_not_void: Result /= Void

	generator: STRING_8
			-- Name of current object's generating class
			-- (base class of the type of which it is a direct instance)
			-- (from ANY)
		ensure -- from ANY
			generator_not_void: Result /= Void
			generator_not_empty: not Result.is_empty

	root_object: detachable ANY
			-- Root object of object graph

	serializer: SED_READER_WRITER
			-- Serializer used to encode data
	
feature -- Comparison

	frozen deep_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void
			-- or attached to isomorphic object structures?
			-- (from ANY)
		ensure -- from ANY
			instance_free: class
			shallow_implies_deep: standard_equal (a, b) implies Result
			both_or_none_void: (a = Void) implies (Result = (b = Void))
			same_type: (Result and (a /= Void)) implies (b /= Void and then a.same_type (b))
			symmetric: Result implies deep_equal (b, a)

	frozen equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void or attached
			-- to objects considered equal?
			-- (from ANY)
		ensure -- from ANY
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.is_equal (b))

	frozen is_deep_equal alias "≡≡≡" (other: SED_SESSION_SERIALIZER): BOOLEAN
			-- Are Current and other attached to isomorphic object structures?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			shallow_implies_deep: standard_is_equal (other) implies Result
			same_type: Result implies same_type (other)
			symmetric: Result implies other.is_deep_equal (Current)

	is_equal (other: SED_SESSION_SERIALIZER): BOOLEAN
			-- Is other attached to an object considered
			-- equal to current object?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			symmetric: Result implies other ~ Current
			consistent: standard_is_equal (other) implies Result

	frozen standard_equal (a: detachable ANY; b: like arg #1): BOOLEAN
			-- Are a and b either both void or attached to
			-- field-by-field identical objects of the same type?
			-- Always uses default object comparison criterion.
			-- (from ANY)
		ensure -- from ANY
			instance_free: class
			definition: Result = (a = Void and b = Void) or else ((a /= Void and b /= Void) and then a.standard_is_equal (b))

	frozen standard_is_equal alias "" (other: SED_SESSION_SERIALIZER): BOOLEAN
			-- Is other attached to an object of the same type
			-- as current object, and field-by-field identical to it?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			same_type: Result implies same_type (other)
			symmetric: Result implies other.standard_is_equal (Current)
	
feature -- Status report

	conforms_to (other: ANY): BOOLEAN
			-- Does type of current object conform to type
			-- of other (as per Eiffel: The Language, chapter 13)?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void

	is_root_object_set: BOOLEAN
			-- Is root object of object graph set?

	is_traversing_mode_set: BOOLEAN
			-- Is traversing mode set?

	same_type (other: ANY): BOOLEAN
			-- Is type of current object identical to type of other?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			definition: Result = (conforms_to (other) and other.conforms_to (Current))
	
feature -- Element change

	set_breadth_first_traversing_mode
			-- Change graph traversing to breadth first.
		ensure
			traversing_mode_set: is_traversing_mode_set
			breadth_first_mode: attached {OBJECT_GRAPH_BREADTH_FIRST_TRAVERSABLE} traversable

	set_depth_first_traversing_mode
			-- Change graph traversing to depth first.
		ensure
			traversing_mode_set: is_traversing_mode_set
			depth_first_mode: attached {OBJECT_GRAPH_DEPTH_FIRST_TRAVERSABLE} traversable

	set_root_object (an_object: like root_object)
			-- Make 'an_object' the root_object.
		require
			an_object_not_void: an_object /= Void
			traversing_mode_set: is_traversing_mode_set
		ensure
			root_object_set: root_object = an_object and is_root_object_set
			root_object_identity: root_object = traversable.root_object

	set_serializer (a_serializer: like serializer)
			-- Set serializer with a_serializer.
		require
			a_serializer_not_void: a_serializer /= Void
			a_serializer_ready: a_serializer.is_ready_for_writing
		ensure
			serializer_set: serializer = a_serializer
	
feature -- Duplication

	copy (other: SED_SESSION_SERIALIZER)
			-- Update current object using fields of object attached
			-- to other, so as to yield equal objects.
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		ensure -- from ANY
			is_equal: Current ~ other

	frozen deep_copy (other: SED_SESSION_SERIALIZER)
			-- Effect equivalent to that of:
			--		copy (other . deep_twin)
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		ensure -- from ANY
			deep_equal: deep_equal (Current, other)

	frozen deep_twin: SED_SESSION_SERIALIZER
			-- New object structure recursively duplicated from Current.
			-- (from ANY)
		ensure -- from ANY
			deep_twin_not_void: Result /= Void
			deep_equal: deep_equal (Current, Result)

	frozen standard_copy (other: SED_SESSION_SERIALIZER)
			-- Copy every field of other onto corresponding field
			-- of current object.
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
			type_identity: same_type (other)
		ensure -- from ANY
			is_standard_equal: standard_is_equal (other)

	frozen standard_twin: SED_SESSION_SERIALIZER
			-- New object field-by-field identical to other.
			-- Always uses default copying semantics.
			-- (from ANY)
		ensure -- from ANY
			standard_twin_not_void: Result /= Void
			equal: standard_equal (Result, Current)

	frozen twin: SED_SESSION_SERIALIZER
			-- New object equal to Current
			-- twin calls copy; to change copying/twinning semantics, redefine copy.
			-- (from ANY)
		ensure -- from ANY
			twin_not_void: Result /= Void
			is_equal: Result ~ Current
	
feature -- Basic operations

	frozen default: detachable SED_SESSION_SERIALIZER
			-- Default value of object's type
			-- (from ANY)

	frozen default_pointer: POINTER
			-- Default value of type POINTER
			-- (Avoid the need to write p.default for
			-- some p of type POINTER.)
			-- (from ANY)
		ensure -- from ANY
			instance_free: class

	default_rescue
			-- Process exception for routines with no Rescue clause.
			-- (Default: do nothing.)
			-- (from ANY)

	frozen do_nothing
			-- Execute a null action.
			-- (from ANY)
		ensure -- from ANY
			instance_free: class

	frozen encode
			-- Encode object graph starting with the root object.
		require
			traversing_mode_set: is_traversing_mode_set
			root_object_set: is_root_object_set
	
feature -- Output

	Io: STD_FILES
			-- Handle to standard file setup
			-- (from ANY)
		ensure -- from ANY
			instance_free: class
			io_not_void: Result /= Void

	out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from ANY)
		ensure -- from ANY
			out_not_void: Result /= Void

	print (o: detachable ANY)
			-- Write terse external representation of o
			-- on standard output.
			-- (from ANY)
		ensure -- from ANY
			instance_free: class

	frozen tagged_out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from ANY)
		ensure -- from ANY
			tagged_out_not_void: Result /= Void
	
feature -- Platform

	Operating_environment: OPERATING_ENVIRONMENT
			-- Objects available from the operating system
			-- (from ANY)
		ensure -- from ANY
			instance_free: class
			operating_environment_not_void: Result /= Void
	
invariant
	reflector_not_void: reflector /= Void
	reflected_object_not_void: reflected_object /= Void
	traversable_not_void: traversable /= Void
	serializer_not_void: serializer /= Void
	object_indexes_not_void: object_indexes /= Void

		-- from ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)

note
	library: "EiffelBase: Library of reusable components for Eiffel."
	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 SED_SESSION_SERIALIZER

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