note
	description: "String - Integer/Natural conversion overflow checker"
	library: "Free implementation of ELKS library"
	status: "See notice at end of class."
	legal: "See notice at end of class."
	date: "$Date: 2017-03-23 20:42:57 +0000 (Thu, 23 Mar 2017) $"
	revision: "$Revision: 100036 $"

class 
	INTEGER_OVERFLOW_CHECKER

create 
	make

feature {NONE} -- Initialization

	default_create
			-- Process instances of classes with no creation clause.
			-- (Default: do nothing.)
			-- (from ANY)
		do
		end

	make
			-- Initialize.
		do
			create integer_overflow_state1.make_empty (Type_count * 2 + 1);
			integer_overflow_state1.extend (0)
			create integer_overflow_state2.make_empty (Type_count * 2 + 1);
			integer_overflow_state2.extend (0);
			integer_overflow_state1.extend (({INTEGER_8}.max_value // 10).to_natural_64);
			integer_overflow_state2.extend (({INTEGER_8}.max_value \\ 10).to_natural_64);
			integer_overflow_state1.extend (({INTEGER_16}.max_value // 10).to_natural_64);
			integer_overflow_state2.extend (({INTEGER_16}.max_value \\ 10).to_natural_64);
			integer_overflow_state1.extend (({INTEGER_32}.max_value // 10).to_natural_64);
			integer_overflow_state2.extend (({INTEGER_32}.max_value \\ 10).to_natural_64);
			integer_overflow_state1.extend (({INTEGER_64}.max_value // 10).to_natural_64);
			integer_overflow_state2.extend (({INTEGER_64}.max_value \\ 10).to_natural_64);
			integer_overflow_state1.extend ((- ({INTEGER_8}.min_value // 10)).to_natural_64);
			integer_overflow_state2.extend ((- ({INTEGER_8}.min_value \\ 10)).to_natural_64);
			integer_overflow_state1.extend ((- ({INTEGER_16}.min_value // 10)).to_natural_64);
			integer_overflow_state2.extend ((- ({INTEGER_16}.min_value \\ 10)).to_natural_64);
			integer_overflow_state1.extend ((- ({INTEGER_32}.min_value // 10)).to_natural_64);
			integer_overflow_state2.extend ((- ({INTEGER_32}.min_value \\ 10)).to_natural_64);
			integer_overflow_state1.extend ((- ({INTEGER_64}.min_value // 10)).to_natural_64);
			integer_overflow_state2.extend ((- ({INTEGER_64}.min_value \\ 10)).to_natural_64)
			create natural_overflow_state1.make_empty (Type_count + 1);
			natural_overflow_state1.extend (0)
			create natural_overflow_state2.make_empty (Type_count + 1);
			natural_overflow_state2.extend (0);
			natural_overflow_state1.extend (({NATURAL_8}.max_value // 10).to_natural_64);
			natural_overflow_state2.extend (({NATURAL_8}.max_value \\ 10).to_natural_64);
			natural_overflow_state1.extend (({NATURAL_16}.max_value // 10).to_natural_64);
			natural_overflow_state2.extend (({NATURAL_16}.max_value \\ 10).to_natural_64);
			natural_overflow_state1.extend (({NATURAL_32}.max_value // 10).to_natural_64);
			natural_overflow_state2.extend (({NATURAL_32}.max_value \\ 10).to_natural_64);
			natural_overflow_state1.extend (({NATURAL_64}.max_value // 10).to_natural_64);
			natural_overflow_state2.extend (({NATURAL_64}.max_value \\ 10).to_natural_64)
		end
	
feature -- Access

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

	generator: STRING_8
			-- Name of current object's generating class
			-- (base class of the type of which it is a direct instance)
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			generator_not_void: Result /= Void
			generator_not_empty: not Result.is_empty
		end
	
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)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.is_deep_equal (b)
			end
		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)
		end

	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)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.is_equal (b)
			end
		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))
		end

	frozen is_deep_equal alias "≡≡≡" (other: INTEGER_OVERFLOW_CHECKER): BOOLEAN
			-- Are Current and other attached to isomorphic object structures?
			-- (from ANY)
		require -- from ANY
			other_not_void: other /= Void
		external
			"built_in"
		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)
		end

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

	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)
		do
			if a = Void then
				Result := b = Void
			else
				Result := b /= Void and then a.standard_is_equal (b)
			end
		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))
		end

	frozen standard_is_equal alias "≜" (other: INTEGER_OVERFLOW_CHECKER): 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
		external
			"built_in"
		ensure -- from ANY
			same_type: Result implies same_type (other)
			symmetric: Result implies other.standard_is_equal (Current)
		end
	
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
		external
			"built_in"
		end

	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
		external
			"built_in"
		ensure -- from ANY
			definition: Result = (conforms_to (other) and other.conforms_to (Current))
		end
	
feature -- Duplication

	frozen clone (other: detachable ANY): like other
		obsolete "Use `twin' instead. [2017-05-31]"
			-- Void if other is void; otherwise new object
			-- equal to other
			--
			-- For non-void other, clone calls copy;
			-- to change copying/cloning semantics, redefine copy.
			-- (from ANY)
		do
			if other /= Void then
				Result := other.twin
			end
		ensure -- from ANY
			instance_free: class
			equal: Result ~ other
		end

	copy (other: INTEGER_OVERFLOW_CHECKER)
			-- 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)
		external
			"built_in"
		ensure -- from ANY
			is_equal: Current ~ other
		end

	frozen deep_clone (other: detachable ANY): like other
		obsolete "Use `deep_twin' instead. [2017-05-31]"
			-- Void if other is void: otherwise, new object structure
			-- recursively duplicated from the one attached to other
			-- (from ANY)
		do
			if other /= Void then
				Result := other.deep_twin
			end
		ensure -- from ANY
			instance_free: class
			deep_equal: deep_equal (other, Result)
		end

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

	frozen deep_twin: INTEGER_OVERFLOW_CHECKER
			-- New object structure recursively duplicated from Current.
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			deep_twin_not_void: Result /= Void
			deep_equal: deep_equal (Current, Result)
		end

	frozen standard_clone (other: detachable ANY): like other
		obsolete "Use `standard_twin' instead. [2017-05-31]"
			-- Void if other is void; otherwise new object
			-- field-by-field identical to other.
			-- Always uses default copying semantics.
			-- (from ANY)
		do
			if other /= Void then
				Result := other.standard_twin
			end
		ensure -- from ANY
			instance_free: class
			equal: standard_equal (Result, other)
		end

	frozen standard_copy (other: INTEGER_OVERFLOW_CHECKER)
			-- 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)
		external
			"built_in"
		ensure -- from ANY
			is_standard_equal: standard_is_equal (other)
		end

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

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

	frozen as_attached: attached INTEGER_OVERFLOW_CHECKER
		obsolete "Remove calls to this feature. [2017-05-31]"
			-- Attached version of Current.
			-- (Can be used during transitional period to convert
			-- non-void-safe classes to void-safe ones.)
			-- (from ANY)
		do
			Result := Current
		end

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

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

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

	frozen do_nothing
			-- Execute a null action.
			-- (from ANY)
		do
		ensure -- from ANY
			instance_free: class
		end
	
feature {NONE} -- Implementation

	integer_overflow_state1: SPECIAL [like max_natural_type]

	integer_overflow_state2: SPECIAL [like max_natural_type]

	natural_overflow_state1: SPECIAL [like max_natural_type]

	natural_overflow_state2: SPECIAL [like max_natural_type]
			-- Arrays to check conversion overflow.
	
feature -- Output

	Io: STD_FILES
			-- Handle to standard file setup
			-- (from ANY)
		once
			create Result;
			Result.set_output_default
		ensure -- from ANY
			instance_free: class
			io_not_void: Result /= Void
		end

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

	print (o: detachable ANY)
			-- Write terse external representation of o
			-- on standard output.
			-- (from ANY)
		local
			s: READABLE_STRING_8
		do
			if attached o then
				s := o.out
				if attached {READABLE_STRING_32} s as s32 then
					Io.put_string_32 (s32)
				elseif attached {READABLE_STRING_8} s as s8 then
					Io.put_string (s8)
				else
					Io.put_string_32 (s.as_string_32)
				end
			end
		ensure -- from ANY
			instance_free: class
		end

	frozen tagged_out: STRING_8
			-- New string containing terse printable representation
			-- of current object
			-- (from ANY)
		external
			"built_in"
		ensure -- from ANY
			tagged_out_not_void: Result /= Void
		end
	
feature -- Overflow checking

	will_overflow (part1: like max_natural_type; part2: like max_natural_type; type: INTEGER_32; sign: INTEGER_32): BOOLEAN
			-- Will part1 * 10 + part2 with sign overflow
			-- if we convert it to an number of type?			
		require
			type_valid: integer_natural_type_valid (type)
		local
			l_index: INTEGER_32
		do
			if type /= Type_no_limitation then
				if type = Type_integer_8 or type = Type_integer_16 or type = Type_integer_32 or type = Type_integer_64 then
					l_index := sign * 4 + type
					Result := part1 > integer_overflow_state1.item (l_index) or (part1 = integer_overflow_state1.item (l_index) and part2 > integer_overflow_state2.item (l_index))
				elseif sign = 1 then
					Result := part1 > 0 or part2 > 0
				else
					l_index := type - Type_integer_natural_separator
					Result := part1 > natural_overflow_state1.item (l_index) or (part1 = natural_overflow_state1.item (l_index) and part2 > natural_overflow_state2.item (l_index))
				end
			end
		end
	
feature -- Platform

	Operating_environment: OPERATING_ENVIRONMENT
			-- Objects available from the operating system
			-- (from ANY)
		once
			create Result
		ensure -- from ANY
			instance_free: class
			operating_environment_not_void: Result /= Void
		end
	
feature {NONE} -- Retrieval

	frozen internal_correct_mismatch
			-- Called from runtime to perform a proper dynamic dispatch on correct_mismatch
			-- from MISMATCH_CORRECTOR.
			-- (from ANY)
		local
			l_msg: STRING_32
			l_exc: EXCEPTIONS
		do
			if attached {MISMATCH_CORRECTOR} Current as l_corrector then
				l_corrector.correct_mismatch
			else
				create l_msg.make_from_string ("Mismatch: ".as_string_32)
				create l_exc;
				l_msg.append (generating_type.name_32);
				l_exc.raise_retrieval_exception (l_msg)
			end
		end
	
feature -- Type checking

	double_type_valid (type: INTEGER_32): BOOLEAN
			-- Is type a valid double type?
			-- (from NUMERIC_INFORMATION)
		do
			Result := type = Type_double
		ensure -- from NUMERIC_INFORMATION
			instance_free: class
		end

	integer_natural_type_valid (type: INTEGER_32): BOOLEAN
			-- Is type a valid integer/natural type?
			-- (from NUMERIC_INFORMATION)
		do
			Result := (type = Type_no_limitation) or (type = Type_integer_8) or (type = Type_integer_16) or (type = Type_integer_32) or (type = Type_integer_64) or (type = Type_natural_8) or (type = Type_natural_16) or (type = Type_natural_32) or (type = Type_natural_64)
		ensure -- from NUMERIC_INFORMATION
			instance_free: class
		end

	integer_type_valid (type: INTEGER_32): BOOLEAN
			-- Is type a valid integer type?
			-- (from NUMERIC_INFORMATION)
		do
			Result := (type = Type_integer_8) or (type = Type_integer_16) or (type = Type_integer_32) or (type = Type_integer_64)
		ensure -- from NUMERIC_INFORMATION
			instance_free: class
		end

	natural_type_valid (type: INTEGER_32): BOOLEAN
			-- Is type a valid natural type?
			-- (from NUMERIC_INFORMATION)
		do
			Result := (type = Type_natural_8) or (type = Type_natural_16) or (type = Type_natural_32) or (type = Type_natural_64)
		ensure -- from NUMERIC_INFORMATION
			instance_free: class
		end

	real_double_type_valid (type: INTEGER_32): BOOLEAN
			-- Is type a valid real/double type?
			-- (from NUMERIC_INFORMATION)
		do
			Result := type = Type_no_limitation or type = Type_real or type = Type_double
		ensure -- from NUMERIC_INFORMATION
			instance_free: class
		end

	real_type_valid (type: INTEGER_32): BOOLEAN
			-- Is type a valid real type?
			-- (from NUMERIC_INFORMATION)
		do
			Result := type = Type_real
		ensure -- from NUMERIC_INFORMATION
			instance_free: class
		end
	
feature -- Types

	max_integer_type: INTEGER_64
			-- INTEGER type of max word length
			-- (from NUMERIC_INFORMATION)
		do
		ensure -- from NUMERIC_INFORMATION
			instance_free: class
		end

	max_natural_type: NATURAL_64
			-- NATURAL type of max word length
			-- (from NUMERIC_INFORMATION)
		do
		ensure -- from NUMERIC_INFORMATION
			instance_free: class
		end

	Type_count: INTEGER_32 = 4
			-- Number of types of integer/natural in Eiffel
			-- (from NUMERIC_INFORMATION)

	Type_double: INTEGER_32 = 101
			-- Real/Double type indicators
			-- (from NUMERIC_INFORMATION)

	Type_integer: INTEGER_32 = 3
			-- Was declared in NUMERIC_INFORMATION as synonym of Type_integer_32.
			-- (from NUMERIC_INFORMATION)

	Type_integer_16: INTEGER_32 = 2
			-- (from NUMERIC_INFORMATION)

	Type_integer_32: INTEGER_32 = 3
			-- Was declared in NUMERIC_INFORMATION as synonym of Type_integer.
			-- (from NUMERIC_INFORMATION)

	Type_integer_64: INTEGER_32 = 4
			-- (from NUMERIC_INFORMATION)

	Type_integer_8: INTEGER_32 = 1
			-- (from NUMERIC_INFORMATION)

	Type_integer_natural_separator: INTEGER_32 = 10
			-- (from NUMERIC_INFORMATION)

	Type_natural: INTEGER_32 = 13
			-- Was declared in NUMERIC_INFORMATION as synonym of Type_natural_32.
			-- (from NUMERIC_INFORMATION)

	Type_natural_16: INTEGER_32 = 12
			-- (from NUMERIC_INFORMATION)

	Type_natural_32: INTEGER_32 = 13
			-- Was declared in NUMERIC_INFORMATION as synonym of Type_natural.
			-- (from NUMERIC_INFORMATION)

	Type_natural_64: INTEGER_32 = 14
			-- Integer/natural type indicators
			-- (from NUMERIC_INFORMATION)

	Type_natural_8: INTEGER_32 = 11
			-- (from NUMERIC_INFORMATION)

	Type_no_limitation: INTEGER_32 = 0
			-- Type representing a number sequence (no length limitation)
			-- (from NUMERIC_INFORMATION)

	Type_real: INTEGER_32 = 100
			-- (from NUMERIC_INFORMATION)
	
invariant
		-- from ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)

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 INTEGER_OVERFLOW_CHECKER

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