note
	description: "[
					  Representation of a JVM Label Mark.
					  A `JVM_LABEL_MARK' points to a `JVM_LABEL'.
					  Since the jump offset of (forward) jumps cannot be known at the time
					  the jump should be appended to the byte code of a method, we need to
					  store label marks, that point to a symbolic jump tarket.
		Once the position of the label is known (the label is closed) , we can go
					  back to the label mark and generate the actual jump offset.
					  ]"
	legal: "See notice at end of class."
	status: "See notice at end of class."
					  date: "$Date$"
					  revision: "$Revision$"

class
	JVM_LABEL_MARK

create
	make

feature {NONE} -- Initialisation

	make (a_label: JVM_LABEL; pos: INTEGER)
			-- `a_label' is the symbolic target position
			-- `pos' is the byte code position (starting at 1) in the
			-- methods byte code where the target will be written to.
		require
			valid_label: a_label /= Void
			valid_pos: pos > 0
		do
			label := a_label
			byte_code_position := pos
		ensure
			label_set: label = a_label
			byte_code_position_set: byte_code_position = pos
		end
			
feature -- Access
			
	label: JVM_LABEL
			-- the label `Current' is pointing to.
			-- This will be used to calculate the actual jump offset
			-- once the label is closed.
			
	byte_code_position: INTEGER
			-- absolute position (starting at 1) of the label_mark's
			-- jump instruction in the
			-- method's byte code. Exactly at this point the jump offset
			-- will be written at.
			
	jump_offset: INTEGER
			-- relative jump offset.
			-- If the `Result' is positive it means we will jump forward.
			-- If the `Result' is negative it means we will jump backwards.
		require
			label_closed: label.is_closed
		do
			Result := label.byte_code_position - byte_code_position
		end
																	
feature {ANY} -- Basic operations
			
invariant
	label_not_void: label /= Void
	byte_code_position_valid: byte_code_position > 0
																	
note
	copyright:	"Copyright (c) 1984-2006, Eiffel Software"
	license:	"GPL version 2 (see http://www.eiffel.com/licensing/gpl.txt)"
	licensing_options:	"http://www.eiffel.com/licensing"
	copying: "[
			This file is part of Eiffel Software's Eiffel Development Environment.
			
			Eiffel Software's Eiffel Development Environment is free
			software; you can redistribute it and/or modify it under
			the terms of the GNU General Public License as published
			by the Free Software Foundation, version 2 of the License
			(available at the URL listed under "license" above).
			
			Eiffel Software's Eiffel Development Environment is
			distributed in the hope that it will be useful,	but
			WITHOUT ANY WARRANTY; without even the implied warranty
			of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
			See the	GNU General Public License for more details.
			
			You should have received a copy of the GNU General Public
			License along with Eiffel Software's Eiffel Development
			Environment; if not, write to the Free Software Foundation,
			Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
		]"
	source: "[
			 Eiffel Software
			 356 Storke Road, Goleta, CA 93117 USA
			 Telephone 805-685-1006, Fax 805-685-6869
			 Website http://www.eiffel.com
			 Customer support http://support.eiffel.com
		]"

end