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	/*
	* Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code 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
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*
	*/

	package jdk.internal.access.foreign;

	import jdk.internal.misc.ScopedMemoryAccess;

	/**
	* This abstract class is required to allow implementations of the {@code MemorySegment} interface (which is defined inside
	* an incubating module) to be accessed from the memory access var handles.
	*/
	public abstract class MemorySegmentProxy {
	/**
	* Check that memory access is within spatial bounds and that access is compatible with segment access modes.
	* @throws UnsupportedOperationException if underlying segment has incompatible access modes (e.g. attempting to write
	* a read-only segment).
	* @throws IndexOutOfBoundsException if access is out-of-bounds.
	*/
	public abstract void checkAccess(long offset, long length, boolean readOnly);
	public abstract long unsafeGetOffset();
	public abstract Object unsafeGetBase();
	public abstract boolean isSmall();
	public abstract ScopedMemoryAccess.Scope scope();

	/* Helper functions for offset computations. These are required so that we can avoid issuing long opcodes
	* (e.g. LMUL, LADD) when we're operating on 'small' segments (segments whose length can be expressed with an int).
	* C2 BCE code is very sensitive to the kind of opcode being emitted, and this workaround allows us to rescue
	* BCE when working with small segments. This workaround should be dropped when JDK-8223051 is resolved.
	*/

	public static long addOffsets(long op1, long op2, MemorySegmentProxy segmentProxy) {
	if (segmentProxy.isSmall()) {
	// force ints for BCE
	if (op1 > Integer.MAX_VALUE \|\| op2 > Integer.MAX_VALUE
	\|\| op1 < Integer.MIN_VALUE \|\| op2 < Integer.MIN_VALUE) {
	throw overflowException(Integer.MIN_VALUE, Integer.MAX_VALUE);
	}
	int i1 = (int)op1;
	int i2 = (int)op2;
	try {
	return Math.addExact(i1, i2);
	} catch (ArithmeticException ex) {
	throw overflowException(Integer.MIN_VALUE, Integer.MAX_VALUE);
	}
	} else {
	try {
	return Math.addExact(op1, op2);
	} catch (ArithmeticException ex) {
	throw overflowException(Long.MIN_VALUE, Long.MAX_VALUE);
	}
	}
	}

	public static long multiplyOffsets(long op1, long op2, MemorySegmentProxy segmentProxy) {
	if (segmentProxy.isSmall()) {
	if (op1 > Integer.MAX_VALUE \|\| op2 > Integer.MAX_VALUE
	\|\| op1 < Integer.MIN_VALUE \|\| op2 < Integer.MIN_VALUE) {
	throw overflowException(Integer.MIN_VALUE, Integer.MAX_VALUE);
	}
	// force ints for BCE
	int i1 = (int)op1;
	int i2 = (int)op2;
	try {
	return Math.multiplyExact(i1, i2);
	} catch (ArithmeticException ex) {
	throw overflowException(Integer.MIN_VALUE, Integer.MAX_VALUE);
	}
	} else {
	try {
	return Math.multiplyExact(op1, op2);
	} catch (ArithmeticException ex) {
	throw overflowException(Long.MIN_VALUE, Long.MAX_VALUE);
	}
	}
	}

	private static IndexOutOfBoundsException overflowException(long min, long max) {
	return new IndexOutOfBoundsException(String.format("Overflow occurred during offset computation ; offset exceeded range { %d .. %d }", min, max));
	}
	}

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