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	/*
	* Copyright (c) 2008, 2013, 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 sun.invoke.util;

	import java.lang.invoke.MethodHandle;
	import java.lang.invoke.MethodHandles;
	import java.lang.invoke.MethodHandles.Lookup;
	import java.lang.invoke.MethodType;
	import java.util.EnumMap;

	public class ValueConversions {
	private static final Class<?> THIS_CLASS = ValueConversions.class;
	private static final Lookup IMPL_LOOKUP = MethodHandles.lookup();

	/** Thread-safe canonicalized mapping from Wrapper to MethodHandle
	* with unsynchronized reads and synchronized writes.
	* It's safe to publish MethodHandles by data race because they are immutable. */
	private static class WrapperCache {
	/** EnumMap uses preconstructed array internally, which is constant during it's lifetime. */
	private final EnumMap<Wrapper, MethodHandle> map = new EnumMap<>(Wrapper.class);

	public MethodHandle get(Wrapper w) {
	return map.get(w);
	}
	public synchronized MethodHandle put(final Wrapper w, final MethodHandle mh) {
	// Simulate CAS to avoid racy duplication
	MethodHandle prev = map.putIfAbsent(w, mh);
	if (prev != null) return prev;
	return mh;
	}
	}

	private static WrapperCache[] newWrapperCaches(int n) {
	WrapperCache[] caches = new WrapperCache[n];
	for (int i = 0; i < n; i++)
	caches[i] = new WrapperCache();
	return caches;
	}

	/// Converting references to values.

	// There are several levels of this unboxing conversions:
	// no conversions: exactly Integer.valueOf, etc.
	// implicit conversions sanctioned by JLS 5.1.2, etc.
	// explicit conversions as allowed by explicitCastArguments

	static int unboxInteger(Integer x) {
	return x;
	}
	static int unboxInteger(Object x, boolean cast) {
	if (x instanceof Integer)
	return (Integer) x;
	return primitiveConversion(Wrapper.INT, x, cast).intValue();
	}

	static byte unboxByte(Byte x) {
	return x;
	}
	static byte unboxByte(Object x, boolean cast) {
	if (x instanceof Byte)
	return (Byte) x;
	return primitiveConversion(Wrapper.BYTE, x, cast).byteValue();
	}

	static short unboxShort(Short x) {
	return x;
	}
	static short unboxShort(Object x, boolean cast) {
	if (x instanceof Short)
	return (Short) x;
	return primitiveConversion(Wrapper.SHORT, x, cast).shortValue();
	}

	static boolean unboxBoolean(Boolean x) {
	return x;
	}
	static boolean unboxBoolean(Object x, boolean cast) {
	if (x instanceof Boolean)
	return (Boolean) x;
	return (primitiveConversion(Wrapper.BOOLEAN, x, cast).intValue() & 1) != 0;
	}

	static char unboxCharacter(Character x) {
	return x;
	}
	static char unboxCharacter(Object x, boolean cast) {
	if (x instanceof Character)
	return (Character) x;
	return (char) primitiveConversion(Wrapper.CHAR, x, cast).intValue();
	}

	static long unboxLong(Long x) {
	return x;
	}
	static long unboxLong(Object x, boolean cast) {
	if (x instanceof Long)
	return (Long) x;
	return primitiveConversion(Wrapper.LONG, x, cast).longValue();
	}

	static float unboxFloat(Float x) {
	return x;
	}
	static float unboxFloat(Object x, boolean cast) {
	if (x instanceof Float)
	return (Float) x;
	return primitiveConversion(Wrapper.FLOAT, x, cast).floatValue();
	}

	static double unboxDouble(Double x) {
	return x;
	}
	static double unboxDouble(Object x, boolean cast) {
	if (x instanceof Double)
	return (Double) x;
	return primitiveConversion(Wrapper.DOUBLE, x, cast).doubleValue();
	}

	private static MethodType unboxType(Wrapper wrap, int kind) {
	if (kind == 0)
	return MethodType.methodType(wrap.primitiveType(), wrap.wrapperType());
	return MethodType.methodType(wrap.primitiveType(), Object.class, boolean.class);
	}

	private static final WrapperCache[] UNBOX_CONVERSIONS = newWrapperCaches(4);

	private static MethodHandle unbox(Wrapper wrap, int kind) {
	// kind 0 -> strongly typed with NPE
	// kind 1 -> strongly typed but zero for null,
	// kind 2 -> asType rules: accept multiple box types but only widening conversions with NPE
	// kind 3 -> explicitCastArguments rules: allow narrowing conversions, zero for null
	WrapperCache cache = UNBOX_CONVERSIONS[kind];
	MethodHandle mh = cache.get(wrap);
	if (mh != null) {
	return mh;
	}
	// slow path
	switch (wrap) {
	case OBJECT:
	case VOID:
	throw new IllegalArgumentException("unbox "+wrap);
	}
	// look up the method
	String name = "unbox" + wrap.wrapperSimpleName();
	MethodType type = unboxType(wrap, kind);
	try {
	mh = IMPL_LOOKUP.findStatic(THIS_CLASS, name, type);
	} catch (ReflectiveOperationException ex) {
	mh = null;
	}
	if (mh != null) {
	if (kind > 0) {
	boolean cast = (kind != 2);
	mh = MethodHandles.insertArguments(mh, 1, cast);
	}
	if (kind == 1) { // casting but exact (null -> zero)
	mh = mh.asType(unboxType(wrap, 0));
	}
	return cache.put(wrap, mh);
	}
	throw new IllegalArgumentException("cannot find unbox adapter for " + wrap
	+ (kind <= 1 ? " (exact)" : kind == 3 ? " (cast)" : ""));
	}

	/** Return an exact unboxer for the given primitive type. */
	public static MethodHandle unboxExact(Wrapper type) {
	return unbox(type, 0);
	}

	/** Return an exact unboxer for the given primitive type, with optional null-to-zero conversion.
	* The boolean says whether to throw an NPE on a null value (false means unbox a zero).
	* The type of the unboxer is of a form like (Integer)int.
	*/
	public static MethodHandle unboxExact(Wrapper type, boolean throwNPE) {
	return unbox(type, throwNPE ? 0 : 1);
	}

	/** Return a widening unboxer for the given primitive type.
	* Widen narrower primitive boxes to the given type.
	* Do not narrow any primitive values or convert null to zero.
	* The type of the unboxer is of a form like (Object)int.
	*/
	public static MethodHandle unboxWiden(Wrapper type) {
	return unbox(type, 2);
	}

	/** Return a casting unboxer for the given primitive type.
	* Widen or narrow primitive values to the given type, or convert null to zero, as needed.
	* The type of the unboxer is of a form like (Object)int.
	*/
	public static MethodHandle unboxCast(Wrapper type) {
	return unbox(type, 3);
	}

	static private final Integer ZERO_INT = 0, ONE_INT = 1;

	/// Primitive conversions
	/**
	* Produce a Number which represents the given value {@code x}
	* according to the primitive type of the given wrapper {@code wrap}.
	* Caller must invoke intValue, byteValue, longValue (etc.) on the result
	* to retrieve the desired primitive value.
	*/
	public static Number primitiveConversion(Wrapper wrap, Object x, boolean cast) {
	// Maybe merge this code with Wrapper.convert/cast.
	Number res;
	if (x == null) {
	if (!cast) return null;
	return ZERO_INT;
	}
	if (x instanceof Number) {
	res = (Number) x;
	} else if (x instanceof Boolean) {
	res = ((boolean)x ? ONE_INT : ZERO_INT);
	} else if (x instanceof Character) {
	res = (int)(char)x;
	} else {
	// this will fail with the required ClassCastException:
	res = (Number) x;
	}
	Wrapper xwrap = Wrapper.findWrapperType(x.getClass());
	if (xwrap == null \|\| !cast && !wrap.isConvertibleFrom(xwrap))
	// this will fail with the required ClassCastException:
	return (Number) wrap.wrapperType().cast(x);
	return res;
	}

	/**
	* The JVM verifier allows boolean, byte, short, or char to widen to int.
	* Support exactly this conversion, from a boxed value type Boolean,
	* Byte, Short, Character, or Integer.
	*/
	public static int widenSubword(Object x) {
	if (x instanceof Integer)
	return (int) x;
	else if (x instanceof Boolean)
	return fromBoolean((boolean) x);
	else if (x instanceof Character)
	return (char) x;
	else if (x instanceof Short)
	return (short) x;
	else if (x instanceof Byte)
	return (byte) x;
	else
	// Fail with a ClassCastException.
	return (int) x;
	}

	/// Converting primitives to references

	static Integer boxInteger(int x) {
	return x;
	}

	static Byte boxByte(byte x) {
	return x;
	}

	static Short boxShort(short x) {
	return x;
	}

	static Boolean boxBoolean(boolean x) {
	return x;
	}

	static Character boxCharacter(char x) {
	return x;
	}

	static Long boxLong(long x) {
	return x;
	}

	static Float boxFloat(float x) {
	return x;
	}

	static Double boxDouble(double x) {
	return x;
	}

	private static MethodType boxType(Wrapper wrap) {
	// be exact, since return casts are hard to compose
	Class<?> boxType = wrap.wrapperType();
	return MethodType.methodType(boxType, wrap.primitiveType());
	}

	private static final WrapperCache[] BOX_CONVERSIONS = newWrapperCaches(1);

	public static MethodHandle boxExact(Wrapper wrap) {
	WrapperCache cache = BOX_CONVERSIONS[0];
	MethodHandle mh = cache.get(wrap);
	if (mh != null) {
	return mh;
	}
	// look up the method
	String name = "box" + wrap.wrapperSimpleName();
	MethodType type = boxType(wrap);
	try {
	mh = IMPL_LOOKUP.findStatic(THIS_CLASS, name, type);
	} catch (ReflectiveOperationException ex) {
	mh = null;
	}
	if (mh != null) {
	return cache.put(wrap, mh);
	}
	throw new IllegalArgumentException("cannot find box adapter for " + wrap);
	}

	/// Constant functions

	static void ignore(Object x) {
	// no value to return; this is an unbox of null
	}

	static void empty() {
	}

	static Object zeroObject() {
	return null;
	}

	static int zeroInteger() {
	return 0;
	}

	static long zeroLong() {
	return 0;
	}

	static float zeroFloat() {
	return 0;
	}

	static double zeroDouble() {
	return 0;
	}

	private static final WrapperCache[] CONSTANT_FUNCTIONS = newWrapperCaches(2);

	public static MethodHandle zeroConstantFunction(Wrapper wrap) {
	WrapperCache cache = CONSTANT_FUNCTIONS[0];
	MethodHandle mh = cache.get(wrap);
	if (mh != null) {
	return mh;
	}
	// slow path
	MethodType type = MethodType.methodType(wrap.primitiveType());
	switch (wrap) {
	case VOID:
	mh = EMPTY;
	break;
	case OBJECT:
	case INT: case LONG: case FLOAT: case DOUBLE:
	try {
	mh = IMPL_LOOKUP.findStatic(THIS_CLASS, "zero"+wrap.wrapperSimpleName(), type);
	} catch (ReflectiveOperationException ex) {
	mh = null;
	}
	break;
	}
	if (mh != null) {
	return cache.put(wrap, mh);
	}

	// use zeroInt and cast the result
	if (wrap.isSubwordOrInt() && wrap != Wrapper.INT) {
	mh = MethodHandles.explicitCastArguments(zeroConstantFunction(Wrapper.INT), type);
	return cache.put(wrap, mh);
	}
	throw new IllegalArgumentException("cannot find zero constant for " + wrap);
	}

	private static final MethodHandle CAST_REFERENCE, IGNORE, EMPTY;
	static {
	try {
	MethodType idType = MethodType.genericMethodType(1);
	MethodType ignoreType = idType.changeReturnType(void.class);
	CAST_REFERENCE = IMPL_LOOKUP.findVirtual(Class.class, "cast", idType);
	IGNORE = IMPL_LOOKUP.findStatic(THIS_CLASS, "ignore", ignoreType);
	EMPTY = IMPL_LOOKUP.findStatic(THIS_CLASS, "empty", ignoreType.dropParameterTypes(0, 1));
	} catch (NoSuchMethodException \| IllegalAccessException ex) {
	throw newInternalError("uncaught exception", ex);
	}
	}

	public static MethodHandle ignore() {
	return IGNORE;
	}

	/** Return a method that casts its second argument (an Object) to the given type (a Class). */
	public static MethodHandle cast() {
	return CAST_REFERENCE;
	}

	/// Primitive conversions.
	// These are supported directly by the JVM, usually by a single instruction.
	// In the case of narrowing to a subword, there may be a pair of instructions.
	// In the case of booleans, there may be a helper routine to manage a 1-bit value.
	// This is the full 8x8 matrix (minus the diagonal).

	// narrow double to all other types:
	static float doubleToFloat(double x) { // bytecode: d2f
	return (float) x;
	}
	static long doubleToLong(double x) { // bytecode: d2l
	return (long) x;
	}
	static int doubleToInt(double x) { // bytecode: d2i
	return (int) x;
	}
	static short doubleToShort(double x) { // bytecodes: d2i, i2s
	return (short) x;
	}
	static char doubleToChar(double x) { // bytecodes: d2i, i2c
	return (char) x;
	}
	static byte doubleToByte(double x) { // bytecodes: d2i, i2b
	return (byte) x;
	}
	static boolean doubleToBoolean(double x) {
	return toBoolean((byte) x);
	}

	// widen float:
	static double floatToDouble(float x) { // bytecode: f2d
	return x;
	}
	// narrow float:
	static long floatToLong(float x) { // bytecode: f2l
	return (long) x;
	}
	static int floatToInt(float x) { // bytecode: f2i
	return (int) x;
	}
	static short floatToShort(float x) { // bytecodes: f2i, i2s
	return (short) x;
	}
	static char floatToChar(float x) { // bytecodes: f2i, i2c
	return (char) x;
	}
	static byte floatToByte(float x) { // bytecodes: f2i, i2b
	return (byte) x;
	}
	static boolean floatToBoolean(float x) {
	return toBoolean((byte) x);
	}

	// widen long:
	static double longToDouble(long x) { // bytecode: l2d
	return x;
	}
	static float longToFloat(long x) { // bytecode: l2f
	return x;
	}
	// narrow long:
	static int longToInt(long x) { // bytecode: l2i
	return (int) x;
	}
	static short longToShort(long x) { // bytecodes: f2i, i2s
	return (short) x;
	}
	static char longToChar(long x) { // bytecodes: f2i, i2c
	return (char) x;
	}
	static byte longToByte(long x) { // bytecodes: f2i, i2b
	return (byte) x;
	}
	static boolean longToBoolean(long x) {
	return toBoolean((byte) x);
	}

	// widen int:
	static double intToDouble(int x) { // bytecode: i2d
	return x;
	}
	static float intToFloat(int x) { // bytecode: i2f
	return x;
	}
	static long intToLong(int x) { // bytecode: i2l
	return x;
	}
	// narrow int:
	static short intToShort(int x) { // bytecode: i2s
	return (short) x;
	}
	static char intToChar(int x) { // bytecode: i2c
	return (char) x;
	}
	static byte intToByte(int x) { // bytecode: i2b
	return (byte) x;
	}
	static boolean intToBoolean(int x) {
	return toBoolean((byte) x);
	}

	// widen short:
	static double shortToDouble(short x) { // bytecode: i2d (implicit 's2i')
	return x;
	}
	static float shortToFloat(short x) { // bytecode: i2f (implicit 's2i')
	return x;
	}
	static long shortToLong(short x) { // bytecode: i2l (implicit 's2i')
	return x;
	}
	static int shortToInt(short x) { // (implicit 's2i')
	return x;
	}
	// narrow short:
	static char shortToChar(short x) { // bytecode: i2c (implicit 's2i')
	return (char)x;
	}
	static byte shortToByte(short x) { // bytecode: i2b (implicit 's2i')
	return (byte)x;
	}
	static boolean shortToBoolean(short x) {
	return toBoolean((byte) x);
	}

	// widen char:
	static double charToDouble(char x) { // bytecode: i2d (implicit 'c2i')
	return x;
	}
	static float charToFloat(char x) { // bytecode: i2f (implicit 'c2i')
	return x;
	}
	static long charToLong(char x) { // bytecode: i2l (implicit 'c2i')
	return x;
	}
	static int charToInt(char x) { // (implicit 'c2i')
	return x;
	}
	// narrow char:
	static short charToShort(char x) { // bytecode: i2s (implicit 'c2i')
	return (short)x;
	}
	static byte charToByte(char x) { // bytecode: i2b (implicit 'c2i')
	return (byte)x;
	}
	static boolean charToBoolean(char x) {
	return toBoolean((byte) x);
	}

	// widen byte:
	static double byteToDouble(byte x) { // bytecode: i2d (implicit 'b2i')
	return x;
	}
	static float byteToFloat(byte x) { // bytecode: i2f (implicit 'b2i')
	return x;
	}
	static long byteToLong(byte x) { // bytecode: i2l (implicit 'b2i')
	return x;
	}
	static int byteToInt(byte x) { // (implicit 'b2i')
	return x;
	}
	static short byteToShort(byte x) { // bytecode: i2s (implicit 'b2i')
	return (short)x;
	}
	static char byteToChar(byte x) { // bytecode: i2b (implicit 'b2i')
	return (char)x;
	}
	// narrow byte to boolean:
	static boolean byteToBoolean(byte x) {
	return toBoolean(x);
	}

	// widen boolean to all types:
	static double booleanToDouble(boolean x) {
	return fromBoolean(x);
	}
	static float booleanToFloat(boolean x) {
	return fromBoolean(x);
	}
	static long booleanToLong(boolean x) {
	return fromBoolean(x);
	}
	static int booleanToInt(boolean x) {
	return fromBoolean(x);
	}
	static short booleanToShort(boolean x) {
	return fromBoolean(x);
	}
	static char booleanToChar(boolean x) {
	return (char)fromBoolean(x);
	}
	static byte booleanToByte(boolean x) {
	return fromBoolean(x);
	}

	// helpers to force boolean into the conversion scheme:
	static boolean toBoolean(byte x) {
	// see javadoc for MethodHandles.explicitCastArguments
	return ((x & 1) != 0);
	}
	static byte fromBoolean(boolean x) {
	// see javadoc for MethodHandles.explicitCastArguments
	return (x ? (byte)1 : (byte)0);
	}

	private static final WrapperCache[] CONVERT_PRIMITIVE_FUNCTIONS = newWrapperCaches(Wrapper.values().length);

	public static MethodHandle convertPrimitive(Wrapper wsrc, Wrapper wdst) {
	WrapperCache cache = CONVERT_PRIMITIVE_FUNCTIONS[wsrc.ordinal()];
	MethodHandle mh = cache.get(wdst);
	if (mh != null) {
	return mh;
	}
	// slow path
	Class<?> src = wsrc.primitiveType();
	Class<?> dst = wdst.primitiveType();
	MethodType type = MethodType.methodType(dst, src);
	if (wsrc == wdst) {
	mh = MethodHandles.identity(src);
	} else {
	assert(src.isPrimitive() && dst.isPrimitive());
	try {
	mh = IMPL_LOOKUP.findStatic(THIS_CLASS, src.getSimpleName()+"To"+capitalize(dst.getSimpleName()), type);
	} catch (ReflectiveOperationException ex) {
	mh = null;
	}
	}
	if (mh != null) {
	assert(mh.type() == type) : mh;
	return cache.put(wdst, mh);
	}

	throw new IllegalArgumentException("cannot find primitive conversion function for " +
	src.getSimpleName()+" -> "+dst.getSimpleName());
	}

	public static MethodHandle convertPrimitive(Class<?> src, Class<?> dst) {
	return convertPrimitive(Wrapper.forPrimitiveType(src), Wrapper.forPrimitiveType(dst));
	}

	private static String capitalize(String x) {
	return Character.toUpperCase(x.charAt(0))+x.substring(1);
	}

	// handy shared exception makers (they simplify the common case code)
	private static InternalError newInternalError(String message, Throwable cause) {
	return new InternalError(message, cause);
	}
	private static InternalError newInternalError(Throwable cause) {
	return new InternalError(cause);
	}
	}

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