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*
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* accompanied this code).
*
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package jdk.nashorn.internal.lookup;
import static jdk.nashorn.internal.runtime.ECMAErrors.typeError;
import static jdk.nashorn.internal.runtime.ScriptRuntime.UNDEFINED;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import jdk.nashorn.internal.runtime.JSType;
import jdk.nashorn.internal.runtime.ScriptRuntime;
/**
* MethodHandle Lookup management for Nashorn.
*/
public final class Lookup {
/**
* A global singleton that points to the {@link MethodHandleFunctionality}. This is basically
* a collection of wrappers to the standard methods in {@link MethodHandle}, {@link MethodHandles} and
* {@link java.lang.invoke.MethodHandles.Lookup}, but instrumentation and debugging purposes we need
* intercept points.
* <p>
* All method handle operations in Nashorn should go through this field, not directly to the classes
* in {@code java.lang.invoke}
*/
public static final MethodHandleFunctionality MH = MethodHandleFactory.getFunctionality();
/** Method handle to the empty getter */
public static final MethodHandle EMPTY_GETTER = findOwnMH("emptyGetter", Object.class, Object.class);
/** Method handle to the empty setter */
public static final MethodHandle EMPTY_SETTER = findOwnMH("emptySetter", void.class, Object.class, Object.class);
/** Method handle to a getter or setter that only throws type error */
public static final MethodHandle TYPE_ERROR_THROWER = findOwnMH("typeErrorThrower", Object.class, Object.class);
/** Method handle to the most generic of getters, the one that returns an Object */
public static final MethodType GET_OBJECT_TYPE = MH.type(Object.class, Object.class);
/** Method handle to the most generic of setters, the one that takes an Object */
public static final MethodType SET_OBJECT_TYPE = MH.type(void.class, Object.class, Object.class);
/** Method handle to the primitive getters, the one that returns an long/int/double */
public static final MethodType GET_PRIMITIVE_TYPE = MH.type(long.class, Object.class);
/** Method handle to the primitive getters, the one that returns an long/int/double */
public static final MethodType SET_PRIMITIVE_TYPE = MH.type(void.class, Object.class, long.class);
private Lookup() {
}
/**
* Empty getter implementation. Nop
* @param self self reference
* @return undefined
*/
public static Object emptyGetter(final Object self) {
return UNDEFINED;
}
/**
* Empty setter implementation. Nop
* @param self self reference
* @param value value (ignored)
*/
public static void emptySetter(final Object self, final Object value) {
// do nothing!!
}
/**
* Return a method handle to the empty getter, with a different
* return type value. It will still be undefined cast to whatever
* return value property was specified
*
* @param type return value type
*
* @return undefined as return value type
*/
public static MethodHandle emptyGetter(final Class<?> type) {
return filterReturnType(EMPTY_GETTER, type);
}
/**
* Getter function that always throws type error
*
* @param self self reference
* @return undefined (but throws error before return point)
*/
public static Object typeErrorThrower(final Object self) {
throw typeError("strict.getter.setter.poison", ScriptRuntime.safeToString(self));
}
/**
* This method filters primitive argument types using JavaScript semantics. For example,
* an (int) cast of a double in Java land is not the same thing as invoking toInt32 on it.
* If you are returning values to JavaScript that have to be of a specific type, this is
* the correct return value filter to use, as the explicitCastArguments just uses the
* Java boxing equivalents
*
* @param mh method handle for which to filter argument value
* @param n argument index
* @param from old argument type, the new one is given by the sent method handle
* @return method handle for appropriate argument type conversion
*/
public static MethodHandle filterArgumentType(final MethodHandle mh, final int n, final Class<?> from) {
final Class<?> to = mh.type().parameterType(n);
if (from == int.class) {
//fallthru
} else if (from == long.class) {
if (to == int.class) {
return MH.filterArguments(mh, n, JSType.TO_INT32_L.methodHandle());
}
//fallthru
} else if (from == double.class) {
if (to == int.class) {
return MH.filterArguments(mh, n, JSType.TO_INT32_D.methodHandle());
} else if (to == long.class) {
return MH.filterArguments(mh, n, JSType.TO_UINT32_D.methodHandle());
}
//fallthru
} else if (!from.isPrimitive()) {
if (to == int.class) {
return MH.filterArguments(mh, n, JSType.TO_INT32.methodHandle());
} else if (to == long.class) {
return MH.filterArguments(mh, n, JSType.TO_UINT32.methodHandle());
} else if (to == double.class) {
return MH.filterArguments(mh, n, JSType.TO_NUMBER.methodHandle());
} else if (!to.isPrimitive()) {
return mh;
}
assert false : "unsupported Lookup.filterReturnType type " + from + " -> " + to;
}
//use a standard cast - we don't need to check JavaScript special cases
return MH.explicitCastArguments(mh, mh.type().changeParameterType(n, from));
}
/**
* This method filters primitive return types using JavaScript semantics. For example,
* an (int) cast of a double in Java land is not the same thing as invoking toInt32 on it.
* If you are returning values to JavaScript that have to be of a specific type, this is
* the correct return value filter to use, as the explicitCastArguments just uses the
* Java boxing equivalents
*
* @param mh method handle for which to filter return value
* @param type new return type
* @return method handle for appropriate return type conversion
*/
public static MethodHandle filterReturnType(final MethodHandle mh, final Class<?> type) {
final Class<?> retType = mh.type().returnType();
if (retType == int.class) {
//fallthru
} else if (retType == long.class) {
if (type == int.class) {
return MH.filterReturnValue(mh, JSType.TO_INT32_L.methodHandle());
}
//fallthru
} else if (retType == double.class) {
if (type == int.class) {
return MH.filterReturnValue(mh, JSType.TO_INT32_D.methodHandle());
} else if (type == long.class) {
return MH.filterReturnValue(mh, JSType.TO_UINT32_D.methodHandle());
}
//fallthru
} else if (!retType.isPrimitive()) {
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