com.oracle.truffle.api.interop.Message Maven / Gradle / Ivy
Show all versions of truffle-api Show documentation
/*
* Copyright (c) 2014, 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 com.oracle.truffle.api.interop;
import com.oracle.truffle.api.TruffleLanguage.Env;
import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.api.interop.ForeignAccess.Factory;
import com.oracle.truffle.api.nodes.Node;
/**
* Inter-operability is based on sending messages. Standard messages are defined as as constants
* like {@link #IS_NULL} or factory methods in this class, but one can always define their own,
* specialized messages.
*
* @since 0.8 or earlier
*/
public abstract class Message {
/**
* One can define their own extended message by subclassing. The expectation is that the
* subclass will have public constructor and its {@link #equals(java.lang.Object)} and
* {@link #hashCode()} methods will operate on the class equivalence. Only then the subclass
* will work properly with {@link #valueOf(java.lang.String)} and
* {@link #toString(com.oracle.truffle.api.interop.Message)} methods.
*
* @since 0.8 or earlier
*/
protected Message() {
}
/**
* Message to read an object field. The
* {@link Factory#access(com.oracle.truffle.api.interop.Message) target} created for this
* message accepts (in addition to a
* {@link ForeignAccess#getReceiver(com.oracle.truffle.api.frame.Frame) receiver}) a single
* {@link ForeignAccess#getArguments(com.oracle.truffle.api.frame.Frame) argument} identifying a
* field to read - e.g. either {@link String} or an {@link Integer} - if access to an array at
* particular index is requested. The code that wants to send this message should use:
*
*
* {@link ForeignAccess}.{@link ForeignAccess#execute(com.oracle.truffle.api.nodes.Node, com.oracle.truffle.api.frame.VirtualFrame, com.oracle.truffle.api.interop.TruffleObject, java.lang.Object...) execute}(
* {@link Message#READ}.{@link Message#createNode()}, {@link VirtualFrame currentFrame}, receiver, nameOfTheField
* );
*
*
* Where receiver is the {@link TruffleObject foreign object} to access and
* nameOfTheField is the name (or index) of its field.
*
* To achieve good performance it is essential to cache/keep reference to the
* {@link Message#createNode() created node}.
*
* @since 0.8 or earlier
*/
public static final Message READ = Read.INSTANCE;
/**
* Converts {@link TruffleObject truffle value} to Java primitive type. Primitive types are
* subclasses of {@link Number}, {@link Boolean}, {@link Character} and {@link String}. Before
* sending the {@link #UNBOX} message, it is desirable to send the {@link #IS_BOXED} one and
* verify that the object can really be unboxed. To unbox an object, use:
*
*
* {@link ForeignAccess}.{@link ForeignAccess#execute(com.oracle.truffle.api.nodes.Node, com.oracle.truffle.api.frame.VirtualFrame, com.oracle.truffle.api.interop.TruffleObject, java.lang.Object...) execute}(
* {@link Message#UNBOX}.{@link Message#createNode()}, {@link VirtualFrame currentFrame}, objectToUnbox
* );
*
*
* The returned value should be subclass of {@link Number}, {@link Boolean}, {@link Character}
* or {@link String}.
*
* To achieve good performance it is essential to cache/keep reference to the
* {@link Message#createNode() created node}.
*
* @since 0.8 or earlier
*/
public static final Message UNBOX = Unbox.INSTANCE;
/**
* Message to write a field. The {@link Factory#access(com.oracle.truffle.api.interop.Message)
* target} created for this message accepts the object to modify as a
* {@link ForeignAccess#getReceiver(com.oracle.truffle.api.frame.Frame) receiver} and two
* {@link ForeignAccess#getArguments(com.oracle.truffle.api.frame.Frame) arguments}. The first
* one identifies a field to read - e.g. either {@link String} or an {@link Integer} - if access
* to an array at particular index is requested. The second one is the value to assign to such
* field. Use following style to construct field modification message:
*
*
* {@link ForeignAccess}.{@link ForeignAccess#execute(com.oracle.truffle.api.nodes.Node, com.oracle.truffle.api.frame.VirtualFrame, com.oracle.truffle.api.interop.TruffleObject, java.lang.Object...) execute}(
* {@link Message#WRITE}.{@link Message#createNode()}, {@link VirtualFrame currentFrame}, receiver, nameOfTheField, newValue
* );
*
*
* Where receiver is the {@link TruffleObject foreign object} to access,
* nameOfTheField is the name (or index) of its field and newValue is
* the value to assign to the receiver's field.
*
* To achieve good performance it is essential to cache/keep reference to the
* {@link Message#createNode() created node}.
*
* @since 0.8 or earlier
*/
public static final Message WRITE = Write.INSTANCE;
/**
* Creates a non-object oriented execution message. In contrast to {@link #createInvoke(int)}
* messages, which are more suitable for dealing with object oriented style of programming,
* messages created by this method are more suitable for execution where one can explicitly
* control all passed in arguments.
*
* To inter-operate with a non-OOP language like C - for example to execute its
* function:
*
*
* double add(double a, double b) {
* return a + b;
* }
*
*
* One can obtain reference to the add function (for example by
* {@link Env#importSymbol(java.lang.String) importing it as a global symbol}) and store it into
* variable addFunction. Then it's time to check the object is executable by
* sending it the {@link #IS_EXECUTABLE} message. If the answer is true one can:
*
*
* {@link ForeignAccess}.{@link ForeignAccess#execute(com.oracle.truffle.api.nodes.Node, com.oracle.truffle.api.frame.VirtualFrame, com.oracle.truffle.api.interop.TruffleObject, java.lang.Object...) execute}(
* {@link Message#createExecute(int) Message.createExecute}(2).{@link Message#createNode()}, {@link VirtualFrame currentFrame}, addFunction, valueOfA, valueOfB
* );
*
*
* The valueOfA and valueOfB should be double or
* {@link Double} or at least be {@link #UNBOX unboxable} to such type.
*
* One can use this method to talk to object oriented language as well, however one needs to pay
* attention to provide all necessary arguments manually - usually an OOP language requires the
* first argument to represent this or self and only then pass in the
* additional arguments. It may be easier to use {@link #createInvoke(int)} message which is
* more suitable for object oriented languages and handles (if supported) the arguments
* manipulation automatically.
*
*
*
*
* All messages created by this method are {@link Object#equals(java.lang.Object) equal} to each
* other regardless of the value of argumentsLength.
*
* @param argumentsLength number of parameters to pass to the target
* @return execute message
* @since 0.8 or earlier
*/
public static Message createExecute(int argumentsLength) {
return Execute.create(Execute.EXECUTE, argumentsLength);
}
/**
* Message to check executability of a
* {@link ForeignAccess#getReceiver(com.oracle.truffle.api.frame.Frame) foreign object}.
*
* Calling {@link Factory#access(com.oracle.truffle.api.interop.Message) the target} created for
* this message accepts {@link ForeignAccess#getArguments(com.oracle.truffle.api.frame.Frame) no
* arguments} and a single non-null
* {@link ForeignAccess#getReceiver(com.oracle.truffle.api.frame.Frame) receiver}. The call
* should yield value of {@link Boolean}. Either {@link Boolean#TRUE} if the receiver can be
* executed (e.g. accepts {@link #createExecute(int)} message, or {@link Boolean#FALSE}
* otherwise. This is the way to send the IS_EXECUTABLE message:
*
*
* {@link Boolean} canBeExecuted = ({@link Boolean}) {@link ForeignAccess}.execute(
* {@link Message#IS_EXECUTABLE}.{@link Message#createNode()}, {@link VirtualFrame currentFrame}, receiver
* );
*
*
* To achieve good performance it is essential to cache/keep reference to the
* {@link Message#createNode() created node}.
*
* @since 0.8 or earlier
*/
public static final Message IS_EXECUTABLE = IsExecutable.INSTANCE;
/**
* Creates an object oriented execute message. Unlike {@link #createExecute(int)} the receiver
* of the message isn't the actual function to invoke, but an object. The object has the
* function as a field, or as a field of its class, or whatever is appropriate for an object
* oriented language.
*
* Languages that don't support object oriented semantics do not and should not implement this
* message. When the invoke message isn't supported, the caller is expected to fall back into
* following basic operations:
*
* - sending {@link #READ} message to access the field
* - verify the result {@link #IS_EXECUTABLE}, if so continue by
* - sending {@link #createExecute(int) execute message}
*
*
* The last step is problematic, as it is not clear whether to pass just the execution
* arguments, or prefix them with the original receiver (aka this or
* self). Object oriented languages would in general welcome obtaining the
* receiving object as first argument, non-object languages like C would get confused
* by doing so. However it is not possible for the caller to find out what language one is
* sending message to - only the set of supported messages is known. As a result it is
* recommended for object oriented languages to support the {@link #createInvoke(int)} message
* and handle the semantics the way it is natural to them. Languages like C shouldn't
* implement {@link #createInvoke(int)} and just support primitive operations like
* {@link #createExecute(int)} and {@link #READ}.
*
* When accessing a method of an object in an object oriented manner, one is supposed to send
* the {@link #createInvoke(int)} message first. Only when that fails, fallback to non-object
* oriented workflow with {@link #createExecute(int)}. Imagine there is a Java class
* with add method and its instance:
*
*
* public class Arith {
* public double add(double a, double b) {
* return a + b;
* }
* }
* Arith obj = new Arith();
*
*
* To access obj's add method one should use:
*
*
* try {
* {@link ForeignAccess}.{@link ForeignAccess#execute(com.oracle.truffle.api.nodes.Node, com.oracle.truffle.api.frame.VirtualFrame, com.oracle.truffle.api.interop.TruffleObject, java.lang.Object...) execute}(
* {@link Message#createInvoke(int) Message.createInvoke}(2).{@link Message#createNode()}, {@link VirtualFrame currentFrame}, obj, "add", valueOfA, valueOfB
* );
* } catch ({@link IllegalArgumentException} ex) {
* // access the language via {@link #createExecute(int)}
* }
*
*
* The valueOfA and valueOfB should be double or
* {@link Double} or at least be {@link #UNBOX unboxable} to such type.
*
* All messages created by this method are {@link Object#equals(java.lang.Object) equal} to each
* other regardless of the value of argumentsLength. The expected behavior of this
* message is to perform {@link #READ} first and on the result invoke
* {@link #createExecute(int)}.
*
* @param argumentsLength number of parameters to pass to the target
* @return message combining read & execute messages tailored for use with object oriented
* languages
* @since 0.8 or earlier
*/
public static Message createInvoke(int argumentsLength) {
return Execute.create(Execute.INVOKE, argumentsLength);
}
/**
* Creates an allocation message. All messages created by this method are
* {@link Object#equals(java.lang.Object) equal} to each other regardless of the value of
* argumentsLength. The expected behavior of this message is to allocate a new
* instance of the {@link ForeignAccess#getReceiver(com.oracle.truffle.api.frame.Frame)
* receiver} and then perform its constructor with appropriate number of arguments.
*
* @param argumentsLength number of parameters to pass to the target
* @return new instance message
* @since 0.8 or earlier
*/
public static Message createNew(int argumentsLength) {
return Execute.create(Execute.NEW, argumentsLength);
}
/**
* Check for null message. The Truffle languages are suggested to have their own
* object representing null like values in their languages. For purposes of
* inter-operability it is essential to canonicalize such values from time to time - sending
* this message is a way to recognize such null representing values:
*
*
* {@link Boolean} isNull = ({@link Boolean}) {@link ForeignAccess}.execute(
* {@link Message#IS_NULL}.{@link Message#createNode()}, {@link VirtualFrame currentFrame}, objectToCheckForNull
* );
*
*
*
* Calling {@link Factory#access(com.oracle.truffle.api.interop.Message) the target} created for
* this message should yield value of {@link Boolean}.
*
* To achieve good performance it is essential to cache/keep reference to the
* {@link Message#createNode() created node}.
*
* @since 0.8 or earlier
*/
public static final Message IS_NULL = IsNull.INSTANCE;
/**
* Message to check for having a size.
*
* Calling {@link Factory#access(com.oracle.truffle.api.interop.Message) the target} created for
* this message should yield value of {@link Boolean}.
*
* @since 0.8 or earlier
*/
public static final Message HAS_SIZE = HasSize.INSTANCE;
/**
* Getter of the size. If {@link #HAS_SIZE supported}, this message allows to obtain a size (of
* an array).
*
* Calling {@link Factory#access(com.oracle.truffle.api.interop.Message) the target} created for
* this message should yield value of {@link Integer}.
*
* @since 0.8 or earlier
*/
public static final Message GET_SIZE = GetSize.INSTANCE;
/**
* Check for value being boxed. Can the {@link TruffleObject foreign object} be converted to one
* of the basic Java types? Many languages have a special representation for types like number,
* string, etc. To ensure inter-operability, these types should support unboxing - if they do,
* they should handle this message and return {@link Boolean#TRUE}. The way to check whether an
* object is boxed is:
*
*
* {@link Boolean} isBoxed = ({@link Boolean}) {@link ForeignAccess}.execute(
* {@link Message#IS_BOXED}.{@link Message#createNode()}, {@link VirtualFrame currentFrame}, objectToCheck
* );
*
*
* Calling {@link Factory#accessMessage(com.oracle.truffle.api.interop.Message) the target}
* created for this message should yield value of {@link Boolean}. If the object responds with
* {@link Boolean#TRUE}, it is safe to continue by sending it {@link #UNBOX} message.
*
* @since 0.8 or earlier
*/
public static final Message IS_BOXED = IsBoxed.INSTANCE;
/**
* Compares types of two messages. Messages are encouraged to implement this method. All
* standard ones ({@link #IS_NULL}, {@link #READ}, etc.) do so. Messages obtained via the same
* {@link #createExecute(int) method} are equal, messages obtained by different methods or
* fields are not.
*
* @param message the object to compare to
* @return true, if the structure of the message is that same as of this one.
* @since 0.8 or earlier
*/
@Override
public abstract boolean equals(Object message);
/**
* When re-implementing {@link #equals(java.lang.Object)}, it is generally recommended to also
* implement hashCode().
*
* @return hash code
* @since 0.8 or earlier
*/
@Override
public abstract int hashCode();
/**
* Creates an AST node for this message. The node can be inserted into AST of your language and
* will handle communication with the foreign language.
*
* @return node to be inserted into your AST and passed back to
* {@link ForeignAccess#execute(com.oracle.truffle.api.nodes.Node, com.oracle.truffle.api.frame.VirtualFrame, com.oracle.truffle.api.interop.TruffleObject, java.lang.Object[])}
* method.
* @since 0.8 or earlier
*/
public final Node createNode() {
return new ForeignObjectAccessHeadNode(this);
}
/**
* Converts the message into canonical string representation. The converted string can be
* stored, persisted, transfered and later passed to {@link #valueOf(java.lang.String)} to
* construct the message again.
*
* @param message the message to convert
* @return canonical string representation
* @since 0.9
*/
public static String toString(Message message) {
if (Message.READ == message) {
return "READ"; // NOI18N
}
if (Message.WRITE == message) {
return "WRITE"; // NOI18N
}
if (Message.UNBOX == message) {
return "UNBOX"; // NOI18N
}
if (Message.GET_SIZE == message) {
return "GET_SIZE"; // NOI18N
}
if (Message.HAS_SIZE == message) {
return "HAS_SIZE"; // NOI18N
}
if (Message.IS_NULL == message) {
return "IS_NULL"; // NOI18N
}
if (Message.IS_BOXED == message) {
return "IS_BOXED"; // NOI18N
}
if (Message.IS_EXECUTABLE == message) {
return "IS_EXECUTABLE"; // NOI18N
}
if (message instanceof Execute) {
return ((Execute) message).name();
}
return message.getClass().getName();
}
/**
* Converts string representation into real message. If the string was obtained by
* {@link #toString(com.oracle.truffle.api.interop.Message)} method, it is guaranteed to be
* successfully recognized (if the classpath of the system remains the same).
*
* @param message canonical string representation of a message
* @return the message
* @throws IllegalArgumentException if the string does not represent known message
* @since 0.9
*/
public static Message valueOf(String message) {
try {
return (Message) Message.class.getField(message.toUpperCase()).get(null);
} catch (Exception ex) {
try {
String factory = "create" + Character.toUpperCase(message.charAt(0)) + message.substring(1).toLowerCase();
return (Message) Message.class.getMethod(factory, int.class).invoke(null, 0);
} catch (Exception ex2) {
try {
ClassLoader l = Message.class.getClassLoader();
if (l == null) {
l = ClassLoader.getSystemClassLoader();
}
return (Message) Class.forName(message, false, l).newInstance();
} catch (Exception ex1) {
throw new IllegalArgumentException("Cannot find message for " + message, ex);
}
}
}
}
}