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GraalVM is an ecosystem for compiling and running applications written in multiple languages. GraalVM removes the isolation between programming languages and enables interoperability in a shared runtime.

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/*
 * Copyright (c) 2013, 2017, 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 org.graalvm.nativeimage.c.struct;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.graalvm.word.LocationIdentity;
import org.graalvm.word.PointerBase;
import org.graalvm.word.WordBase;

/**
 * Denotes Java interface that imports a C pointer type. The interface must extend
 * {@link PointerBase}, i.e., it is a word type. There is never a Java class that implements the
 * interface.
 * 
 * If the method has a non-void return type that is not the annotated interface, it is a read-method
 * of the pointer. Calls of the method are replaced with a memory read. The possible signatures are
 * {@code ValueType read([IntType index], [LocationIdentity locationIdentity]);}
 * 

 * If the method has the return type void, it is a write-method of the pointer. Calls of the method
 * are replaced with a memory write. The possible signatures are
 * {@code void write([IntType index], ValueType value, [LocationIdentity locationIdentity]);}
 * 

 * If the return type of the method is the annotated interface, it is an address computation for an
 * array access. Calls of the method are replaced with address arithmetic. The possible signatures
 * are {@code PointerType addressOf(IntType index);}
 * 

 * The receiver is the pointer that is accessed, i.e., the base address of the memory access.
 * 

 * The {@code ValueType} must be the Java-equivalent of the C type used in the pointer definition.
 * 

 * The optional parameter {@code index} (always the first parameter when it is present) denotes an
 * index, i.e., the receiver is treated as an array of the pointers. The type must be a primitive
 * integer type or a {@link WordBase word type}. Address arithmetic is used to scale the index with
 * the size of the value type.
 * 

 * The optional parameter {@code locationIdentity} specifies the {@link LocationIdentity} to be used
 * for the memory access. Two memory accesses with two different location identities are guaranteed
 * to not alias. The parameter cannot be used together with the {@link UniqueLocationIdentity}
 * annotation, which is another way of providing a location identity for the memory access.
 * 
 * @since 1.0
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
public @interface CPointerTo {

    /**
     * The value type, as a reference to a Java interface that is either annotated with
     * {@link CStruct} or {@link CPointerTo}.
     * 

     * Exactly one of the properties {@link #value()} and {@link CPointerTo#nameOfCType()} must be
     * specified.
     *
     * @since 1.0
     */
    Class value() default WordBase.class;

    /**
     * The value type, as C type name.
     * 
     * Exactly one of the properties {@link #value()} and {@link CPointerTo#nameOfCType()} must be
     * specified.
     *
     * @since 1.0
     */
    String nameOfCType() default "";
}