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 * Copyright (c) 2009, 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.

 *

 * 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.

 *

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package jdk.vm.ci.meta;

/**

 * Represents the runtime representation of the constant pool that is used by the compiler when

 * parsing bytecode. Provides methods to look up a constant pool entry without performing

 * resolution. They are used during compilation.

 */

public interface ConstantPool {

    /**

     * Returns the number of entries the constant pool.

     *

     * @return number of entries in the constant pool

     */

    int length();

    /**

     * Ensures that the type referenced by the specified constant pool entry is loaded and

     * initialized. This can be used to compile time resolve a type. It works for field, method, or

     * type constant pool entries.

     *

     * @param cpi the index of the constant pool entry that references the type

     * @param opcode the opcode of the instruction that references the type

     */

    void loadReferencedType(int cpi, int opcode);

    /**

     * Looks up a reference to a field. If {@code opcode} is non-negative, then resolution checks

     * any of these checks fail, an unresolved field reference is returned.

     *

     * @param cpi the constant pool index

     * @param opcode the opcode of the instruction for which the lookup is being performed or

     *            {@code -1}

     * @return a reference to the field at {@code cpi} in this pool

     * @throws ClassFormatError if the entry at {@code cpi} is not a field

     */

    /**

     * Looks up a reference to a method. If {@code opcode} is non-negative, then resolution checks

     * specific to the bytecode it denotes are performed if the method is already resolved. Should

     * any of these checks fail, an unresolved method reference is returned.

     *

     * @param cpi the constant pool index

     * @param opcode the opcode of the instruction for which the lookup is being performed or

     *            {@code -1}

     * @return a reference to the method at {@code cpi} in this pool

     * @throws ClassFormatError if the entry at {@code cpi} is not a method

     */

    JavaMethod lookupMethod(int cpi, int opcode);

    /**

     * Looks up a reference to a type. If {@code opcode} is non-negative, then resolution checks

     * specific to the bytecode it denotes are performed if the type is already resolved. Should any

     * of these checks fail, an unresolved type reference is returned.

     *

     * @param cpi the constant pool index

     * @param opcode the opcode of the instruction for which the lookup is being performed or

     *            {@code -1}

     * @return a reference to the compiler interface type

     */

    JavaType lookupType(int cpi, int opcode);

    /**

     * Looks up an Utf8 string.

     *

     * @param cpi the constant pool index

     * @return the Utf8 string at index {@code cpi} in this constant pool

     */

    String lookupUtf8(int cpi);

    /**

     * Looks up a method signature.

     *

     * @param cpi the constant pool index

     * @return the method signature at index {@code cpi} in this constant pool

     */

    Signature lookupSignature(int cpi);

    /**

     * Looks up a constant at the specified index.

     *

     * @param cpi the constant pool index

     * @return the {@code Constant} or {@code JavaType} instance representing the constant pool

     *         entry

     */

    Object lookupConstant(int cpi);

    /**

     * Looks up the appendix at the specified index.

     *

     * @param cpi the constant pool index

     * @param opcode the opcode of the instruction for which the lookup is being performed or

     *            {@code -1}

     * @return the appendix if it exists and is resolved or {@code null}

     */

    JavaConstant lookupAppendix(int cpi, int opcode);

}