JDK14/Java14源码在线阅读

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 *
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 * 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
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 * 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
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/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file:
 *
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2011 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package jdk.internal.org.objectweb.asm;

/**
 * A non standard class, field, method or code attribute, as defined in the Java Virtual Machine
 * Specification (JVMS).
 *
 * @see <a href= "https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7">JVMS
 *     4.7</a>
 * @see <a href= "https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.3">JVMS
 *     4.7.3</a>
 * @author Eric Bruneton
 * @author Eugene Kuleshov
 */
public class Attribute {

    /** The type of this attribute, also called its name in the JVMS. */
    public final String type;

    /**
      * The raw content of this attribute, only used for unknown attributes (see {@link #isUnknown()}).
      * The 6 header bytes of the attribute (attribute_name_index and attribute_length) are <i>not</i>
      * included.
      */
    private byte[] content;

    /**
      * The next attribute in this attribute list (Attribute instances can be linked via this field to
      * store a list of class, field, method or code attributes). May be {@literal null}.
      */
    Attribute nextAttribute;

    /**
      * Constructs a new empty attribute.
      *
      * @param type the type of the attribute.
      */
    protected Attribute(final String type) {
        this.type = type;
    }

    /**
      * Returns {@literal true} if this type of attribute is unknown. This means that the attribute
      * content can't be parsed to extract constant pool references, labels, etc. Instead, the
      * attribute content is read as an opaque byte array, and written back as is. This can lead to
      * invalid attributes, if the content actually contains constant pool references, labels, or other
      * symbolic references that need to be updated when there are changes to the constant pool, the
      * method bytecode, etc. The default implementation of this method always returns {@literal true}.
      *
      * @return {@literal true} if this type of attribute is unknown.
      */
    public boolean isUnknown() {
        return true;
    }

    /**
      * Returns {@literal true} if this type of attribute is a code attribute.
      *
      * @return {@literal true} if this type of attribute is a code attribute.
      */
    public boolean isCodeAttribute() {
        return false;
    }

    /**
      * Returns the labels corresponding to this attribute.
      *
      * @return the labels corresponding to this attribute, or {@literal null} if this attribute is not
      *     a code attribute that contains labels.
      */
    protected Label[] getLabels() {
        return new Label[0];
    }

    /**
      * Reads a {@link #type} attribute. This method must return a <i>new</i> {@link Attribute} object,
      * of type {@link #type}, corresponding to the 'length' bytes starting at 'offset', in the given
      * ClassReader.
      *
      * @param classReader the class that contains the attribute to be read.
      * @param offset index of the first byte of the attribute's content in {@link ClassReader#b}. The
      *     6 attribute header bytes (attribute_name_index and attribute_length) are not taken into
      *     account here.
      * @param length the length of the attribute's content (excluding the 6 attribute header bytes).
      * @param charBuffer the buffer to be used to call the ClassReader methods requiring a
      *     'charBuffer' parameter.
      * @param codeAttributeOffset index of the first byte of content of the enclosing Code attribute
      *     in {@link ClassReader#b}, or -1 if the attribute to be read is not a code attribute. The 6
      *     attribute header bytes (attribute_name_index and attribute_length) are not taken into
      *     account here.
      * @param labels the labels of the method's code, or {@literal null} if the attribute to be read
      *     is not a code attribute.
      * @return a <i>new</i> {@link Attribute} object corresponding to the specified bytes.
      */
    protected Attribute read(
            final ClassReader classReader,
            final int offset,
            final int length,
            final char[] charBuffer,
            final int codeAttributeOffset,
            final Label[] labels) {
        Attribute attribute = new Attribute(type);
        attribute.content = new byte[length];
        System.arraycopy(classReader.b, offset, attribute.content, 0, length);
        return attribute;
    }

    /**
      * Returns the byte array form of the content of this attribute. The 6 header bytes
      * (attribute_name_index and attribute_length) must <i>not</i> be added in the returned
      * ByteVector.
      *
      * @param classWriter the class to which this attribute must be added. This parameter can be used
      *     to add the items that corresponds to this attribute to the constant pool of this class.
      * @param code the bytecode of the method corresponding to this code attribute, or {@literal null}
      *     if this attribute is not a code attribute. Corresponds to the 'code' field of the Code
      *     attribute.
      * @param codeLength the length of the bytecode of the method corresponding to this code
      *     attribute, or 0 if this attribute is not a code attribute. Corresponds to the 'code_length'
      *     field of the Code attribute.
      * @param maxStack the maximum stack size of the method corresponding to this code attribute, or
      *     -1 if this attribute is not a code attribute.
      * @param maxLocals the maximum number of local variables of the method corresponding to this code
      *     attribute, or -1 if this attribute is not a code attribute.
      * @return the byte array form of this attribute.
      */
    protected ByteVector write(
            final ClassWriter classWriter,
            final byte[] code,
            final int codeLength,
            final int maxStack,
            final int maxLocals) {
        return new ByteVector(content);
    }

    /**
      * Returns the number of attributes of the attribute list that begins with this attribute.
      *
      * @return the number of attributes of the attribute list that begins with this attribute.
      */
    final int getAttributeCount() {
        int count = 0;
        Attribute attribute = this;
        while (attribute != null) {
            count += 1;
            attribute = attribute.nextAttribute;
        }
        return count;
    }

    /**
      * Returns the total size in bytes of all the attributes in the attribute list that begins with
      * this attribute. This size includes the 6 header bytes (attribute_name_index and
      * attribute_length) per attribute. Also adds the attribute type names to the constant pool.
      *
      * @param symbolTable where the constants used in the attributes must be stored.
      * @return the size of all the attributes in this attribute list. This size includes the size of
      *     the attribute headers.
      */
    final int computeAttributesSize(final SymbolTable symbolTable) {
        final byte[] code = null;
        final int codeLength = 0;
        final int maxStack = -1;
        final int maxLocals = -1;
        return computeAttributesSize(symbolTable, code, codeLength, maxStack, maxLocals);
    }

    /**
      * Returns the total size in bytes of all the attributes in the attribute list that begins with
      * this attribute. This size includes the 6 header bytes (attribute_name_index and
      * attribute_length) per attribute. Also adds the attribute type names to the constant pool.
      *
      * @param symbolTable where the constants used in the attributes must be stored.
      * @param code the bytecode of the method corresponding to these code attributes, or {@literal
      *     null} if they are not code attributes. Corresponds to the 'code' field of the Code
      *     attribute.
      * @param codeLength the length of the bytecode of the method corresponding to these code
      *     attributes, or 0 if they are not code attributes. Corresponds to the 'code_length' field of
      *     the Code attribute.
      * @param maxStack the maximum stack size of the method corresponding to these code attributes, or
      *     -1 if they are not code attributes.
      * @param maxLocals the maximum number of local variables of the method corresponding to these
      *     code attributes, or -1 if they are not code attribute.
      * @return the size of all the attributes in this attribute list. This size includes the size of
      *     the attribute headers.
      */
    final int computeAttributesSize(
            final SymbolTable symbolTable,
            final byte[] code,
            final int codeLength,
            final int maxStack,
            final int maxLocals) {
        final ClassWriter classWriter = symbolTable.classWriter;
        int size = 0;
        Attribute attribute = this;
        while (attribute != null) {
            symbolTable.addConstantUtf8(attribute.type);
            size += 6 + attribute.write(classWriter, code, codeLength, maxStack, maxLocals).length;
            attribute = attribute.nextAttribute;
        }
        return size;
    }

    /**
      * Puts all the attributes of the attribute list that begins with this attribute, in the given
      * byte vector. This includes the 6 header bytes (attribute_name_index and attribute_length) per
      * attribute.
      *
      * @param symbolTable where the constants used in the attributes must be stored.
      * @param output where the attributes must be written.
      */
    final void putAttributes(final SymbolTable symbolTable, final ByteVector output) {
        final byte[] code = null;
        final int codeLength = 0;
        final int maxStack = -1;
        final int maxLocals = -1;
        putAttributes(symbolTable, code, codeLength, maxStack, maxLocals, output);
    }

    /**
      * Puts all the attributes of the attribute list that begins with this attribute, in the given
      * byte vector. This includes the 6 header bytes (attribute_name_index and attribute_length) per
      * attribute.
      *
      * @param symbolTable where the constants used in the attributes must be stored.
      * @param code the bytecode of the method corresponding to these code attributes, or {@literal
      *     null} if they are not code attributes. Corresponds to the 'code' field of the Code
      *     attribute.
      * @param codeLength the length of the bytecode of the method corresponding to these code
      *     attributes, or 0 if they are not code attributes. Corresponds to the 'code_length' field of
      *     the Code attribute.
      * @param maxStack the maximum stack size of the method corresponding to these code attributes, or
      *     -1 if they are not code attributes.
      * @param maxLocals the maximum number of local variables of the method corresponding to these
      *     code attributes, or -1 if they are not code attribute.
      * @param output where the attributes must be written.
      */
    final void putAttributes(
            final SymbolTable symbolTable,
            final byte[] code,
            final int codeLength,
            final int maxStack,
            final int maxLocals,
            final ByteVector output) {
        final ClassWriter classWriter = symbolTable.classWriter;
        Attribute attribute = this;
        while (attribute != null) {
            ByteVector attributeContent =
                    attribute.write(classWriter, code, codeLength, maxStack, maxLocals);
            // Put attribute_name_index and attribute_length.

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