    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one
    003 * or more contributor license agreements.  See the NOTICE file
    004 * distributed with this work for additional information
    005 * regarding copyright ownership.  The ASF licenses this file
    006 * to you under the Apache License, Version 2.0 (the
    007 * "License"); you may not use this file except in compliance
    008 * with the License.  You may obtain a copy of the License at
    009 *
    010 *   https://www.apache.org/licenses/LICENSE-2.0
    011 *
    012 * Unless required by applicable law or agreed to in writing,
    013 * software distributed under the License is distributed on an
    014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    015 * KIND, either express or implied.  See the License for the
    016 * specific language governing permissions and limitations
    017 * under the License.
    018 */
    019
    020package org.apache.bcel.classfile;
    021
    022import java.io.DataInput;
    023import java.io.DataOutputStream;
    024import java.io.IOException;
    025import java.util.Arrays;
    026
    027import org.apache.bcel.Const;
    028import org.apache.commons.lang3.ArrayUtils;
    029
    030/**
    031 * This class represents a bootstrap method attribute, i.e., the bootstrap method ref, the number of bootstrap arguments
    032 * and an array of the bootstrap arguments.
    033 *
    034 * @see <a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.23"> The class File Format :
    035 *      The BootstrapMethods Attribute</a>
    036 * @since 6.0
    037 */
    038public class BootstrapMethod implements Cloneable {
    039
    040    static final BootstrapMethod[] EMPTY_ARRAY = {};
    041
    042    /** Index of the CONSTANT_MethodHandle_info structure in the constant_pool table */
    043    private int bootstrapMethodRef;
    044
    045    /** Array of references to the constant_pool table */
    046    private int[] bootstrapArguments;
    047
    048    /**
    049     * Initialize from another object.
    050     *
    051     * @param c Source to copy.
    052     */
    053    public BootstrapMethod(final BootstrapMethod c) {
    054        this(c.getBootstrapMethodRef(), c.getBootstrapArguments());
    055    }
    056
    057    /**
    058     * Constructs object from input stream.
    059     *
    060     * @param input Input stream
    061     * @throws IOException if an I/O error occurs.
    062     */
    063    BootstrapMethod(final DataInput input) throws IOException {
    064        this(input.readUnsignedShort(), input.readUnsignedShort());
    065
    066        for (int i = 0; i < bootstrapArguments.length; i++) {
    067            bootstrapArguments[i] = input.readUnsignedShort();
    068        }
    069    }
    070
    071    // helper method
    072    private BootstrapMethod(final int bootstrapMethodRef, final int numBootstrapArguments) {
    073        this(bootstrapMethodRef, new int[numBootstrapArguments]);
    074    }
    075
    076    /**
    077     * @param bootstrapMethodRef int index into constant_pool of CONSTANT_MethodHandle
    078     * @param bootstrapArguments int[] indices into constant_pool of CONSTANT_[type]_info
    079     */
    080    public BootstrapMethod(final int bootstrapMethodRef, final int[] bootstrapArguments) {
    081        this.bootstrapMethodRef = bootstrapMethodRef;
    082        setBootstrapArguments(bootstrapArguments);
    083    }
    084
    085    /**
    086     * @return deep copy of this object
    087     */
    088    public BootstrapMethod copy() {
    089        try {
    090            return (BootstrapMethod) clone();
    091        } catch (final CloneNotSupportedException ignore) {
    092            // TODO should this throw?
    093        }
    094        return null;
    095    }
    096
    097    /**
    098     * Dump object to file stream in binary format.
    099     *
    100     * @param file Output file stream
    101     * @throws IOException if an I/O error occurs.
    102     */
    103    public final void dump(final DataOutputStream file) throws IOException {
    104        file.writeShort(bootstrapMethodRef);
    105        file.writeShort(bootstrapArguments.length);
    106        for (final int bootstrapArgument : bootstrapArguments) {
    107            file.writeShort(bootstrapArgument);
    108        }
    109    }
    110
    111    /**
    112     * @return int[] of bootstrap_method indices into constant_pool of CONSTANT_[type]_info
    113     */
    114    public int[] getBootstrapArguments() {
    115        return bootstrapArguments;
    116    }
    117
    118    /**
    119     * @return index into constant_pool of bootstrap_method
    120     */
    121    public int getBootstrapMethodRef() {
    122        return bootstrapMethodRef;
    123    }
    124
    125    /**
    126     * @return count of number of boostrap arguments
    127     */
    128    public int getNumBootstrapArguments() {
    129        return bootstrapArguments.length;
    130    }
    131
    132    /**
    133     * @param bootstrapArguments int[] indices into constant_pool of CONSTANT_[type]_info
    134     */
    135    public void setBootstrapArguments(final int[] bootstrapArguments) {
    136        this.bootstrapArguments = ArrayUtils.nullToEmpty(bootstrapArguments);
    137    }
    138
    139    /**
    140     * @param bootstrapMethodRef int index into constant_pool of CONSTANT_MethodHandle
    141     */
    142    public void setBootstrapMethodRef(final int bootstrapMethodRef) {
    143        this.bootstrapMethodRef = bootstrapMethodRef;
    144    }
    145
    146    /**
    147     * @return String representation.
    148     */
    149    @Override
    150    public final String toString() {
    151        return "BootstrapMethod(" + bootstrapMethodRef + ", " + bootstrapArguments.length + ", " + Arrays.toString(bootstrapArguments) + ")";
    152    }
    153
    154    /**
    155     * @return Resolved string representation
    156     */
    157    public final String toString(final ConstantPool constantPool) {
    158        final StringBuilder buf = new StringBuilder();
    159        final String bootstrapMethodName = constantPool.constantToString(bootstrapMethodRef, Const.CONSTANT_MethodHandle);
    160        buf.append(Utility.compactClassName(bootstrapMethodName, false));
    161        final int bootstrapArgumentsLen = bootstrapArguments.length;
    162        if (bootstrapArgumentsLen > 0) {
    163            buf.append("\nMethod Arguments:");
    164            for (int i = 0; i < bootstrapArgumentsLen; i++) {
    165                buf.append("\n  ").append(i).append(": ");
    166                buf.append(constantPool.constantToString(constantPool.getConstant(bootstrapArguments[i])));
    167            }
    168        }
    169        return buf.toString();
    170    }
    171}