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