    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;
    026
    027/**
    028 * This class represents a bootstrap method attribute, i.e., the bootstrap method ref, the number of bootstrap arguments
    029 * and an array of the bootstrap arguments.
    030 *
    031 * @see <a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.23"> The class File Format :
    032 *      The BootstrapMethods Attribute</a>
    033 * @since 6.0
    034 */
    035public class BootstrapMethod implements Cloneable {
    036
    037    /** Index of the CONSTANT_MethodHandle_info structure in the constant_pool table */
    038    private int bootstrapMethodRef;
    039
    040    /** Array of references to the constant_pool table */
    041    private int[] bootstrapArguments;
    042
    043    /**
    044     * Initialize from another object.
    045     */
    046    public BootstrapMethod(final BootstrapMethod c) {
    047        this(c.getBootstrapMethodRef(), c.getBootstrapArguments());
    048    }
    049
    050    /**
    051     * Construct object from input stream.
    052     *
    053     * @param input Input stream
    054     * @throws IOException if an I/O error occurs.
    055     */
    056    BootstrapMethod(final DataInput input) throws IOException {
    057        this(input.readUnsignedShort(), input.readUnsignedShort());
    058
    059        for (int i = 0; i < bootstrapArguments.length; i++) {
    060            bootstrapArguments[i] = input.readUnsignedShort();
    061        }
    062    }
    063
    064    // helper method
    065    private BootstrapMethod(final int bootstrapMethodRef, final int numBootstrapArguments) {
    066        this(bootstrapMethodRef, new int[numBootstrapArguments]);
    067    }
    068
    069    /**
    070     * @param bootstrapMethodRef int index into constant_pool of CONSTANT_MethodHandle
    071     * @param bootstrapArguments int[] indices into constant_pool of CONSTANT_[type]_info
    072     */
    073    public BootstrapMethod(final int bootstrapMethodRef, final int[] bootstrapArguments) {
    074        this.bootstrapMethodRef = bootstrapMethodRef;
    075        this.bootstrapArguments = bootstrapArguments;
    076    }
    077
    078    /**
    079     * @return deep copy of this object
    080     */
    081    public BootstrapMethod copy() {
    082        try {
    083            return (BootstrapMethod) clone();
    084        } catch (final CloneNotSupportedException e) {
    085            // TODO should this throw?
    086        }
    087        return null;
    088    }
    089
    090    /**
    091     * Dump object to file stream in binary format.
    092     *
    093     * @param file Output file stream
    094     * @throws IOException if an I/O error occurs.
    095     */
    096    public final void dump(final DataOutputStream file) throws IOException {
    097        file.writeShort(bootstrapMethodRef);
    098        file.writeShort(bootstrapArguments.length);
    099        for (final int bootstrapArgument : bootstrapArguments) {
    100            file.writeShort(bootstrapArgument);
    101        }
    102    }
    103
    104    /**
    105     * @return int[] of bootstrap_method indices into constant_pool of CONSTANT_[type]_info
    106     */
    107    public int[] getBootstrapArguments() {
    108        return bootstrapArguments;
    109    }
    110
    111    /**
    112     * @return index into constant_pool of bootstrap_method
    113     */
    114    public int getBootstrapMethodRef() {
    115        return bootstrapMethodRef;
    116    }
    117
    118    /**
    119     * @return count of number of boostrap arguments
    120     */
    121    public int getNumBootstrapArguments() {
    122        return bootstrapArguments.length;
    123    }
    124
    125    /**
    126     * @param bootstrapArguments int[] indices into constant_pool of CONSTANT_[type]_info
    127     */
    128    public void setBootstrapArguments(final int[] bootstrapArguments) {
    129        this.bootstrapArguments = bootstrapArguments;
    130    }
    131
    132    /**
    133     * @param bootstrapMethodRef int index into constant_pool of CONSTANT_MethodHandle
    134     */
    135    public void setBootstrapMethodRef(final int bootstrapMethodRef) {
    136        this.bootstrapMethodRef = bootstrapMethodRef;
    137    }
    138
    139    /**
    140     * @return String representation.
    141     */
    142    @Override
    143    public final String toString() {
    144        return "BootstrapMethod(" + bootstrapMethodRef + ", " + bootstrapArguments.length + ", " + Arrays.toString(bootstrapArguments) + ")";
    145    }
    146
    147    /**
    148     * @return Resolved string representation
    149     */
    150    public final String toString(final ConstantPool constantPool) {
    151        final StringBuilder buf = new StringBuilder();
    152        final String bootstrapMethodName = constantPool.constantToString(bootstrapMethodRef, Const.CONSTANT_MethodHandle);
    153        buf.append(Utility.compactClassName(bootstrapMethodName, false));
    154        final int bootstrapArgumentsLen = bootstrapArguments.length;
    155        if (bootstrapArgumentsLen > 0) {
    156            buf.append("\nMethod Arguments:");
    157            for (int i = 0; i < bootstrapArgumentsLen; i++) {
    158                buf.append("\n  ").append(i).append(": ");
    159                buf.append(constantPool.constantToString(constantPool.getConstant(bootstrapArguments[i])));
    160            }
    161        }
    162        return buf.toString();
    163    }
    164}