    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     * @param c Source to copy.
    047     */
    048    public BootstrapMethod(final BootstrapMethod c) {
    049        this(c.getBootstrapMethodRef(), c.getBootstrapArguments());
    050    }
    051
    052    /**
    053     * Construct object from input stream.
    054     *
    055     * @param input Input stream
    056     * @throws IOException if an I/O error occurs.
    057     */
    058    BootstrapMethod(final DataInput input) throws IOException {
    059        this(input.readUnsignedShort(), input.readUnsignedShort());
    060
    061        for (int i = 0; i < bootstrapArguments.length; i++) {
    062            bootstrapArguments[i] = input.readUnsignedShort();
    063        }
    064    }
    065
    066    // helper method
    067    private BootstrapMethod(final int bootstrapMethodRef, final int numBootstrapArguments) {
    068        this(bootstrapMethodRef, new int[numBootstrapArguments]);
    069    }
    070
    071    /**
    072     * @param bootstrapMethodRef int index into constant_pool of CONSTANT_MethodHandle
    073     * @param bootstrapArguments int[] indices into constant_pool of CONSTANT_[type]_info
    074     */
    075    public BootstrapMethod(final int bootstrapMethodRef, final int[] bootstrapArguments) {
    076        this.bootstrapMethodRef = bootstrapMethodRef;
    077        this.bootstrapArguments = bootstrapArguments;
    078    }
    079
    080    /**
    081     * @return deep copy of this object
    082     */
    083    public BootstrapMethod copy() {
    084        try {
    085            return (BootstrapMethod) clone();
    086        } catch (final CloneNotSupportedException e) {
    087            // TODO should this throw?
    088        }
    089        return null;
    090    }
    091
    092    /**
    093     * Dump object to file stream in binary format.
    094     *
    095     * @param file Output file stream
    096     * @throws IOException if an I/O error occurs.
    097     */
    098    public final void dump(final DataOutputStream file) throws IOException {
    099        file.writeShort(bootstrapMethodRef);
    100        file.writeShort(bootstrapArguments.length);
    101        for (final int bootstrapArgument : bootstrapArguments) {
    102            file.writeShort(bootstrapArgument);
    103        }
    104    }
    105
    106    /**
    107     * @return int[] of bootstrap_method indices into constant_pool of CONSTANT_[type]_info
    108     */
    109    public int[] getBootstrapArguments() {
    110        return bootstrapArguments;
    111    }
    112
    113    /**
    114     * @return index into constant_pool of bootstrap_method
    115     */
    116    public int getBootstrapMethodRef() {
    117        return bootstrapMethodRef;
    118    }
    119
    120    /**
    121     * @return count of number of boostrap arguments
    122     */
    123    public int getNumBootstrapArguments() {
    124        return bootstrapArguments.length;
    125    }
    126
    127    /**
    128     * @param bootstrapArguments int[] indices into constant_pool of CONSTANT_[type]_info
    129     */
    130    public void setBootstrapArguments(final int[] bootstrapArguments) {
    131        this.bootstrapArguments = bootstrapArguments;
    132    }
    133
    134    /**
    135     * @param bootstrapMethodRef int index into constant_pool of CONSTANT_MethodHandle
    136     */
    137    public void setBootstrapMethodRef(final int bootstrapMethodRef) {
    138        this.bootstrapMethodRef = bootstrapMethodRef;
    139    }
    140
    141    /**
    142     * @return String representation.
    143     */
    144    @Override
    145    public final String toString() {
    146        return "BootstrapMethod(" + bootstrapMethodRef + ", " + bootstrapArguments.length + ", " + Arrays.toString(bootstrapArguments) + ")";
    147    }
    148
    149    /**
    150     * @return Resolved string representation
    151     */
    152    public final String toString(final ConstantPool constantPool) {
    153        final StringBuilder buf = new StringBuilder();
    154        final String bootstrapMethodName = constantPool.constantToString(bootstrapMethodRef, Const.CONSTANT_MethodHandle);
    155        buf.append(Utility.compactClassName(bootstrapMethodName, false));
    156        final int bootstrapArgumentsLen = bootstrapArguments.length;
    157        if (bootstrapArgumentsLen > 0) {
    158            buf.append("\nMethod Arguments:");
    159            for (int i = 0; i < bootstrapArgumentsLen; i++) {
    160                buf.append("\n  ").append(i).append(": ");
    161                buf.append(constantPool.constantToString(constantPool.getConstant(bootstrapArguments[i])));
    162            }
    163        }
    164        return buf.toString();
    165    }
    166}