    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 */
    017package org.apache.bcel.classfile;
    018
    019import java.io.DataInput;
    020import java.io.DataOutputStream;
    021import java.io.IOException;
    022import java.util.Arrays;
    023
    024import org.apache.bcel.Const;
    025import org.apache.bcel.util.Args;
    026import org.apache.commons.lang3.ArrayUtils;
    027
    028/**
    029 * This class represents a chunk of Java byte code contained in a method. It is instantiated by the
    030 * <em>Attribute.readAttribute()</em> method. A <em>Code</em> attribute contains informations about operand stack, local
    031 * variables, byte code and the exceptions handled within this method.
    032 *
    033 * This attribute has attributes itself, namely <em>LineNumberTable</em> which is used for debugging purposes and
    034 * <em>LocalVariableTable</em> which contains information about the local variables.
    035 *
    036 * <pre>
    037 * Code_attribute {
    038 *   u2 attribute_name_index;
    039 *   u4 attribute_length;
    040 *   u2 max_stack;
    041 *   u2 max_locals;
    042 *   u4 code_length;
    043 *   u1 code[code_length];
    044 *   u2 exception_table_length;
    045 *   {
    046 *     u2 start_pc;
    047 *     u2 end_pc;
    048 *     u2 handler_pc;
    049 *     u2 catch_type;
    050 *   } exception_table[exception_table_length];
    051 *   u2 attributes_count;
    052 *   attribute_info attributes[attributes_count];
    053 * }
    054 * </pre>
    055 * @see Attribute
    056 * @see CodeException
    057 * @see LineNumberTable
    058 * @see LocalVariableTable
    059 */
    060public final class Code extends Attribute {
    061
    062    private int maxStack; // Maximum size of stack used by this method // TODO this could be made final (setter is not used)
    063    private int maxLocals; // Number of local variables // TODO this could be made final (setter is not used)
    064    private byte[] code; // Actual byte code
    065    private CodeException[] exceptionTable; // Table of handled exceptions
    066    private Attribute[] attributes; // or LocalVariable
    067
    068    /**
    069     * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
    070     * physical copy.
    071     *
    072     * @param code The source Code.
    073     */
    074    public Code(final Code code) {
    075        this(code.getNameIndex(), code.getLength(), code.getMaxStack(), code.getMaxLocals(), code.getCode(), code.getExceptionTable(), code.getAttributes(),
    076                code.getConstantPool());
    077    }
    078
    079    /**
    080     * @param nameIndex Index pointing to the name <em>Code</em>
    081     * @param length Content length in bytes
    082     * @param file Input stream
    083     * @param constantPool Array of constants
    084     */
    085    Code(final int nameIndex, final int length, final DataInput file, final ConstantPool constantPool) throws IOException {
    086        // Initialize with some default values which will be overwritten later
    087        this(nameIndex, length, file.readUnsignedShort(), file.readUnsignedShort(), (byte[]) null, (CodeException[]) null, (Attribute[]) null, constantPool);
    088        final int codeLength = Args.requireU4(file.readInt(), 1, "Code length attribute");
    089        code = new byte[codeLength]; // Read byte code
    090        file.readFully(code);
    091        /*
    092         * Read exception table that contains all regions where an exception handler is active, i.e., a try { ... } catch ()
    093         * block.
    094         */
    095        final int exceptionTableLength = file.readUnsignedShort();
    096        exceptionTable = new CodeException[exceptionTableLength];
    097        for (int i = 0; i < exceptionTableLength; i++) {
    098            exceptionTable[i] = new CodeException(file);
    099        }
    100        /*
    101         * Read all attributes, currently 'LineNumberTable' and 'LocalVariableTable'
    102         */
    103        final int attributesCount = file.readUnsignedShort();
    104        attributes = new Attribute[attributesCount];
    105        for (int i = 0; i < attributesCount; i++) {
    106            attributes[i] = Attribute.readAttribute(file, constantPool);
    107        }
    108        /*
    109         * Adjust length, because of setAttributes in this(), s.b. length is incorrect, because it didn't take the internal
    110         * attributes into account yet! Very subtle bug, fixed in 3.1.1.
    111         */
    112        super.setLength(length);
    113    }
    114
    115    /**
    116     * @param nameIndex Index pointing to the name <em>Code</em>
    117     * @param length Content length in bytes
    118     * @param maxStack Maximum size of stack
    119     * @param maxLocals Number of local variables
    120     * @param code Actual byte code
    121     * @param exceptionTable of handled exceptions
    122     * @param attributes Attributes of code: LineNumber or LocalVariable
    123     * @param constantPool Array of constants
    124     */
    125    public Code(final int nameIndex, final int length, final int maxStack, final int maxLocals, final byte[] code, final CodeException[] exceptionTable,
    126        final Attribute[] attributes, final ConstantPool constantPool) {
    127        super(Const.ATTR_CODE, nameIndex, length, constantPool);
    128        this.maxStack = Args.requireU2(maxStack, "maxStack");
    129        this.maxLocals = Args.requireU2(maxLocals, "maxLocals");
    130        this.code = ArrayUtils.nullToEmpty(code);
    131        this.exceptionTable = ArrayUtils.nullToEmpty(exceptionTable, CodeException[].class);
    132        Args.requireU2(this.exceptionTable.length, "exceptionTable.length");
    133        this.attributes = attributes != null ? attributes : EMPTY_ARRAY;
    134        super.setLength(calculateLength()); // Adjust length
    135    }
    136
    137    /**
    138     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    139     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    140     *
    141     * @param v Visitor object
    142     */
    143    @Override
    144    public void accept(final Visitor v) {
    145        v.visitCode(this);
    146    }
    147
    148    /**
    149     * @return the full size of this code attribute, minus its first 6 bytes, including the size of all its contained
    150     *         attributes
    151     */
    152    private int calculateLength() {
    153        int len = 0;
    154        if (attributes != null) {
    155            for (final Attribute attribute : attributes) {
    156                len += attribute.getLength() + 6 /* attribute header size */;
    157            }
    158        }
    159        return len + getInternalLength();
    160    }
    161
    162    /**
    163     * @return deep copy of this attribute
    164     *
    165     * @param constantPool the constant pool to duplicate
    166     */
    167    @Override
    168    public Attribute copy(final ConstantPool constantPool) {
    169        final Code c = (Code) clone();
    170        if (code != null) {
    171            c.code = code.clone();
    172        }
    173        c.setConstantPool(constantPool);
    174        c.exceptionTable = new CodeException[exceptionTable.length];
    175        Arrays.setAll(c.exceptionTable, i -> exceptionTable[i].copy());
    176        c.attributes = new Attribute[attributes.length];
    177        Arrays.setAll(c.attributes, i -> attributes[i].copy(constantPool));
    178        return c;
    179    }
    180
    181    /**
    182     * Dump code attribute to file stream in binary format.
    183     *
    184     * @param file Output file stream
    185     * @throws IOException if an I/O error occurs.
    186     */
    187    @Override
    188    public void dump(final DataOutputStream file) throws IOException {
    189        super.dump(file);
    190        file.writeShort(maxStack);
    191        file.writeShort(maxLocals);
    192        file.writeInt(code.length);
    193        file.write(code, 0, code.length);
    194        file.writeShort(exceptionTable.length);
    195        for (final CodeException exception : exceptionTable) {
    196            exception.dump(file);
    197        }
    198        file.writeShort(attributes.length);
    199        for (final Attribute attribute : attributes) {
    200            attribute.dump(file);
    201        }
    202    }
    203
    204    /**
    205     * @return Collection of code attributes.
    206     * @see Attribute
    207     */
    208    public Attribute[] getAttributes() {
    209        return attributes;
    210    }
    211
    212    /**
    213     * @return Actual byte code of the method.
    214     */
    215    public byte[] getCode() {
    216        return code;
    217    }
    218
    219    /**
    220     * @return Table of handled exceptions.
    221     * @see CodeException
    222     */
    223    public CodeException[] getExceptionTable() {
    224        return exceptionTable;
    225    }
    226
    227    /**
    228     * @return the internal length of this code attribute (minus the first 6 bytes) and excluding all its attributes
    229     */
    230    private int getInternalLength() {
    231        return 2 /* maxStack */ + 2 /* maxLocals */ + 4 /* code length */
    232            + code.length /* byte-code */
    233            + 2 /* exception-table length */
    234            + 8 * (exceptionTable == null ? 0 : exceptionTable.length) /* exception table */
    235            + 2 /* attributes count */;
    236    }
    237
    238    /**
    239     * @return LineNumberTable of Code, if it has one
    240     */
    241    public LineNumberTable getLineNumberTable() {
    242        for (final Attribute attribute : attributes) {
    243            if (attribute instanceof LineNumberTable) {
    244                return (LineNumberTable) attribute;
    245            }
    246        }
    247        return null;
    248    }
    249
    250    /**
    251     * @return LocalVariableTable of Code, if it has one
    252     */
    253    public LocalVariableTable getLocalVariableTable() {
    254        for (final Attribute attribute : attributes) {
    255            if (attribute instanceof LocalVariableTable) {
    256                return (LocalVariableTable) attribute;
    257            }
    258        }
    259        return null;
    260    }
    261
    262    /**
    263     * @return Number of local variables.
    264     */
    265    public int getMaxLocals() {
    266        return maxLocals;
    267    }
    268
    269    /**
    270     * @return Maximum size of stack used by this method.
    271     */
    272    public int getMaxStack() {
    273        return maxStack;
    274    }
    275
    276    /**
    277     * Finds the attribute of {@link StackMap} instance.
    278     * @return StackMap of Code, if it has one, else null.
    279     * @since 6.8.0
    280     */
    281    public StackMap getStackMap() {
    282        for (final Attribute attribute : attributes) {
    283            if (attribute instanceof StackMap) {
    284                return (StackMap) attribute;
    285            }
    286        }
    287        return null;
    288    }
    289
    290    /**
    291     * @param attributes the attributes to set for this Code
    292     */
    293    public void setAttributes(final Attribute[] attributes) {
    294        this.attributes = attributes != null ? attributes : EMPTY_ARRAY;
    295        super.setLength(calculateLength()); // Adjust length
    296    }
    297
    298    /**
    299     * @param code byte code
    300     */
    301    public void setCode(final byte[] code) {
    302        this.code = ArrayUtils.nullToEmpty(code);
    303        super.setLength(calculateLength()); // Adjust length
    304    }
    305
    306    /**
    307     * @param exceptionTable exception table
    308     */
    309    public void setExceptionTable(final CodeException[] exceptionTable) {
    310        this.exceptionTable = exceptionTable != null ? exceptionTable : CodeException.EMPTY_ARRAY;
    311        super.setLength(calculateLength()); // Adjust length
    312    }
    313
    314    /**
    315     * @param maxLocals maximum number of local variables
    316     */
    317    public void setMaxLocals(final int maxLocals) {
    318        this.maxLocals = maxLocals;
    319    }
    320
    321    /**
    322     * @param maxStack maximum stack size
    323     */
    324    public void setMaxStack(final int maxStack) {
    325        this.maxStack = maxStack;
    326    }
    327
    328    /**
    329     * @return String representation of code chunk.
    330     */
    331    @Override
    332    public String toString() {
    333        return toString(true);
    334    }
    335
    336    /**
    337     * Converts this object to a String.
    338     *
    339     * @param verbose Provides verbose output when true.
    340     * @return String representation of code chunk.
    341     */
    342    public String toString(final boolean verbose) {
    343        final StringBuilder buf = new StringBuilder(100); // CHECKSTYLE IGNORE MagicNumber
    344        buf.append("Code(maxStack = ").append(maxStack).append(", maxLocals = ").append(maxLocals).append(", code_length = ").append(code.length).append(")\n")
    345            .append(Utility.codeToString(code, super.getConstantPool(), 0, -1, verbose));
    346        if (exceptionTable.length > 0) {
    347            buf.append("\nException handler(s) = \n").append("From\tTo\tHandler\tType\n");
    348            for (final CodeException exception : exceptionTable) {
    349                buf.append(exception.toString(super.getConstantPool(), verbose)).append("\n");
    350            }
    351        }
    352        if (attributes.length > 0) {
    353            buf.append("\nAttribute(s) = ");
    354            for (final Attribute attribute : attributes) {
    355                buf.append("\n").append(attribute.getName()).append(":");
    356                buf.append("\n").append(attribute);
    357            }
    358        }
    359        return buf.toString();
    360    }
    361}