    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 */
    019package org.apache.bcel.classfile;
    020
    021import java.io.DataInput;
    022import java.io.DataOutputStream;
    023import java.io.IOException;
    024import java.util.Arrays;
    025
    026import org.apache.bcel.Const;
    027import org.apache.bcel.util.Args;
    028import org.apache.commons.lang3.ArrayUtils;
    029
    030/**
    031 * This class represents a chunk of Java byte code contained in a method. It is instantiated by the
    032 * <em>Attribute.readAttribute()</em> method. A <em>Code</em> attribute contains informations about operand stack, local
    033 * variables, byte code and the exceptions handled within this method.
    034 *
    035 * This attribute has attributes itself, namely <em>LineNumberTable</em> which is used for debugging purposes and
    036 * <em>LocalVariableTable</em> which contains information about the local variables.
    037 *
    038 * <pre>
    039 * Code_attribute {
    040 *   u2 attribute_name_index;
    041 *   u4 attribute_length;
    042 *   u2 max_stack;
    043 *   u2 max_locals;
    044 *   u4 code_length;
    045 *   u1 code[code_length];
    046 *   u2 exception_table_length;
    047 *   {
    048 *     u2 start_pc;
    049 *     u2 end_pc;
    050 *     u2 handler_pc;
    051 *     u2 catch_type;
    052 *   } exception_table[exception_table_length];
    053 *   u2 attributes_count;
    054 *   attribute_info attributes[attributes_count];
    055 * }
    056 * </pre>
    057 * @see Attribute
    058 * @see CodeException
    059 * @see LineNumberTable
    060 * @see LocalVariableTable
    061 */
    062public final class Code extends Attribute {
    063
    064    private int maxStack; // Maximum size of stack used by this method // TODO this could be made final (setter is not used)
    065    private int maxLocals; // Number of local variables // TODO this could be made final (setter is not used)
    066    private byte[] code; // Actual byte code
    067    private CodeException[] exceptionTable; // Table of handled exceptions
    068    private Attribute[] attributes; // or LocalVariable
    069
    070    /**
    071     * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
    072     * physical copy.
    073     *
    074     * @param code The source Code.
    075     */
    076    public Code(final Code code) {
    077        this(code.getNameIndex(), code.getLength(), code.getMaxStack(), code.getMaxLocals(), code.getCode(), code.getExceptionTable(), code.getAttributes(),
    078                code.getConstantPool());
    079    }
    080
    081    /**
    082     * @param nameIndex Index pointing to the name <em>Code</em>
    083     * @param length Content length in bytes
    084     * @param file Input stream
    085     * @param constantPool Array of constants
    086     */
    087    Code(final int nameIndex, final int length, final DataInput file, final ConstantPool constantPool) throws IOException {
    088        // Initialize with some default values which will be overwritten later
    089        this(nameIndex, length, file.readUnsignedShort(), file.readUnsignedShort(), (byte[]) null, (CodeException[]) null, (Attribute[]) null, constantPool);
    090        final int codeLength = Args.requireU4(file.readInt(), 1, "Code length attribute");
    091        code = new byte[codeLength]; // Read byte code
    092        file.readFully(code);
    093        /*
    094         * Read exception table that contains all regions where an exception handler is active, i.e., a try { ... } catch ()
    095         * block.
    096         */
    097        final int exceptionTableLength = file.readUnsignedShort();
    098        exceptionTable = new CodeException[exceptionTableLength];
    099        for (int i = 0; i < exceptionTableLength; i++) {
    100            exceptionTable[i] = new CodeException(file);
    101        }
    102        /*
    103         * Read all attributes, currently 'LineNumberTable' and 'LocalVariableTable'
    104         */
    105        final int attributesCount = file.readUnsignedShort();
    106        attributes = new Attribute[attributesCount];
    107        for (int i = 0; i < attributesCount; i++) {
    108            attributes[i] = readAttribute(file, constantPool);
    109        }
    110        /*
    111         * Adjust length, because of setAttributes in this(), s.b. length is incorrect, because it didn't take the internal
    112         * attributes into account yet! Very subtle bug, fixed in 3.1.1.
    113         */
    114        super.setLength(length);
    115    }
    116
    117    /**
    118     * @param nameIndex Index pointing to the name <em>Code</em>
    119     * @param length Content length in bytes
    120     * @param maxStack Maximum size of stack
    121     * @param maxLocals Number of local variables
    122     * @param code Actual byte code
    123     * @param exceptionTable of handled exceptions
    124     * @param attributes Attributes of code: LineNumber or LocalVariable
    125     * @param constantPool Array of constants
    126     */
    127    public Code(final int nameIndex, final int length, final int maxStack, final int maxLocals, final byte[] code, final CodeException[] exceptionTable,
    128        final Attribute[] attributes, final ConstantPool constantPool) {
    129        super(Const.ATTR_CODE, nameIndex, length, constantPool);
    130        this.maxStack = Args.requireU2(maxStack, "maxStack");
    131        this.maxLocals = Args.requireU2(maxLocals, "maxLocals");
    132        this.code = ArrayUtils.nullToEmpty(code);
    133        this.exceptionTable = ArrayUtils.nullToEmpty(exceptionTable, CodeException[].class);
    134        Args.requireU2(this.exceptionTable.length, "exceptionTable.length");
    135        this.attributes = attributes != null ? attributes : EMPTY_ARRAY;
    136        super.setLength(calculateLength()); // Adjust length
    137    }
    138
    139    /**
    140     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    141     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    142     *
    143     * @param v Visitor object
    144     */
    145    @Override
    146    public void accept(final Visitor v) {
    147        v.visitCode(this);
    148    }
    149
    150    /**
    151     * @return the full size of this code attribute, minus its first 6 bytes, including the size of all its contained
    152     *         attributes
    153     */
    154    private int calculateLength() {
    155        int len = 0;
    156        if (attributes != null) {
    157            for (final Attribute attribute : attributes) {
    158                len += attribute.getLength() + 6 /* attribute header size */;
    159            }
    160        }
    161        return len + getInternalLength();
    162    }
    163
    164    /**
    165     * @return deep copy of this attribute
    166     * @param constantPool the constant pool to duplicate
    167     */
    168    @Override
    169    public Attribute copy(final ConstantPool constantPool) {
    170        final Code c = (Code) clone();
    171        if (code != null) {
    172            c.code = code.clone();
    173        }
    174        c.setConstantPool(constantPool);
    175        c.exceptionTable = new CodeException[exceptionTable.length];
    176        Arrays.setAll(c.exceptionTable, i -> exceptionTable[i].copy());
    177        c.attributes = new Attribute[attributes.length];
    178        Arrays.setAll(c.attributes, i -> attributes[i].copy(constantPool));
    179        return c;
    180    }
    181
    182    /**
    183     * Dump code attribute to file stream in binary format.
    184     *
    185     * @param file Output file stream
    186     * @throws IOException if an I/O error occurs.
    187     */
    188    @Override
    189    public void dump(final DataOutputStream file) throws IOException {
    190        super.dump(file);
    191        file.writeShort(maxStack);
    192        file.writeShort(maxLocals);
    193        file.writeInt(code.length);
    194        file.write(code, 0, code.length);
    195        file.writeShort(exceptionTable.length);
    196        for (final CodeException exception : exceptionTable) {
    197            exception.dump(file);
    198        }
    199        file.writeShort(attributes.length);
    200        for (final Attribute attribute : attributes) {
    201            attribute.dump(file);
    202        }
    203    }
    204
    205    /**
    206     * @return Collection of code attributes.
    207     * @see Attribute
    208     */
    209    public Attribute[] getAttributes() {
    210        return attributes;
    211    }
    212
    213    /**
    214     * @return Actual byte code of the method.
    215     */
    216    public byte[] getCode() {
    217        return code;
    218    }
    219
    220    /**
    221     * @return Table of handled exceptions.
    222     * @see CodeException
    223     */
    224    public CodeException[] getExceptionTable() {
    225        return exceptionTable;
    226    }
    227
    228    /**
    229     * @return the internal length of this code attribute (minus the first 6 bytes) and excluding all its attributes
    230     */
    231    private int getInternalLength() {
    232        return 2 /* maxStack */ + 2 /* maxLocals */ + 4 /* code length */
    233            + code.length /* byte-code */
    234            + 2 /* exception-table length */
    235            + 8 * (exceptionTable == null ? 0 : exceptionTable.length) /* exception table */
    236            + 2 /* attributes count */;
    237    }
    238
    239    /**
    240     * @return LineNumberTable of Code, if it has one
    241     */
    242    public LineNumberTable getLineNumberTable() {
    243        for (final Attribute attribute : attributes) {
    244            if (attribute instanceof LineNumberTable) {
    245                return (LineNumberTable) attribute;
    246            }
    247        }
    248        return null;
    249    }
    250
    251    /**
    252     * @return LocalVariableTable of Code, if it has one
    253     */
    254    public LocalVariableTable getLocalVariableTable() {
    255        for (final Attribute attribute : attributes) {
    256            if (attribute instanceof LocalVariableTable) {
    257                return (LocalVariableTable) attribute;
    258            }
    259        }
    260        return null;
    261    }
    262
    263    /**
    264     * Gets the local variable type table attribute {@link LocalVariableTypeTable}.
    265     * @return LocalVariableTypeTable of Code, if it has one, null otherwise.
    266     * @since 6.10.0
    267     */
    268    public LocalVariableTypeTable getLocalVariableTypeTable() {
    269        for (final Attribute attribute : attributes) {
    270            if (attribute instanceof LocalVariableTypeTable) {
    271                return (LocalVariableTypeTable) attribute;
    272            }
    273        }
    274        return null;
    275    }
    276
    277    /**
    278     * @return Number of local variables.
    279     */
    280    public int getMaxLocals() {
    281        return maxLocals;
    282    }
    283
    284    /**
    285     * @return Maximum size of stack used by this method.
    286     */
    287    public int getMaxStack() {
    288        return maxStack;
    289    }
    290
    291    /**
    292     * Finds the attribute of {@link StackMap} instance.
    293     * @return StackMap of Code, if it has one, else null.
    294     * @since 6.8.0
    295     */
    296    public StackMap getStackMap() {
    297        for (final Attribute attribute : attributes) {
    298            if (attribute instanceof StackMap) {
    299                return (StackMap) attribute;
    300            }
    301        }
    302        return null;
    303    }
    304
    305    /**
    306     * @param attributes the attributes to set for this Code
    307     */
    308    public void setAttributes(final Attribute[] attributes) {
    309        this.attributes = attributes != null ? attributes : EMPTY_ARRAY;
    310        super.setLength(calculateLength()); // Adjust length
    311    }
    312
    313    /**
    314     * @param code byte code
    315     */
    316    public void setCode(final byte[] code) {
    317        this.code = ArrayUtils.nullToEmpty(code);
    318        super.setLength(calculateLength()); // Adjust length
    319    }
    320
    321    /**
    322     * @param exceptionTable exception table
    323     */
    324    public void setExceptionTable(final CodeException[] exceptionTable) {
    325        this.exceptionTable = exceptionTable != null ? exceptionTable : CodeException.EMPTY_ARRAY;
    326        super.setLength(calculateLength()); // Adjust length
    327    }
    328
    329    /**
    330     * @param maxLocals maximum number of local variables
    331     */
    332    public void setMaxLocals(final int maxLocals) {
    333        this.maxLocals = maxLocals;
    334    }
    335
    336    /**
    337     * @param maxStack maximum stack size
    338     */
    339    public void setMaxStack(final int maxStack) {
    340        this.maxStack = maxStack;
    341    }
    342
    343    /**
    344     * @return String representation of code chunk.
    345     */
    346    @Override
    347    public String toString() {
    348        return toString(true);
    349    }
    350
    351    /**
    352     * Converts this object to a String.
    353     *
    354     * @param verbose Provides verbose output when true.
    355     * @return String representation of code chunk.
    356     */
    357    public String toString(final boolean verbose) {
    358        final StringBuilder buf = new StringBuilder(100); // CHECKSTYLE IGNORE MagicNumber
    359        buf.append("Code(maxStack = ").append(maxStack).append(", maxLocals = ").append(maxLocals).append(", code_length = ").append(code.length).append(")\n")
    360            .append(Utility.codeToString(code, super.getConstantPool(), 0, -1, verbose));
    361        if (exceptionTable.length > 0) {
    362            buf.append("\nException handler(s) = \n").append("From\tTo\tHandler\tType\n");
    363            for (final CodeException exception : exceptionTable) {
    364                buf.append(exception.toString(super.getConstantPool(), verbose)).append("\n");
    365            }
    366        }
    367        if (attributes.length > 0) {
    368            buf.append("\nAttribute(s) = ");
    369            for (final Attribute attribute : attributes) {
    370                buf.append("\n").append(attribute.getName()).append(":");
    371                buf.append("\n").append(attribute);
    372            }
    373        }
    374        return buf.toString();
    375    }
    376}