Code.java

  1. /*
  2.  * Licensed to the Apache Software Foundation (ASF) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * The ASF licenses this file to You under the Apache License, Version 2.0
  6.  * (the "License"); you may not use this file except in compliance with
  7.  * the License.  You may obtain a copy of the License at
  8.  *
  9.  *      http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  *  Unless required by applicable law or agreed to in writing, software
  12.  *  distributed under the License is distributed on an "AS IS" BASIS,
  13.  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  *  See the License for the specific language governing permissions and
  15.  *  limitations under the License.
  16.  */
  17. package org.apache.bcel.classfile;

  19. import java.io.DataInput;
  20. import java.io.DataOutputStream;
  21. import java.io.IOException;
  22. import java.util.Arrays;

  24. import org.apache.bcel.Const;
  25. import org.apache.bcel.util.Args;
  26. import org.apache.commons.lang3.ArrayUtils;

  28. /**
  29.  * This class represents a chunk of Java byte code contained in a method. It is instantiated by the
  30.  * <em>Attribute.readAttribute()</em> method. A <em>Code</em> attribute contains informations about operand stack, local
  31.  * variables, byte code and the exceptions handled within this method.
  32.  *
  33.  * This attribute has attributes itself, namely <em>LineNumberTable</em> which is used for debugging purposes and
  34.  * <em>LocalVariableTable</em> which contains information about the local variables.
  35.  *
  36.  * <pre>
  37.  * Code_attribute {
  38.  *   u2 attribute_name_index;
  39.  *   u4 attribute_length;
  40.  *   u2 max_stack;
  41.  *   u2 max_locals;
  42.  *   u4 code_length;
  43.  *   u1 code[code_length];
  44.  *   u2 exception_table_length;
  45.  *   {
  46.  *     u2 start_pc;
  47.  *     u2 end_pc;
  48.  *     u2 handler_pc;
  49.  *     u2 catch_type;
  50.  *   } exception_table[exception_table_length];
  51.  *   u2 attributes_count;
  52.  *   attribute_info attributes[attributes_count];
  53.  * }
  54.  * </pre>
  55.  * @see Attribute
  56.  * @see CodeException
  57.  * @see LineNumberTable
  58.  * @see LocalVariableTable
  59.  */
  60. public final class Code extends Attribute {

  62.     private int maxStack; // Maximum size of stack used by this method // TODO this could be made final (setter is not used)
  63.     private int maxLocals; // Number of local variables // TODO this could be made final (setter is not used)
  64.     private byte[] code; // Actual byte code
  65.     private CodeException[] exceptionTable; // Table of handled exceptions
  66.     private Attribute[] attributes; // or LocalVariable

  68.     /**
  69.      * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
  70.      * physical copy.
  71.      *
  72.      * @param code The source Code.
  73.      */
  74.     public Code(final Code code) {
  75.         this(code.getNameIndex(), code.getLength(), code.getMaxStack(), code.getMaxLocals(), code.getCode(), code.getExceptionTable(), code.getAttributes(),
  76.                 code.getConstantPool());
  77.     }

  79.     /**
  80.      * @param nameIndex Index pointing to the name <em>Code</em>
  81.      * @param length Content length in bytes
  82.      * @param file Input stream
  83.      * @param constantPool Array of constants
  84.      */
  85.     Code(final int nameIndex, final int length, final DataInput file, final ConstantPool constantPool) throws IOException {
  86.         // Initialize with some default values which will be overwritten later
  87.         this(nameIndex, length, file.readUnsignedShort(), file.readUnsignedShort(), (byte[]) null, (CodeException[]) null, (Attribute[]) null, constantPool);
  88.         final int codeLength = Args.requireU4(file.readInt(), 1, "Code length attribute");
  89.         code = new byte[codeLength]; // Read byte code
  90.         file.readFully(code);
  91.         /*
  92.          * Read exception table that contains all regions where an exception handler is active, i.e., a try { ... } catch ()
  93.          * block.
  94.          */
  95.         final int exceptionTableLength = file.readUnsignedShort();
  96.         exceptionTable = new CodeException[exceptionTableLength];
  97.         for (int i = 0; i < exceptionTableLength; i++) {
  98.             exceptionTable[i] = new CodeException(file);
  99.         }
  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] = 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.     }

  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.     }

  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.     }

  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.     }

  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.     }

  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.     }

  204.     /**
  205.      * @return Collection of code attributes.
  206.      * @see Attribute
  207.      */
  208.     public Attribute[] getAttributes() {
  209.         return attributes;
  210.     }

  212.     /**
  213.      * @return Actual byte code of the method.
  214.      */
  215.     public byte[] getCode() {
  216.         return code;
  217.     }

  219.     /**
  220.      * @return Table of handled exceptions.
  221.      * @see CodeException
  222.      */
  223.     public CodeException[] getExceptionTable() {
  224.         return exceptionTable;
  225.     }

  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.     }

  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.     }

  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.     }

  262.     /**
  263.      * Gets the local variable type table attribute {@link LocalVariableTypeTable}.
  264.      * @return LocalVariableTypeTable of Code, if it has one, null otherwise.
  265.      * @since 6.10.0
  266.      */
  267.     public LocalVariableTypeTable getLocalVariableTypeTable() {
  268.         for (final Attribute attribute : attributes) {
  269.             if (attribute instanceof LocalVariableTypeTable) {
  270.                 return (LocalVariableTypeTable) attribute;
  271.             }
  272.         }
  273.         return null;
  274.     }

  276.     /**
  277.      * @return Number of local variables.
  278.      */
  279.     public int getMaxLocals() {
  280.         return maxLocals;
  281.     }

  283.     /**
  284.      * @return Maximum size of stack used by this method.
  285.      */
  286.     public int getMaxStack() {
  287.         return maxStack;
  288.     }

  290.     /**
  291.      * Finds the attribute of {@link StackMap} instance.
  292.      * @return StackMap of Code, if it has one, else null.
  293.      * @since 6.8.0
  294.      */
  295.     public StackMap getStackMap() {
  296.         for (final Attribute attribute : attributes) {
  297.             if (attribute instanceof StackMap) {
  298.                 return (StackMap) attribute;
  299.             }
  300.         }
  301.         return null;
  302.     }

  304.     /**
  305.      * @param attributes the attributes to set for this Code
  306.      */
  307.     public void setAttributes(final Attribute[] attributes) {
  308.         this.attributes = attributes != null ? attributes : EMPTY_ARRAY;
  309.         super.setLength(calculateLength()); // Adjust length
  310.     }

  312.     /**
  313.      * @param code byte code
  314.      */
  315.     public void setCode(final byte[] code) {
  316.         this.code = ArrayUtils.nullToEmpty(code);
  317.         super.setLength(calculateLength()); // Adjust length
  318.     }

  320.     /**
  321.      * @param exceptionTable exception table
  322.      */
  323.     public void setExceptionTable(final CodeException[] exceptionTable) {
  324.         this.exceptionTable = exceptionTable != null ? exceptionTable : CodeException.EMPTY_ARRAY;
  325.         super.setLength(calculateLength()); // Adjust length
  326.     }

  328.     /**
  329.      * @param maxLocals maximum number of local variables
  330.      */
  331.     public void setMaxLocals(final int maxLocals) {
  332.         this.maxLocals = maxLocals;
  333.     }

  335.     /**
  336.      * @param maxStack maximum stack size
  337.      */
  338.     public void setMaxStack(final int maxStack) {
  339.         this.maxStack = maxStack;
  340.     }

  342.     /**
  343.      * @return String representation of code chunk.
  344.      */
  345.     @Override
  346.     public String toString() {
  347.         return toString(true);
  348.     }

  350.     /**
  351.      * Converts this object to a String.
  352.      *
  353.      * @param verbose Provides verbose output when true.
  354.      * @return String representation of code chunk.
  355.      */
  356.     public String toString(final boolean verbose) {
  357.         final StringBuilder buf = new StringBuilder(100); // CHECKSTYLE IGNORE MagicNumber
  358.         buf.append("Code(maxStack = ").append(maxStack).append(", maxLocals = ").append(maxLocals).append(", code_length = ").append(code.length).append(")\n")
  359.             .append(Utility.codeToString(code, super.getConstantPool(), 0, -1, verbose));
  360.         if (exceptionTable.length > 0) {
  361.             buf.append("\nException handler(s) = \n").append("From\tTo\tHandler\tType\n");
  362.             for (final CodeException exception : exceptionTable) {
  363.                 buf.append(exception.toString(super.getConstantPool(), verbose)).append("\n");
  364.             }
  365.         }
  366.         if (attributes.length > 0) {
  367.             buf.append("\nAttribute(s) = ");
  368.             for (final Attribute attribute : attributes) {
  369.                 buf.append("\n").append(attribute.getName()).append(":");
  370.                 buf.append("\n").append(attribute);
  371.             }
  372.         }
  373.         return buf.toString();
  374.     }
  375. }
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