classwriter.java

开源的java 编辑器源代码

/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (C) 2000 INRIA, France Telecom
 * Copyright (C) 2002 France Telecom
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Contact: [e-mail]
 *
 * Author: Eric Bruneton
 */

package org.objectweb.asm;

/**
 * A {@link ClassVisitor ClassVisitor} that generates Java class files. More
 * precisely this visitor generates a byte array conforming to the Java class
 * file format. It can be used alone, to generate a Java class "from scratch",
 * or with one or more {@link ClassReader ClassReader} and adapter class
 * visitor to generate a modified class from one or more existing Java classes.
 */

public class ClassWriter implements ClassVisitor {

  /**
   * The type of CONSTANT_Class constant pool items.
   */

  final static int CLASS = 7;

  /**
   * The type of CONSTANT_Fieldref constant pool items.
   */

  final static int FIELD = 9;

  /**
   * The type of CONSTANT_Methodref constant pool items.
   */

  final static int METH = 10;

  /**
   * The type of CONSTANT_InterfaceMethodref constant pool items.
   */

  final static int IMETH = 11;

  /**
   * The type of CONSTANT_String constant pool items.
   */

  final static int STR = 8;

  /**
   * The type of CONSTANT_Integer constant pool items.
   */

  final static int INT = 3;

  /**
   * The type of CONSTANT_Float constant pool items.
   */

  final static int FLOAT = 4;

  /**
   * The type of CONSTANT_Long constant pool items.
   */

  final static int LONG = 5;

  /**
   * The type of CONSTANT_Double constant pool items.
   */

  final static int DOUBLE = 6;

  /**
   * The type of CONSTANT_NameAndType constant pool items.
   */

  final static int NAME_TYPE = 12;

  /**
   * The type of CONSTANT_Utf8 constant pool items.
   */

  final static int UTF8 = 1;

  /**
   * Index of the next item to be added in the constant pool.
   */

  private short index;

  /**
   * The constant pool of this class.
   */

  private ByteVector pool;

  /**
   * The constant pool's hash table data.
   */

  private Item[] table;

  /**
   * The threshold of the constant pool's hash table.
   */

  private int threshold;

  /**
   * The access flags of this class.
   */

  private int access;

  /**
   * The constant pool item that contains the internal name of this class.
   */

  private int name;

  /**
   * The constant pool item that contains the internal name of the super class
   * of this class.
   */

  private int superName;

  /**
   * Number of interfaces implemented or extended by this class or interface.
   */

  private int interfaceCount;

  /**
   * The interfaces implemented or extended by this class or interface. More
   * precisely, this array contains the indexes of the constant pool items
   * that contain the internal names of these interfaces.
   */

  private int[] interfaces;

  /**
   * The constant pool item that contains the name of the source file from
   * which this class was compiled.
   */

  private Item sourceFile;

  /**
   * Number of fields of this class.
   */

  private int fieldCount;

  /**
   * The fields of this class.
   */

  private ByteVector fields;

  /**
   * <tt>true</tt> if the maximum stack size and number of local variables must
   * be automatically computed.
   */

  private boolean computeMaxs;

  /**
   * The methods of this class. These methods are stored in a linked list of
   * {@link CodeWriter CodeWriter} objects, linked to each other by their {@link
   * CodeWriter#next} field. This field stores the first element of this list.
   */

  CodeWriter firstMethod;

  /**
   * The methods of this class. These methods are stored in a linked list of
   * {@link CodeWriter CodeWriter} objects, linked to each other by their {@link
   * CodeWriter#next} field. This field stores the last element of this list.
   */

  CodeWriter lastMethod;

  /**
   * The number of entries in the InnerClasses attribute.
   */

  private int innerClassesCount;

  /**
   * The InnerClasses attribute.
   */

  private ByteVector innerClasses;

  /**
   * A reusable key used to look for items in the hash {@link #table table}.
   */

  Item key;

  /**
   * A reusable key used to look for items in the hash {@link #table table}.
   */

  Item key2;

  /**
   * A reusable key used to look for items in the hash {@link #table table}.
   */

  Item key3;

  /**
   * The type of instructions without any label.
   */

  final static int NOARG_INSN = 0;

  /**
   * The type of instructions with an signed byte label.
   */

  final static int SBYTE_INSN = 1;

  /**
   * The type of instructions with an signed short label.
   */

  final static int SHORT_INSN = 2;

  /**
   * The type of instructions with a local variable index label.
   */

  final static int VAR_INSN = 3;

  /**
   * The type of instructions with an implicit local variable index label.
   */

  final static int IMPLVAR_INSN = 4;

  /**
   * The type of instructions with a type descriptor argument.
   */

  final static int TYPE_INSN = 5;

  /**
   * The type of field and method invocations instructions.
   */

  final static int FIELDORMETH_INSN = 6;

  /**
   * The type of the INVOKEINTERFACE instruction.
   */

  final static int ITFMETH_INSN = 7;

  /**
   * The type of instructions with a 2 bytes bytecode offset label.
   */

  final static int LABEL_INSN = 8;

  /**
   * The type of instructions with a 4 bytes bytecode offset label.
   */

  final static int LABELW_INSN = 9;

  /**
   * The type of the LDC instruction.
   */

  final static int LDC_INSN = 10;

  /**
   * The type of the LDC_W and LDC2_W instructions.
   */

  final static int LDCW_INSN = 11;

  /**
   * The type of the IINC instruction.
   */

  final static int IINC_INSN = 12;

  /**
   * The type of the TABLESWITCH instruction.
   */

  final static int TABL_INSN = 13;

  /**
   * The type of the LOOKUPSWITCH instruction.
   */

  final static int LOOK_INSN = 14;

  /**
   * The type of the MULTIANEWARRAY instruction.
   */

  final static int MANA_INSN = 15;

  /**
   * The type of the WIDE instruction.
   */

  final static int WIDE_INSN = 16;

  /**
   * The instruction types of all JVM opcodes.
   */

  static byte[] TYPE;

  // --------------------------------------------------------------------------
  // Static initializer
  // --------------------------------------------------------------------------

  /**
   * Computes the instruction types of JVM opcodes.
   */

  static {
    int i;
    byte[] b = new byte[220];
    String s =
      "AAAAAAAAAAAAAAAABCKLLDDDDDEEEEEEEEEEEEEEEEEEEEAAAAAAAADDDDDEEEEEEEEE" +
      "EEEEEEEEEEEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAMAAA" +
      "AAAAAAAAAAAAAAAAAIIIIIIIIIIIIIIIIDNOAAAAAAGGGGGGGHAFBFAAFFAAQPIIJJII" +
      "IIIIIIIIIIIIIIII";
    for (i = 0; i < b.length; ++i) {
      b[i] = (byte)(s.charAt(i) - 'A');
    }
    TYPE = b;

    /* code to generate the above string

    // SBYTE_INSN instructions
    b[Constants.NEWARRAY] = SBYTE_INSN;
    b[Constants.BIPUSH] = SBYTE_INSN;

    // SHORT_INSN instructions
    b[Constants.SIPUSH] = SHORT_INSN;

    // (IMPL)VAR_INSN instructions
    b[Constants.RET] = VAR_INSN;
    for (i = Constants.ILOAD; i <= Constants.ALOAD; ++i) {
      b[i] = VAR_INSN;
    }
    for (i = Constants.ISTORE; i <= Constants.ASTORE; ++i) {
      b[i] = VAR_INSN;
    }
    for (i = 26; i <= 45; ++i) { // ILOAD_0 to ALOAD_3
      b[i] = IMPLVAR_INSN;
    }
    for (i = 59; i <= 78; ++i) { // ISTORE_0 to ASTORE_3
      b[i] = IMPLVAR_INSN;
    }

    // TYPE_INSN instructions
    b[Constants.NEW] = TYPE_INSN;
    b[Constants.ANEWARRAY] = TYPE_INSN;
    b[Constants.CHECKCAST] = TYPE_INSN;
    b[Constants.INSTANCEOF] = TYPE_INSN;

    // (Set)FIELDORMETH_INSN instructions
    for (i = Constants.GETSTATIC; i <= Constants.INVOKESTATIC; ++i) {
      b[i] = FIELDORMETH_INSN;
    }
    b[Constants.INVOKEINTERFACE] = ITFMETH_INSN;

    // LABEL(W)_INSN instructions
    for (i = Constants.IFEQ; i <= Constants.JSR; ++i) {
      b[i] = LABEL_INSN;
    }
    b[Constants.IFNULL] = LABEL_INSN;
    b[Constants.IFNONNULL] = LABEL_INSN;
    b[200] = LABELW_INSN; // GOTO_W
    b[201] = LABELW_INSN; // JSR_W
    // temporary opcodes used internally by ASM - see Label and CodeWriter
    for (i = 202; i < 220; ++i) {
      b[i] = LABEL_INSN;
    }

    // LDC(_W) instructions
    b[Constants.LDC] = LDC_INSN;
    b[19] = LDCW_INSN; // LDC_W
    b[20] = LDCW_INSN; // LDC2_W

    // special instructions
    b[Constants.IINC] = IINC_INSN;
    b[Constants.TABLESWITCH] = TABL_INSN;
    b[Constants.LOOKUPSWITCH] = LOOK_INSN;
    b[Constants.MULTIANEWARRAY] = MANA_INSN;
    b[196] = WIDE_INSN; // WIDE

    for (i = 0; i < b.length; ++i) {
      System.err.print((char)('A' + b[i]));
    }
    System.err.println();
    */
  }

  // --------------------------------------------------------------------------
  // Constructor
  // --------------------------------------------------------------------------

  /**
   * Constructs a new {@link ClassWriter ClassWriter} object.
   *
   * @param computeMaxs <tt>true</tt> if the maximum stack size and the maximum
   *      number of local variables must be automatically computed. If this flag
   *      is <tt>true</tt>, then the arguments of the {@link
   *      CodeVisitor#visitMaxs visitMaxs} method of the {@link CodeVisitor
   *      CodeVisitor} returned by the {@link #visitMethod visitMethod} method
   *      will be ignored, and computed automatically from the signature and
   *      the bytecode of each method.
   */

  public ClassWriter (final boolean computeMaxs) {
    index = 1;
    pool = new ByteVector();
    table = new Item[64];
    threshold = (int)(0.75d*table.length);
    key = new Item();
    key2 = new Item();
    key3 = new Item();
    this.computeMaxs = computeMaxs;
  }

  // --------------------------------------------------------------------------
  // Implementation of the ClassVisitor interface
  // --------------------------------------------------------------------------

  public void visit (
    final int access,
    final String name,
    final String superName,
    final String[] interfaces,
    final String sourceFile)
  {
    this.access = access;
    this.name = newClass(name).index;
    this.superName = superName == null ? 0 : newClass(superName).index;
    if (interfaces != null && interfaces.length > 0) {
      interfaceCount = interfaces.length;
      this.interfaces = new int[interfaceCount];
      for (int i = 0; i < interfaceCount; ++i) {
        this.interfaces[i] = newClass(interfaces[i]).index;
      }
    }