methodwriter.java

jboss规则引擎

/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2005 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.drools.asm;

/**
 * A {@link MethodVisitor} that generates methods in bytecode form. Each visit
 * method of this class appends the bytecode corresponding to the visited
 * instruction to a byte vector, in the order these methods are called.
 * 
 * @author Eric Bruneton
 */
class MethodWriter
    implements
    MethodVisitor {

    /**
     * Next method writer (see {@link ClassWriter#firstMethod firstMethod}).
     */
    MethodWriter               next;

    /**
     * The class writer to which this method must be added.
     */
    ClassWriter                cw;

    /**
     * Access flags of this method.
     */
    private int                access;

    /**
     * The index of the constant pool item that contains the name of this
     * method.
     */
    private int                name;

    /**
     * The index of the constant pool item that contains the descriptor of this
     * method.
     */
    private int                desc;

    /**
     * The descriptor of this method.
     */
    private String             descriptor;

    /**
     * If not zero, indicates that the code of this method must be copied from
     * the ClassReader associated to this writer in <code>cw.cr</code>. More
     * precisely, this field gives the index of the first byte to copied from
     * <code>cw.cr.b</code>.
     */
    int                        classReaderOffset;

    /**
     * If not zero, indicates that the code of this method must be copied from
     * the ClassReader associated to this writer in <code>cw.cr</code>. More
     * precisely, this field gives the number of bytes to copied from
     * <code>cw.cr.b</code>.
     */
    int                        classReaderLength;

    /**
     * The signature of this method.
     */
    String                     signature;

    /**
     * Number of exceptions that can be thrown by this method.
     */
    int                        exceptionCount;

    /**
     * The exceptions that can be thrown by this method. More precisely, this
     * array contains the indexes of the constant pool items that contain the
     * internal names of these exception classes.
     */
    int[]                      exceptions;

    /**
     * The annotation default attribute of this method. May be <tt>null</tt>.
     */
    private ByteVector         annd;

    /**
     * The runtime visible annotations of this method. May be <tt>null</tt>.
     */
    private AnnotationWriter   anns;

    /**
     * The runtime invisible annotations of this method. May be <tt>null</tt>.
     */
    private AnnotationWriter   ianns;

    /**
     * The runtime visible parameter annotations of this method. May be
     * <tt>null</tt>.
     */
    private AnnotationWriter[] panns;

    /**
     * The runtime invisible parameter annotations of this method. May be
     * <tt>null</tt>.
     */
    private AnnotationWriter[] ipanns;

    /**
     * The non standard attributes of the method.
     */
    private Attribute          attrs;

    /**
     * The bytecode of this method.
     */
    private ByteVector         code = new ByteVector();

    /**
     * Maximum stack size of this method.
     */
    private int                maxStack;

    /**
     * Maximum number of local variables for this method.
     */
    private int                maxLocals;

    /**
     * Number of entries in the catch table of this method.
     */
    private int                catchCount;

    /**
     * The catch table of this method.
     */
    private Handler            catchTable;

    /**
     * The last element in the catchTable handler list.
     */
    private Handler            lastHandler;

    /**
     * Number of entries in the LocalVariableTable attribute.
     */
    private int                localVarCount;

    /**
     * The LocalVariableTable attribute.
     */
    private ByteVector         localVar;

    /**
     * Number of entries in the LocalVariableTypeTable attribute.
     */
    private int                localVarTypeCount;

    /**
     * The LocalVariableTypeTable attribute.
     */
    private ByteVector         localVarType;

    /**
     * Number of entries in the LineNumberTable attribute.
     */
    private int                lineNumberCount;

    /**
     * The LineNumberTable attribute.
     */
    private ByteVector         lineNumber;

    /**
     * The non standard attributes of the method's code.
     */
    private Attribute          cattrs;

    /**
     * Indicates if some jump instructions are too small and need to be resized.
     */
    private boolean            resize;

    /*
     * Fields for the control flow graph analysis algorithm (used to compute the
     * maximum stack size). A control flow graph contains one node per "basic
     * block", and one edge per "jump" from one basic block to another. Each
     * node (i.e., each basic block) is represented by the Label object that
     * corresponds to the first instruction of this basic block. Each node also
     * stores the list of its successors in the graph, as a linked list of Edge
     * objects.
     */

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

    /**
     * The (relative) stack size after the last visited instruction. This size
     * is relative to the beginning of the current basic block, i.e., the true
     * stack size after the last visited instruction is equal to the {@link
     * Label#beginStackSize beginStackSize} of the current basic block plus
     * <tt>stackSize</tt>.
     */
    private int                stackSize;

    /**
     * The (relative) maximum stack size after the last visited instruction.
     * This size is relative to the beginning of the current basic block, i.e.,
     * the true maximum stack size after the last visited instruction is equal
     * to the {@link Label#beginStackSize beginStackSize} of the current basic
     * block plus <tt>stackSize</tt>.
     */
    private int                maxStackSize;

    /**
     * The current basic block. This block is the basic block to which the next
     * instruction to be visited must be added.
     */
    private Label              currentBlock;

    /**
     * The basic block stack used by the control flow analysis algorithm. This
     * stack is represented by a linked list of {@link Label Label} objects,
     * linked to each other by their {@link Label#next} field. This stack must
     * not be confused with the JVM stack used to execute the JVM instructions!
     */
    private Label              blockStack;

    /**
     * The stack size variation corresponding to each JVM instruction. This
     * stack variation is equal to the size of the values produced by an
     * instruction, minus the size of the values consumed by this instruction.
     */
    private final static int[] SIZE;

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

    /**
     * Computes the stack size variation corresponding to each JVM instruction.
     */
    static {
        int i;
        final int[] b = new int[202];
        final String s = "EFFFFFFFFGGFFFGGFFFEEFGFGFEEEEEEEEEEEEEEEEEEEEDEDEDDDDD" + "CDCDEEEEEEEEEEEEEEEEEEEEBABABBBBDCFFFGGGEDCDCDCDCDCDCDCDCD" + "CDCEEEEDDDDDDDCDCDCEFEFDDEEFFDEDEEEBDDBBDDDDDDCCCCCCCCEFED" + "DDCDCDEEEEEEEEEEFEEEEEEDDEEDDEE";
        for ( i = 0; i < b.length; ++i ) {
            b[i] = s.charAt( i ) - 'E';
        }
        SIZE = b;

        // code to generate the above string
        //
        // int NA = 0; // not applicable (unused opcode or variable size opcode)
        //
        // b = new int[] {
        // 0, //NOP, // visitInsn
        // 1, //ACONST_NULL, // -
        // 1, //ICONST_M1, // -
        // 1, //ICONST_0, // -
        // 1, //ICONST_1, // -
        // 1, //ICONST_2, // -
        // 1, //ICONST_3, // -
        // 1, //ICONST_4, // -
        // 1, //ICONST_5, // -
        // 2, //LCONST_0, // -
        // 2, //LCONST_1, // -
        // 1, //FCONST_0, // -
        // 1, //FCONST_1, // -
        // 1, //FCONST_2, // -
        // 2, //DCONST_0, // -
        // 2, //DCONST_1, // -
        // 1, //BIPUSH, // visitIntInsn
        // 1, //SIPUSH, // -
        // 1, //LDC, // visitLdcInsn
        // NA, //LDC_W, // -
        // NA, //LDC2_W, // -
        // 1, //ILOAD, // visitVarInsn
        // 2, //LLOAD, // -
        // 1, //FLOAD, // -
        // 2, //DLOAD, // -
        // 1, //ALOAD, // -
        // NA, //ILOAD_0, // -
        // NA, //ILOAD_1, // -
        // NA, //ILOAD_2, // -
        // NA, //ILOAD_3, // -
        // NA, //LLOAD_0, // -
        // NA, //LLOAD_1, // -
        // NA, //LLOAD_2, // -
        // NA, //LLOAD_3, // -
        // NA, //FLOAD_0, // -
        // NA, //FLOAD_1, // -
        // NA, //FLOAD_2, // -
        // NA, //FLOAD_3, // -
        // NA, //DLOAD_0, // -
        // NA, //DLOAD_1, // -
        // NA, //DLOAD_2, // -
        // NA, //DLOAD_3, // -
        // NA, //ALOAD_0, // -