localvariablessorter.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.commons;

import org.drools.asm.Label;
import org.drools.asm.MethodAdapter;
import org.drools.asm.MethodVisitor;
import org.drools.asm.Opcodes;
import org.drools.asm.Type;

/**
 * A {@link MethodAdapter} that renumbers local variables in their order of
 * appearance. This adapter allows one to easily add new local variables to a
 * method.
 * 
 * @author Chris Nokleberg
 * @author Eric Bruneton
 */
public class LocalVariablesSorter extends MethodAdapter {

    /**
     * Mapping from old to new local variable indexes. A local variable at index
     * i of size 1 is remapped to 'mapping[2*i]', while a local variable at
     * index i of size 2 is remapped to 'mapping[2*i+1]'.
     */
    private int[]       mapping = new int[40];

    protected final int firstLocal;

    private int         nextLocal;

    public LocalVariablesSorter(final int access,
                                final String desc,
                                final MethodVisitor mv) {
        super( mv );
        final Type[] args = Type.getArgumentTypes( desc );
        this.nextLocal = ((Opcodes.ACC_STATIC & access) != 0) ? 0 : 1;
        for ( int i = 0; i < args.length; i++ ) {
            this.nextLocal += args[i].getSize();
        }
        this.firstLocal = this.nextLocal;
    }

    public void visitVarInsn(final int opcode,
                             final int var) {
        int size;
        switch ( opcode ) {
            case Opcodes.LLOAD :
            case Opcodes.LSTORE :
            case Opcodes.DLOAD :
            case Opcodes.DSTORE :
                size = 2;
                break;
            default :
                size = 1;
        }
        this.mv.visitVarInsn( opcode,
                              remap( var,
                                     size ) );
    }

    public void visitIincInsn(final int var,
                              final int increment) {
        this.mv.visitIincInsn( remap( var,
                                      1 ),
                               increment );
    }

    public void visitMaxs(final int maxStack,
                          final int maxLocals) {
        this.mv.visitMaxs( maxStack,
                           this.nextLocal );
    }

    public void visitLocalVariable(final String name,
                                   final String desc,
                                   final String signature,
                                   final Label start,
                                   final Label end,
                                   final int index) {
        final int size = "J".equals( desc ) || "D".equals( desc ) ? 2 : 1;
        this.mv.visitLocalVariable( name,
                                    desc,
                                    signature,
                                    start,
                                    end,
                                    remap( index,
                                           size ) );
    }

    // -------------

    protected int newLocal(final int size) {
        final int var = this.nextLocal;
        this.nextLocal += size;
        return var;
    }

    private int remap(final int var,
                      final int size) {
        if ( var < this.firstLocal ) {
            return var;
        }
        final int key = 2 * var + size - 1;
        final int length = this.mapping.length;
        if ( key >= length ) {
            final int[] newMapping = new int[Math.max( 2 * length,
                                                       key + 1 )];
            System.arraycopy( this.mapping,
                              0,
                              newMapping,
                              0,
                              length );
            this.mapping = newMapping;
        }
        int value = this.mapping[key];
        if ( value == 0 ) {
            value = this.nextLocal + 1;
            this.mapping[key] = value;
            this.nextLocal += size;
        }
        return value - 1;
    }

}