org.ow2.asm/asm-commons/4.2 : org/objectweb/asm/commons/LocalVariablesSorter.java

LocalVariablesSorter
http://asm.objectweb.org/asm-commons/: A very small and fast Java bytecode manipulation framework (ObjectWeb)
Eric Bruneton
Eugene Kuleshov
Remi Forax
ASM: a very small and fast Java bytecode manipulation framework
Copyright (c) 2000-2011 INRIA, France Telecom
All rights reserved.
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/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2011 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.objectweb.asm.commons;

import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;

A MethodVisitor that renumbers local variables in their order of appearance. This adapter allows one to easily add new local variables to a method. It may be used by inheriting from this class, but the preferred way of using it is via delegation: the next visitor in the chain can indeed add new locals when needed by calling newLocal on this adapter (this requires a reference back to this LocalVariablesSorter). 
Author: Chris Nokleberg, Eugene Kuleshov, Eric Bruneton/**
 * A {@link MethodVisitor} that renumbers local variables in their order of
 * appearance. This adapter allows one to easily add new local variables to a
 * method. It may be used by inheriting from this class, but the preferred way
 * of using it is via delegation: the next visitor in the chain can indeed add
 * new locals when needed by calling {@link #newLocal} on this adapter (this
 * requires a reference back to this {@link LocalVariablesSorter}).
 * 
 * @author Chris Nokleberg
 * @author Eugene Kuleshov
 * @author Eric Bruneton
 */
public class LocalVariablesSorter extends MethodVisitor {

    private static final Type OBJECT_TYPE = Type
            .getObjectType("java/lang/Object");

    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]'.
/**
     * 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];

    Array used to store stack map local variable types after remapping.
/**
     * Array used to store stack map local variable types after remapping.
     */
    private Object[] newLocals = new Object[20];

    Index of the first local variable, after formal parameters.
/**
     * Index of the first local variable, after formal parameters.
     */
    protected final int firstLocal;

    Index of the next local variable to be created by newLocal. /**
     * Index of the next local variable to be created by {@link #newLocal}.
     */
    protected int nextLocal;

    Indicates if at least one local variable has moved due to remapping.
/**
     * Indicates if at least one local variable has moved due to remapping.
     */
    private boolean changed;

    Creates a new LocalVariablesSorter. Subclasses must not use
this constructor. Instead, they must use the LocalVariablesSorter(int, int, String, MethodVisitor) version. 
Params: access – 
           access flags of the adapted method.
desc –  the method's descriptor (see Type).
mv – 
           the method visitor to which this adapter delegates calls./**
     * Creates a new {@link LocalVariablesSorter}. <i>Subclasses must not use
     * this constructor</i>. Instead, they must use the
     * {@link #LocalVariablesSorter(int, int, String, MethodVisitor)} version.
     * 
     * @param access
     *            access flags of the adapted method.
     * @param desc
     *            the method's descriptor (see {@link Type Type}).
     * @param mv
     *            the method visitor to which this adapter delegates calls.
     */
    public LocalVariablesSorter(final int access, final String desc,
            final MethodVisitor mv) {
        this(Opcodes.ASM4, access, desc, mv);
    }

    Creates a new LocalVariablesSorter. 
Params: api –  the ASM API version implemented by this visitor. Must be one of Opcodes.ASM4.
access – 
           access flags of the adapted method.
desc –  the method's descriptor (see Type).
mv – 
           the method visitor to which this adapter delegates calls./**
     * Creates a new {@link LocalVariablesSorter}.
     * 
     * @param api
     *            the ASM API version implemented by this visitor. Must be one
     *            of {@link Opcodes#ASM4}.
     * @param access
     *            access flags of the adapted method.
     * @param desc
     *            the method's descriptor (see {@link Type Type}).
     * @param mv
     *            the method visitor to which this adapter delegates calls.
     */
    protected LocalVariablesSorter(final int api, final int access,
            final String desc, final MethodVisitor mv) {
        super(api, mv);
        Type[] args = Type.getArgumentTypes(desc);
        nextLocal = (Opcodes.ACC_STATIC & access) == 0 ? 1 : 0;
        for (int i = 0; i < args.length; i++) {
            nextLocal += args[i].getSize();
        }
        firstLocal = nextLocal;
    }

    @Override
    public void visitVarInsn(final int opcode, final int var) {
        Type type;
        switch (opcode) {
        case Opcodes.LLOAD:
        case Opcodes.LSTORE:
            type = Type.LONG_TYPE;
            break;

        case Opcodes.DLOAD:
        case Opcodes.DSTORE:
            type = Type.DOUBLE_TYPE;
            break;

        case Opcodes.FLOAD:
        case Opcodes.FSTORE:
            type = Type.FLOAT_TYPE;
            break;

        case Opcodes.ILOAD:
        case Opcodes.ISTORE:
            type = Type.INT_TYPE;
            break;

        default:
            // case Opcodes.ALOAD:
            // case Opcodes.ASTORE:
            // case RET:
            type = OBJECT_TYPE;
            break;
        }
        mv.visitVarInsn(opcode, remap(var, type));
    }

    @Override
    public void visitIincInsn(final int var, final int increment) {
        mv.visitIincInsn(remap(var, Type.INT_TYPE), increment);
    }

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

    @Override
    public void visitLocalVariable(final String name, final String desc,
            final String signature, final Label start, final Label end,
            final int index) {
        int newIndex = remap(index, Type.getType(desc));
        mv.visitLocalVariable(name, desc, signature, start, end, newIndex);
    }

    @Override
    public void visitFrame(final int type, final int nLocal,
            final Object[] local, final int nStack, final Object[] stack) {
        if (type != Opcodes.F_NEW) { // uncompressed frame
            throw new IllegalStateException(
                    "ClassReader.accept() should be called with EXPAND_FRAMES flag");
        }

        if (!changed) { // optimization for the case where mapping = identity
            mv.visitFrame(type, nLocal, local, nStack, stack);
            return;
        }

        // creates a copy of newLocals
        Object[] oldLocals = new Object[newLocals.length];
        System.arraycopy(newLocals, 0, oldLocals, 0, oldLocals.length);

        updateNewLocals(newLocals);

        // copies types from 'local' to 'newLocals'
        // 'newLocals' already contains the variables added with 'newLocal'

        int index = 0; // old local variable index
        int number = 0; // old local variable number
        for (; number < nLocal; ++number) {
            Object t = local[number];
            int size = t == Opcodes.LONG || t == Opcodes.DOUBLE ? 2 : 1;
            if (t != Opcodes.TOP) {
                Type typ = OBJECT_TYPE;
                if (t == Opcodes.INTEGER) {
                    typ = Type.INT_TYPE;
                } else if (t == Opcodes.FLOAT) {
                    typ = Type.FLOAT_TYPE;
                } else if (t == Opcodes.LONG) {
                    typ = Type.LONG_TYPE;
                } else if (t == Opcodes.DOUBLE) {
                    typ = Type.DOUBLE_TYPE;
                } else if (t instanceof String) {
                    typ = Type.getObjectType((String) t);
                }
                setFrameLocal(remap(index, typ), t);
            }
            index += size;
        }

        // removes TOP after long and double types as well as trailing TOPs

        index = 0;
        number = 0;
        for (int i = 0; index < newLocals.length; ++i) {
            Object t = newLocals[index++];
            if (t != null && t != Opcodes.TOP) {
                newLocals[i] = t;
                number = i + 1;
                if (t == Opcodes.LONG || t == Opcodes.DOUBLE) {
                    index += 1;
                }
            } else {
                newLocals[i] = Opcodes.TOP;
            }
        }

        // visits remapped frame
        mv.visitFrame(type, number, newLocals, nStack, stack);

        // restores original value of 'newLocals'
        newLocals = oldLocals;
    }

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

    Creates a new local variable of the given type.
Params: type – 
           the type of the local variable to be created.
Returns: the identifier of the newly created local variable./**
     * Creates a new local variable of the given type.
     * 
     * @param type
     *            the type of the local variable to be created.
     * @return the identifier of the newly created local variable.
     */
    public int newLocal(final Type type) {
        Object t;
        switch (type.getSort()) {
        case Type.BOOLEAN:
        case Type.CHAR:
        case Type.BYTE:
        case Type.SHORT:
        case Type.INT:
            t = Opcodes.INTEGER;
            break;
        case Type.FLOAT:
            t = Opcodes.FLOAT;
            break;
        case Type.LONG:
            t = Opcodes.LONG;
            break;
        case Type.DOUBLE:
            t = Opcodes.DOUBLE;
            break;
        case Type.ARRAY:
            t = type.getDescriptor();
            break;
        // case Type.OBJECT:
        default:
            t = type.getInternalName();
            break;
        }
        int local = newLocalMapping(type);
        setLocalType(local, type);
        setFrameLocal(local, t);
        changed = true;
        return local;
    }

    Notifies subclasses that a new stack map frame is being visited. The array argument contains the stack map frame types corresponding to the local variables added with newLocal. This method can update these types in place for the stack map frame being visited. The default implementation of this method does nothing, i.e. a local variable added with newLocal will have the same type in all stack map frames. But this behavior is not always the desired one, for instance if a local variable is added in the middle of a try/catch block: the frame for the exception handler should have a TOP type for this new local. 
Params: newLocals –  the stack map frame types corresponding to the local variables added with newLocal (and null for the others). The format of this array is the same as in MethodVisitor.visitFrame, except that long and double types use two slots. The types for the current stack map frame must be updated in place in this array./**
     * Notifies subclasses that a new stack map frame is being visited. The
     * array argument contains the stack map frame types corresponding to the
     * local variables added with {@link #newLocal}. This method can update
     * these types in place for the stack map frame being visited. The default
     * implementation of this method does nothing, i.e. a local variable added
     * with {@link #newLocal} will have the same type in all stack map frames.
     * But this behavior is not always the desired one, for instance if a local
     * variable is added in the middle of a try/catch block: the frame for the
     * exception handler should have a TOP type for this new local.
     * 
     * @param newLocals
     *            the stack map frame types corresponding to the local variables
     *            added with {@link #newLocal} (and null for the others). The
     *            format of this array is the same as in
     *            {@link MethodVisitor#visitFrame}, except that long and double
     *            types use two slots. The types for the current stack map frame
     *            must be updated in place in this array.
     */
    protected void updateNewLocals(Object[] newLocals) {
    }

    Notifies subclasses that a local variable has been added or remapped. The
default implementation of this method does nothing.
Params: local –  a local variable identifier, as returned by 
           newLocal().
type – 
           the type of the value being stored in the local variable./**
     * Notifies subclasses that a local variable has been added or remapped. The
     * default implementation of this method does nothing.
     * 
     * @param local
     *            a local variable identifier, as returned by {@link #newLocal
     *            newLocal()}.
     * @param type
     *            the type of the value being stored in the local variable.
     */
    protected void setLocalType(final int local, final Type type) {
    }

    private void setFrameLocal(final int local, final Object type) {
        int l = newLocals.length;
        if (local >= l) {
            Object[] a = new Object[Math.max(2 * l, local + 1)];
            System.arraycopy(newLocals, 0, a, 0, l);
            newLocals = a;
        }
        newLocals[local] = type;
    }

    private int remap(final int var, final Type type) {
        if (var + type.getSize() <= firstLocal) {
            return var;
        }
        int key = 2 * var + type.getSize() - 1;
        int size = mapping.length;
        if (key >= size) {
            int[] newMapping = new int[Math.max(2 * size, key + 1)];
            System.arraycopy(mapping, 0, newMapping, 0, size);
            mapping = newMapping;
        }
        int value = mapping[key];
        if (value == 0) {
            value = newLocalMapping(type);
            setLocalType(value, type);
            mapping[key] = value + 1;
        } else {
            value--;
        }
        if (value != var) {
            changed = true;
        }
        return value;
    }

    protected int newLocalMapping(final Type type) {
        int local = nextLocal;
        nextLocal += type.getSize();
        return local;
    }
}
Params:	type – the type of the local variable to be created.
Returns:	the identifier of the newly created local variable.
/

org.ow2.asm/ asm-commons/ 4.2/ org/objectweb/asm/commons/LocalVariablesSorter.java
