stacksizeupdater.java

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/* $Id: StackSizeUpdater.java,v 1.14.2.1 2006/01/16 22:57:55 eric Exp $
 *
 * ProGuard -- shrinking, optimization, and obfuscation of Java class files.
 *
 * Copyright (c) 2002-2006 Eric Lafortune ([e-mail])
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This program 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 General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.classfile.editor;

import proguard.classfile.*;
import proguard.classfile.util.ClassUtil;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.annotation.*;
import proguard.classfile.instruction.*;
import proguard.classfile.visitor.*;

/**
 * This AttrInfoVisitor computes and updates the maximum stack size of the
 * code attributes that it visits.
 *
 * @author Eric Lafortune
 */
class      StackSizeUpdater
implements AttrInfoVisitor,
           InstructionVisitor,
           ExceptionInfoVisitor
{
    //*
    private static final boolean DEBUG = false;
    /*/
    private static boolean DEBUG       = true;
    //*/


    private boolean[] evaluated;

    private boolean exitInstructionBlock;

    private int stackSize;
    private int maxStackSize;


    /**
     * Creates a new StackSizeUpdater.
     * @param codeLength an estimate of the maximum length of all the code that
     *                   will be visited.
     */
    public StackSizeUpdater(int codeLength)
    {
        evaluated = new boolean[codeLength];
    }


    // Implementations for AttrInfoVisitor.

    public void visitUnknownAttrInfo(ClassFile classFile, UnknownAttrInfo unknownAttrInfo) {}
    public void visitInnerClassesAttrInfo(ClassFile classFile, InnerClassesAttrInfo innerClassesAttrInfo) {}
    public void visitEnclosingMethodAttrInfo(ClassFile classFile, EnclosingMethodAttrInfo enclosingMethodAttrInfo) {}
    public void visitConstantValueAttrInfo(ClassFile classFile, FieldInfo fieldInfo, ConstantValueAttrInfo constantValueAttrInfo) {}
    public void visitExceptionsAttrInfo(ClassFile classFile, MethodInfo methodInfo, ExceptionsAttrInfo exceptionsAttrInfo) {}
    public void visitLineNumberTableAttrInfo(ClassFile classFile, MethodInfo methodInfo, CodeAttrInfo codeAttrInfo, LineNumberTableAttrInfo lineNumberTableAttrInfo) {}
    public void visitLocalVariableTableAttrInfo(ClassFile classFile, MethodInfo methodInfo, CodeAttrInfo codeAttrInfo, LocalVariableTableAttrInfo localVariableTableAttrInfo) {}
    public void visitLocalVariableTypeTableAttrInfo(ClassFile classFile, MethodInfo methodInfo, CodeAttrInfo codeAttrInfo, LocalVariableTypeTableAttrInfo localVariableTypeTableAttrInfo) {}
    public void visitSourceFileAttrInfo(ClassFile classFile, SourceFileAttrInfo sourceFileAttrInfo) {}
    public void visitSourceDirAttrInfo(ClassFile classFile, SourceDirAttrInfo sourceDirAttrInfo) {}
    public void visitDeprecatedAttrInfo(ClassFile classFile, DeprecatedAttrInfo deprecatedAttrInfo) {}
    public void visitSyntheticAttrInfo(ClassFile classFile, SyntheticAttrInfo syntheticAttrInfo) {}
    public void visitSignatureAttrInfo(ClassFile classFile, SignatureAttrInfo signatureAttrInfo) {}
    public void visitRuntimeVisibleAnnotationAttrInfo(ClassFile classFile, RuntimeVisibleAnnotationsAttrInfo runtimeVisibleAnnotationsAttrInfo) {}
    public void visitRuntimeInvisibleAnnotationAttrInfo(ClassFile classFile, RuntimeInvisibleAnnotationsAttrInfo runtimeInvisibleAnnotationsAttrInfo) {}
    public void visitRuntimeVisibleParameterAnnotationAttrInfo(ClassFile classFile, RuntimeVisibleParameterAnnotationsAttrInfo runtimeVisibleParameterAnnotationsAttrInfo) {}
    public void visitRuntimeInvisibleParameterAnnotationAttrInfo(ClassFile classFile, RuntimeInvisibleParameterAnnotationsAttrInfo runtimeInvisibleParameterAnnotationsAttrInfo) {}
    public void visitAnnotationDefaultAttrInfo(ClassFile classFile, AnnotationDefaultAttrInfo annotationDefaultAttrInfo) {}


    public void visitCodeAttrInfo(ClassFile classFile, MethodInfo methodInfo, CodeAttrInfo codeAttrInfo)
    {
//        DEBUG =
//            classFile.getName().equals("abc/Def") &&
//            methodInfo.getName(classFile).equals("abc");

        if (DEBUG)
        {
            System.out.println("Class "+ClassUtil.externalClassName(classFile.getName()));
            System.out.println("Method "+ClassUtil.externalFullMethodDescription(classFile.getName(),
                                                                                 0,
                                                                                 methodInfo.getName(classFile),
                                                                                 methodInfo.getDescriptor(classFile)));
        }

        // Try to reuse the previous array.
        int codeLength = codeAttrInfo.u4codeLength;
        if (evaluated.length < codeLength)
        {
            evaluated = new boolean[codeLength];
        }
        else
        {
            for (int index = 0; index < codeLength; index++)
            {
                evaluated[index] = false;
            }
        }

        // The initial stack is always empty.
        stackSize    = 0;
        maxStackSize = 0;

        // Evaluate the instruction block starting at the entry point of the method.
        evaluateInstructionBlock(classFile, methodInfo, codeAttrInfo, 0);

        // Evaluate the exception handlers.
        codeAttrInfo.exceptionsAccept(classFile, methodInfo, this);

        // Update the maximum stack size.
        codeAttrInfo.u2maxStack = maxStackSize;
    }


    // Implementations for InstructionVisitor.

    public void visitSimpleInstruction(ClassFile classFile, MethodInfo methodInfo, CodeAttrInfo codeAttrInfo, int offset, SimpleInstruction simpleInstruction)
    {
        byte opcode = simpleInstruction.opcode;

        // Some simple instructions exit from the current instruction block.
        exitInstructionBlock =
            opcode == InstructionConstants.OP_IRETURN ||
            opcode == InstructionConstants.OP_LRETURN ||
            opcode == InstructionConstants.OP_FRETURN ||
            opcode == InstructionConstants.OP_DRETURN ||
            opcode == InstructionConstants.OP_ARETURN ||
            opcode == InstructionConstants.OP_RETURN  ||
            opcode == InstructionConstants.OP_ATHROW;
    }

    public void visitCpInstruction(ClassFile classFile, MethodInfo methodInfo, CodeAttrInfo codeAttrInfo, int offset, CpInstruction cpInstruction)
    {
        // Constant pool instructions never end the current instruction block.
        exitInstructionBlock = false;
    }

    public void visitVariableInstruction(ClassFile classFile, MethodInfo methodInfo, CodeAttrInfo codeAttrInfo, int offset, VariableInstruction variableInstruction)
    {
        byte opcode = variableInstruction.opcode;

        // The ret instruction end the current instruction block.
        exitInstructionBlock =
            opcode == InstructionConstants.OP_RET;
    }

    public void visitBranchInstruction(ClassFile classFile, MethodInfo methodInfo, CodeAttrInfo codeAttrInfo, int offset, BranchInstruction branchInstruction)
    {
        byte opcode = branchInstruction.opcode;

        // Evaluate the target instruction blocks.
        evaluateInstructionBlock(classFile,
                                 methodInfo,
                                 codeAttrInfo,
                                 offset +
                                 branchInstruction.branchOffset);

        // Evaluate the instructions after a subroutine branch.
        if (opcode == InstructionConstants.OP_JSR ||
            opcode == InstructionConstants.OP_JSR_W)
        {
            // We assume subroutine calls (jsr and jsr_w instructions) don't
            // change the stack, other than popping the return value.
            stackSize -= 1;

            evaluateInstructionBlock(classFile,