/*
* ProGuard -- shrinking, optimization, obfuscation, and preverification
* of Java bytecode.
*
* Copyright (c) 2002-2010 Eric Lafortune (eric@graphics.cornell.edu)
*
* 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.instruction;
import proguard.classfile.*;
import proguard.classfile.attribute.CodeAttribute;
import proguard.classfile.constant.*;
import proguard.classfile.constant.visitor.ConstantVisitor;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.ClassUtil;
/**
* This Instruction represents an instruction that refers to an entry in the
* constant pool.
*
* @author Eric Lafortune
*/
public class ConstantInstruction extends Instruction
implements ConstantVisitor
{
public int constantIndex;
public int constant;
// Fields acting as return parameters for the ConstantVisitor methods.
private int parameterStackDelta;
private int typeStackDelta;
/**
* Creates an uninitialized ConstantInstruction.
*/
public ConstantInstruction() {}
/**
* Creates a new ConstantInstruction with the given opcode and constant pool
* index.
*/
public ConstantInstruction(byte opcode, int constantIndex)
{
this(opcode, constantIndex, 0);
}
/**
* Creates a new ConstantInstruction with the given opcode, constant pool
* index, and constant.
*/
public ConstantInstruction(byte opcode, int constantIndex, int constant)
{
this.opcode = opcode;
this.constantIndex = constantIndex;
this.constant = constant;
}
/**
* Copies the given instruction into this instruction.
* @param constantInstruction the instruction to be copied.
* @return this instruction.
*/
public ConstantInstruction copy(ConstantInstruction constantInstruction)
{
this.opcode = constantInstruction.opcode;
this.constantIndex = constantInstruction.constantIndex;
this.constant = constantInstruction.constant;
return this;
}
// Implementations for Instruction.
public byte canonicalOpcode()
{
// Remove the _w extension, if any.
switch (opcode)
{
case InstructionConstants.OP_LDC_W:
case InstructionConstants.OP_LDC2_W: return InstructionConstants.OP_LDC;
default: return opcode;
}
}
public Instruction shrink()
{
// Do we need a short index or a long index?
if (requiredConstantIndexSize() == 1)
{
// Can we replace the long instruction by a short instruction?
if (opcode == InstructionConstants.OP_LDC_W)
{
opcode = InstructionConstants.OP_LDC;
}
}
else
{
// Should we replace the short instruction by a long instruction?
if (opcode == InstructionConstants.OP_LDC)
{
opcode = InstructionConstants.OP_LDC_W;
}
}
return this;
}
protected void readInfo(byte[] code, int offset)
{
int constantIndexSize = constantIndexSize();
int constantSize = constantSize();
constantIndex = readValue(code, offset, constantIndexSize); offset += constantIndexSize;
constant = readValue(code, offset, constantSize);
}
protected void writeInfo(byte[] code, int offset)
{
int constantIndexSize = constantIndexSize();
int constantSize = constantSize();
if (requiredConstantIndexSize() > constantIndexSize)
{
throw new IllegalArgumentException("Instruction has invalid constant index size ("+this.toString(offset)+")");
}
writeValue(code, offset, constantIndex, constantIndexSize); offset += constantIndexSize;
writeValue(code, offset, constant, constantSize);
}
public int length(int offset)
{
return 1 + constantIndexSize() + constantSize();
}
public void accept(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, InstructionVisitor instructionVisitor)
{
instructionVisitor.visitConstantInstruction(clazz, method, codeAttribute, offset, this);
}
public int stackPopCount(Clazz clazz)
{
int stackPopCount = super.stackPopCount(clazz);
// Some special cases.
switch (opcode)
{
case InstructionConstants.OP_MULTIANEWARRAY:
// For each dimension, an integer size is popped from the stack.
stackPopCount += constant;
break;
case InstructionConstants.OP_PUTSTATIC:
case InstructionConstants.OP_PUTFIELD:
// The field value is be popped from the stack.
clazz.constantPoolEntryAccept(constantIndex, this);
stackPopCount += typeStackDelta;
break;
case InstructionConstants.OP_INVOKEVIRTUAL:
case InstructionConstants.OP_INVOKESPECIAL:
case InstructionConstants.OP_INVOKESTATIC:
case InstructionConstants.OP_INVOKEINTERFACE:
// The some parameters may be popped from the stack.
clazz.constantPoolEntryAccept(constantIndex, this);
stackPopCount += parameterStackDelta;
break;
}
return stackPopCount;
}
public int stackPushCount(Clazz clazz)
{
int stackPushCount = super.stackPushCount(clazz);
// Some special cases.
switch (opcode)
{
case InstructionConstants.OP_GETSTATIC:
case InstructionConstants.OP_GETFIELD:
case InstructionConstants.OP_INVOKEVIRTUAL:
case InstructionConstants.OP_INVOKESPECIAL:
case InstructionConstants.OP_INVOKESTATIC:
case InstructionConstants.OP_INVOKEINTERFACE:
// The field value or a return value may be pushed onto the stack.
clazz.constantPoolEntryAccept(constantIndex, this);
stackPushCount += typeStackDelta;
break;
}
return stackPushCount;
}
// Implementations for ConstantVisitor.
public void visitIntegerConstant(Clazz clazz, IntegerConstant integerConstant) {}
public void visitLongConstant(Clazz clazz, LongConstant longConstant) {}
public void visitFloatConstant(Clazz clazz, FloatConstant floatConstant) {}
public void visitDoubleConstant(Clazz clazz, DoubleConstant doubleConstant) {}
public void visitStringConstant(Clazz clazz, StringConstant stringConstant) {}
public void visitUtf8Constant(Clazz clazz, Utf8Constant utf8Constant) {}
public void visitClassConstant(Clazz clazz, ClassConstant classConstant) {}
public void visitNameAndTypeConstant(Clazz clazz, NameAndTypeConstant nameAndTypeConstant) {}
public void visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant)
{
String type = fieldrefConstant.getType(clazz);
typeStackDelta = ClassUtil.internalTypeSize(ClassUtil.internalMethodReturnType(type));
}
public void visitInterfaceMethodrefConstant(Clazz clazz, InterfaceMethodrefConstant interfaceMethodrefConstant)
{
visitRefConstant(clazz, interfaceMethodrefConstant);
}
public void visitMethodrefConstant(Clazz clazz, MethodrefConstant methodrefConstant)
{
visitRefConstant(clazz, methodrefConstant);
}
private void visitRefConstant(Clazz clazz, RefConstant methodrefConstant)
{
String type = methodrefConstant.getType(clazz);
parameterStackDelta = ClassUtil.internalMethodParameterSize(type);
typeStackDelta = ClassUtil.internalTypeSize(ClassUtil.internalMethodReturnType(type));
}
// Implementations for Object.
public String toString()
{
return getName()+" #"+constantIndex;
}
// Small utility methods.
/**
* Returns the constant pool index size for this instruction.
*/
private int constantIndexSize()
{
return opcode == InstructionConstants.OP_LDC ? 1 :
2;
}
/**
* Returns the constant size for this instruction.
*/
private int constantSize()
{
return opcode == InstructionConstants.OP_MULTIANEWARRAY ? 1 :
opcode == InstructionConstants.OP_INVOKEINTERFACE ? 2 :
0;
}
/**
* Computes the required constant pool index size for this instruction's
* constant pool index.
*/
private int requiredConstantIndexSize()
{
return (constantIndex & 0xff) == constantIndex ? 1 :
(constantIndex & 0xffff) == constantIndex ? 2 :
4;
}
}