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/*
* ProGuard -- shrinking, optimization, obfuscation, and preverification
* of Java bytecode.
*
* Copyright (c) 2002-2014 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.instruction.visitor.InstructionVisitor;
/**
* This Instruction represents a simple instruction without variable arguments
* or constant pool references.
*
* @author Eric Lafortune
*/
public class SimpleInstruction extends Instruction
{
public int constant;
/**
* Creates an uninitialized SimpleInstruction.
*/
public SimpleInstruction() {}
/**
* Creates a new SimpleInstruction with the given opcode.
*/
public SimpleInstruction(byte opcode)
{
this(opcode, embeddedConstant(opcode));
}
/**
* Creates a new SimpleInstruction with the given opcode and constant.
*/
public SimpleInstruction(byte opcode, int constant)
{
this.opcode = opcode;
this.constant = constant;
}
/**
* Copies the given instruction into this instruction.
* @param simpleInstruction the instruction to be copied.
* @return this instruction.
*/
public SimpleInstruction copy(SimpleInstruction simpleInstruction)
{
this.opcode = simpleInstruction.opcode;
this.constant = simpleInstruction.constant;
return this;
}
/**
* Return the embedded constant of the given opcode, or 0 if the opcode
* doesn't have one.
*/
private static int embeddedConstant(byte opcode)
{
switch (opcode)
{
case InstructionConstants.OP_ICONST_M1: return -1;
case InstructionConstants.OP_ICONST_1:
case InstructionConstants.OP_LCONST_1:
case InstructionConstants.OP_FCONST_1:
case InstructionConstants.OP_DCONST_1: return 1;
case InstructionConstants.OP_ICONST_2:
case InstructionConstants.OP_FCONST_2: return 2;
case InstructionConstants.OP_ICONST_3: return 3;
case InstructionConstants.OP_ICONST_4: return 4;
case InstructionConstants.OP_ICONST_5: return 5;
default: return 0;
}
}
// Implementations for Instruction.
public byte canonicalOpcode()
{
// Replace any _1, _2, _3,... extension by _0.
switch (opcode)
{
case InstructionConstants.OP_ICONST_M1:
case InstructionConstants.OP_ICONST_0:
case InstructionConstants.OP_ICONST_1:
case InstructionConstants.OP_ICONST_2:
case InstructionConstants.OP_ICONST_3:
case InstructionConstants.OP_ICONST_4:
case InstructionConstants.OP_ICONST_5:
case InstructionConstants.OP_BIPUSH:
case InstructionConstants.OP_SIPUSH: return InstructionConstants.OP_ICONST_0;
case InstructionConstants.OP_LCONST_0:
case InstructionConstants.OP_LCONST_1: return InstructionConstants.OP_LCONST_0;
case InstructionConstants.OP_FCONST_0:
case InstructionConstants.OP_FCONST_1:
case InstructionConstants.OP_FCONST_2: return InstructionConstants.OP_FCONST_0;
case InstructionConstants.OP_DCONST_0:
case InstructionConstants.OP_DCONST_1: return InstructionConstants.OP_DCONST_0;
default: return opcode;
}
}
public Instruction shrink()
{
// Reconstruct the opcode of the shortest instruction, if there are
// any alternatives.
switch (opcode)
{
case InstructionConstants.OP_ICONST_M1:
case InstructionConstants.OP_ICONST_0:
case InstructionConstants.OP_ICONST_1:
case InstructionConstants.OP_ICONST_2:
case InstructionConstants.OP_ICONST_3:
case InstructionConstants.OP_ICONST_4:
case InstructionConstants.OP_ICONST_5:
case InstructionConstants.OP_BIPUSH:
case InstructionConstants.OP_SIPUSH:
switch (requiredConstantSize())
{
case 0:
opcode = (byte)(InstructionConstants.OP_ICONST_0 + constant);
break;
case 1:
opcode = InstructionConstants.OP_BIPUSH;
break;
case 2:
opcode = InstructionConstants.OP_SIPUSH;
break;
}
break;
case InstructionConstants.OP_LCONST_0:
case InstructionConstants.OP_LCONST_1:
opcode = (byte)(InstructionConstants.OP_LCONST_0 + constant);
break;
case InstructionConstants.OP_FCONST_0:
case InstructionConstants.OP_FCONST_1:
case InstructionConstants.OP_FCONST_2:
opcode = (byte)(InstructionConstants.OP_FCONST_0 + constant);
break;
case InstructionConstants.OP_DCONST_0:
case InstructionConstants.OP_DCONST_1:
opcode = (byte)(InstructionConstants.OP_DCONST_0 + constant);
break;
}
return this;
}
protected void readInfo(byte[] code, int offset)
{
int constantSize = constantSize();
// Also initialize embedded constants that are different from 0.
constant = constantSize == 0 ?
embeddedConstant(opcode) :
readSignedValue(code, offset, constantSize);
}
protected void writeInfo(byte[] code, int offset)
{
int constantSize = constantSize();
if (requiredConstantSize() > constantSize)
{
throw new IllegalArgumentException("Instruction has invalid constant size ("+this.toString(offset)+")");
}
writeSignedValue(code, offset, constant, constantSize);
}
public int length(int offset)
{
return 1 + constantSize();
}
public void accept(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, InstructionVisitor instructionVisitor)
{
instructionVisitor.visitSimpleInstruction(clazz, method, codeAttribute, offset, this);
}
// Implementations for Object.
public String toString()
{
return getName() +
(constantSize() > 0 ? " "+constant : "");
}
// Small utility methods.
/**
* Returns the constant size for this instruction.
*/
private int constantSize()
{
return opcode == InstructionConstants.OP_BIPUSH ||
opcode == InstructionConstants.OP_NEWARRAY ? 1 :
opcode == InstructionConstants.OP_SIPUSH ? 2 :
0;
}
/**
* Computes the required constant size for this instruction.
*/
private int requiredConstantSize()
{
return constant >= -1 && constant <= 5 ? 0 :
(byte)constant == constant ? 1 :
(short)constant == constant ? 2 :
4;
}
}
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