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ProGuardCORE is a free library to read, analyze, modify, and write Java class files.
/*
* ProGuardCORE -- library to process Java bytecode.
*
* Copyright (c) 2002-2020 Guardsquare NV
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package proguard.classfile.instruction;
import proguard.classfile.*;
import proguard.classfile.attribute.CodeAttribute;
import proguard.classfile.constant.*;
import proguard.classfile.constant.visitor.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.ClassUtil;
import java.util.Objects;
/**
* This {@link 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.
/**
* Returns whether a particular instance of an instruction may throw
* an exception.
*
* In particular, this takes into account that an ldc with a class,
* method type or method ref constant operand may throw exceptions
* while other constants may not.
*/
@Override
public boolean mayInstanceThrowExceptions(Clazz clazz)
{
if (this.canonicalOpcode() == Instruction.OP_LDC)
{
ConstantMayThrowChecker classConstantChecker = new ConstantMayThrowChecker();
clazz.constantPoolEntryAccept(this.constantIndex, classConstantChecker);
return classConstantChecker.mayThrow;
}
else
{
return super.mayInstanceThrowExceptions(clazz);
}
}
public byte canonicalOpcode()
{
// Remove the _w extension, if any.
return
opcode == Instruction.OP_LDC_W ? Instruction.OP_LDC :
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 == Instruction.OP_LDC_W)
{
opcode = Instruction.OP_LDC;
}
}
else
{
// Should we replace the short instruction by a long instruction?
if (opcode == Instruction.OP_LDC)
{
opcode = Instruction.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 String toString(Clazz clazz, int offset)
{
StringBuilder builder = new StringBuilder("[" + offset + "] " + this.toString()+" = ");
// Append the constant in readable form.
clazz.constantPoolEntryAccept(constantIndex, new ConstantStringBuilder(builder));
return builder.toString();
}
public int stackPopCount(Clazz clazz)
{
int stackPopCount = super.stackPopCount(clazz);
// Some special cases.
switch (opcode)
{
case Instruction.OP_MULTIANEWARRAY:
// For each dimension, an integer size is popped from the stack.
stackPopCount += constant;
break;
case Instruction.OP_PUTSTATIC:
case Instruction.OP_PUTFIELD:
// The field value is be popped from the stack.
clazz.constantPoolEntryAccept(constantIndex, this);
stackPopCount += typeStackDelta;
break;
case Instruction.OP_INVOKEVIRTUAL:
case Instruction.OP_INVOKESPECIAL:
case Instruction.OP_INVOKESTATIC:
case Instruction.OP_INVOKEINTERFACE:
case Instruction.OP_INVOKEDYNAMIC:
// 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 Instruction.OP_GETSTATIC:
case Instruction.OP_GETFIELD:
case Instruction.OP_INVOKEVIRTUAL:
case Instruction.OP_INVOKESPECIAL:
case Instruction.OP_INVOKESTATIC:
case Instruction.OP_INVOKEINTERFACE:
case Instruction.OP_INVOKEDYNAMIC:
// 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 visitPrimitiveArrayConstant(Clazz clazz, PrimitiveArrayConstant primitiveArrayConstant) {}
public void visitStringConstant(Clazz clazz, StringConstant stringConstant) {}
public void visitUtf8Constant(Clazz clazz, Utf8Constant utf8Constant) {}
public void visitMethodHandleConstant(Clazz clazz, MethodHandleConstant methodHandleConstant) {}
public void visitClassConstant(Clazz clazz, ClassConstant classConstant) {}
public void visitMethodTypeConstant(Clazz clazz, MethodTypeConstant methodTypeConstant) {}
public void visitModuleConstant(Clazz clazz, ModuleConstant moduleConstant) {}
public void visitPackageConstant(Clazz clazz, PackageConstant packageConstant) {}
public void visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant)
{
String type = fieldrefConstant.getType(clazz);
typeStackDelta = ClassUtil.internalTypeSize(ClassUtil.internalMethodReturnType(type));
}
public void visitDynamicConstant(Clazz clazz, DynamicConstant dynamicConstant)
{
clazz.constantPoolEntryAccept(dynamicConstant.u2nameAndTypeIndex, this);
}
public void visitInvokeDynamicConstant(Clazz clazz, InvokeDynamicConstant invokeDynamicConstant)
{
clazz.constantPoolEntryAccept(invokeDynamicConstant.u2nameAndTypeIndex, this);
}
public void visitInterfaceMethodrefConstant(Clazz clazz, InterfaceMethodrefConstant interfaceMethodrefConstant)
{
clazz.constantPoolEntryAccept(interfaceMethodrefConstant.u2nameAndTypeIndex, this);
}
public void visitMethodrefConstant(Clazz clazz, MethodrefConstant methodrefConstant)
{
clazz.constantPoolEntryAccept(methodrefConstant.u2nameAndTypeIndex, this);
}
public void visitNameAndTypeConstant(Clazz clazz, NameAndTypeConstant nameAndTypeConstant)
{
String type = nameAndTypeConstant.getType(clazz);
parameterStackDelta = ClassUtil.internalMethodParameterSize(type);
typeStackDelta = ClassUtil.internalTypeSize(ClassUtil.internalMethodReturnType(type));
}
// Implementations for Object.
@Override
public String toString()
{
return getName()+" #"+constantIndex+(constantSize() == 0 ? "" : ", "+constant);
}
@Override
public boolean equals(Object o)
{
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
ConstantInstruction that = (ConstantInstruction)o;
return opcode == that.opcode &&
constantIndex == that.constantIndex &&
constant == that.constant;
}
@Override
public int hashCode()
{
return Objects.hash(opcode, constantIndex, constant);
}
// Small utility methods.
/**
* Returns the constant pool index size for this instruction.
*/
private int constantIndexSize()
{
return opcode == Instruction.OP_LDC ? 1 :
2;
}
/**
* Returns the constant size for this instruction.
*/
private int constantSize()
{
return opcode == Instruction.OP_MULTIANEWARRAY ? 1 :
opcode == Instruction.OP_INVOKEDYNAMIC ||
opcode == Instruction.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;
}
private static class ConstantMayThrowChecker implements ConstantVisitor
{
public boolean mayThrow = false;
@Override
public void visitAnyConstant(Clazz clazz, Constant constant) { }
@Override
public void visitClassConstant(Clazz clazz, ClassConstant classConstant)
{
this.mayThrow = true;
}
@Override
public void visitMethodHandleConstant(Clazz clazz, MethodHandleConstant methodHandleConstant)
{
this.mayThrow = true;
}
@Override
public void visitMethodTypeConstant(Clazz clazz, MethodTypeConstant methodTypeConstant)
{
this.mayThrow = true;
}
}
}
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