/*
* FindBugs - Find bugs in Java programs
* Copyright (C) 2005 Dave Brosius <dbrosius@users.sourceforge.net>
* Copyright (C) 2005 University of Maryland
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package edu.umd.cs.findbugs.detect;
import java.util.HashSet;
import java.util.Set;
import org.apache.bcel.classfile.Code;
import org.apache.bcel.classfile.Constant;
import org.apache.bcel.classfile.ConstantDouble;
import org.apache.bcel.classfile.ConstantFloat;
import org.apache.bcel.classfile.ConstantLong;
import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.BytecodeScanningDetector;
import edu.umd.cs.findbugs.StatelessDetector;
/**
* Find occurrences of Math using constants, where the result of the calculation
* can be determined statically. Replacing the math formula with the constant
* performs better, and sometimes is more accurate.
*
* @author Dave Brosius
*/
public class UnnecessaryMath extends BytecodeScanningDetector implements StatelessDetector {
static final int SEEN_NOTHING = 0;
static final int SEEN_DCONST = 1;
private final BugReporter bugReporter;
private int state = SEEN_NOTHING;
private double constValue;
@edu.umd.cs.findbugs.internalAnnotations.StaticConstant
private static final Set<String> zeroMethods = new HashSet<String>() {
{
add("acos");
add("asin");
add("atan");
add("atan2");
add("cbrt");
add("cos");
add("cosh");
add("exp");
add("expm1");
add("log");
add("log10");
add("pow");
add("sin");
add("sinh");
add("sqrt");
add("tan");
add("tanh");
add("toDegrees");
add("toRadians");
}
};
@edu.umd.cs.findbugs.internalAnnotations.StaticConstant
private static final Set<String> oneMethods = new HashSet<String>() {
{
add("acos");
add("asin");
add("atan");
add("cbrt");
add("exp");
add("log");
add("log10");
add("pow");
add("sqrt");
add("toDegrees");
}
};
@edu.umd.cs.findbugs.internalAnnotations.StaticConstant
private static final Set<String> anyMethods = new HashSet<String>() {
{
add("abs");
add("ceil");
add("floor");
add("rint");
add("round");
}
};
public UnnecessaryMath(BugReporter bugReporter) {
this.bugReporter = bugReporter;
}
@Override
public void visit(Code obj) {
// Don't complain about unnecessary math calls in class initializers,
// since they may be there to improve readability.
if (getMethod().getName().equals("<clinit>")) {
return;
}
state = SEEN_NOTHING;
super.visit(obj);
}
@Override
public void sawOpcode(int seen) {
if (state == SEEN_NOTHING) {
if ((seen == DCONST_0) || (seen == DCONST_1)) {
constValue = seen - DCONST_0;
state = SEEN_DCONST;
} else if ((seen == LDC2_W) || (seen == LDC_W)) {
state = SEEN_DCONST;
Constant c = this.getConstantRefOperand();
if (c instanceof ConstantDouble) {
constValue = ((ConstantDouble) c).getBytes();
} else if (c instanceof ConstantFloat) {
constValue = ((ConstantFloat) c).getBytes();
} else if (c instanceof ConstantLong) {
constValue = ((ConstantLong) c).getBytes();
} else {
state = SEEN_NOTHING;
}
}
} else if (state == SEEN_DCONST) {
if (seen == INVOKESTATIC) {
state = SEEN_NOTHING;
if (getDottedClassConstantOperand().equals("java.lang.Math")) {
String methodName = getNameConstantOperand();
if (((constValue == 0.0) && zeroMethods.contains(methodName))
|| ((constValue == 1.0) && oneMethods.contains(methodName)) || (anyMethods.contains(methodName))) {
bugReporter.reportBug(new BugInstance(this, "UM_UNNECESSARY_MATH", LOW_PRIORITY).addClassAndMethod(this)
.addSourceLine(this));
}
}
}
state = SEEN_NOTHING;
}
}
}