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/*
* Copyright (C) 2011 The Android Open Source Project
*
* 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 com.android.tools.lint.checks;
import com.android.annotations.NonNull;
import com.android.annotations.Nullable;
import com.android.tools.lint.detector.api.Category;
import com.android.tools.lint.detector.api.ClassContext;
import com.android.tools.lint.detector.api.Detector;
import com.android.tools.lint.detector.api.Issue;
import com.android.tools.lint.detector.api.Scope;
import com.android.tools.lint.detector.api.Severity;
import com.android.tools.lint.detector.api.Speed;
import org.objectweb.asm.tree.ClassNode;
import org.objectweb.asm.tree.MethodInsnNode;
import org.objectweb.asm.tree.MethodNode;
import java.util.Arrays;
import java.util.List;
/**
* Looks for usages of {@link java.lang.Math} methods which can be replaced with
* {@code android.util.FloatMath} methods to avoid casting.
*/
public class MathDetector extends Detector implements Detector.ClassScanner {
/** The main issue discovered by this detector */
public static final Issue ISSUE = Issue.create(
"FloatMath", //$NON-NLS-1$
"Suggests replacing android.util.FloatMath calls with java.lang.Math",
"In older versions of Android, using android.util.FloatMath was recommended " +
"for performance reasons when operating on floats. However, on modern hardware " +
"doubles are just as fast as float (though they take more memory), and in " +
"recent versions of Android, FloatMath is actually slower than using java.lang.Math " +
"due to the way the JIT optimizes java.lang.Math. Therefore, you should use " +
"Math instead of FloatMath if you are only targeting Froyo and above.",
Category.PERFORMANCE,
3,
Severity.WARNING,
MathDetector.class,
Scope.CLASS_FILE_SCOPE).setMoreInfo(
"http://developer.android.com/guide/practices/design/performance.html#avoidfloat"); //$NON-NLS-1$
/** Constructs a new {@link MathDetector} check */
public MathDetector() {
}
@Override
public @NonNull Speed getSpeed() {
return Speed.FAST;
}
// ---- Implements ClassScanner ----
@Override
@Nullable
public List<String> getApplicableCallNames() {
return Arrays.asList(
"sin", //$NON-NLS-1$
"cos", //$NON-NLS-1$
"ceil", //$NON-NLS-1$
"sqrt", //$NON-NLS-1$
"floor" //$NON-NLS-1$
);
}
@Override
public void checkCall(@NonNull ClassContext context, @NonNull ClassNode classNode,
@NonNull MethodNode method, @NonNull MethodInsnNode call) {
String owner = call.owner;
if (owner.equals("android/util/FloatMath") //$NON-NLS-1$
&& context.getProject().getMinSdk() >= 8) {
String message = String.format(
"Use java.lang.Math#%1$s instead of android.util.FloatMath#%1$s() " +
"since it is faster as of API 8", call.name);
context.report(ISSUE, method, context.getLocation(call), message, null /*data*/);
}
}
}
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