/*
* Copyright 2016 Google Inc. All Rights Reserved.
*
* 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.google.errorprone.bugpatterns;
import static com.google.errorprone.BugPattern.Category.JDK;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.matchers.Matchers.allOf;
import static com.google.errorprone.matchers.Matchers.hasAnnotation;
import static com.google.errorprone.matchers.Matchers.isSubtypeOf;
import static com.google.errorprone.matchers.Matchers.methodHasArity;
import static com.google.errorprone.matchers.Matchers.methodIsNamed;
import static com.google.errorprone.matchers.Matchers.methodReturns;
import static com.google.errorprone.suppliers.Suppliers.INT_TYPE;
import com.google.common.collect.ImmutableList;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.JUnitMatchers;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.ReturnTree;
import com.sun.source.tree.StatementTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.Tree.Kind;
import com.sun.source.util.TreePath;
import com.sun.tools.javac.code.Symbol.MethodSymbol;
import com.sun.tools.javac.code.Symbol.TypeSymbol;
import com.sun.tools.javac.code.Type;
import java.io.InputStream;
import java.util.List;
import javax.lang.model.element.ElementKind;
/** Checks that InputStreams should override int read(byte[], int, int); */
@BugPattern(
name = "InputStreamSlowMultibyteRead",
summary =
"Please also override int read(byte[], int, int), otherwise multi-byte reads from this "
+ "input stream are likely to be slow.",
category = JDK,
severity = WARNING
)
public class InputStreamSlowMultibyteRead extends BugChecker implements ClassTreeMatcher {
private static final Matcher<ClassTree> IS_INPUT_STREAM = isSubtypeOf(InputStream.class);
private static final Matcher<MethodTree> READ_INT_METHOD =
allOf(methodIsNamed("read"), methodReturns(INT_TYPE), methodHasArity(0));
@Override
public Description matchClass(ClassTree classTree, VisitorState state) {
if (!IS_INPUT_STREAM.matches(classTree, state)) {
return Description.NO_MATCH;
}
TypeSymbol thisClassSymbol = ASTHelpers.getSymbol(classTree);
if (thisClassSymbol.getKind() != ElementKind.CLASS) {
return Description.NO_MATCH;
}
// Find the method that overrides the single-byte read. It should also override the multibyte
// read.
MethodTree readByteMethod =
classTree
.getMembers()
.stream()
.filter(MethodTree.class::isInstance)
.map(MethodTree.class::cast)
.filter(m -> READ_INT_METHOD.matches(m, state))
.findFirst()
.orElse(null);
if (readByteMethod == null) {
return Description.NO_MATCH;
}
Type byteArrayType = state.arrayTypeForType(state.getSymtab().byteType);
Type intType = state.getSymtab().intType;
MethodSymbol multiByteReadMethod =
ASTHelpers.resolveExistingMethod(
state,
thisClassSymbol,
state.getName("read"),
ImmutableList.of(byteArrayType, intType, intType),
ImmutableList.of());
return multiByteReadMethod.owner.equals(thisClassSymbol)
? Description.NO_MATCH
: maybeMatchReadByte(readByteMethod, state);
}
private Description maybeMatchReadByte(MethodTree readByteMethod, VisitorState state) {
// Methods that return a constant expression are likely to be 'dummy streams', for which
// the multibyte read is OK.
List<? extends StatementTree> statements = readByteMethod.getBody().getStatements();
if (statements.size() == 1) {
Tree tree = statements.get(0);
if (tree.getKind() == Kind.RETURN
&& ASTHelpers.constValue(((ReturnTree) tree).getExpression()) != null) {
return Description.NO_MATCH;
}
}
// Streams within JUnit test cases are likely to be OK as well.
TreePath enclosingPath =
ASTHelpers.findPathFromEnclosingNodeToTopLevel(state.getPath(), ClassTree.class);
while (enclosingPath != null) {
ClassTree klazz = (ClassTree) enclosingPath.getLeaf();
if (JUnitMatchers.isTestCaseDescendant.matches(klazz, state)
|| hasAnnotation(JUnitMatchers.JUNIT4_RUN_WITH_ANNOTATION).matches(klazz, state)) {
return Description.NO_MATCH;
}
enclosingPath =
ASTHelpers.findPathFromEnclosingNodeToTopLevel(enclosingPath, ClassTree.class);
}
return describeMatch(readByteMethod);
}
}