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// Copyright 2014 The Bazel Authors. 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.devtools.build.lib.query2.engine;
import com.google.common.base.Predicate;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.devtools.build.lib.query2.engine.QueryEnvironment.Argument;
import com.google.devtools.build.lib.query2.engine.QueryEnvironment.QueryFunction;
import com.google.devtools.build.lib.query2.engine.QueryEnvironment.QueryTaskFuture;
import java.util.List;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
/**
* An abstract class that provides generic regex filter expression. Actual
* expression are implemented by the subclasses.
*/
public abstract class RegexFilterExpression implements QueryFunction {
protected RegexFilterExpression() {
}
@Override
public <T> QueryTaskFuture<Void> eval(
final QueryEnvironment<T> env,
VariableContext<T> context,
QueryExpression expression,
final List<Argument> args,
Callback<T> callback) {
String rawPattern = getPattern(args);
final Pattern compiledPattern;
try {
compiledPattern = Pattern.compile(rawPattern);
} catch (PatternSyntaxException e) {
return env.immediateFailedFuture(new QueryException(
expression,
String.format(
"illegal '%s' pattern regexp '%s': %s",
getName(),
rawPattern,
e.getMessage())));
}
// Note that Patttern#matcher is thread-safe and so this Predicate can safely be used
// concurrently.
final Predicate<T> matchFilter = new Predicate<T>() {
@Override
public boolean apply(T target) {
for (String str : getFilterStrings(env, args, target)) {
if ((str != null) && compiledPattern.matcher(str).find()) {
return true;
}
}
return false;
}
};
return env.eval(
Iterables.getLast(args).getExpression(),
context,
new FilteredCallback<>(callback, matchFilter));
}
/**
* Returns string for the given target that must be matched against pattern.
* May return null, in which case matching is guaranteed to fail.
*/
protected abstract <T> String getFilterString(
QueryEnvironment<T> env, List<Argument> args, T target);
/**
* Returns a list of strings for the given target that must be matched against
* pattern. The filter matches if *any* of these strings matches.
*
* <p>Unless subclasses have an explicit reason to override this method, it's fine
* to keep the default implementation that just delegates to {@link #getFilterString}.
* Overriding this method is useful for subclasses that want to match against a
* universe of possible values. For example, with configurable attributes, an
* attribute might have different values depending on the build configuration. One
* may wish the filter to match if *any* of those values matches.
*/
protected <T> Iterable<String> getFilterStrings(
QueryEnvironment<T> env, List<Argument> args, T target) {
String filterString = getFilterString(env, args, target);
return filterString == null ? ImmutableList.<String>of() : ImmutableList.of(filterString);
}
protected abstract String getPattern(List<Argument> args);
private static class FilteredCallback<T> implements Callback<T> {
private final Callback<T> parentCallback;
private final Predicate<T> retainIfTrue;
private FilteredCallback(Callback<T> parentCallback, Predicate<T> retainIfTrue) {
this.parentCallback = parentCallback;
this.retainIfTrue = retainIfTrue;
}
@Override
public void process(Iterable<T> partialResult) throws QueryException, InterruptedException {
Iterable<T> filter = Iterables.filter(partialResult, retainIfTrue);
if (!Iterables.isEmpty(filter)) {
parentCallback.process(filter);
}
}
@Override
public String toString() {
return "filtered parentCallback of : " + retainIfTrue;
}
}
}
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