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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.skyframe;
import com.google.devtools.build.lib.vfs.ModifiedFileSet;
import com.google.devtools.build.lib.vfs.Root;
import com.google.devtools.common.options.OptionsClassProvider;
import java.io.Closeable;
import javax.annotation.Nullable;
/**
* Interface for computing modifications of files under a package path entry.
*
* <p> Skyframe has a {@link DiffAwareness} instance per package-path entry, and each instance is
* responsible for all files under its path entry. At the beginning of each incremental build,
* skyframe queries for changes using {@link #getDiff}. Ideally, {@link #getDiff} should be
* constant-time; if it were linear in the number of files of interest, we might as well just
* detect modifications manually.
*/
public interface DiffAwareness extends Closeable {
/** Factory for creating {@link DiffAwareness} instances. */
public interface Factory {
/**
* Returns a {@link DiffAwareness} instance suitable for managing changes to files under the
* given package path entry, or {@code null} if this factory cannot create such an instance.
*
* <p>Skyframe has a collection of factories, and will create a {@link DiffAwareness} instance
* per package path entry using one of the factories that returns a non-null value.
*/
@Nullable
DiffAwareness maybeCreate(Root pathEntry);
}
/** Opaque view of the filesystem under a package path entry at a specific point in time. */
interface View {
}
/**
* Returns the live view of the filesystem under the package path entry.
*
* @throws BrokenDiffAwarenessException if something is wrong and the caller should discard this
* {@link DiffAwareness} instance. The {@link DiffAwareness} is expected to close itself in
* this case.
*/
View getCurrentView(OptionsClassProvider options) throws BrokenDiffAwarenessException;
/**
* Returns the set of files of interest that have been modified between the given two views.
*
* <p>The given views must have come from previous calls to {@link #getCurrentView} on the
* {@link DiffAwareness} instance (i.e. using a {@link View} from another instance is not
* supported).
*
* @throws IncompatibleViewException if the given views are not compatible with this
* {@link DiffAwareness} instance. This probably indicates a bug.
* @throws BrokenDiffAwarenessException if something is wrong and the caller should discard this
* {@link DiffAwareness} instance. The {@link DiffAwareness} is expected to close itself in
* this case.
*/
ModifiedFileSet getDiff(View oldView, View newView)
throws IncompatibleViewException, BrokenDiffAwarenessException;
/** @return the name of this implementation */
String name();
/**
* Must be called whenever the {@link DiffAwareness} object is to be discarded. Using a
* {@link DiffAwareness} instance after calling {@link #close} on it is unspecified behavior.
*/
@Override
void close();
}
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