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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.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.devtools.build.lib.util.Pair;
import com.google.devtools.build.lib.vfs.Dirent;
import com.google.devtools.build.lib.vfs.FileStatus;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.Symlinks;
import com.google.devtools.build.lib.vfs.UnixGlob;
import java.io.IOException;
import java.util.Collection;
/**
* A per-build cache of filesystem operations for Skyframe invocations of legacy package loading.
*/
public class PerBuildSyscallCache implements UnixGlob.FilesystemCalls {
private final LoadingCache<Pair<Path, Symlinks>, FileStatus> statCache;
private final LoadingCache<Pair<Path, Symlinks>, Pair<Collection<Dirent>, IOException>>
readdirCache;
private static final FileStatus NO_STATUS = new FakeFileStatus();
/**
* Create a new per-build filesystem cache.
*
* @param maxStats Max stat results to keep in cache, or -1 for unbounded.
* @param maxReaddirs Max readdir results to keep in cache, or -1 for unbounded.
*/
public PerBuildSyscallCache(int maxStats, int maxReaddirs) {
statCache = newStatMap(maxStats);
readdirCache = newReaddirMap(maxReaddirs);
}
public static PerBuildSyscallCache newUnboundedCache() {
return new PerBuildSyscallCache(-1, -1);
}
@Override
public Collection<Dirent> readdir(Path path, Symlinks symlinks) throws IOException {
Pair<Collection<Dirent>, IOException> result =
readdirCache.getUnchecked(Pair.of(path, symlinks));
Collection<Dirent> entries = result.getFirst();
if (entries != null) {
return entries;
}
throw result.getSecond();
}
@Override
public FileStatus statNullable(Path path, Symlinks symlinks) {
FileStatus status = statCache.getUnchecked(Pair.of(path, symlinks));
return (status == NO_STATUS) ? null : status;
}
// This is used because the cache implementations don't allow null.
private static final class FakeFileStatus implements FileStatus {
@Override
public long getLastChangeTime() {
throw new UnsupportedOperationException();
}
@Override
public long getNodeId() {
throw new UnsupportedOperationException();
}
@Override
public long getLastModifiedTime() {
throw new UnsupportedOperationException();
}
@Override
public long getSize() {
throw new UnsupportedOperationException();
}
@Override
public boolean isDirectory() {
throw new UnsupportedOperationException();
}
@Override
public boolean isFile() {
throw new UnsupportedOperationException();
}
@Override
public boolean isSymbolicLink() {
throw new UnsupportedOperationException();
}
}
/**
* A cache of stat calls.
* Input: (path, following_symlinks)
* Output: FileStatus
*/
private static LoadingCache<Pair<Path, Symlinks>, FileStatus> newStatMap(int maxStats) {
return builderWithOptionalMax(maxStats).build(
new CacheLoader<Pair<Path, Symlinks>, FileStatus>() {
@Override
public FileStatus load(Pair<Path, Symlinks> p) {
FileStatus f = p.first.statNullable(p.second);
return (f == null) ? NO_STATUS : f;
}
});
}
/**
* A cache of readdir calls.
* Input: (path, following_symlinks)
* Output: A union of (Dirents, IOException).
*/
private static
LoadingCache<Pair<Path, Symlinks>, Pair<Collection<Dirent>, IOException>> newReaddirMap(
int maxReaddirs) {
return builderWithOptionalMax(maxReaddirs).build(
new CacheLoader<Pair<Path, Symlinks>, Pair<Collection<Dirent>, IOException>>() {
@Override
public Pair<Collection<Dirent>, IOException> load(Pair<Path, Symlinks> p) {
try {
// TODO(bazel-team): Consider storing the Collection of Dirent values more compactly
// by reusing DirectoryEntryListingStateValue#CompactSortedDirents.
return Pair.of(p.first.readdir(p.second), null);
} catch (IOException e) {
return Pair.of(null, e);
}
}
});
}
private static CacheBuilder<Object, Object> builderWithOptionalMax(int maxEntries) {
CacheBuilder<Object, Object> builder = CacheBuilder.newBuilder();
if (maxEntries >= 0) {
builder = builder.maximumSize(maxEntries);
}
return builder;
}
}
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