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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.google.gerrit.server.permissions;
import com.google.auto.value.AutoValue;
import com.google.common.cache.Cache;
import com.google.common.collect.ImmutableList;
import com.google.common.flogger.FluentLogger;
import com.google.gerrit.common.data.AccessSection;
import com.google.gerrit.server.cache.CacheModule;
import com.google.gerrit.server.util.MostSpecificComparator;
import com.google.inject.Inject;
import com.google.inject.Module;
import com.google.inject.Singleton;
import com.google.inject.name.Named;
import java.util.ArrayList;
import java.util.IdentityHashMap;
import java.util.List;
/**
* Caches the order AccessSections should be sorted for evaluation.
*
* <p>Access specifications for a more specific ref (eg. refs/heads/master rather than refs/heads/*)
* take precedence in ACL evaluations. So for each combination of (ref, list of access specs) we
* have to order the access specs by their distance from the ref to be matched. This is expensive,
* so cache the sorted ordering.
*/
@Singleton
public class SectionSortCache {
private static final FluentLogger logger = FluentLogger.forEnclosingClass();
private static final String CACHE_NAME = "permission_sort";
public static Module module() {
return new CacheModule() {
@Override
protected void configure() {
cache(CACHE_NAME, EntryKey.class, EntryVal.class);
bind(SectionSortCache.class);
}
};
}
private final Cache<EntryKey, EntryVal> cache;
@Inject
SectionSortCache(@Named(CACHE_NAME) Cache<EntryKey, EntryVal> cache) {
this.cache = cache;
}
// Sorts the given sections, but does not disturb ordering between equally exact sections.
void sort(String ref, List<AccessSection> sections) {
final int cnt = sections.size();
if (cnt <= 1) {
return;
}
EntryKey key = EntryKey.create(ref, sections);
EntryVal val = cache.getIfPresent(key);
if (val != null) {
int[] srcIdx = val.order;
if (srcIdx != null) {
AccessSection[] srcList = copy(sections);
for (int i = 0; i < cnt; i++) {
sections.set(i, srcList[srcIdx[i]]);
}
} else {
// Identity transform. No sorting is required.
}
} else {
boolean poison = false;
IdentityHashMap<AccessSection, Integer> srcMap = new IdentityHashMap<>();
for (int i = 0; i < cnt; i++) {
poison |= srcMap.put(sections.get(i), i) != null;
}
sections.sort(new MostSpecificComparator(ref));
int[] srcIdx;
if (isIdentityTransform(sections, srcMap)) {
srcIdx = null;
} else {
srcIdx = new int[cnt];
for (int i = 0; i < cnt; i++) {
srcIdx[i] = srcMap.get(sections.get(i));
}
}
if (poison) {
logger.atSevere().log("Received duplicate AccessSection instances, not caching sort");
} else {
cache.put(key, new EntryVal(srcIdx));
}
}
}
private static AccessSection[] copy(List<AccessSection> sections) {
return sections.toArray(new AccessSection[sections.size()]);
}
private static boolean isIdentityTransform(
List<AccessSection> sections, IdentityHashMap<AccessSection, Integer> srcMap) {
for (int i = 0; i < sections.size(); i++) {
if (i != srcMap.get(sections.get(i))) {
return false;
}
}
return true;
}
@AutoValue
abstract static class EntryKey {
public abstract String ref();
public abstract List<String> patterns();
public abstract int cachedHashCode();
static EntryKey create(String refName, List<AccessSection> sections) {
int hc = refName.hashCode();
List<String> patterns = new ArrayList<>(sections.size());
for (AccessSection s : sections) {
String n = s.getName();
patterns.add(n);
hc = hc * 31 + n.hashCode();
}
return new AutoValue_SectionSortCache_EntryKey(refName, ImmutableList.copyOf(patterns), hc);
}
@Override
public int hashCode() {
return cachedHashCode();
}
}
static final class EntryVal {
/**
* Maps the input index to the output index.
*
* <p>For {@code x == order[y]} the expression means move the item at source position {@code x}
* to the output position {@code y}.
*/
final int[] order;
EntryVal(int[] order) {
this.order = order;
}
}
}
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