Offline By Default

services/url_response_disk_cache/url_response_disk_cache_db.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "services/url_response_disk_cache/url_response_disk_cache_db.h"
+
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
+#include "leveldb/comparator.h"
+#include "leveldb/db.h"
+#include "mojo/public/cpp/bindings/lib/fixed_buffer.h"
+#include "services/url_response_disk_cache/url_response_disk_cache_entry.mojom.h"
+
+namespace mojo {
+namespace {
+
+// List of keys for metadata. All metadata keys must start with a '\1'
+// character.
+const char kVersionKey[] = "\1version";
+
+// TODO(darin): These Serialize / Deserialize methods should not live here.
+// They use private details of the bindings system. Instead, we should provide
+// these as helper functions under mojo/public/cpp/bindings/.
+
+template <typename T>
+void Serialize(T input, std::string* output) {
+  typedef typename mojo::internal::WrapperTraits<T>::DataType DataType;
+  size_t size = GetSerializedSize_(input);
+
+  output->clear();
+  output->resize(size);
+
+  mojo::internal::FixedBuffer buf;
+  buf.Initialize(&output->at(0), size);
+
+  DataType data_type;
+  Serialize_(input.Pass(), &buf, &data_type);
+  std::vector<Handle> handles;
+  data_type->EncodePointersAndHandles(&handles);
+}
+
+template <typename T>
+bool Deserialize(void* data, size_t size, T* output) {
+  typedef typename mojo::internal::WrapperTraits<T>::DataType DataType;
+  mojo::internal::BoundsChecker bounds_checker(data, size, 0);
+  if (!std::remove_pointer<DataType>::type::Validate(data, &bounds_checker)) {
+    return false;
+  }
+  DataType data_type = reinterpret_cast<DataType>(data);
+  std::vector<Handle> handles;
+  data_type->DecodePointersAndHandles(&handles);
+  Deserialize_(data_type, output);
+  return true;
+}
+
+template <typename T>
+bool Deserialize(std::string s, T* output) {
+  return Deserialize(&s.at(0), s.size(), output);
+}
+
+template <typename T>
+bool Deserialize(const leveldb::Slice& s, T* output) {
+  return Deserialize(s.ToString(), output);
+}
+
+// Returns whether the key is for a metadata entry. Metadata entries are
+// declared at the start of this file.
+bool IsMetaDataKey(const leveldb::Slice& s) {
+  return s.size() != 0 && s[0] == '\1';
+}
+
+class KeyComparator : public leveldb::Comparator {
+ public:
+  int Compare(const leveldb::Slice& s1,
+              const leveldb::Slice& s2) const override {
+    if (IsMetaDataKey(s1) != IsMetaDataKey(s2)) {
+      if (IsMetaDataKey(s1))
+        return -1;
+      return 1;
+    }
+
+    if (IsMetaDataKey(s1))
+      return leveldb::BytewiseComparator()->Compare(s1, s2);
+
+    mojo::InternalEntryKeyPtr k1, k2;
+    bool result = Deserialize(s1, &k1) && Deserialize(s2, &k2);
+    DCHECK(result);
+    if (k1->request_origin.get() < k2->request_origin.get())
+      return -1;
+    if (k1->request_origin.get() > k2->request_origin.get())
+      return +1;
+    if (k1->url.get() < k2->url.get())
+      return -1;
+    if (k1->url.get() > k2->url.get())
+      return +1;
+    if (k1->timestamp < k2->timestamp)
+      return 1;
+    if (k1->timestamp > k2->timestamp)
+      return -1;
+    return 0;
+  }
+
+  const char* Name() const override { return "KeyComparator"; }
+  void FindShortestSeparator(std::string*,
+                             const leveldb::Slice&) const override {}
+  void FindShortSuccessor(std::string*) const override {}
+};
+
+class DBIterator : public DBReader::Iterator {

[ppi, 2015/09/08 15:46:26]

Is there any reason not to put the implementations of methods next to the
classes for DBIterator, DBReaderImpl and DBSnapshot?

[qsr, 2015/09/11 15:47:57]

I usually put all my declaration first and the implementation after. But changed
as suggested.

+ public:
+  DBIterator(linked_ptr<leveldb::DB> db, const leveldb::ReadOptions& options);
+
+ private:
+  // Implementation of DBReader::Iterator:
+  bool HasNext() override;
+  void GetNext(InternalEntryKeyPtr* key, CacheEntryPtr* entry) override;
+
+  linked_ptr<leveldb::DB> db_;
+  scoped_ptr<leveldb::Iterator> it_;
+};
+
+class DBReaderImpl : public DBReader {
+ public:
+  DBReaderImpl(linked_ptr<leveldb::DB> db, const leveldb::ReadOptions& options);
+  ~DBReaderImpl() override;
+
+ private:
+  // Implementation of DBReader:
+  scoped_ptr<Iterator> Iterate() override;
+  CacheEntryPtr Get(const std::string& request_origin,
+                    const std::string& url) override;
+
+  linked_ptr<leveldb::DB> db_;
+  leveldb::ReadOptions options_;
+};
+
+class DBSnapshot : public DBReader {
+ public:
+  DBSnapshot(linked_ptr<leveldb::DB> db);
+  ~DBSnapshot() override;
+
+ private:
+  // Implementation of DBReader:
+  scoped_ptr<Iterator> Iterate() override;
+  CacheEntryPtr Get(const std::string& request_origin,
+                    const std::string& url) override;
+
+  linked_ptr<leveldb::DB> db_;
+  leveldb::ReadOptions options_;
+  scoped_ptr<DBReader> db_reader_;
+};
+
+DBIterator::DBIterator(linked_ptr<leveldb::DB> db,
+                       const leveldb::ReadOptions& options)
+    : db_(db) {
+  it_.reset(db_->NewIterator(options));
+  it_->SeekToFirst();
+}
+
+bool DBIterator::HasNext() {
+  while (it_->Valid() && IsMetaDataKey(it_->key())) {
+    it_->Next();
+  }
+  return it_->Valid();
+}
+
+void DBIterator::GetNext(InternalEntryKeyPtr* key, CacheEntryPtr* entry) {
+  DCHECK(it_->Valid());
+  if (key)
+    Deserialize(it_->key(), key);
+  if (entry)
+    Deserialize(it_->value(), entry);
+  it_->Next();
+}
+
+DBReaderImpl::DBReaderImpl(linked_ptr<leveldb::DB> db,
+                           const leveldb::ReadOptions& options)
+    : db_(db), options_(options) {}
+
+// virtual
+DBReaderImpl::~DBReaderImpl() {}
+
+scoped_ptr<DBReader::Iterator> DBReaderImpl::Iterate() {
+  return make_scoped_ptr(new DBIterator(db_, options_));
+}
+
+CacheEntryPtr DBReaderImpl::Get(const std::string& request_origin,
+                                const std::string& url) {
+  InternalEntryKeyPtr key = InternalEntryKey::New();
+  key->request_origin = request_origin;
+  key->url = url;
+  key->timestamp = std::numeric_limits<int64>::max();
+  std::string key_string;
+  Serialize(key.Pass(), &key_string);
+  scoped_ptr<leveldb::Iterator> it(db_->NewIterator(options_));
+  it->Seek(key_string);
+  CacheEntryPtr result;
+  if (it->Valid()) {
+    Deserialize(it->key(), &key);
+    if (key->request_origin == request_origin && key->url == url) {
+      Deserialize(it->value(), &result);
+    }
+  }
+  return result.Pass();
+}
+
+DBSnapshot::DBSnapshot(linked_ptr<leveldb::DB> db) : db_(db) {
+  options_.snapshot = db_->GetSnapshot();
+  db_reader_.reset(new DBReaderImpl(db, options_));
+}
+
+// virtual
+DBSnapshot::~DBSnapshot() {
+  db_->ReleaseSnapshot(options_.snapshot);
+}
+
+scoped_ptr<DBReader::Iterator> DBSnapshot::Iterate() {
+  return db_reader_->Iterate();
+}
+
+CacheEntryPtr DBSnapshot::Get(const std::string& request_origin,
+                              const std::string& url) {
+  return db_reader_->Get(request_origin, url);
+}
+
+}  // namespace
+
+URLResponseDiskCacheDB::URLResponseDiskCacheDB(const base::FilePath& db_path)
+    : comparator_(new KeyComparator) {
+  leveldb::DB* db;
+  leveldb::Options options;
+  options.create_if_missing = true;
+  options.comparator = comparator_.get();
+  leveldb::Status status = leveldb::DB::Open(options, db_path.value(), &db);
+  DCHECK(status.ok()) << status.ToString();
+  db_.reset(db);
+  db_reader_.reset(new DBReaderImpl(db_, leveldb::ReadOptions()));
+}
+
+// virtual

[ppi, 2015/09/08 15:46:26]

I know we do this for // static, but grepping for this comment in the codebase
yields no matches. Maybe skip for consistency?

[qsr, 2015/09/11 15:47:57]

Done.

+URLResponseDiskCacheDB::~URLResponseDiskCacheDB() {}
+
+scoped_ptr<DBReader::Iterator> URLResponseDiskCacheDB::Iterate() {
+  return db_reader_->Iterate();
+}
+
+CacheEntryPtr URLResponseDiskCacheDB::Get(const std::string& request_origin,
+                                          const std::string& url) {
+  return db_reader_->Get(request_origin, url);
+}
+
+uint64_t URLResponseDiskCacheDB::GetVersion() {
+  std::string value;
+  leveldb::Status status =
+      db_->Get(leveldb::ReadOptions(), kVersionKey, &value);
+  if (status.IsNotFound())
+    return 0u;
+  DCHECK(status.ok());
+  uint64_t version;
+  memcpy(&version, value.data(), sizeof(version));
+  return version;
+}
+
+void URLResponseDiskCacheDB::SetVersion(uint64_t version) {
+  leveldb::Status status = db_->Put(
+      leveldb::WriteOptions(), kVersionKey,
+      leveldb::Slice(reinterpret_cast<char*>(&version), sizeof(version)));
+  DCHECK(status.ok());
+}
+
+void URLResponseDiskCacheDB::Put(const std::string& request_origin,
+                                 const std::string& url,
+                                 CacheEntryPtr entry) {
+  InternalEntryKeyPtr key = InternalEntryKey::New();
+  key->request_origin = request_origin;
+  key->url = url;
+  key->timestamp = base::Time::Now().ToInternalValue();
+  std::string key_string;
+  Serialize(key.Pass(), &key_string);
+  std::string entry_string;
+  Serialize(entry.Pass(), &entry_string);
+  leveldb::Status s =
+      db_->Put(leveldb::WriteOptions(), key_string, entry_string);
+  DCHECK(s.ok());
+}
+
+void URLResponseDiskCacheDB::Delete(InternalEntryKeyPtr key) {
+  std::string key_string;
+  Serialize(key.Pass(), &key_string);
+  leveldb::Status s = db_->Delete(leveldb::WriteOptions(), key_string);
+  DCHECK(s.ok());
+}
+
+scoped_ptr<DBReader> URLResponseDiskCacheDB::GetSnapshot() {
+  return make_scoped_ptr(new DBSnapshot(db_));
+}
+
+}  // namespace mojo