Offline By Default

services/url_response_disk_cache/url_response_disk_cache_db.h

+// 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.
+
+#ifndef SERVICES_URL_RESPONSE_DISK_CACHE_URL_RESPONSE_DISK_CACHE_DB_H_
+#define SERVICES_URL_RESPONSE_DISK_CACHE_URL_RESPONSE_DISK_CACHE_DB_H_
+
+#include "base/files/file_path.h"
+#include "base/memory/linked_ptr.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "services/url_response_disk_cache/url_response_disk_cache_entry.mojom.h"
+
+namespace leveldb {
+class Comparator;
+class DB;
+};
+
+namespace mojo {
+
+// Interface describing the read operation on the database.
+class DBReader {
+ public:
+  class Iterator {
+   public:
+    virtual ~Iterator() {}
+
+    virtual bool HasNext() = 0;
+    virtual void GetNext(InternalEntryKeyPtr* key, CacheEntryPtr* entry) = 0;
+  };
+
+  DBReader() {}
+  virtual ~DBReader() {}
+
+  // Returns an iterator over all the entries in the database. For a given
+  // |request_origin| and |url|, entries will be sorted from newest to oldest.
+  virtual scoped_ptr<Iterator> Iterate() = 0;
+  // Returns the newest entry for the given |request_origin| and |url|, or null
+  // if none exist.
+  virtual CacheEntryPtr Get(const std::string& request_origin,
+                            const std::string& url) = 0;
+};
+
+// Specialized database for the cache content.
+class URLResponseDiskCacheDB
+    : public DBReader,
+      public base::RefCountedThreadSafe<URLResponseDiskCacheDB> {
+ public:
+  // Constructs the database. |db_path| is the path to the leveldb database. If
+  // the path exists, the database will be opened, otherwise it will be created.
+  URLResponseDiskCacheDB(const base::FilePath& db_path);
+
+  // Implementation of DBReader:
+  scoped_ptr<Iterator> Iterate() override;

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

This, as opposed to Iterate() on a snapshot, returns an iterator for the live
database. Can you document the contract on how this works when the database
changes underneath?

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

Done.

+  CacheEntryPtr Get(const std::string& request_origin,
+                    const std::string& url) override;
+
+  // Set and get the version of the database.
+  uint64_t GetVersion();
+  void SetVersion(uint64_t version);
+
+  // Put an entry for the given |request_origin| and |url|. Older entry for the
+  // same |request_origin| and |url| will not be removed, but will be shadowed
+  // by the new one.
+  void Put(const std::string& request_origin,
+           const std::string& url,
+           CacheEntryPtr entry);
+  // Delete the entry for the given |key|.
+  void Delete(InternalEntryKeyPtr key);
+
+  // Returns a snapshot of the database in its current state.
+  scoped_ptr<DBReader> GetSnapshot();
+
+ private:
+  friend class base::RefCountedThreadSafe<URLResponseDiskCacheDB>;
+  ~URLResponseDiskCacheDB() override;
+
+  scoped_ptr<leveldb::Comparator> comparator_;
+  linked_ptr<leveldb::DB> db_;
+  scoped_ptr<DBReader> db_reader_;
+};
+
+}  // namespace
+
+#endif  // SERVICES_URL_RESPONSE_DISK_CACHE_URL_RESPONSE_DISK_CACHE_DB_H_