chrome/browser/sync_file_system/drive_backend/leveldb_wrapper.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_LEVELDB_WRAPPER_H_
   6 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_LEVELDB_WRAPPER_H_
   7
   8 #include <map>
   9 #include <string>
  10
  11 #include "base/macros.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "third_party/leveldatabase/src/include/leveldb/slice.h"
  14
  15 namespace leveldb {
  16 class DB;
  17 class Iterator;
  18 class Slice;
  19 class Status;
  20 class WriteBatch;
  21 }
  22
  23 namespace sync_file_system {
  24 namespace drive_backend {
  25
  26 class SliceComparator {
  27  public:
  28   bool operator()(const leveldb::Slice& a, const leveldb::Slice& b) const {
  29     return a.compare(b) < 0;
  30   }
  31 };
  32
  33 // LevelDBWrapper class wraps leveldb::DB and leveldb::WriteBatch to provide
  34 // transparent access to pre-commit data.
  35 // Put() and Delete() update data on memory, and Get() can access to those data
  36 // and also data on disk.  Those data on memory are written down on disk when
  37 // Commit() is called.
  38 class LevelDBWrapper {
  39  private:
  40   enum Operation {
  41     PUT_OPERATION,
  42     DELETE_OPERATION,
  43   };
  44   typedef std::pair<Operation, std::string> Transaction;
  45   typedef std::map<std::string, Transaction, SliceComparator>
  46       PendingOperationMap;
  47
  48  public:
  49   class Iterator {
  50    public:
  51     explicit Iterator(LevelDBWrapper* db);
  52     ~Iterator();
  53
  54     bool Valid();
  55     void Seek(const std::string& target);
  56     void SeekToFirst();
  57     void SeekToLast();
  58     void Next();
  59     void Delete();
  60     leveldb::Slice key();
  61     leveldb::Slice value();
  62
  63    private:
  64     // Advances internal iterators to be valid.
  65     void AdvanceIterators();
  66
  67     LevelDBWrapper* db_;  // do not own
  68     scoped_ptr<leveldb::Iterator> db_iterator_;
  69     PendingOperationMap::iterator map_iterator_;
  70
  71     DISALLOW_COPY_AND_ASSIGN(Iterator);
  72   };
  73
  74   explicit LevelDBWrapper(scoped_ptr<leveldb::DB> db);
  75   ~LevelDBWrapper();
  76
  77   // Wrapping methods of leveldb::WriteBatch
  78   void Put(const std::string& key, const std::string& value);
  79   void Delete(const std::string& key);
  80
  81   // Wrapping methods of leveldb::DB
  82   leveldb::Status Get(const std::string& key, std::string* value);
  83   scoped_ptr<Iterator> NewIterator();
  84
  85   // Commits pending transactions to |db_| and clears cached transactions.
  86   // Returns true if the commitment succeeds.
  87   leveldb::Status Commit();
  88
  89   // Clears pending transactions.
  90   void Clear();
  91
  92   // Returns the number of pending PUT/DELETE operations.
  93   // Each counter counts operations independently, so operations on a key
  94   // may be counted more than once.
  95   int64 num_puts() { return num_puts_; }
  96   int64 num_deletes() { return num_deletes_; }
  97
  98   // TODO(peria): Rename this method to GetLevelDBForTesting, after removing
  99   // usages of drive_backend::MigrateDatabaseFromVxToVy() under
 100   // drive_backend_v1/.
 101   leveldb::DB* GetLevelDB();
 102
 103  private:
 104   scoped_ptr<leveldb::DB> db_;
 105
 106   PendingOperationMap pending_;
 107   int64 num_puts_;
 108   int64 num_deletes_;
 109
 110   DISALLOW_COPY_AND_ASSIGN(LevelDBWrapper);
 111 };
 112
 113 }  // namespace drive_backend
 114 }  // namespace sync_file_system
 115
 116 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_LEVELDB_WRAPPER_H_