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      1 // Copyright (c) 2013 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 CONTENT_BROWSER_INDEXED_DB_LEVELDB_LEVELDB_TRANSACTION_H_
      6 #define CONTENT_BROWSER_INDEXED_DB_LEVELDB_LEVELDB_TRANSACTION_H_
      7 
      8 #include <map>
      9 #include <set>
     10 #include <string>
     11 
     12 #include "base/gtest_prod_util.h"
     13 #include "base/memory/ref_counted.h"
     14 #include "base/memory/scoped_ptr.h"
     15 #include "base/strings/string_piece.h"
     16 #include "content/browser/indexed_db/leveldb/leveldb_comparator.h"
     17 #include "content/browser/indexed_db/leveldb/leveldb_database.h"
     18 #include "content/browser/indexed_db/leveldb/leveldb_iterator.h"
     19 
     20 namespace content {
     21 
     22 class LevelDBWriteBatch;
     23 
     24 class CONTENT_EXPORT LevelDBTransaction
     25     : public base::RefCounted<LevelDBTransaction> {
     26  public:
     27   void Put(const base::StringPiece& key, std::string* value);
     28   void Remove(const base::StringPiece& key);
     29   virtual leveldb::Status Get(const base::StringPiece& key,
     30                               std::string* value,
     31                               bool* found);
     32   virtual leveldb::Status Commit();
     33   void Rollback();
     34 
     35   scoped_ptr<LevelDBIterator> CreateIterator();
     36 
     37  protected:
     38   virtual ~LevelDBTransaction();
     39   explicit LevelDBTransaction(LevelDBDatabase* db);
     40   friend class IndexedDBClassFactory;
     41 
     42  private:
     43   friend class base::RefCounted<LevelDBTransaction>;
     44   FRIEND_TEST_ALL_PREFIXES(LevelDBDatabaseTest, Transaction);
     45   FRIEND_TEST_ALL_PREFIXES(LevelDBDatabaseTest, TransactionCommitTest);
     46   FRIEND_TEST_ALL_PREFIXES(LevelDBDatabaseTest, TransactionIterator);
     47 
     48   struct Record {
     49     Record();
     50     ~Record();
     51     std::string key;
     52     std::string value;
     53     bool deleted;
     54   };
     55 
     56   class Comparator {
     57    public:
     58     explicit Comparator(const LevelDBComparator* comparator)
     59         : comparator_(comparator) {}
     60     bool operator()(const base::StringPiece& a,
     61                     const base::StringPiece& b) const {
     62       return comparator_->Compare(a, b) < 0;
     63     }
     64 
     65    private:
     66     const LevelDBComparator* comparator_;
     67   };
     68 
     69   typedef std::map<base::StringPiece, Record*, Comparator> DataType;
     70 
     71   class DataIterator : public LevelDBIterator {
     72    public:
     73     static scoped_ptr<DataIterator> Create(LevelDBTransaction* transaction);
     74     virtual ~DataIterator();
     75 
     76     virtual bool IsValid() const OVERRIDE;
     77     virtual leveldb::Status SeekToLast() OVERRIDE;
     78     virtual leveldb::Status Seek(const base::StringPiece& slice) OVERRIDE;
     79     virtual leveldb::Status Next() OVERRIDE;
     80     virtual leveldb::Status Prev() OVERRIDE;
     81     virtual base::StringPiece Key() const OVERRIDE;
     82     virtual base::StringPiece Value() const OVERRIDE;
     83     bool IsDeleted() const;
     84 
     85    private:
     86     explicit DataIterator(LevelDBTransaction* transaction);
     87     DataType* data_;
     88     DataType::iterator iterator_;
     89 
     90     DISALLOW_COPY_AND_ASSIGN(DataIterator);
     91   };
     92 
     93   class TransactionIterator : public LevelDBIterator {
     94    public:
     95     virtual ~TransactionIterator();
     96     static scoped_ptr<TransactionIterator> Create(
     97         scoped_refptr<LevelDBTransaction> transaction);
     98 
     99     virtual bool IsValid() const OVERRIDE;
    100     virtual leveldb::Status SeekToLast() OVERRIDE;
    101     virtual leveldb::Status Seek(const base::StringPiece& target) OVERRIDE;
    102     virtual leveldb::Status Next() OVERRIDE;
    103     virtual leveldb::Status Prev() OVERRIDE;
    104     virtual base::StringPiece Key() const OVERRIDE;
    105     virtual base::StringPiece Value() const OVERRIDE;
    106     void DataChanged();
    107 
    108    private:
    109     enum Direction { FORWARD, REVERSE };
    110 
    111     explicit TransactionIterator(scoped_refptr<LevelDBTransaction> transaction);
    112     void HandleConflictsAndDeletes();
    113     void SetCurrentIteratorToSmallestKey();
    114     void SetCurrentIteratorToLargestKey();
    115     void RefreshDataIterator() const;
    116     bool DataIteratorIsLower() const;
    117     bool DataIteratorIsHigher() const;
    118 
    119     scoped_refptr<LevelDBTransaction> transaction_;
    120     const LevelDBComparator* comparator_;
    121     mutable scoped_ptr<DataIterator> data_iterator_;
    122     scoped_ptr<LevelDBIterator> db_iterator_;
    123     LevelDBIterator* current_;
    124 
    125     Direction direction_;
    126     mutable bool data_changed_;
    127 
    128     DISALLOW_COPY_AND_ASSIGN(TransactionIterator);
    129   };
    130 
    131   void Set(const base::StringPiece& key, std::string* value, bool deleted);
    132   void Clear();
    133   void RegisterIterator(TransactionIterator* iterator);
    134   void UnregisterIterator(TransactionIterator* iterator);
    135   void NotifyIterators();
    136 
    137   LevelDBDatabase* db_;
    138   const LevelDBSnapshot snapshot_;
    139   const LevelDBComparator* comparator_;
    140   Comparator data_comparator_;
    141   DataType data_;
    142   bool finished_;
    143   std::set<TransactionIterator*> iterators_;
    144 
    145   DISALLOW_COPY_AND_ASSIGN(LevelDBTransaction);
    146 };
    147 
    148 // Reads go straight to the database, ignoring any writes cached in
    149 // write_batch_, and writes are write-through, without consolidation.
    150 class LevelDBDirectTransaction {
    151  public:
    152   static scoped_ptr<LevelDBDirectTransaction> Create(LevelDBDatabase* db);
    153 
    154   ~LevelDBDirectTransaction();
    155   void Put(const base::StringPiece& key, const std::string* value);
    156   leveldb::Status Get(const base::StringPiece& key,
    157                       std::string* value,
    158                       bool* found);
    159   void Remove(const base::StringPiece& key);
    160   leveldb::Status Commit();
    161 
    162  private:
    163   explicit LevelDBDirectTransaction(LevelDBDatabase* db);
    164 
    165   LevelDBDatabase* db_;
    166   scoped_ptr<LevelDBWriteBatch> write_batch_;
    167   bool finished_;
    168 
    169   DISALLOW_COPY_AND_ASSIGN(LevelDBDirectTransaction);
    170 };
    171 
    172 }  // namespace content
    173 
    174 #endif  // CONTENT_BROWSER_INDEXED_DB_LEVELDB_LEVELDB_TRANSACTION_H_
    175