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#       1                 :            : // Copyright (c) 2011 The LevelDB 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. See the AUTHORS file for names of contributors.
#       4                 :            : 
#       5                 :            : #ifndef STORAGE_LEVELDB_DB_MEMTABLE_H_
#       6                 :            : #define STORAGE_LEVELDB_DB_MEMTABLE_H_
#       7                 :            : 
#       8                 :            : #include <string>
#       9                 :            : 
#      10                 :            : #include "db/dbformat.h"
#      11                 :            : #include "db/skiplist.h"
#      12                 :            : #include "leveldb/db.h"
#      13                 :            : #include "util/arena.h"
#      14                 :            : 
#      15                 :            : namespace leveldb {
#      16                 :            : 
#      17                 :            : class InternalKeyComparator;
#      18                 :            : class MemTableIterator;
#      19                 :            : 
#      20                 :            : class MemTable {
#      21                 :            :  public:
#      22                 :            :   // MemTables are reference counted.  The initial reference count
#      23                 :            :   // is zero and the caller must call Ref() at least once.
#      24                 :            :   explicit MemTable(const InternalKeyComparator& comparator);
#      25                 :            : 
#      26                 :            :   MemTable(const MemTable&) = delete;
#      27                 :            :   MemTable& operator=(const MemTable&) = delete;
#      28                 :            : 
#      29                 :            :   // Increase reference count.
#      30                 :   10098472 :   void Ref() { ++refs_; }
#      31                 :            : 
#      32                 :            :   // Drop reference count.  Delete if no more references exist.
#      33                 :   10098472 :   void Unref() {
#      34                 :   10098472 :     --refs_;
#      35                 :   10098472 :     assert(refs_ >= 0);
#      36         [ +  + ]:   10098472 :     if (refs_ <= 0) {
#      37                 :       3160 :       delete this;
#      38                 :       3160 :     }
#      39                 :   10098472 :   }
#      40                 :            : 
#      41                 :            :   // Returns an estimate of the number of bytes of data in use by this
#      42                 :            :   // data structure. It is safe to call when MemTable is being modified.
#      43                 :            :   size_t ApproximateMemoryUsage();
#      44                 :            : 
#      45                 :            :   // Return an iterator that yields the contents of the memtable.
#      46                 :            :   //
#      47                 :            :   // The caller must ensure that the underlying MemTable remains live
#      48                 :            :   // while the returned iterator is live.  The keys returned by this
#      49                 :            :   // iterator are internal keys encoded by AppendInternalKey in the
#      50                 :            :   // db/format.{h,cc} module.
#      51                 :            :   Iterator* NewIterator();
#      52                 :            : 
#      53                 :            :   // Add an entry into memtable that maps key to value at the
#      54                 :            :   // specified sequence number and with the specified type.
#      55                 :            :   // Typically value will be empty if type==kTypeDeletion.
#      56                 :            :   void Add(SequenceNumber seq, ValueType type, const Slice& key,
#      57                 :            :            const Slice& value);
#      58                 :            : 
#      59                 :            :   // If memtable contains a value for key, store it in *value and return true.
#      60                 :            :   // If memtable contains a deletion for key, store a NotFound() error
#      61                 :            :   // in *status and return true.
#      62                 :            :   // Else, return false.
#      63                 :            :   bool Get(const LookupKey& key, std::string* value, Status* s);
#      64                 :            : 
#      65                 :            :  private:
#      66                 :            :   friend class MemTableIterator;
#      67                 :            :   friend class MemTableBackwardIterator;
#      68                 :            : 
#      69                 :            :   struct KeyComparator {
#      70                 :            :     const InternalKeyComparator comparator;
#      71                 :       3160 :     explicit KeyComparator(const InternalKeyComparator& c) : comparator(c) {}
#      72                 :            :     int operator()(const char* a, const char* b) const;
#      73                 :            :   };
#      74                 :            : 
#      75                 :            :   typedef SkipList<const char*, KeyComparator> Table;
#      76                 :            : 
#      77                 :            :   ~MemTable();  // Private since only Unref() should be used to delete it
#      78                 :            : 
#      79                 :            :   KeyComparator comparator_;
#      80                 :            :   int refs_;
#      81                 :            :   Arena arena_;
#      82                 :            :   Table table_;
#      83                 :            : };
#      84                 :            : 
#      85                 :            : }  // namespace leveldb
#      86                 :            : 
#      87                 :            : #endif  // STORAGE_LEVELDB_DB_MEMTABLE_H_