- // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file. See the AUTHORS file for names of contributors.
- //
- // WriteBatch holds a collection of updates to apply atomically to a DB.
- //
- // The updates are applied in the order in which they are added
- // to the WriteBatch. For example, the value of "key" will be "v3"
- // after the following batch is written:
- //
- // batch.Put("key", "v1");
- // batch.Delete("key");
- // batch.Put("key", "v2");
- // batch.Put("key", "v3");
- //
- // Multiple threads can invoke const methods on a WriteBatch without
- // external synchronization, but if any of the threads may call a
- // non-const method, all threads accessing the same WriteBatch must use
- // external synchronization.
-
- #ifndef STORAGE_LEVELDB_INCLUDE_WRITE_BATCH_H_
- #define STORAGE_LEVELDB_INCLUDE_WRITE_BATCH_H_
-
- #include <string>
-
- #include "leveldb/export.h"
- #include "leveldb/status.h"
-
- namespace leveldb {
-
- class Slice;
-
- class LEVELDB_EXPORT WriteBatch {
- public:
- class LEVELDB_EXPORT Handler {
- public:
- virtual ~Handler();
- virtual void Put(const Slice& key, const Slice& value) = 0;
- virtual void Put(const Slice& key, const Slice& value,uint64_t ttl){};
- virtual void Delete(const Slice& key) = 0;
- };
- WriteBatch();
-
- // Intentionally copyable.
- WriteBatch(const WriteBatch&) = default;
- WriteBatch& operator=(const WriteBatch&) = default;
-
- ~WriteBatch();
-
- // Store the mapping "key->value" in the database.
- void Put(const Slice& key, const Slice& value);
-
- void Put_for_ttl(const Slice& key, const Slice& value,uint64_t ttl);
-
-
- // If the database contains a mapping for "key", erase it. Else do nothing.
- void Delete(const Slice& key);
-
- // Clear all updates buffered in this batch.
- void Clear();
-
- // The size of the database changes caused by this batch.
- //
- // This number is tied to implementation details, and may change across
- // releases. It is intended for LevelDB usage metrics.
- size_t ApproximateSize() const;
-
- // Copies the operations in "source" to this batch.
- //
- // This runs in O(source size) time. However, the constant factor is better
- // than calling Iterate() over the source batch with a Handler that replicates
- // the operations into this batch.
- void Append(const WriteBatch& source);
-
- // Support for iterating over the contents of a batch.
- Status Iterate(Handler* handler) const;
-
- private:
- friend class WriteBatchInternal;
-
- std::string rep_; // See comment in write_batch.cc for the format of rep_
- };
-
- } // namespace leveldb
-
- #endif // STORAGE_LEVELDB_INCLUDE_WRITE_BATCH_H_
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