ceph/src/rocksdb/table/block_builder.h

   1 //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under the BSD-style license found in the
   3 //  LICENSE file in the root directory of this source tree. An additional grant
   4 //  of patent rights can be found in the PATENTS file in the same directory.
   5 //
   6 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
   7 // Use of this source code is governed by a BSD-style license that can be
   8 // found in the LICENSE file. See the AUTHORS file for names of contributors.
   9
  10 #pragma once
  11 #include <vector>
  12
  13 #include <stdint.h>
  14 #include "rocksdb/slice.h"
  15
  16 namespace rocksdb {
  17
  18 class BlockBuilder {
  19  public:
  20   BlockBuilder(const BlockBuilder&) = delete;
  21   void operator=(const BlockBuilder&) = delete;
  22
  23   explicit BlockBuilder(int block_restart_interval,
  24                         bool use_delta_encoding = true);
  25
  26   // Reset the contents as if the BlockBuilder was just constructed.
  27   void Reset();
  28
  29   // REQUIRES: Finish() has not been called since the last call to Reset().
  30   // REQUIRES: key is larger than any previously added key
  31   void Add(const Slice& key, const Slice& value);
  32
  33   // Finish building the block and return a slice that refers to the
  34   // block contents.  The returned slice will remain valid for the
  35   // lifetime of this builder or until Reset() is called.
  36   Slice Finish();
  37
  38   // Returns an estimate of the current (uncompressed) size of the block
  39   // we are building.
  40   inline size_t CurrentSizeEstimate() const { return estimate_; }
  41
  42   // Returns an estimated block size after appending key and value.
  43   size_t EstimateSizeAfterKV(const Slice& key, const Slice& value) const;
  44
  45   // Return true iff no entries have been added since the last Reset()
  46   bool empty() const {
  47     return buffer_.empty();
  48   }
  49
  50  private:
  51   const int          block_restart_interval_;
  52   const bool         use_delta_encoding_;
  53
  54   std::string           buffer_;    // Destination buffer
  55   std::vector<uint32_t> restarts_;  // Restart points
  56   size_t                estimate_;
  57   int                   counter_;   // Number of entries emitted since restart
  58   bool                  finished_;  // Has Finish() been called?
  59   std::string           last_key_;
  60 };
  61
  62 }  // namespace rocksdb