ceph/src/rocksdb/table/block_based/block_builder.h

   1 //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under both the GPLv2 (found in the
   3 //  COPYING file in the root directory) and Apache 2.0 License
   4 //  (found in the LICENSE.Apache file in the root 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 #include "rocksdb/table.h"
  16 #include "table/block_based/data_block_hash_index.h"
  17
  18 namespace ROCKSDB_NAMESPACE {
  19
  20 class BlockBuilder {
  21  public:
  22   BlockBuilder(const BlockBuilder&) = delete;
  23   void operator=(const BlockBuilder&) = delete;
  24
  25   explicit BlockBuilder(int block_restart_interval,
  26                         bool use_delta_encoding = true,
  27                         bool use_value_delta_encoding = false,
  28                         BlockBasedTableOptions::DataBlockIndexType index_type =
  29                             BlockBasedTableOptions::kDataBlockBinarySearch,
  30                         double data_block_hash_table_util_ratio = 0.75);
  31
  32   // Reset the contents as if the BlockBuilder was just constructed.
  33   void Reset();
  34
  35   // Swap the contents in BlockBuilder with buffer, then reset the BlockBuilder.
  36   void SwapAndReset(std::string& buffer);
  37
  38   // REQUIRES: Finish() has not been called since the last call to Reset().
  39   // REQUIRES: key is larger than any previously added key
  40   void Add(const Slice& key, const Slice& value,
  41            const Slice* const delta_value = nullptr);
  42
  43   // Finish building the block and return a slice that refers to the
  44   // block contents.  The returned slice will remain valid for the
  45   // lifetime of this builder or until Reset() is called.
  46   Slice Finish();
  47
  48   // Returns an estimate of the current (uncompressed) size of the block
  49   // we are building.
  50   inline size_t CurrentSizeEstimate() const {
  51     return estimate_ + (data_block_hash_index_builder_.Valid()
  52                             ? data_block_hash_index_builder_.EstimateSize()
  53                             : 0);
  54   }
  55
  56   // Returns an estimated block size after appending key and value.
  57   size_t EstimateSizeAfterKV(const Slice& key, const Slice& value) const;
  58
  59   // Return true iff no entries have been added since the last Reset()
  60   bool empty() const { return buffer_.empty(); }
  61
  62  private:
  63   const int block_restart_interval_;
  64   // TODO(myabandeh): put it into a separate IndexBlockBuilder
  65   const bool use_delta_encoding_;
  66   // Refer to BlockIter::DecodeCurrentValue for format of delta encoded values
  67   const bool use_value_delta_encoding_;
  68
  69   std::string buffer_;              // Destination buffer
  70   std::vector<uint32_t> restarts_;  // Restart points
  71   size_t estimate_;
  72   int counter_;    // Number of entries emitted since restart
  73   bool finished_;  // Has Finish() been called?
  74   std::string last_key_;
  75   DataBlockHashIndexBuilder data_block_hash_index_builder_;
  76 };
  77
  78 }  // namespace ROCKSDB_NAMESPACE