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   // REQUIRES: Finish() has not been called since the last call to Reset().
36   // REQUIRES: key is larger than any previously added key
37   void Add(const Slice& key, const Slice& value,
38            const Slice* const delta_value = nullptr);
39 
40   // Finish building the block and return a slice that refers to the
41   // block contents.  The returned slice will remain valid for the
42   // lifetime of this builder or until Reset() is called.
43   Slice Finish();
44 
45   // Returns an estimate of the current (uncompressed) size of the block
46   // we are building.
CurrentSizeEstimate()47   inline size_t CurrentSizeEstimate() const {
48     return estimate_ + (data_block_hash_index_builder_.Valid()
49                             ? data_block_hash_index_builder_.EstimateSize()
50                             : 0);
51   }
52 
53   // Returns an estimated block size after appending key and value.
54   size_t EstimateSizeAfterKV(const Slice& key, const Slice& value) const;
55 
56   // Return true iff no entries have been added since the last Reset()
empty()57   bool empty() const { return buffer_.empty(); }
58 
59  private:
60   const int block_restart_interval_;
61   // TODO(myabandeh): put it into a separate IndexBlockBuilder
62   const bool use_delta_encoding_;
63   // Refer to BlockIter::DecodeCurrentValue for format of delta encoded values
64   const bool use_value_delta_encoding_;
65 
66   std::string buffer_;              // Destination buffer
67   std::vector<uint32_t> restarts_;  // Restart points
68   size_t estimate_;
69   int counter_;    // Number of entries emitted since restart
70   bool finished_;  // Has Finish() been called?
71   std::string last_key_;
72   DataBlockHashIndexBuilder data_block_hash_index_builder_;
73 };
74 
75 }  // namespace ROCKSDB_NAMESPACE
76