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 <stdint.h>
  12
  13 #include <vector>
  14
  15 #include "rocksdb/slice.h"
  16 #include "rocksdb/table.h"
  17 #include "table/block_based/data_block_hash_index.h"
  18
  19 namespace ROCKSDB_NAMESPACE {
  20
  21 class BlockBuilder {
  22  public:
  23   BlockBuilder(const BlockBuilder&) = delete;
  24   void operator=(const BlockBuilder&) = delete;
  25
  26   explicit BlockBuilder(int block_restart_interval,
  27                         bool use_delta_encoding = true,
  28                         bool use_value_delta_encoding = false,
  29                         BlockBasedTableOptions::DataBlockIndexType index_type =
  30                             BlockBasedTableOptions::kDataBlockBinarySearch,
  31                         double data_block_hash_table_util_ratio = 0.75);
  32
  33   // Reset the contents as if the BlockBuilder was just constructed.
  34   void Reset();
  35
  36   // Swap the contents in BlockBuilder with buffer, then reset the BlockBuilder.
  37   void SwapAndReset(std::string& buffer);
  38
  39   // REQUIRES: Finish() has not been called since the last call to Reset().
  40   // REQUIRES: key is larger than any previously added key
  41   // DO NOT mix with AddWithLastKey() between Resets. For efficiency, use
  42   // AddWithLastKey() in contexts where previous added key is already known
  43   // and delta encoding might be used.
  44   void Add(const Slice& key, const Slice& value,
  45            const Slice* const delta_value = nullptr);
  46
  47   // A faster version of Add() if the previous key is already known for all
  48   // Add()s.
  49   // REQUIRES: Finish() has not been called since the last call to Reset().
  50   // REQUIRES: key is larger than any previously added key
  51   // REQUIRES: if AddWithLastKey has been called since last Reset(), last_key
  52   // is the key from most recent AddWithLastKey. (For convenience, last_key
  53   // is ignored on first call after creation or Reset().)
  54   // DO NOT mix with Add() between Resets.
  55   void AddWithLastKey(const Slice& key, const Slice& value,
  56                       const Slice& last_key,
  57                       const Slice* const delta_value = nullptr);
  58
  59   // Finish building the block and return a slice that refers to the
  60   // block contents.  The returned slice will remain valid for the
  61   // lifetime of this builder or until Reset() is called.
  62   Slice Finish();
  63
  64   // Returns an estimate of the current (uncompressed) size of the block
  65   // we are building.
  66   inline size_t CurrentSizeEstimate() const {
  67     return estimate_ + (data_block_hash_index_builder_.Valid()
  68                             ? data_block_hash_index_builder_.EstimateSize()
  69                             : 0);
  70   }
  71
  72   // Returns an estimated block size after appending key and value.
  73   size_t EstimateSizeAfterKV(const Slice& key, const Slice& value) const;
  74
  75   // Return true iff no entries have been added since the last Reset()
  76   bool empty() const { return buffer_.empty(); }
  77
  78  private:
  79   inline void AddWithLastKeyImpl(const Slice& key, const Slice& value,
  80                                  const Slice& last_key,
  81                                  const Slice* const delta_value,
  82                                  size_t buffer_size);
  83
  84   const int block_restart_interval_;
  85   // TODO(myabandeh): put it into a separate IndexBlockBuilder
  86   const bool use_delta_encoding_;
  87   // Refer to BlockIter::DecodeCurrentValue for format of delta encoded values
  88   const bool use_value_delta_encoding_;
  89
  90   std::string buffer_;              // Destination buffer
  91   std::vector<uint32_t> restarts_;  // Restart points
  92   size_t estimate_;
  93   int counter_;    // Number of entries emitted since restart
  94   bool finished_;  // Has Finish() been called?
  95   std::string last_key_;
  96   DataBlockHashIndexBuilder data_block_hash_index_builder_;
  97 #ifndef NDEBUG
  98   bool add_with_last_key_called_ = false;
  99 #endif
 100 };
 101
 102 }  // namespace ROCKSDB_NAMESPACE