ceph/src/rocksdb/utilities/col_buf_decoder.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 #pragma once
   7 #include <cstdio>
   8 #include <cstring>
   9 #include <memory>
  10 #include <string>
  11 #include <unordered_map>
  12 #include <vector>
  13 #include "util/coding.h"
  14 #include "utilities/col_buf_encoder.h"
  15
  16 namespace rocksdb {
  17
  18 struct ColDeclaration;
  19
  20 // ColBufDecoder is a class to decode column buffers. It can be populated from a
  21 // ColDeclaration. Before starting decoding, a Init() method should be called.
  22 // Each time it takes a column value into Decode() method.
  23 class ColBufDecoder {
  24  public:
  25   virtual ~ColBufDecoder() = 0;
  26   virtual size_t Init(const char* src) { return 0; }
  27   virtual size_t Decode(const char* src, char** dest) = 0;
  28   static ColBufDecoder* NewColBufDecoder(const ColDeclaration& col_declaration);
  29
  30  protected:
  31   std::string buffer_;
  32   static inline bool IsRunLength(ColCompressionType type) {
  33     return type == kColRle || type == kColRleVarint ||
  34            type == kColRleDeltaVarint || type == kColRleDict;
  35   }
  36 };
  37
  38 class FixedLengthColBufDecoder : public ColBufDecoder {
  39  public:
  40   explicit FixedLengthColBufDecoder(
  41       size_t size, ColCompressionType col_compression_type = kColNoCompression,
  42       bool nullable = false, bool big_endian = false)
  43       : size_(size),
  44         col_compression_type_(col_compression_type),
  45         nullable_(nullable),
  46         big_endian_(big_endian) {}
  47
  48   size_t Init(const char* src) override;
  49   size_t Decode(const char* src, char** dest) override;
  50   ~FixedLengthColBufDecoder() {}
  51
  52  private:
  53   size_t size_;
  54   ColCompressionType col_compression_type_;
  55   bool nullable_;
  56   bool big_endian_;
  57
  58   // for decoding
  59   std::vector<uint64_t> dict_vec_;
  60   uint64_t remain_runs_;
  61   uint64_t run_val_;
  62   uint64_t last_val_;
  63 };
  64
  65 class LongFixedLengthColBufDecoder : public ColBufDecoder {
  66  public:
  67   LongFixedLengthColBufDecoder(size_t size, bool nullable)
  68       : size_(size), nullable_(nullable) {}
  69
  70   size_t Decode(const char* src, char** dest) override;
  71   ~LongFixedLengthColBufDecoder() {}
  72
  73  private:
  74   size_t size_;
  75   bool nullable_;
  76 };
  77
  78 class VariableLengthColBufDecoder : public ColBufDecoder {
  79  public:
  80   size_t Decode(const char* src, char** dest) override;
  81   ~VariableLengthColBufDecoder() {}
  82 };
  83
  84 class VariableChunkColBufDecoder : public VariableLengthColBufDecoder {
  85  public:
  86   size_t Init(const char* src) override;
  87   size_t Decode(const char* src, char** dest) override;
  88   explicit VariableChunkColBufDecoder(ColCompressionType col_compression_type)
  89       : col_compression_type_(col_compression_type) {}
  90   VariableChunkColBufDecoder() : col_compression_type_(kColNoCompression) {}
  91
  92  private:
  93   ColCompressionType col_compression_type_;
  94   std::unordered_map<uint64_t, uint64_t> dictionary_;
  95   std::vector<uint64_t> dict_vec_;
  96 };
  97
  98 struct KVPairColBufDecoders {
  99   std::vector<std::unique_ptr<ColBufDecoder>> key_col_bufs;
 100   std::vector<std::unique_ptr<ColBufDecoder>> value_col_bufs;
 101   std::unique_ptr<ColBufDecoder> value_checksum_buf;
 102
 103   explicit KVPairColBufDecoders(const KVPairColDeclarations& kvp_cd) {
 104     for (auto kcd : *kvp_cd.key_col_declarations) {
 105       key_col_bufs.emplace_back(
 106           std::move(ColBufDecoder::NewColBufDecoder(kcd)));
 107     }
 108     for (auto vcd : *kvp_cd.value_col_declarations) {
 109       value_col_bufs.emplace_back(
 110           std::move(ColBufDecoder::NewColBufDecoder(vcd)));
 111     }
 112     value_checksum_buf.reset(
 113         ColBufDecoder::NewColBufDecoder(*kvp_cd.value_checksum_declaration));
 114   }
 115 };
 116 }  // namespace rocksdb