ceph/src/rocksdb/db/wide/wide_column_serialization.h

   1 //  Copyright (c) Meta Platforms, Inc. and affiliates.
   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 #pragma once
   7
   8 #include <cstdint>
   9 #include <string>
  10
  11 #include "rocksdb/rocksdb_namespace.h"
  12 #include "rocksdb/status.h"
  13 #include "rocksdb/wide_columns.h"
  14
  15 namespace ROCKSDB_NAMESPACE {
  16
  17 class Slice;
  18
  19 // Wide-column serialization/deserialization primitives.
  20 //
  21 // The two main parts of the layout are 1) a sorted index containing the column
  22 // names and column value sizes and 2) the column values themselves. Keeping the
  23 // index and the values separate will enable selectively reading column values
  24 // down the line. Note that currently the index has to be fully parsed in order
  25 // to find out the offset of each column value.
  26 //
  27 // Legend: cn = column name, cv = column value, cns = column name size, cvs =
  28 // column value size.
  29 //
  30 //      +----------+--------------+----------+-------+----------+---...
  31 //      | version  | # of columns |  cns 1   | cn 1  |  cvs 1   |
  32 //      +----------+--------------+------------------+--------- +---...
  33 //      | varint32 |   varint32   | varint32 | bytes | varint32 |
  34 //      +----------+--------------+----------+-------+----------+---...
  35 //
  36 //      ... continued ...
  37 //
  38 //          ...---+----------+-------+----------+-------+---...---+-------+
  39 //                |  cns N   | cn N  |  cvs N   | cv 1  |         | cv N  |
  40 //          ...---+----------+-------+----------+-------+---...---+-------+
  41 //                | varint32 | bytes | varint32 | bytes |         | bytes |
  42 //          ...---+----------+-------+----------+-------+---...---+-------+
  43
  44 class WideColumnSerialization {
  45  public:
  46   static Status Serialize(const WideColumns& columns, std::string& output);
  47   static Status Serialize(const Slice& value_of_default,
  48                           const WideColumns& other_columns,
  49                           std::string& output);
  50
  51   static Status Deserialize(Slice& input, WideColumns& columns);
  52
  53   static WideColumns::const_iterator Find(const WideColumns& columns,
  54                                           const Slice& column_name);
  55   static Status GetValueOfDefaultColumn(Slice& input, Slice& value);
  56
  57   static constexpr uint32_t kCurrentVersion = 1;
  58
  59  private:
  60   static Status SerializeImpl(const Slice* value_of_default,
  61                               const WideColumns& columns, std::string& output);
  62 };
  63
  64 inline Status WideColumnSerialization::Serialize(const WideColumns& columns,
  65                                                  std::string& output) {
  66   constexpr Slice* value_of_default = nullptr;
  67
  68   return SerializeImpl(value_of_default, columns, output);
  69 }
  70
  71 inline Status WideColumnSerialization::Serialize(
  72     const Slice& value_of_default, const WideColumns& other_columns,
  73     std::string& output) {
  74   return SerializeImpl(&value_of_default, other_columns, output);
  75 }
  76
  77 }  // namespace ROCKSDB_NAMESPACE