ceph/src/rocksdb/utilities/cassandra/serialize.h

   1 //  Copyright (c) 2017-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 /**
   7  * Helper functions which serialize and deserialize integers
   8  * into bytes in big endian.
   9  */
  10
  11 #pragma once
  12
  13 namespace ROCKSDB_NAMESPACE {
  14 namespace cassandra {
  15 namespace {
  16 const int64_t kCharMask = 0xFFLL;
  17 const int32_t kBitsPerByte = 8;
  18 }
  19
  20 template<typename T>
  21 void Serialize(T val, std::string* dest);
  22
  23 template<typename T>
  24 T Deserialize(const char* src, std::size_t offset=0);
  25
  26 // Specializations
  27 template<>
  28 inline void Serialize<int8_t>(int8_t t, std::string* dest) {
  29   dest->append(1, static_cast<char>(t & kCharMask));
  30 }
  31
  32 template<>
  33 inline void Serialize<int32_t>(int32_t t, std::string* dest) {
  34   for (unsigned long i = 0; i < sizeof(int32_t); i++) {
  35      dest->append(1, static_cast<char>(
  36        (t >> (sizeof(int32_t) - 1 - i) * kBitsPerByte) & kCharMask));
  37   }
  38 }
  39
  40 template<>
  41 inline void Serialize<int64_t>(int64_t t, std::string* dest) {
  42   for (unsigned long i = 0; i < sizeof(int64_t); i++) {
  43      dest->append(
  44        1, static_cast<char>(
  45          (t >> (sizeof(int64_t) - 1 - i) * kBitsPerByte) & kCharMask));
  46   }
  47 }
  48
  49 template<>
  50 inline int8_t Deserialize<int8_t>(const char* src, std::size_t offset) {
  51   return static_cast<int8_t>(src[offset]);
  52 }
  53
  54 template<>
  55 inline int32_t Deserialize<int32_t>(const char* src, std::size_t offset) {
  56   int32_t result = 0;
  57   for (unsigned long i = 0; i < sizeof(int32_t); i++) {
  58     result |= static_cast<int32_t>(static_cast<unsigned char>(src[offset + i]))
  59         << ((sizeof(int32_t) - 1 - i) * kBitsPerByte);
  60   }
  61   return result;
  62 }
  63
  64 template<>
  65 inline int64_t Deserialize<int64_t>(const char* src, std::size_t offset) {
  66   int64_t result = 0;
  67   for (unsigned long i = 0; i < sizeof(int64_t); i++) {
  68     result |= static_cast<int64_t>(static_cast<unsigned char>(src[offset + i]))
  69         << ((sizeof(int64_t) - 1 - i) * kBitsPerByte);
  70   }
  71   return result;
  72 }
  73
  74 } // namepsace cassandrda
  75 }  // namespace ROCKSDB_NAMESPACE