Electroneum
util.h
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27 #pragma once
28 
29 #include <cstddef>
30 #include <cstring>
31 #include <lmdb.h>
32 #include <type_traits>
33 #include <utility>
34 
35 #include "span.h"
36 
40 #define ELECTRONEUM_FIELD(obj, field) \
41  obj , decltype(std::declval<obj>().field) , offsetof(obj, field)
42 
44 #define ELECTRONEUM_SORT_BY(obj, field) \
45  &::lmdb::less< \
46  lmdb::native_type<decltype(std::declval<obj>().field)>, \
47  offsetof(obj, field) \
48  >
49 
51 #define ELECTRONEUM_COMPARE(obj, field) \
52  &::lmdb::compare< \
53  decltype(std::declval<obj>().field), \
54  offsetof(obj, field) \
55  >
56 
57 namespace lmdb
58 {
60  template<typename T>
61  struct identity
62  {
63  using type = T;
64  };
65 
74  template<typename T>
75  using native_type = typename std::conditional<
76  std::is_enum<T>::value, std::underlying_type<T>, identity<T>
77  >::type::type;
78 
80  template<typename T, typename U = typename std::underlying_type<T>::type>
81  inline constexpr U to_native(T value) noexcept
82  {
83  return U(value);
84  }
85 
87  template<typename T>
88  inline MDB_val to_val(T&& value) noexcept
89  {
90  // lmdb does not touch user data, so const_cast is acceptable
91  static_assert(!std::is_rvalue_reference<T&&>(), "cannot use temporary value");
92  void const* const temp = reinterpret_cast<void const*>(std::addressof(value));
93  return MDB_val{sizeof(value), const_cast<void*>(temp)};
94  }
95 
98  {
99  return {static_cast<const std::uint8_t*>(value.mv_data), value.mv_size};
100  }
101 
110  template<typename T, std::size_t offset = 0>
111  inline int less(MDB_val const* left, MDB_val const* right) noexcept
112  {
113  if (!left || !right || left->mv_size < sizeof(T) + offset || right->mv_size < sizeof(T) + offset)
114  {
115  assert("invalid use of custom comparison" == 0);
116  return -1;
117  }
118 
119  T left_val;
120  T right_val;
121  std::memcpy(std::addressof(left_val), static_cast<char*>(left->mv_data) + offset, sizeof(T));
122  std::memcpy(std::addressof(right_val), static_cast<char*>(right->mv_data) + offset, sizeof(T));
123  return left_val < right_val ? -1 : bool(right_val < left_val);
124  }
125 
134  template<typename T, std::size_t offset = 0>
135  inline int compare(MDB_val const* left, MDB_val const* right) noexcept
136  {
137  static_assert(!epee::has_padding<T>(), "memcmp will not work");
138  if (!left || !right || left->mv_size < sizeof(T) + offset || right->mv_size < sizeof(T) + offset)
139  {
140  assert("invalid use of custom comparison" == 0);
141  return -1;
142  }
143  return std::memcmp(
144  static_cast<char*>(left->mv_data) + offset,
145  static_cast<char*>(right->mv_data) + offset,
146  sizeof(T)
147  );
148  }
149 } // lmdb
const uint32_t T[512]
Lightning memory-mapped database library.
unsigned char uint8_t
Definition: stdint.h:124
int compare(MDB_val const *left, MDB_val const *right) noexcept
Definition: util.h:135
int less(MDB_val const *left, MDB_val const *right) noexcept
Definition: util.h:111
Generic structure used for passing keys and data in and out of the database.
Definition: lmdb.h:286
Prevent instantiation of std::underlying_type<T> when T is not enum.
Definition: util.h:61
const GenericPointer< typename T::ValueType > T2 value
Definition: pointer.h:1225
void * memcpy(void *a, const void *b, size_t c)
int bool
Definition: stdbool.h:36
MDB_val to_val(T &&value) noexcept
Definition: util.h:88
constexpr U to_native(T value) noexcept
Definition: util.h:81
typename std::conditional< std::is_enum< T >::value, std::underlying_type< T >, identity< T > >::type::type native_type
Definition: util.h:77
constexpr epee::span< const std::uint8_t > to_byte_span(MDB_val value) noexcept
Definition: util.h:97