Electroneum
database.h
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27 #pragma once
28 
29 #include <atomic>
30 #include <cstddef>
31 #include <lmdb.h>
32 #include <memory>
33 #include <type_traits>
34 
35 #include "common/expect.h"
36 #include "lmdb/error.h"
37 #include "lmdb/transaction.h"
38 
39 namespace lmdb
40 {
42  struct close_env
43  {
44  void operator()(MDB_env* ptr) const noexcept
45  {
46  if (ptr)
47  mdb_env_close(ptr);
48  }
49  };
50 
51  using environment = std::unique_ptr<MDB_env, close_env>;
52 
54  expect<environment> open_environment(const char* path, MDB_dbi max_dbs) noexcept;
55 
57  struct context
58  {
59  std::atomic<std::size_t> active;
60  std::atomic_flag lock;
61  };
62 
64  class database
65  {
66  environment env;
67  context ctx;
68 
70  MDB_env* handle() const noexcept { return env.get(); }
71 
72  expect<write_txn> do_create_txn(unsigned int flags) noexcept;
73 
74  public:
75  database(environment env);
76 
77  database(database&&) = delete;
78  database(database const&) = delete;
79 
80  virtual ~database() noexcept;
81 
82  database& operator=(database&&) = delete;
83  database& operator=(database const&) = delete;
84 
89  expect<void> resize() noexcept;
90 
92  expect<read_txn> create_read_txn(suspended_txn txn = nullptr) noexcept;
93 
96 
99 
101  expect<void> commit(write_txn txn) noexcept;
102 
112  template<typename F>
113  typename std::result_of<F(MDB_txn&)>::type try_write(F f, unsigned attempts = 3)
114  {
115  for (unsigned i = 0; i < attempts; ++i)
116  {
118  if (!txn)
119  return txn.error();
120 
121  ELECTRONEUM_PRECOND(*txn != nullptr);
122  const auto wrote = f(*(*txn));
123  if (wrote)
124  {
126  return wrote;
127  }
128  if (wrote != lmdb::error(MDB_MAP_FULL))
129  return wrote;
130 
131  txn->reset();
132  ELECTRONEUM_CHECK(this->resize());
133  }
134  return {lmdb::error(MDB_MAP_FULL)};
135  }
136  };
137 } // lmdb
138 
Context given to LMDB.
Definition: database.h:57
void operator()(MDB_env *ptr) const noexcept
Definition: database.h:44
virtual ~database() noexcept
Definition: database.cpp:124
expect< read_txn > create_read_txn(suspended_txn txn=nullptr) noexcept
Definition: database.cpp:147
Lightning memory-mapped database library.
std::unique_ptr< MDB_txn, abort_txn > suspended_txn
Definition: transaction.h:92
std::unique_ptr< MDB_txn, abort_write_txn > write_txn
Definition: transaction.h:94
struct MDB_env MDB_env
Opaque structure for a database environment.
Definition: lmdb.h:260
expect< environment > open_environment(const char *path, MDB_dbi max_dbs) noexcept
Definition: database.cpp:78
std::unique_ptr< MDB_env, close_env > environment
Definition: database.h:51
database(environment env)
Definition: database.cpp:113
std::error_code error() const noexcept
Definition: expect.h:276
std::unique_ptr< MDB_txn, release_read_txn > read_txn
Definition: transaction.h:93
std::atomic_flag lock
Definition: database.h:60
expect< void > resize() noexcept
Definition: database.cpp:129
std::atomic< std::size_t > active
Definition: database.h:59
Definition: expect.h:70
expect< write_txn > create_write_txn() noexcept
Definition: database.cpp:174
#define ELECTRONEUM_CHECK(...)
Check expect<void> and return errors in current scope.
Definition: expect.h:47
expect< void > commit(write_txn txn) noexcept
Commit the read-write transaction.
Definition: database.cpp:179
unsigned int MDB_dbi
A handle for an individual database in the DB environment.
Definition: lmdb.h:270
database & operator=(database &&)=delete
Closes LMDB environment handle.
Definition: database.h:42
#define MDB_MAP_FULL
Definition: lmdb.h:451
const T & move(const T &t)
Definition: gtest-port.h:1317
std::result_of< F(MDB_txn &)>::type try_write(F f, unsigned attempts=3)
Definition: database.h:113
#define ELECTRONEUM_PRECOND(...)
If precondition fails, return ::error::kInvalidArgument in current scope.
Definition: expect.h:39
#define F(s)
expect< suspended_txn > reset_txn(read_txn txn) noexcept
Definition: database.cpp:166
Manages a LMDB environment for safe memory-map resizing. Thread-safe.
Definition: database.h:64
error
Tracks LMDB error codes.
Definition: error.h:44
void mdb_env_close(MDB_env *env)
Close the environment and release the memory map.