1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
|
// Copyright (c) 2018-2022, The Monero Project
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are
// permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
// of conditions and the following disclaimer in the documentation and/or other
// materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its contributors may be
// used to endorse or promote products derived from this software without specific
// prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#pragma once
#include <atomic>
#include <cstddef>
#include <lmdb.h>
#include <memory>
#include <type_traits>
#include "common/expect.h"
#include "lmdb/error.h"
#include "lmdb/transaction.h"
namespace lmdb
{
//! Closes LMDB environment handle.
struct close_env
{
void operator()(MDB_env* ptr) const noexcept
{
if (ptr)
mdb_env_close(ptr);
}
};
using environment = std::unique_ptr<MDB_env, close_env>;
//! \return LMDB environment at `path` with a max of `max_dbs` tables.
expect<environment> open_environment(const char* path, MDB_dbi max_dbs) noexcept;
//! Context given to LMDB.
struct context
{
std::atomic<std::size_t> active;
std::atomic_flag lock;
};
//! Manages a LMDB environment for safe memory-map resizing. Thread-safe.
class database
{
environment env;
context ctx;
//! \return The LMDB environment associated with the object.
MDB_env* handle() const noexcept { return env.get(); }
expect<write_txn> do_create_txn(unsigned int flags) noexcept;
public:
database(environment env);
database(database&&) = delete;
database(database const&) = delete;
virtual ~database() noexcept;
database& operator=(database&&) = delete;
database& operator=(database const&) = delete;
/*!
Resize the memory map for the LMDB environment. Will block until
all reads/writes on the environment complete.
*/
expect<void> resize() noexcept;
//! \return A read only LMDB transaction, reusing `txn` if provided.
expect<read_txn> create_read_txn(suspended_txn txn = nullptr) noexcept;
//! \return `txn` after releasing context.
expect<suspended_txn> reset_txn(read_txn txn) noexcept;
//! \return A read-write LMDB transaction.
expect<write_txn> create_write_txn() noexcept;
//! Commit the read-write transaction.
expect<void> commit(write_txn txn) noexcept;
/*!
Create a write transaction, pass it to `f`, then try to commit
the write if `f` succeeds.
\tparam F must be callable with signature `expect<T>(MDB_txn&)`.
\param f must be re-startable if `lmdb::error(MDB_MAP_FULL)`.
\return The result of calling `f`.
*/
template<typename F>
typename std::result_of<F(MDB_txn&)>::type try_write(F f, unsigned attempts = 3)
{
for (unsigned i = 0; i < attempts; ++i)
{
expect<write_txn> txn = create_write_txn();
if (!txn)
return txn.error();
MONERO_PRECOND(*txn != nullptr);
const auto wrote = f(*(*txn));
if (wrote)
{
MONERO_CHECK(commit(std::move(*txn)));
return wrote;
}
if (wrote != lmdb::error(MDB_MAP_FULL))
return wrote;
txn->reset();
MONERO_CHECK(this->resize());
}
return {lmdb::error(MDB_MAP_FULL)};
}
};
} // lmdb
|
