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author | Lee Clagett <code@leeclagett.com> | 2018-09-26 23:54:27 -0400 |
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committer | Lee Clagett <code@leeclagett.com> | 2019-03-19 17:52:26 +0000 |
commit | 0c7e7bce18558ea04e120b5fddcf4d22c0abc785 (patch) | |
tree | 5211e26db0ebe41908dc37780ce6f993e9471b6f /src/lmdb/database.h | |
parent | Merge pull request #5201 (diff) | |
download | monero-0c7e7bce18558ea04e120b5fddcf4d22c0abc785.tar.xz |
Adding classes, functions, and utilities for common LMDB operations.
Diffstat (limited to 'src/lmdb/database.h')
-rw-r--r-- | src/lmdb/database.h | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/src/lmdb/database.h b/src/lmdb/database.h new file mode 100644 index 000000000..269f8c8a1 --- /dev/null +++ b/src/lmdb/database.h @@ -0,0 +1,138 @@ +// Copyright (c) 2018, 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 + |