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Vinnie Falco
436
include/nudb/basic_store.hpp
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436
include/nudb/basic_store.hpp
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//
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// Copyright (c) 2015-2016 Vinnie Falco (vinnie dot falco at gmail dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#ifndef NUDB_BASIC_STORE_HPP
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#define NUDB_BASIC_STORE_HPP
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#include <nudb/file.hpp>
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#include <nudb/type_traits.hpp>
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#include <nudb/detail/cache.hpp>
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#include <nudb/detail/gentex.hpp>
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#include <nudb/detail/mutex.hpp>
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#include <nudb/detail/pool.hpp>
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#include <boost/optional.hpp>
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#include <chrono>
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#include <mutex>
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#include <thread>
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namespace nudb {
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/** A high performance, insert-only key/value database for SSDs.
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To create a database first call the @ref create
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free function. Then construct a @ref basic_store and
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call @ref open on it:
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@code
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error_code ec;
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create<xxhasher>(
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"db.dat", "db.key", "db.log",
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1, make_salt(), 8, 4096, 0.5f, ec);
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basic_store<xxhasher, native_file> db;
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db.open("db.dat", "db.key", "db.log", ec);
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@endcode
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@tparam Hasher The hash function to use. This type
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must meet the requirements of @b Hasher.
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@tparam File The type of File object to use. This type
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must meet the requirements of @b File.
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*/
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template<class Hasher, class File>
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class basic_store
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{
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public:
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using hash_type = Hasher;
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using file_type = File;
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private:
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using clock_type =
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std::chrono::steady_clock;
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using time_point =
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typename clock_type::time_point;
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struct state
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{
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File df;
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File kf;
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File lf;
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path_type dp;
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path_type kp;
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path_type lp;
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Hasher hasher;
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detail::pool p0;
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detail::pool p1;
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detail::cache c1;
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detail::key_file_header kh;
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std::size_t rate = 0;
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time_point when = clock_type::now();
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state(state const&) = delete;
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state& operator=(state const&) = delete;
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state(state&&) = default;
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state& operator=(state&&) = default;
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state(File&& df_, File&& kf_, File&& lf_,
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path_type const& dp_, path_type const& kp_,
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path_type const& lp_,
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detail::key_file_header const& kh_);
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};
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bool open_ = false;
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// Use optional because some
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// members cannot be default-constructed.
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//
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boost::optional<state> s_; // State of an open database
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std::size_t frac_; // accumulates load
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std::size_t thresh_; // split threshold
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nbuck_t buckets_; // number of buckets
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nbuck_t modulus_; // hash modulus
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std::mutex u_; // serializes insert()
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detail::gentex g_;
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boost::shared_mutex m_;
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std::thread t_;
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std::condition_variable_any cv_;
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error_code ec_;
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std::atomic<bool> ecb_; // `true` when ec_ set
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std::size_t dataWriteSize_;
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std::size_t logWriteSize_;
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public:
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/** Default constructor.
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A default constructed database is initially closed.
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*/
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basic_store() = default;
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/// Copy constructor (disallowed)
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basic_store(basic_store const&) = delete;
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/// Copy assignment (disallowed)
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basic_store& operator=(basic_store const&) = delete;
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/** Destroy the database.
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Files are closed, memory is freed, and data that has not been
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committed is discarded. To ensure that all inserted data is
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written, it is necessary to call @ref close before destroying
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the @ref basic_store.
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This function ignores errors returned by @ref close; to receive
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those errors it is necessary to call @ref close before the
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@ref basic_store is destroyed.
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*/
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~basic_store();
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/** Returns `true` if the database is open.
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@par Thread safety
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Safe to call concurrently with any function
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except @ref open or @ref close.
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*/
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bool
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is_open() const
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{
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return open_;
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}
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/** Return the path to the data file.
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@par Requirements
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The database must be open.
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@par Thread safety
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Safe to call concurrently with any function
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except @ref open or @ref close.
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@return The data file path.
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*/
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path_type const&
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dat_path() const;
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/** Return the path to the key file.
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@par Requirements
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The database must be open.
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@par Thread safety
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Safe to call concurrently with any function
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except @ref open or @ref close.
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@return The key file path.
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*/
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path_type const&
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key_path() const;
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/** Return the path to the log file.
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@par Requirements
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The database must be open.
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@par Thread safety
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Safe to call concurrently with any function
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except @ref open or @ref close.
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@return The log file path.
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*/
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path_type const&
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log_path() const;
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/** Return the appnum associated with the database.
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This is an unsigned 64-bit integer associated with the
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database and defined by the application. It is set
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once when the database is created in a call to
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@ref create.
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@par Requirements
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The database must be open.
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@par Thread safety
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Safe to call concurrently with any function
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except @ref open or @ref close.
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@return The appnum.
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*/
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std::uint64_t
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appnum() const;
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/** Return the key size associated with the database.
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The key size is defined by the application when the
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database is created in a call to @ref create. The
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key size cannot be changed on an existing database.
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@par Requirements
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The database must be open.
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@par Thread safety
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Safe to call concurrently with any function
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except @ref open or @ref close.
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@return The size of keys in the database.
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*/
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std::size_t
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key_size() const;
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/** Return the block size associated with the database.
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The block size is defined by the application when the
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database is created in a call to @ref create or when a
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key file is regenerated in a call to @ref rekey. The
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block size cannot be changed on an existing key file.
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Instead, a new key file may be created with a different
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block size.
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@par Requirements
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The database must be open.
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@par Thread safety
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Safe to call concurrently with any function
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except @ref open or @ref close.
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@return The size of blocks in the key file.
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*/
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std::size_t
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block_size() const;
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/** Close the database.
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All data is committed before closing.
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If an error occurs, the database is still closed.
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@par Requirements
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The database must be open.
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@par Thread safety
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Not thread safe. The caller is responsible for
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ensuring that no other member functions are
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called concurrently.
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@param ec Set to the error, if any occurred.
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*/
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void
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close(error_code& ec);
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/** Open a database.
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The database identified by the specified data, key, and
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log file paths is opened. If a log file is present, the
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recovery mechanism is invoked to restore database integrity
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before the function returns.
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@par Requirements
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The database must be not be open.
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@par Thread safety
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Not thread safe. The caller is responsible for
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ensuring that no other member functions are
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called concurrently.
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@param dat_path The path to the data file.
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@param key_path The path to the key file.
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@param log_path The path to the log file.
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@param ec Set to the error, if any occurred.
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@param args Optional arguments passed to @b File constructors.
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*/
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template<class... Args>
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void
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open(
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path_type const& dat_path,
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path_type const& key_path,
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path_type const& log_path,
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error_code& ec,
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Args&&... args);
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/** Fetch a value.
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The function checks the database for the specified
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key, and invokes the callback if it is found. If
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the key is not found, `ec` is set to @ref error::key_not_found.
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If any other errors occur, `ec` is set to the
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corresponding error.
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@par Requirements
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The database must be open.
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@par Thread safety
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Safe to call concurrently with any function except
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@ref close.
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@note If the implementation encounters an error while
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committing data to the database, this function will
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immediately return with `ec` set to the error which
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occurred. All subsequent calls to @ref fetch will
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return the same error until the database is closed.
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@param key A pointer to a memory buffer of at least
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@ref key_size() bytes, containing the key to be searched
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for.
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@param callback A function which will be called with the
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value data if the fetch is successful. The equivalent
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signature must be:
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@code
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void callback(
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void const* buffer, // A buffer holding the value
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std::size_t size // The size of the value in bytes
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);
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@endcode
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The buffer provided to the callback remains valid
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until the callback returns, ownership is not transferred.
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@param ec Set to the error, if any occurred.
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*/
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template<class Callback>
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void
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fetch(void const* key, Callback && callback, error_code& ec);
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/** Insert a value.
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This function attempts to insert the specified key/value
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pair into the database. If the key already exists,
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`ec` is set to @ref error::key_exists. If an error
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occurs, `ec` is set to the corresponding error.
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@par Requirements
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The database must be open.
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@par Thread safety
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Safe to call concurrently with any function except
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@ref close.
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@note If the implementation encounters an error while
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committing data to the database, this function will
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immediately return with `ec` set to the error which
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occurred. All subsequent calls to @ref insert will
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return the same error until the database is closed.
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@param key A buffer holding the key to be inserted. The
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size of the buffer should be at least the `key_size`
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associated with the open database.
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@param data A buffer holding the value to be inserted.
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@param bytes The size of the buffer holding the value
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data. This value must be greater than 0 and no more
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than 0xffffffff.
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@param ec Set to the error, if any occurred.
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*/
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void
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insert(void const* key, void const* data,
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nsize_t bytes, error_code& ec);
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private:
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template<class Callback>
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void
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fetch(detail::nhash_t h, void const* key,
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detail::bucket b, Callback && callback, error_code& ec);
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bool
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exists(detail::nhash_t h, void const* key,
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detail::shared_lock_type* lock, detail::bucket b, error_code& ec);
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void
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split(detail::bucket& b1, detail::bucket& b2,
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detail::bucket& tmp, nbuck_t n1, nbuck_t n2,
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nbuck_t buckets, nbuck_t modulus,
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detail::bulk_writer<File>& w, error_code& ec);
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detail::bucket
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load(nbuck_t n, detail::cache& c1,
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detail::cache& c0, void* buf, error_code& ec);
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void
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commit(detail::unique_lock_type& m,
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std::size_t& work, error_code& ec);
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void
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run();
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};
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} // nudb
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#include <nudb/impl/basic_store.ipp>
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#endif
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