1 // Copyright (c) 2020-2021 The Limenka developers
2 // Distributed under the MIT software license, see the accompanying
3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
4 5 #ifndef LIMENKA_WALLET_SQLITE_H
6 #define LIMENKA_WALLET_SQLITE_H
7 8 #include <sync.h>
9 #include <wallet/db.h>
10 11 struct bilingual_str;
12 13 struct sqlite3_stmt;
14 struct sqlite3;
15 16 namespace wallet {
17 class SQLiteDatabase;
18 19 /** RAII class that provides a database cursor */
20 class SQLiteCursor : public DatabaseCursor
21 {
22 public:
23 sqlite3_stmt* m_cursor_stmt{nullptr};
24 // Copies of the prefix things for the prefix cursor.
25 // Prevents SQLite from accessing temp variables for the prefix things.
26 std::vector<std::byte> m_prefix_range_start;
27 std::vector<std::byte> m_prefix_range_end;
28 29 explicit SQLiteCursor() = default;
30 explicit SQLiteCursor(std::vector<std::byte> start_range, std::vector<std::byte> end_range)
31 : m_prefix_range_start(std::move(start_range)),
32 m_prefix_range_end(std::move(end_range))
33 {}
34 ~SQLiteCursor() override;
35 36 Status Next(DataStream& key, DataStream& value) override;
37 };
38 39 /** Class responsible for executing SQL statements in SQLite databases.
40 * Methods are virtual so they can be overridden by unit tests testing unusual database conditions. */
41 class SQliteExecHandler
42 {
43 public:
44 virtual ~SQliteExecHandler() = default;
45 virtual int Exec(SQLiteDatabase& database, const std::string& statement);
46 };
47 48 /** RAII class that provides access to a WalletDatabase */
49 class SQLiteBatch : public DatabaseBatch
50 {
51 private:
52 SQLiteDatabase& m_database;
53 std::unique_ptr<SQliteExecHandler> m_exec_handler{std::make_unique<SQliteExecHandler>()};
54 55 sqlite3_stmt* m_read_stmt{nullptr};
56 sqlite3_stmt* m_insert_stmt{nullptr};
57 sqlite3_stmt* m_overwrite_stmt{nullptr};
58 sqlite3_stmt* m_delete_stmt{nullptr};
59 sqlite3_stmt* m_delete_prefix_stmt{nullptr};
60 61 /** Whether this batch has started a database transaction and whether it owns SQLiteDatabase::m_write_semaphore.
62 * If the batch starts a db tx, it acquires the semaphore and sets this to true, keeping the semaphore
63 * until the transaction ends to prevent other batch objects from writing to the database.
64 *
65 * If this batch did not start a transaction, the semaphore is acquired transiently when writing and m_txn
66 * is not set.
67 *
68 * m_txn is different from HasActiveTxn() as it is only true when this batch has started the transaction,
69 * not just when any batch has started a transaction.
70 */
71 bool m_txn{false};
72 73 void SetupSQLStatements();
74 bool ExecStatement(sqlite3_stmt* stmt, Span<const std::byte> blob);
75 76 bool ReadKey(DataStream&& key, DataStream& value) override;
77 bool WriteKey(DataStream&& key, DataStream&& value, bool overwrite = true) override;
78 bool EraseKey(DataStream&& key) override;
79 bool HasKey(DataStream&& key) override;
80 bool ErasePrefix(Span<const std::byte> prefix) override;
81 82 public:
83 explicit SQLiteBatch(SQLiteDatabase& database);
84 ~SQLiteBatch() override { Close(); }
85 86 void SetExecHandler(std::unique_ptr<SQliteExecHandler>&& handler) { m_exec_handler = std::move(handler); }
87 88 /* No-op. See comment on SQLiteDatabase::Flush */
89 void Flush() override {}
90 91 void Close() override;
92 93 std::unique_ptr<DatabaseCursor> GetNewCursor() override;
94 std::unique_ptr<DatabaseCursor> GetNewPrefixCursor(Span<const std::byte> prefix) override;
95 bool TxnBegin() override;
96 bool TxnCommit() override;
97 bool TxnAbort() override;
98 bool HasActiveTxn() override { return m_txn; }
99 };
100 101 /** An instance of this class represents one SQLite3 database.
102 **/
103 class SQLiteDatabase : public WalletDatabase
104 {
105 private:
106 const bool m_mock{false};
107 108 const fs::path m_dir_path;
109 110 const std::string m_file_path;
111 112 /**
113 * This mutex protects SQLite initialization and shutdown.
114 * sqlite3_config() and sqlite3_shutdown() are not thread-safe (sqlite3_initialize() is).
115 * Concurrent threads that execute SQLiteDatabase::SQLiteDatabase() should have just one
116 * of them do the init and the rest wait for it to complete before all can proceed.
117 */
118 static Mutex g_sqlite_mutex;
119 static int g_sqlite_count GUARDED_BY(g_sqlite_mutex);
120 121 void Cleanup() noexcept EXCLUSIVE_LOCKS_REQUIRED(!g_sqlite_mutex);
122 123 public:
124 SQLiteDatabase() = delete;
125 126 /** Create DB handle to real database */
127 SQLiteDatabase(const fs::path& dir_path, const fs::path& file_path, const DatabaseOptions& options, bool mock = false);
128 129 ~SQLiteDatabase();
130 131 // Batches must acquire this semaphore on writing, and release when done writing.
132 // This ensures that only one batch is modifying the database at a time.
133 CSemaphore m_write_semaphore;
134 135 bool Verify(bilingual_str& error);
136 137 /** Open the database if it is not already opened */
138 void Open() override;
139 140 /** Close the database */
141 void Close() override;
142 143 /* These functions are unused */
144 void AddRef() override { assert(false); }
145 void RemoveRef() override { assert(false); }
146 147 /** Rewrite the entire database on disk */
148 bool Rewrite(const char* skip = nullptr) override;
149 150 /** Back up the entire database to a file.
151 */
152 bool Backup(const std::string& dest) const override;
153 154 /** No-ops
155 *
156 * SQLite always flushes everything to the database file after each transaction
157 * (each Read/Write/Erase that we do is its own transaction unless we called
158 * TxnBegin) so there is no need to have Flush or Periodic Flush.
159 *
160 * There is no DB env to reload, so ReloadDbEnv has nothing to do
161 */
162 void Flush() override {}
163 bool PeriodicFlush() override { return false; }
164 void ReloadDbEnv() override {}
165 166 void IncrementUpdateCounter() override { ++nUpdateCounter; }
167 168 std::string Filename() override { return m_file_path; }
169 /** Return paths to all database created files */
170 std::vector<fs::path> Files() override
171 {
172 std::vector<fs::path> files;
173 files.emplace_back(m_dir_path / fs::PathFromString(m_file_path));
174 files.emplace_back(m_dir_path / fs::PathFromString(m_file_path + "-journal"));
175 return files;
176 }
177 std::string Format() override { return "sqlite"; }
178 179 /** Make a SQLiteBatch connected to this database */
180 std::unique_ptr<DatabaseBatch> MakeBatch(bool flush_on_close = true) override;
181 182 /** Return true if there is an on-going txn in this connection */
183 bool HasActiveTxn();
184 185 sqlite3* m_db{nullptr};
186 bool m_use_unsafe_sync;
187 };
188 189 std::unique_ptr<SQLiteDatabase> MakeSQLiteDatabase(const fs::path& path, const DatabaseOptions& options, DatabaseStatus& status, bilingual_str& error);
190 191 std::string SQLiteDatabaseVersion();
192 } // namespace wallet
193 194 #endif // LIMENKA_WALLET_SQLITE_H
195