Database() constructor to wrap an existing sqlite3*, leaving it open …

…on destruct
SRombauts · Jan 23, 2021 · 4590c8e · 4590c8e
1 parent c0818e4
commit 4590c8e
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Showing 2 changed files with 50 additions and 6 deletions.
diff --git a/include/SQLiteCpp/Database.h b/include/SQLiteCpp/Database.h
@@ -201,6 +201,21 @@ class Database
 
     #endif // c++17
 
+    /**
+     * @brief Wrap an existing sqlite3* connection opened by other means.
+     *
+     * When the Database object is constructed as a wrapper, its destruction does NOT automatically
+     * sqlite3_close() the connection. In this case (only), Statement objects may outlive the Database object with
+     * which they were constructed, so long as the underlying connection remains open.
+     *
+     * @param[in] apSQLite          Existing sqlite3* connection to be wrapped
+     * @param[in] aBusyTimeoutMs    Amount of milliseconds to wait before returning SQLITE_BUSY (see setBusyTimeout())
+     *
+     * @throw SQLite::Exception in case of error
+     */
+    Database(sqlite3*  apSQLite,
+             const int aBusyTimeoutMs = 0);
+
     // Database is non-copyable
     Database(const Database&) = delete;
     Database& operator=(const Database&) = delete;
@@ -217,7 +232,12 @@ class Database
      *
      * @warning assert in case of error
      */
-    ~Database() = default;
+    ~Database()
+    {
+        if (!mCloseOnDestruct) {
+            mSQLitePtr.release();  // prevent Deleter
+        }
+    }
 
     // Deleter functor to use with smart pointers to close the SQLite database connection in an RAII fashion.
     struct Deleter
@@ -414,7 +434,7 @@ class Database
     /// Return UTF-8 encoded English language explanation of the most recent failed API call (if any).
     const char* getErrorMsg() const noexcept;
 
-    /// Return the filename used to open the database.
+    /// Return the filename used to open the database; empty if the Database wrapped existing sqlite3*
     const std::string& getFilename() const noexcept
     {
         return mFilename;
@@ -536,10 +556,7 @@ class Database
     static Header getHeaderInfo(const std::string& aFilename);
 
     // Parse SQLite header data from a database file.
-    Header getHeaderInfo()
-    {
-        return getHeaderInfo(mFilename);
-    }
+    Header getHeaderInfo();
 
     /**
      * @brief BackupType for the backup() method
@@ -571,6 +588,7 @@ class Database
 private:
     // TODO: perhaps switch to having Statement sharing a pointer to the Connexion
     std::unique_ptr<sqlite3, Deleter> mSQLitePtr;   ///< Pointer to SQLite Database Connection Handle
+    bool mCloseOnDestruct;                          ///< true iff ~Database() is to use sqlite3_close() on mSQLitePtr
     std::string mFilename;                          ///< UTF-8 filename used to open the database
 };
 

diff --git a/src/Database.cpp b/src/Database.cpp
@@ -71,6 +71,7 @@ Database::Database(const char* apFilename,
                    const int   aFlags         /* = SQLite::OPEN_READONLY*/,
                    const int   aBusyTimeoutMs /* = 0 */,
                    const char* apVfs          /* = nullptr*/) :
+    mCloseOnDestruct(true),
     mFilename(apFilename)
 {
     sqlite3* handle;
@@ -86,6 +87,19 @@ Database::Database(const char* apFilename,
     }
 }
 
+// Wrap an existing sqlite3* connection opened by other means.
+Database::Database(sqlite3*  apSQLite,
+                   const int aBusyTimeoutMs /* = 0 */) :
+    mCloseOnDestruct(false)
+{
+    SQLITECPP_ASSERT(apSQLite != nullptr, "Database(nullptr)");
+    mSQLitePtr.reset(apSQLite);
+    if (aBusyTimeoutMs > 0)
+    {
+        setBusyTimeout(aBusyTimeoutMs);
+    }
+}
+
 // Deleter functor to use with smart pointers to close the SQLite database connection in an RAII fashion.
 void Database::Deleter::operator()(sqlite3* apSQLite)
 {
@@ -432,6 +446,18 @@ Header Database::getHeaderInfo(const std::string& aFilename)
     return h;
 }
 
+Header Database::getHeaderInfo()
+{
+    if (!mFilename.empty())
+    {
+        return getHeaderInfo(mFilename);
+    }
+    const char *zFilename = sqlite3_db_filename(mSQLitePtr.get(), nullptr);
+    return getHeaderInfo(std::string(zFilename ? zFilename : ""));
+}
+
+
+
 void Database::backup(const char* apFilename, BackupType aType)
 {
     // Open the database file identified by apFilename