Implemented backup_to_dbh/backup_from_dbh (#30)

SQLite.xs

@@ -259,6 +259,28 @@ backup_to_file(dbh, filename)
     OUTPUT:
         RETVAL
 
+static int
+backup_from_dbh(dbh, from)
+    SV *dbh
+    SV *from
+    ALIAS:
+        DBD::SQLite::db::sqlite_backup_from_dbh = 1
+    CODE:
+        RETVAL = sqlite_db_backup_from_dbh(aTHX_ dbh, from);
+    OUTPUT:
+        RETVAL
+
+static int
+backup_to_dbh(dbh, to)
+    SV *dbh
+    SV *to
+    ALIAS:
+        DBD::SQLite::db::sqlite_backup_to_dbh = 1
+    CODE:
+        RETVAL = sqlite_db_backup_to_dbh(aTHX_ dbh, to);
+    OUTPUT:
+        RETVAL
+
 HV*
 table_column_metadata(dbh, dbname, tablename, columnname)
     SV* dbh

dbdimp.c

@@ -2615,6 +2615,49 @@ sqlite_db_backup_from_file(pTHX_ SV *dbh, char *filename)
 #endif
 }
 
+int
+sqlite_db_backup_from_dbh(pTHX_ SV *dbh, SV *from)
+{
+    D_imp_dbh(dbh);
+
+#if SQLITE_VERSION_NUMBER >= 3006011
+    int rc;
+    sqlite3_backup *pBackup;
+
+    imp_dbh_t *imp_dbh_from = (imp_dbh_t *)DBIh_COM(from);
+
+    if (!DBIc_ACTIVE(imp_dbh)) {
+        sqlite_error(dbh, -2, "attempt to backup from file on inactive database handle");
+        return FALSE;
+    }
+
+    if (!DBIc_ACTIVE(imp_dbh_from)) {
+        sqlite_error(dbh, -2, "attempt to backup from inactive database handle");
+        return FALSE;
+    }
+
+    croak_if_db_is_null();
+
+    /* COMPAT: sqlite3_backup_* are only available for 3006011 or newer */
+    pBackup = sqlite3_backup_init(imp_dbh->db, "main", imp_dbh_from->db, "main");
+    if (pBackup) {
+        (void)sqlite3_backup_step(pBackup, -1);
+        (void)sqlite3_backup_finish(pBackup);
+    }
+    rc = sqlite3_errcode(imp_dbh->db);
+
+    if ( rc != SQLITE_OK ) {
+        sqlite_error(dbh, rc, form("sqlite_backup_from_file failed with error %s", sqlite3_errmsg(imp_dbh->db)));
+        return FALSE;
+    }
+
+    return TRUE;
+#else
+    sqlite_error(dbh, SQLITE_ERROR, form("backup feature requires SQLite 3.6.11 and newer"));
+    return FALSE;
+#endif
+}
+
 /* Accesses the SQLite Online Backup API, and copies the currently loaded
  * database into the passed filename.
  * Usual usage of this would be when you're operating on the :memory:
@@ -2663,6 +2706,49 @@ sqlite_db_backup_to_file(pTHX_ SV *dbh, char *filename)
 #endif
 }
 
+int
+sqlite_db_backup_to_dbh(pTHX_ SV *dbh, SV *to)
+{
+    D_imp_dbh(dbh);
+
+#if SQLITE_VERSION_NUMBER >= 3006011
+    int rc;
+    sqlite3_backup *pBackup;
+
+    imp_dbh_t *imp_dbh_to = (imp_dbh_t *)DBIh_COM(to);
+
+    if (!DBIc_ACTIVE(imp_dbh)) {
+        sqlite_error(dbh, -2, "attempt to backup to file on inactive database handle");
+        return FALSE;
+    }
+
+    if (!DBIc_ACTIVE(imp_dbh_to)) {
+        sqlite_error(dbh, -2, "attempt to backup to inactive database handle");
+        return FALSE;
+    }
+
+    croak_if_db_is_null();
+
+    /* COMPAT: sqlite3_backup_* are only available for 3006011 or newer */
+    pBackup = sqlite3_backup_init(imp_dbh_to->db, "main", imp_dbh->db, "main");
+    if (pBackup) {
+        (void)sqlite3_backup_step(pBackup, -1);
+        (void)sqlite3_backup_finish(pBackup);
+    }
+    rc = sqlite3_errcode(imp_dbh_to->db);
+
+    if ( rc != SQLITE_OK ) {
+        sqlite_error(dbh, rc, form("sqlite_backup_to_file failed with error %s", sqlite3_errmsg(imp_dbh->db)));
+        return FALSE;
+    }
+
+    return TRUE;
+#else
+    sqlite_error(dbh, SQLITE_ERROR, form("backup feature requires SQLite 3.6.11 and newer"));
+    return FALSE;
+#endif
+}
+
 int
 sqlite_db_limit(pTHX_ SV *dbh, int id, int new_value)
 {

lib/DBD/SQLite.pm

@@ -47,6 +47,8 @@ sub driver {
         DBD::SQLite::db->install_method('sqlite_set_authorizer');
         DBD::SQLite::db->install_method('sqlite_backup_from_file');
         DBD::SQLite::db->install_method('sqlite_backup_to_file');
+        DBD::SQLite::db->install_method('sqlite_backup_from_dbh');
+        DBD::SQLite::db->install_method('sqlite_backup_to_dbh');
         DBD::SQLite::db->install_method('sqlite_enable_load_extension');
         DBD::SQLite::db->install_method('sqlite_load_extension');
         DBD::SQLite::db->install_method('sqlite_register_fts3_perl_tokenizer');
@@ -2206,6 +2208,19 @@ special :memory: database, and you wish to populate it from an existing DB.
 This method accesses the SQLite Online Backup API, and will take a backup of
 the currently connected database, and write it out to the named file.
 
+=head2 $dbh->sqlite_backup_from_dbh( $another_dbh )
+
+This method accesses the SQLite Online Backup API, and will take a backup of
+the database for the passed handle, copying it to, and overwriting, your current database
+connection. This can be particularly handy if your current connection is to the
+special :memory: database, and you wish to populate it from an existing DB.
+You can use this to backup from an in-memory database to another in-memory database.
+
+=head2 $dbh->sqlite_backup_to_dbh( $another_dbh )
+
+This method accesses the SQLite Online Backup API, and will take a backup of
+the currently connected database, and write it out to the passed database handle.
+
 =head2 $dbh->sqlite_enable_load_extension( $bool )
 
 Calling this method with a true value enables loading (external)

t/34_online_backup.t

@@ -12,7 +12,7 @@ BEGIN { requires_sqlite('3.6.11') }
 use Test::NoWarnings;
 use DBI;
 
-plan tests => 6 * @CALL_FUNCS + 1;
+plan tests => 11 * @CALL_FUNCS + 1;
 
 foreach my $call_func (@CALL_FUNCS) {
 	# Connect to the test db and add some stuff:
@@ -69,3 +69,45 @@ foreach my $call_func (@CALL_FUNCS) {
 
 	unlink $dbfile;
 }
+
+foreach my $call_func (@CALL_FUNCS) {
+	# Connect to the test db and add some stuff:
+	my $foo = connect_ok( dbfile => ':memory:', RaiseError => 1 );
+	$foo->do(
+	    'CREATE TABLE online_backup_test( id INTEGER PRIMARY KEY, foo INTEGER )'
+	);
+	$foo->do("INSERT INTO online_backup_test (foo) VALUES ($$)");
+
+	my $dbh = DBI->connect(
+	    'dbi:SQLite:dbname=:memory:',
+	    undef, undef,
+	    { RaiseError => 1 }
+	);
+
+	ok($dbh->$call_func($foo, 'backup_from_dbh'));
+
+	{
+	    my ($count) = $dbh->selectrow_array(
+	        "SELECT count(foo) FROM online_backup_test WHERE foo=$$"
+	    );
+	    is($count, 1, "Found our process ID in backed-up table");
+	}
+
+	# Add more data then attempt to copy it back to file:
+	$dbh->do(
+	    'CREATE TABLE online_backup_test2 ( id INTEGER PRIMARY KEY, foo INTEGER )'
+	);
+	$dbh->do("INSERT INTO online_backup_test2 (foo) VALUES ($$)");
+
+	# backup to dbh (foo):
+	ok($dbh->$call_func($foo, 'backup_to_dbh'));
+
+	$dbh->disconnect;
+
+	my ($count) = $foo->selectrow_array(
+	    "SELECT count(foo) FROM online_backup_test2 WHERE foo=$$"
+	);
+	is($count, 1, "Found our process ID in table back on disk");
+
+	$foo->disconnect;
+}