add transaction support

Author: Ivan Dlugos

objectbox/box.py

@@ -105,31 +105,33 @@ def _put_many(self, objects) -> None:
             self._entity.set_object_id(objects[k], ids[k])
 
     def get(self, id: int):
-        c_data = ctypes.c_void_p()
-        c_size = ctypes.c_size_t()
-        obx_box_get(self._c_box, id, ctypes.byref(c_data), ctypes.byref(c_size))
+        with self._ob.read_tx():
+            c_data = ctypes.c_void_p()
+            c_size = ctypes.c_size_t()
+            obx_box_get(self._c_box, id, ctypes.byref(c_data), ctypes.byref(c_size))
 
-        data = c_voidp_as_bytes(c_data, c_size.value)
-        return self._entity.unmarshal(data)
+            data = c_voidp_as_bytes(c_data, c_size.value)
+            return self._entity.unmarshal(data)
 
     def get_all(self) -> list:
-        # OBX_bytes_array*
-        c_bytes_array_p = obx_box_get_all(self._c_box)
-
-        try:
-            # OBX_bytes_array
-            c_bytes_array = c_bytes_array_p.contents
-
-            result = list()
-            for i in range(c_bytes_array.count):
-                # OBX_bytes
-                c_bytes = c_bytes_array.data[i]
-                data = c_voidp_as_bytes(c_bytes.data, c_bytes.size)
-                result.append(self._entity.unmarshal(data))
-
-            return result
-        finally:
-            obx_bytes_array_free(c_bytes_array_p)
+        with self._ob.read_tx():
+            # OBX_bytes_array*
+            c_bytes_array_p = obx_box_get_all(self._c_box)
+
+            try:
+                # OBX_bytes_array
+                c_bytes_array = c_bytes_array_p.contents
+
+                result = list()
+                for i in range(c_bytes_array.count):
+                    # OBX_bytes
+                    c_bytes = c_bytes_array.data[i]
+                    data = c_voidp_as_bytes(c_bytes.data, c_bytes.size)
+                    result.append(self._entity.unmarshal(data))
+
+                return result
+            finally:
+                obx_bytes_array_free(c_bytes_array_p)
 
     def remove(self, id_or_object):
         if isinstance(id_or_object, self._entity.cls):

objectbox/c.py

@@ -300,6 +300,21 @@ def c_voidp_as_bytes(voidp, size):
 # obx_err (OBX_store* store);
 obx_store_close = fn('obx_store_close', obx_err, [OBX_store_p])
 
+# OBX_txn* (OBX_store* store);
+obx_txn_begin = fn('obx_txn_begin', OBX_txn_p, [OBX_store_p])
+
+# OBX_txn* (OBX_store* store);
+obx_txn_begin_read = fn('obx_txn_begin_read', OBX_txn_p, [OBX_store_p])
+
+# obx_err (OBX_txn* txn)
+obx_txn_close = fn('obx_txn_close', obx_err, [OBX_txn_p])
+
+# obx_err (OBX_txn* txn);
+obx_txn_abort = fn('obx_txn_abort', obx_err, [OBX_txn_p])
+
+# obx_err (OBX_txn* txn);
+obx_txn_commit = fn('obx_txn_commit', obx_err, [OBX_txn_p])
+
 # OBX_box* (OBX_store* store, obx_schema_id entity_id);
 obx_box = fn('obx_box', OBX_box_p, [OBX_store_p, obx_schema_id])
 

objectbox/objectbox.py

@@ -14,11 +14,16 @@
 
 
 from objectbox.c import *
-
+import objectbox.transaction
 
 class ObjectBox:
     def __init__(self, c_store: OBX_store_p):
         self._c_store = c_store
 
     def __del__(self):
         obx_store_close(self._c_store)
+
+    def read_tx(self):
+        return objectbox.transaction.read(self)
+
+

objectbox/transaction.py

@@ -0,0 +1,42 @@
+# Copyright 2019 ObjectBox Ltd. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from objectbox.c import *
+from contextlib import contextmanager
+
+
+@contextmanager
+def read(ob: 'ObjectBox'):
+    tx = obx_txn_begin_read(ob._c_store)
+    try:
+        yield
+    finally:
+        obx_txn_close(tx)
+
+
+@contextmanager
+def write(ob: 'ObjectBox'):
+    tx = obx_txn_begin(ob._c_store)
+    successful = False
+    try:
+        yield
+        successful = True
+    finally:
+        # this is better than bare `except:` because it doesn't catch stuff like KeyboardInterrupt
+        if successful:
+            obx_txn_commit(tx)
+        else:
+            obx_txn_abort(tx)
+
+        obx_txn_close(tx)