From 20d7c806138f6d63ccd630411b3e4df37eeba44b Mon Sep 17 00:00:00 2001
From: cassiobotaro <cassiobotaro@gmail.com>
Date: Wed, 12 Jan 2022 19:23:18 -0300
Subject: [PATCH] Guarantee empty dictionary when memory is initialized

---
 shared_memory_dict/dict.py | 19 ++++++++++++++-----
 tests/test_dict.py         | 13 +++++++++++++
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/shared_memory_dict/dict.py b/shared_memory_dict/dict.py
index ec66df6..dd83489 100644
--- a/shared_memory_dict/dict.py
+++ b/shared_memory_dict/dict.py
@@ -15,7 +15,11 @@
 )
 
 from .lock import lock
-from .serializers import PickleSerializer, SharedMemoryDictSerializer
+from .serializers import (
+    NULL_BYTE,
+    PickleSerializer,
+    SharedMemoryDictSerializer,
+)
 from .templates import MEMORY_NAME
 
 NOT_GIVEN = object()
@@ -38,6 +42,14 @@ def __init__(
         self._memory_block = self._get_or_create_memory_block(
             MEMORY_NAME.format(name=name), size
         )
+        self._ensure_memory_initialization()
+
+    def _ensure_memory_initialization(self):
+        memory_is_empty = (
+            bytes(self._memory_block.buf).split(NULL_BYTE, 1)[0] == b''
+        )
+        if memory_is_empty:
+            self._save_memory({})
 
     def cleanup(self) -> None:
         if not hasattr(self, '_memory_block'):
@@ -159,10 +171,7 @@ def _get_or_create_memory_block(
         try:
             return SharedMemory(name=name)
         except FileNotFoundError:
-            shm = SharedMemory(name=name, create=True, size=size)
-            data = self._serializer.dumps({})
-            shm.buf[: len(data)] = data
-            return shm
+            return SharedMemory(name=name, create=True, size=size)
 
     def _save_memory(self, db: Dict[str, Any]) -> None:
         data = self._serializer.dumps(db)
diff --git a/tests/test_dict.py b/tests/test_dict.py
index a37e387..e3e3675 100644
--- a/tests/test_dict.py
+++ b/tests/test_dict.py
@@ -5,6 +5,7 @@
 from shared_memory_dict import SharedMemoryDict
 from shared_memory_dict.dict import DEFAULT_SERIALIZER
 from shared_memory_dict.serializers import JSONSerializer
+from multiprocessing.shared_memory import SharedMemory
 
 DEFAULT_MEMORY_SIZE = 1024
 
@@ -16,6 +17,7 @@ def shared_memory_dict(self):
         yield smd
         smd.clear()
         smd.cleanup()
+        smd.shm.unlink()
 
     @pytest.fixture
     def key(self):
@@ -215,3 +217,14 @@ def test_use_custom_serializer_when_specified(self):
             name='unit-tests', size=64, serializer=serializer
         )
         assert smd._serializer is serializer
+
+    def test_shoud_initialize_when_memory_is_empty(self):
+        SharedMemory(name='sm_ut', create=True, size=64)
+        smd = SharedMemoryDict(name='ut', size=64)
+        try:
+            print(smd)
+        except Exception as e:
+            pytest.fail(f'Its should not raises: {e}')
+        smd.clear()
+        smd.cleanup()
+        smd.shm.unlink()