code release

xlib/db/KeyValueDB.py

@@ -0,0 +1,86 @@
+import traceback
+from datetime import datetime
+from pathlib import Path
+
+from xlib.io import FormattedFileIO
+
+
+class KeyValueDB:
+    """
+    Simple key/value database.
+
+    each key/value pickled/unpickled separately,
+    thus unpickling error will not corrupt whole db
+
+     filepath(None) if None, DB will not be saved on disk
+    """
+
+    _KeyValueDB_VERSION = 1
+
+    def __init__(self, filepath = None):
+        self._filepath = Path(filepath) if filepath is not None else None
+        self._save_timestamp = None
+
+        try:
+            d = {}
+            if self._filepath is not None:
+                with FormattedFileIO(self._filepath, 'r+') as f:
+                    ver, = f.read_fmt('I')
+                    if ver == KeyValueDB._KeyValueDB_VERSION:
+                        keys_len, = f.read_fmt('I')
+                        for i in range(keys_len):
+                            obj = f.read_pickled()
+                            if obj is not None:
+                                key, data = obj
+                                d[key] = data
+        except:
+            d = {}
+        self._data = d
+        
+    def clear(self):
+        self._data = {}
+
+    def get_value(self, key, default_value=None):
+        """
+        returns data by key or None
+        """
+        return self._data.get(key, default_value)
+
+    def set_value(self, key, value):
+        """
+        set value by key
+        """
+        self._data[key] = value
+
+        if self._save_timestamp is None:
+            # Save in 1 sec
+            self._save_timestamp = datetime.now().timestamp() + 1.0
+
+    def _save_data(self):
+        if self._filepath is not None:
+            try:
+                with FormattedFileIO(self._filepath, 'w+') as f:
+                    f.write_fmt('I', KeyValueDB._KeyValueDB_VERSION)
+
+                    d = self._data
+                    keys = list(d.keys())
+                    f.write_fmt('I', len(keys))
+                    for key in keys:
+                        f.write_pickled( (key, d[key]) )
+
+                    f.truncate()
+            except e:
+                print(f'Unable to save the data. {traceback.format_exc()}')
+
+    def finish_pending_jobs(self):
+        """finish any pending jobs now"""
+        if self._save_timestamp is not None:
+            self._save_timestamp = None
+            self._save_data()
+
+    def process_messages(self):
+        save_timestamp = self._save_timestamp
+        if save_timestamp is not None and \
+           (datetime.now().timestamp() - save_timestamp) >= 0:
+            self._save_timestamp = None
+            self._save_data()