Persistent HTTP cache based on CacheControl

[mpd-sima.git] / sima / lib / httpcli / cache.py

diff --git a/sima/lib/httpcli/cache.py b/sima/lib/httpcli/cache.py
new file mode 100644 (file)
index 0000000..22c751d
--- /dev/null
+++ b/sima/lib/httpcli/cache.py
@@ -0,0 +1,76 @@
+"""
+The cache object API for implementing caches. The default is just a
+dictionary, which in turns means it is not threadsafe for writing.
+"""
+
+import os
+import base64
+import codecs
+
+from hashlib import md5
+from pickle import load, dump
+from threading import Lock
+
+from .filelock import FileLock
+
+
+class BaseCache:
+
+    def get(self, key):
+        raise NotImplemented()
+
+    def set(self, key, value):
+        raise NotImplemented()
+
+    def delete(self, key):
+        raise NotImplemented()
+
+
+class DictCache(BaseCache):
+
+    def __init__(self, init_dict=None):
+        self.lock = Lock()
+        self.data = init_dict or {}
+
+    def get(self, key):
+        return self.data.get(key, None)
+
+    def set(self, key, value):
+        with self.lock:
+            self.data.update({key: value})
+
+    def delete(self, key):
+        with self.lock:
+            if key in self.data:
+                self.data.pop(key)
+
+
+class FileCache:
+
+    def __init__(self, directory, forever=False):
+        self.directory = directory
+        self.forever = forever
+
+        if not os.path.isdir(self.directory):
+            os.mkdir(self.directory)
+
+    def encode(self, x):
+        return md5(x.encode('utf-8')).hexdigest()
+
+    def _fn(self, name):
+        return os.path.join(self.directory, self.encode(name))
+
+    def get(self, key):
+        name = self._fn(key)
+        if os.path.exists(name):
+            return load(codecs.open(name, 'rb'))
+
+    def set(self, key, value):
+        name = self._fn(key)
+        with FileLock(name):
+            with codecs.open(name, 'w+b') as fh:
+                dump(value, fh)
+
+    def delete(self, key):
+        if not self.forever:
+            os.remove(self._fn(key))