util.cache: New module handling both in-memory and on-file system caching.

slixmpp/util/__init__.py

@@ -13,3 +13,5 @@
 from slixmpp.util.misc_ops import bytes, unicode, hashes, hash, \
                                     num_to_bytes, bytes_to_num, quote, \
                                     XOR
+from slixmpp.util.cache import MemoryCache, MemoryPerJidCache, \
+                               FileSystemCache, FileSystemPerJidCache

slixmpp/util/cache.py

@@ -0,0 +1,105 @@
+"""
+    Slixmpp: The Slick XMPP Library
+    Copyright (C) 2018 Emmanuel Gil Peyrot
+    This file is part of Slixmpp.
+
+    See the file LICENSE for copying permission.
+"""
+
+import os
+import logging
+
+log = logging.getLogger(__name__)
+
+class Cache:
+    def retrieve(self, key):
+        raise NotImplementedError
+
+    def store(self, key, value):
+        raise NotImplementedError
+
+class PerJidCache:
+    def retrieve_by_jid(self, jid, key):
+        raise NotImplementedError
+
+    def store_by_jid(self, jid, key, value):
+        raise NotImplementedError
+
+class MemoryCache(Cache):
+    def __init__(self):
+        self.cache = {}
+
+    def retrieve(self, key):
+        return self.cache.get(key, None)
+
+    def store(self, key, value):
+        self.cache[key] = value
+        return True
+
+class MemoryPerJidCache(PerJidCache):
+    def __init__(self):
+        self.cache = {}
+
+    def retrieve_by_jid(self, jid, key):
+        cache = self.cache.get(jid.bare, None)
+        if cache is None:
+            return None
+        return cache.get(key, None)
+
+    def store_by_jid(self, jid, key, value):
+        cache = self.cache.setdefault(jid.bare, {})
+        cache[key] = value
+        return True
+
+class FileSystemStorage:
+    def __init__(self, encode, decode, binary):
+        self.encode = encode
+        self.decode = decode
+        self.read = 'rb' if binary else 'r'
+        self.write = 'wb' if binary else 'w'
+
+    def _retrieve(self, directory, key):
+        filename = os.path.join(directory, key.replace('/', '_'))
+        try:
+            with open(filename, self.read) as cache_file:
+                return self.decode(cache_file.read())
+        except FileNotFoundError:
+            log.debug('%s not present in cache', key)
+        except OSError:
+            log.debug('Failed to read %s from cache:', key, exc_info=True)
+            return None
+
+    def _store(self, directory, key, value):
+        filename = os.path.join(directory, key.replace('/', '_'))
+        try:
+            os.makedirs(directory, exist_ok=True)
+            with open(filename, self.write) as output:
+                output.write(self.encode(value))
+                return True
+        except OSError:
+            log.debug('Failed to store %s to cache:', key, exc_info=True)
+            return False
+
+class FileSystemCache(Cache, FileSystemStorage):
+    def __init__(self, directory, cache_type, *, encode, decode, binary=False):
+        FileSystemStorage.__init__(self, encode, decode, binary)
+        self.base_dir = os.path.join(directory, cache_type)
+
+    def retrieve(self, key):
+        return self._retrieve(self.base_dir, key)
+
+    def store(self, key, value):
+        return self._store(self.base_dir, key, value)
+
+class FileSystemPerJidCache(PerJidCache, FileSystemStorage):
+    def __init__(self, directory, cache_type, *, encode, decode, binary=False):
+        FileSystemStorage.__init__(self, encode, decode, binary)
+        self.base_dir = os.path.join(directory, cache_type)
+
+    def retrieve_by_jid(self, jid, key):
+        directory = os.path.join(self.base_dir, jid.bare)
+        return self._retrieve(directory, key)
+
+    def store_by_jid(self, jid, key, value):
+        directory = os.path.join(self.base_dir, jid.bare)
+        return self._store(directory, key, value)