Initial YakPanel commit

class/cachelib/memcached.py

@@ -0,0 +1,186 @@
+# -*- coding: utf-8 -*-
+
+import re
+from time import time
+from cachelib._compat import iteritems, to_native
+from cachelib.base import BaseCache, _items
+
+
+_test_memcached_key = re.compile(r'[^\x00-\x21\xff]{1,250}$').match
+
+
+class MemcachedCache(BaseCache):
+
+    """A cache that uses memcached as backend.
+
+    The first argument can either be an object that resembles the API of a
+    :class:`memcache.Client` or a tuple/list of server addresses. In the
+    event that a tuple/list is passed, Werkzeug tries to import the best
+    available memcache library.
+
+    This cache looks into the following packages/modules to find bindings for
+    memcached:
+
+        - ``pylibmc``
+        - ``google.appengine.api.memcached``
+        - ``memcached``
+        - ``libmc``
+
+    Implementation notes:  This cache backend works around some limitations in
+    memcached to simplify the interface.  For example unicode keys are encoded
+    to utf-8 on the fly.  Methods such as :meth:`~BaseCache.get_dict` return
+    the keys in the same format as passed.  Furthermore all get methods
+    silently ignore key errors to not cause problems when untrusted user data
+    is passed to the get methods which is often the case in web applications.
+
+    :param servers: a list or tuple of server addresses or alternatively
+                    a :class:`memcache.Client` or a compatible client.
+    :param default_timeout: the default timeout that is used if no timeout is
+                            specified on :meth:`~BaseCache.set`. A timeout of
+                            0 indicates that the cache never expires.
+    :param key_prefix: a prefix that is added before all keys.  This makes it
+                       possible to use the same memcached server for different
+                       applications.  Keep in mind that
+                       :meth:`~BaseCache.clear` will also clear keys with a
+                       different prefix.
+    """
+
+    def __init__(self, servers=None, default_timeout=300, key_prefix=None):
+        BaseCache.__init__(self, default_timeout)
+        if servers is None or isinstance(servers, (list, tuple)):
+            if servers is None:
+                servers = ['127.0.0.1:11211']
+            self._client = self.import_preferred_memcache_lib(servers)
+            if self._client is None:
+                raise RuntimeError('no memcache module found')
+        else:
+            # NOTE: servers is actually an already initialized memcache
+            # client.
+            self._client = servers
+
+        self.key_prefix = to_native(key_prefix)
+
+    def _normalize_key(self, key):
+        key = to_native(key, 'utf-8')
+        if self.key_prefix:
+            key = self.key_prefix + key
+        return key
+
+    def _normalize_timeout(self, timeout):
+        timeout = BaseCache._normalize_timeout(self, timeout)
+        if timeout > 0:
+            timeout = int(time()) + timeout
+        return timeout
+
+    def get(self, key):
+        key = self._normalize_key(key)
+        # memcached doesn't support keys longer than that.  Because often
+        # checks for so long keys can occur because it's tested from user
+        # submitted data etc we fail silently for getting.
+        if _test_memcached_key(key):
+            return self._client.get(key)
+
+    def get_dict(self, *keys):
+        key_mapping = {}
+        have_encoded_keys = False
+        for key in keys:
+            encoded_key = self._normalize_key(key)
+            if not isinstance(key, str):
+                have_encoded_keys = True
+            if _test_memcached_key(key):
+                key_mapping[encoded_key] = key
+        _keys = list(key_mapping)
+        d = rv = self._client.get_multi(_keys)
+        if have_encoded_keys or self.key_prefix:
+            rv = {}
+            for key, value in iteritems(d):
+                rv[key_mapping[key]] = value
+        if len(rv) < len(keys):
+            for key in keys:
+                if key not in rv:
+                    rv[key] = None
+        return rv
+
+    def add(self, key, value, timeout=None):
+        key = self._normalize_key(key)
+        timeout = self._normalize_timeout(timeout)
+        return self._client.add(key, value, timeout)
+
+    def set(self, key, value, timeout=None):
+        key = self._normalize_key(key)
+        timeout = self._normalize_timeout(timeout)
+        return self._client.set(key, value, timeout)
+
+    def get_many(self, *keys):
+        d = self.get_dict(*keys)
+        return [d[key] for key in keys]
+
+    def set_many(self, mapping, timeout=None):
+        new_mapping = {}
+        for key, value in _items(mapping):
+            key = self._normalize_key(key)
+            new_mapping[key] = value
+
+        timeout = self._normalize_timeout(timeout)
+        failed_keys = self._client.set_multi(new_mapping, timeout)
+        return not failed_keys
+
+    def delete(self, key):
+        key = self._normalize_key(key)
+        if _test_memcached_key(key):
+            return self._client.delete(key)
+
+    def delete_many(self, *keys):
+        new_keys = []
+        for key in keys:
+            key = self._normalize_key(key)
+            if _test_memcached_key(key):
+                new_keys.append(key)
+        return self._client.delete_multi(new_keys)
+
+    def has(self, key):
+        key = self._normalize_key(key)
+        if _test_memcached_key(key):
+            return self._client.append(key, '')
+        return False
+
+    def clear(self):
+        return self._client.flush_all()
+
+    def inc(self, key, delta=1):
+        key = self._normalize_key(key)
+        return self._client.incr(key, delta)
+
+    def dec(self, key, delta=1):
+        key = self._normalize_key(key)
+        return self._client.decr(key, delta)
+
+    def import_preferred_memcache_lib(self, servers):
+        """Returns an initialized memcache client.  Used by the constructor."""
+        try:
+            import pylibmc
+        except ImportError:
+            pass
+        else:
+            return pylibmc.Client(servers)
+
+        try:
+            from google.appengine.api import memcache
+        except ImportError:
+            pass
+        else:
+            return memcache.Client()
+
+        try:
+            import memcache
+        except ImportError:
+            pass
+        else:
+            return memcache.Client(servers)
+
+        try:
+            import libmc
+        except ImportError:
+            pass
+        else:
+            return libmc.Client(servers)