bundling required python dependencies, to make it easier on Tails users

lib/werkzeug/contrib/cache.py

@@ -0,0 +1,679 @@
+# -*- coding: utf-8 -*-
+"""
+    werkzeug.contrib.cache
+    ~~~~~~~~~~~~~~~~~~~~~~
+
+    The main problem with dynamic Web sites is, well, they're dynamic.  Each
+    time a user requests a page, the webserver executes a lot of code, queries
+    the database, renders templates until the visitor gets the page he sees.
+
+    This is a lot more expensive than just loading a file from the file system
+    and sending it to the visitor.
+
+    For most Web applications, this overhead isn't a big deal but once it
+    becomes, you will be glad to have a cache system in place.
+
+    How Caching Works
+    =================
+
+    Caching is pretty simple.  Basically you have a cache object lurking around
+    somewhere that is connected to a remote cache or the file system or
+    something else.  When the request comes in you check if the current page
+    is already in the cache and if so, you're returning it from the cache.
+    Otherwise you generate the page and put it into the cache. (Or a fragment
+    of the page, you don't have to cache the full thing)
+
+    Here is a simple example of how to cache a sidebar for a template::
+
+        def get_sidebar(user):
+            identifier = 'sidebar_for/user%d' % user.id
+            value = cache.get(identifier)
+            if value is not None:
+                return value
+            value = generate_sidebar_for(user=user)
+            cache.set(identifier, value, timeout=60 * 5)
+            return value
+
+    Creating a Cache Object
+    =======================
+
+    To create a cache object you just import the cache system of your choice
+    from the cache module and instantiate it.  Then you can start working
+    with that object:
+
+    >>> from werkzeug.contrib.cache import SimpleCache
+    >>> c = SimpleCache()
+    >>> c.set("foo", "value")
+    >>> c.get("foo")
+    'value'
+    >>> c.get("missing") is None
+    True
+
+    Please keep in mind that you have to create the cache and put it somewhere
+    you have access to it (either as a module global you can import or you just
+    put it into your WSGI application).
+
+    :copyright: (c) 2013 by the Werkzeug Team, see AUTHORS for more details.
+    :license: BSD, see LICENSE for more details.
+"""
+import os
+import re
+import tempfile
+from hashlib import md5
+from time import time
+try:
+    import cPickle as pickle
+except ImportError:
+    import pickle
+
+from werkzeug._compat import iteritems, string_types, text_type, \
+     integer_types, to_bytes
+from werkzeug.posixemulation import rename
+
+
+def _items(mappingorseq):
+    """Wrapper for efficient iteration over mappings represented by dicts
+    or sequences::
+
+        >>> for k, v in _items((i, i*i) for i in xrange(5)):
+        ...    assert k*k == v
+
+        >>> for k, v in _items(dict((i, i*i) for i in xrange(5))):
+        ...    assert k*k == v
+
+    """
+    if hasattr(mappingorseq, "iteritems"):
+        return mappingorseq.iteritems()
+    elif hasattr(mappingorseq, "items"):
+        return mappingorseq.items()
+    return mappingorseq
+
+
+class BaseCache(object):
+    """Baseclass for the cache systems.  All the cache systems implement this
+    API or a superset of it.
+
+    :param default_timeout: the default timeout that is used if no timeout is
+                            specified on :meth:`set`.
+    """
+
+    def __init__(self, default_timeout=300):
+        self.default_timeout = default_timeout
+
+    def get(self, key):
+        """Looks up key in the cache and returns the value for it.
+        If the key does not exist `None` is returned instead.
+
+        :param key: the key to be looked up.
+        """
+        return None
+
+    def delete(self, key):
+        """Deletes `key` from the cache.  If it does not exist in the cache
+        nothing happens.
+
+        :param key: the key to delete.
+        """
+        pass
+
+    def get_many(self, *keys):
+        """Returns a list of values for the given keys.
+        For each key a item in the list is created.  Example::
+
+            foo, bar = cache.get_many("foo", "bar")
+
+        If a key can't be looked up `None` is returned for that key
+        instead.
+
+        :param keys: The function accepts multiple keys as positional
+                     arguments.
+        """
+        return map(self.get, keys)
+
+    def get_dict(self, *keys):
+        """Works like :meth:`get_many` but returns a dict::
+
+            d = cache.get_dict("foo", "bar")
+            foo = d["foo"]
+            bar = d["bar"]
+
+        :param keys: The function accepts multiple keys as positional
+                     arguments.
+        """
+        return dict(zip(keys, self.get_many(*keys)))
+
+    def set(self, key, value, timeout=None):
+        """Adds a new key/value to the cache (overwrites value, if key already
+        exists in the cache).
+
+        :param key: the key to set
+        :param value: the value for the key
+        :param timeout: the cache timeout for the key (if not specified,
+                        it uses the default timeout).
+        """
+        pass
+
+    def add(self, key, value, timeout=None):
+        """Works like :meth:`set` but does not overwrite the values of already
+        existing keys.
+
+        :param key: the key to set
+        :param value: the value for the key
+        :param timeout: the cache timeout for the key or the default
+                        timeout if not specified.
+        """
+        pass
+
+    def set_many(self, mapping, timeout=None):
+        """Sets multiple keys and values from a mapping.
+
+        :param mapping: a mapping with the keys/values to set.
+        :param timeout: the cache timeout for the key (if not specified,
+                        it uses the default timeout).
+        """
+        for key, value in _items(mapping):
+            self.set(key, value, timeout)
+
+    def delete_many(self, *keys):
+        """Deletes multiple keys at once.
+
+        :param keys: The function accepts multiple keys as positional
+                     arguments.
+        """
+        for key in keys:
+            self.delete(key)
+
+    def clear(self):
+        """Clears the cache.  Keep in mind that not all caches support
+        completely clearing the cache.
+        """
+        pass
+
+    def inc(self, key, delta=1):
+        """Increments the value of a key by `delta`.  If the key does
+        not yet exist it is initialized with `delta`.
+
+        For supporting caches this is an atomic operation.
+
+        :param key: the key to increment.
+        :param delta: the delta to add.
+        """
+        self.set(key, (self.get(key) or 0) + delta)
+
+    def dec(self, key, delta=1):
+        """Decrements the value of a key by `delta`.  If the key does
+        not yet exist it is initialized with `-delta`.
+
+        For supporting caches this is an atomic operation.
+
+        :param key: the key to increment.
+        :param delta: the delta to subtract.
+        """
+        self.set(key, (self.get(key) or 0) - delta)
+
+
+class NullCache(BaseCache):
+    """A cache that doesn't cache.  This can be useful for unit testing.
+
+    :param default_timeout: a dummy parameter that is ignored but exists
+                            for API compatibility with other caches.
+    """
+
+
+class SimpleCache(BaseCache):
+    """Simple memory cache for single process environments.  This class exists
+    mainly for the development server and is not 100% thread safe.  It tries
+    to use as many atomic operations as possible and no locks for simplicity
+    but it could happen under heavy load that keys are added multiple times.
+
+    :param threshold: the maximum number of items the cache stores before
+                      it starts deleting some.
+    :param default_timeout: the default timeout that is used if no timeout is
+                            specified on :meth:`~BaseCache.set`.
+    """
+
+    def __init__(self, threshold=500, default_timeout=300):
+        BaseCache.__init__(self, default_timeout)
+        self._cache = {}
+        self.clear = self._cache.clear
+        self._threshold = threshold
+
+    def _prune(self):
+        if len(self._cache) > self._threshold:
+            now = time()
+            for idx, (key, (expires, _)) in enumerate(self._cache.items()):
+                if expires <= now or idx % 3 == 0:
+                    self._cache.pop(key, None)
+
+    def get(self, key):
+        expires, value = self._cache.get(key, (0, None))
+        if expires > time():
+            return pickle.loads(value)
+
+    def set(self, key, value, timeout=None):
+        if timeout is None:
+            timeout = self.default_timeout
+        self._prune()
+        self._cache[key] = (time() + timeout, pickle.dumps(value,
+            pickle.HIGHEST_PROTOCOL))
+
+    def add(self, key, value, timeout=None):
+        if timeout is None:
+            timeout = self.default_timeout
+        if len(self._cache) > self._threshold:
+            self._prune()
+        item = (time() + timeout, pickle.dumps(value,
+            pickle.HIGHEST_PROTOCOL))
+        self._cache.setdefault(key, item)
+
+    def delete(self, key):
+        self._cache.pop(key, None)
+
+
+_test_memcached_key = re.compile(br'[^\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.
+
+    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`.
+    :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_bytes(key_prefix)
+
+    def get(self, key):
+        if isinstance(key, text_type):
+            key = key.encode('utf-8')
+        if self.key_prefix:
+            key = self.key_prefix + key
+        # memcached doesn't support keys longer than that.  Because often
+        # checks for so long keys can occour 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:
+            if isinstance(key, unicode):
+                encoded_key = key.encode('utf-8')
+                have_encoded_keys = True
+            else:
+                encoded_key = key
+            if self.key_prefix:
+                encoded_key = self.key_prefix + encoded_key
+            if _test_memcached_key(key):
+                key_mapping[encoded_key] = key
+        d = rv = self._client.get_multi(key_mapping.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):
+        if timeout is None:
+            timeout = self.default_timeout
+        if isinstance(key, text_type):
+            key = key.encode('utf-8')
+        if self.key_prefix:
+            key = self.key_prefix + key
+        self._client.add(key, value, timeout)
+
+    def set(self, key, value, timeout=None):
+        if timeout is None:
+            timeout = self.default_timeout
+        if isinstance(key, text_type):
+            key = key.encode('utf-8')
+        if self.key_prefix:
+            key = self.key_prefix + key
+        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):
+        if timeout is None:
+            timeout = self.default_timeout
+        new_mapping = {}
+        for key, value in _items(mapping):
+            if isinstance(key, text_type):
+                key = key.encode('utf-8')
+            if self.key_prefix:
+                key = self.key_prefix + key
+            new_mapping[key] = value
+        self._client.set_multi(new_mapping, timeout)
+
+    def delete(self, key):
+        if isinstance(key, unicode):
+            key = key.encode('utf-8')
+        if self.key_prefix:
+            key = self.key_prefix + key
+        if _test_memcached_key(key):
+            self._client.delete(key)
+
+    def delete_many(self, *keys):
+        new_keys = []
+        for key in keys:
+            if isinstance(key, unicode):
+                key = key.encode('utf-8')
+            if self.key_prefix:
+                key = self.key_prefix + key
+            if _test_memcached_key(key):
+                new_keys.append(key)
+        self._client.delete_multi(new_keys)
+
+    def clear(self):
+        self._client.flush_all()
+
+    def inc(self, key, delta=1):
+        if isinstance(key, unicode):
+            key = key.encode('utf-8')
+        if self.key_prefix:
+            key = self.key_prefix + key
+        self._client.incr(key, delta)
+
+    def dec(self, key, delta=1):
+        if isinstance(key, unicode):
+            key = key.encode('utf-8')
+        if self.key_prefix:
+            key = self.key_prefix + key
+        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)
+
+
+# backwards compatibility
+GAEMemcachedCache = MemcachedCache
+
+
+class RedisCache(BaseCache):
+    """Uses the Redis key-value store as a cache backend.
+
+    The first argument can be either a string denoting address of the Redis
+    server or an object resembling an instance of a redis.Redis class.
+
+    Note: Python Redis API already takes care of encoding unicode strings on
+    the fly.
+
+    .. versionadded:: 0.7
+
+    .. versionadded:: 0.8
+       `key_prefix` was added.
+
+    .. versionchanged:: 0.8
+       This cache backend now properly serializes objects.
+
+    .. versionchanged:: 0.8.3
+       This cache backend now supports password authentication.
+
+    :param host: address of the Redis server or an object which API is
+                 compatible with the official Python Redis client (redis-py).
+    :param port: port number on which Redis server listens for connections.
+    :param password: password authentication for the Redis server.
+    :param db: db (zero-based numeric index) on Redis Server to connect.
+    :param default_timeout: the default timeout that is used if no timeout is
+                            specified on :meth:`~BaseCache.set`.
+    :param key_prefix: A prefix that should be added to all keys.
+    """
+
+    def __init__(self, host='localhost', port=6379, password=None,
+                 db=0, default_timeout=300, key_prefix=None):
+        BaseCache.__init__(self, default_timeout)
+        if isinstance(host, string_types):
+            try:
+                import redis
+            except ImportError:
+                raise RuntimeError('no redis module found')
+            self._client = redis.Redis(host=host, port=port, password=password, db=db)
+        else:
+            self._client = host
+        self.key_prefix = key_prefix or ''
+
+    def dump_object(self, value):
+        """Dumps an object into a string for redis.  By default it serializes
+        integers as regular string and pickle dumps everything else.
+        """
+        t = type(value)
+        if t in integer_types:
+            return str(value).encode('ascii')
+        return b'!' + pickle.dumps(value)
+
+    def load_object(self, value):
+        """The reversal of :meth:`dump_object`.  This might be callde with
+        None.
+        """
+        if value is None:
+            return None
+        if value.startswith(b'!'):
+            return pickle.loads(value[1:])
+        try:
+            return int(value)
+        except ValueError:
+            # before 0.8 we did not have serialization.  Still support that.
+            return value
+
+    def get(self, key):
+        return self.load_object(self._client.get(self.key_prefix + key))
+
+    def get_many(self, *keys):
+        if self.key_prefix:
+            keys = [self.key_prefix + key for key in keys]
+        return [self.load_object(x) for x in self._client.mget(keys)]
+
+    def set(self, key, value, timeout=None):
+        if timeout is None:
+            timeout = self.default_timeout
+        dump = self.dump_object(value)
+        self._client.setex(self.key_prefix + key, dump, timeout)
+
+    def add(self, key, value, timeout=None):
+        if timeout is None:
+            timeout = self.default_timeout
+        dump = self.dump_object(value)
+        added = self._client.setnx(self.key_prefix + key, dump)
+        if added:
+            self._client.expire(self.key_prefix + key, timeout)
+
+    def set_many(self, mapping, timeout=None):
+        if timeout is None:
+            timeout = self.default_timeout
+        pipe = self._client.pipeline()
+        for key, value in _items(mapping):
+            dump = self.dump_object(value)
+            pipe.setex(self.key_prefix + key, dump, timeout)
+        pipe.execute()
+
+    def delete(self, key):
+        self._client.delete(self.key_prefix + key)
+
+    def delete_many(self, *keys):
+        if not keys:
+            return
+        if self.key_prefix:
+            keys = [self.key_prefix + key for key in keys]
+        self._client.delete(*keys)
+
+    def clear(self):
+        if self.key_prefix:
+            keys = self._client.keys(self.key_prefix + '*')
+            if keys:
+                self._client.delete(*keys)
+        else:
+            self._client.flushdb()
+
+    def inc(self, key, delta=1):
+        return self._client.incr(self.key_prefix + key, delta)
+
+    def dec(self, key, delta=1):
+        return self._client.decr(self.key_prefix + key, delta)
+
+
+class FileSystemCache(BaseCache):
+    """A cache that stores the items on the file system.  This cache depends
+    on being the only user of the `cache_dir`.  Make absolutely sure that
+    nobody but this cache stores files there or otherwise the cache will
+    randomly delete files therein.
+
+    :param cache_dir: the directory where cache files are stored.
+    :param threshold: the maximum number of items the cache stores before
+                      it starts deleting some.
+    :param default_timeout: the default timeout that is used if no timeout is
+                            specified on :meth:`~BaseCache.set`.
+    :param mode: the file mode wanted for the cache files, default 0600
+    """
+
+    #: used for temporary files by the FileSystemCache
+    _fs_transaction_suffix = '.__wz_cache'
+
+    def __init__(self, cache_dir, threshold=500, default_timeout=300, mode=0o600):
+        BaseCache.__init__(self, default_timeout)
+        self._path = cache_dir
+        self._threshold = threshold
+        self._mode = mode
+        if not os.path.exists(self._path):
+            os.makedirs(self._path)
+
+    def _list_dir(self):
+        """return a list of (fully qualified) cache filenames
+        """
+        return [os.path.join(self._path, fn) for fn in os.listdir(self._path)
+                if not fn.endswith(self._fs_transaction_suffix)]
+
+    def _prune(self):
+        entries = self._list_dir()
+        if len(entries) > self._threshold:
+            now = time()
+            for idx, fname in enumerate(entries):
+                remove = False
+                f = None
+                try:
+                    try:
+                        f = open(fname, 'rb')
+                        expires = pickle.load(f)
+                        remove = expires <= now or idx % 3 == 0
+                    finally:
+                        if f is not None:
+                            f.close()
+                except Exception:
+                    pass
+                if remove:
+                    try:
+                        os.remove(fname)
+                    except (IOError, OSError):
+                        pass
+
+    def clear(self):
+        for fname in self._list_dir():
+            try:
+                os.remove(fname)
+            except (IOError, OSError):
+                pass
+
+    def _get_filename(self, key):
+        if isinstance(key, text_type):
+            key = key.encode('utf-8') #XXX unicode review
+        hash = md5(key).hexdigest()
+        return os.path.join(self._path, hash)
+
+    def get(self, key):
+        filename = self._get_filename(key)
+        try:
+            f = open(filename, 'rb')
+            try:
+                if pickle.load(f) >= time():
+                    return pickle.load(f)
+            finally:
+                f.close()
+            os.remove(filename)
+        except Exception:
+            return None
+
+    def add(self, key, value, timeout=None):
+        filename = self._get_filename(key)
+        if not os.path.exists(filename):
+            self.set(key, value, timeout)
+
+    def set(self, key, value, timeout=None):
+        if timeout is None:
+            timeout = self.default_timeout
+        filename = self._get_filename(key)
+        self._prune()
+        try:
+            fd, tmp = tempfile.mkstemp(suffix=self._fs_transaction_suffix,
+                                       dir=self._path)
+            f = os.fdopen(fd, 'wb')
+            try:
+                pickle.dump(int(time() + timeout), f, 1)
+                pickle.dump(value, f, pickle.HIGHEST_PROTOCOL)
+            finally:
+                f.close()
+            rename(tmp, filename)
+            os.chmod(filename, self._mode)
+        except (IOError, OSError):
+            pass
+
+    def delete(self, key):
+        try:
+            os.remove(self._get_filename(key))
+        except (IOError, OSError):
+            pass