wsgistate / wsgistate / memory.py

# Copyright (c) 2005, the Lawrence Journal-World
# Copyright (c) 2005 Allan Saddi <allan@saddi.com>
# Copyright (c) 2006 L. C. Rees
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'''Thread-safe in-memory cache backend.'''

import copy, time
try:
    import threading
except ImportError:
    import dummy_threading as threading

from wsgistate import synchronized
from wsgistate.simple import SimpleCache
from wsgistate.cache import WsgiMemoize
from wsgistate.session import CookieSession, URLSession, SessionCache

__all__ = ['MemoryCache', 'memoize', 'session', 'urlsession']

def memorymemo_deploy(global_conf, **kw):
    '''Paste Deploy loader for caching.'''
    def decorator(application):
        _memory_memo_cache = MemoryCache(kw.get('cache'), **kw)
        return WsgiMemoize(application, _memory_memo_cache, **kw)
    return decorator

def memorysess_deploy(global_conf, **kw):
    '''Paste Deploy loader for sessions.'''
    def decorator(application):
        _memory_base_cache = MemoryCache(kw.get('cache'), **kw)
        _memory_session_cache = SessionCache(_memory_base_cache, **kw)
        return CookieSession(application, _memory_session_cache, **kw)
    return decorator

def memoryurlsess_deploy(global_conf, **kw):
    '''Paste Deploy loader for URL encoded sessions.

    @param initstr Database initialization string
    '''
    def decorator(application):
        _memory_ubase_cache = MemoryCache(kw.get('cache'), **kw)
        _memory_url_cache = SessionCache(_memory_ubase_cache, **kw)
        return URLSession(application, _memory_url_cache, **kw)
    return decorator

def memoize(**kw):
    '''Decorator for caching.'''
    def decorator(application):
        _mem_memo_cache = MemoryCache(**kw)
        return WsgiMemoize(application, _mem_memo_cache, **kw)
    return decorator

def session(**kw):
    '''Decorator for sessions.'''
    def decorator(application):
        _mem_base_cache = MemoryCache(**kw)
        _mem_session_cache = SessionCache(_mem_base_cache, **kw)
        return CookieSession(application, _mem_session_cache, **kw)
    return decorator

def urlsession(**kw):
    '''Decorator for URL encoded sessions.'''
    def decorator(application):
        _mem_ubase_cache = MemoryCache(**kw)
        _mem_url_cache = SessionCache(_mem_ubase_cache, **kw)
        return URLSession(application, _mem_url_cache, **kw)
    return decorator


class MemoryCache(SimpleCache):

    '''Thread-safe in-memory cache backend.'''

    def __init__(self, *a, **kw):
        super(MemoryCache, self).__init__(*a, **kw)
        self._lock = threading.Condition()

    @synchronized
    def get(self, key, default=None):
        '''Fetch a given key from the cache. If the key does not exist, return
        default, which itself defaults to None.

        @param key Keyword of item in cache.
        @param default Default value (default: None)
        '''
        return copy.deepcopy(super(MemoryCache, self).get(key))

    @synchronized
    def set(self, key, value):
        '''Set a value in the cache.

        @param key Keyword of item in cache.
        @param value Value to be inserted in cache.
        '''
        super(MemoryCache, self).set(key, value)

    @synchronized
    def delete(self, key):
        '''Delete a key from the cache, failing silently.

        @param key Keyword of item in cache.
        '''
        super(MemoryCache, self).delete(key)
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