/usr/share/pyshared/MoinMoin/caching.py is in python-moinmoin 1.9.3-1ubuntu2.
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"""
MoinMoin caching module
@copyright: 2001-2004 by Juergen Hermann <jh@web.de>,
2006-2009 MoinMoin:ThomasWaldmann,
2008 MoinMoin:ThomasPfaff
@license: GNU GPL, see COPYING for details.
"""
import os
import shutil
import tempfile
from MoinMoin import log
logging = log.getLogger(__name__)
from MoinMoin import config
from MoinMoin.util import filesys, lock, pickle, PICKLE_PROTOCOL
class CacheError(Exception):
""" raised if we have trouble locking, reading or writing """
pass
def get_arena_dir(request, arena, scope):
if scope == 'item': # arena is a Page instance
# we could move cache out of the page directory and store it to cache_dir
return arena.getPagePath('cache', check_create=1)
elif scope == 'wiki':
return os.path.join(request.cfg.cache_dir, request.cfg.siteid, arena)
elif scope == 'farm':
return os.path.join(request.cfg.cache_dir, '__common__', arena)
elif scope == 'dir':
# arena is a specific directory, just use it
return arena
return None
def get_cache_list(request, arena, scope):
arena_dir = get_arena_dir(request, arena, scope)
try:
return os.listdir(arena_dir)
except OSError:
return []
class CacheEntry:
def __init__(self, request, arena, key, scope='wiki', do_locking=True,
use_pickle=False, use_encode=False):
""" init a cache entry
@param request: the request object
@param arena: either a string or a page object, when we want to use
page local cache area
@param key: under which key we access the cache content
@param scope: the scope where we are caching:
'item' - an item local cache
'wiki' - a wiki local cache
'farm' - a cache for the whole farm
'dir' - just use some specific directory
@param do_locking: if there should be a lock, normally True
@param use_pickle: if data should be pickled/unpickled (nice for arbitrary cache content)
@param use_encode: if data should be encoded/decoded (nice for readable cache files)
"""
self.request = request
self.key = key
self.locking = do_locking
self.use_pickle = use_pickle
self.use_encode = use_encode
self.arena_dir = get_arena_dir(request, arena, scope)
if not os.path.exists(self.arena_dir):
os.makedirs(self.arena_dir)
self._fname = os.path.join(self.arena_dir, key)
# used by file-like api:
self._lock = None # either a read or a write lock
self._fileobj = None # open cache file object
self._tmp_fname = None # name of temporary file (used for write)
self._mode = None # mode of open file object
def _filename(self):
# DEPRECATED - please use file-like api
return self._fname
def exists(self):
return os.path.exists(self._fname)
def mtime(self):
# DEPRECATED for checking a changed on-disk cache, please use
# self.uid() for this, see below
try:
return os.path.getmtime(self._fname)
except (IOError, OSError):
return 0
def size(self):
try:
return os.path.getsize(self._fname)
except (IOError, OSError):
return 0
def uid(self):
""" Return a value that likely changes when the on-disk cache was updated.
See docstring of MoinMoin.util.filesys.fuid for details.
"""
return filesys.fuid(self._fname)
def needsUpdate(self, filename, attachdir=None):
# following code is not necessary. will trigger exception and give same result
#if not self.exists():
# return 1
try:
ctime = os.path.getmtime(self._fname)
ftime = os.path.getmtime(filename)
except os.error:
return 1
needsupdate = ftime > ctime
# if a page depends on the attachment dir, we check this, too:
if not needsupdate and attachdir:
try:
ftime2 = os.path.getmtime(attachdir)
except os.error:
ftime2 = 0
needsupdate = ftime2 > ctime
return needsupdate
def lock(self, mode, timeout=10.0):
"""
acquire a lock for <mode> ("r" or "w").
we just raise a CacheError if this doesn't work.
Note:
* .open() calls .lock(), .close() calls .unlock() if do_locking is True.
* if you need to do a read-modify-write, you want to use a CacheEntry
with do_locking=False and manually call .lock('w') and .unlock().
"""
lock_dir = os.path.join(self.arena_dir, '__lock__')
if 'r' in mode:
_lock = lock.LazyReadLock(lock_dir, 60.0)
elif 'w' in mode:
_lock = lock.LazyWriteLock(lock_dir, 60.0)
acquired = _lock.acquire(timeout)
if acquired:
self._lock = _lock
else:
self._lock = None
err = "Can't acquire %s lock in %s" % (mode, lock_dir)
logging.error(err)
raise CacheError(err)
def unlock(self):
"""
release the lock.
"""
if self._lock:
self._lock.release()
self._lock = None
# file-like interface ----------------------------------------------------
def open(self, filename=None, mode='r', bufsize=-1):
""" open the cache for reading/writing
Typical usage:
try:
cache.open('r') # open file, create locks
data = cache.read()
finally:
cache.close() # important to close file and remove locks
@param filename: must be None (default - automatically determine filename)
@param mode: 'r' (read, default), 'w' (write)
Note: if mode does not include 'b' (binary), it will be
automatically changed to include 'b'.
@param bufsize: size of read/write buffer (default: -1 meaning automatic)
@return: None (the opened file object is kept in self._fileobj and used
implicitely by read/write/close functions of CacheEntry object.
"""
assert self._fileobj is None, 'caching: trying to open an already opened cache'
assert filename is None, 'caching: giving a filename is not supported (yet?)'
assert 'r' in mode or 'w' in mode, 'caching: mode must contain "r" or "w"'
if 'b' not in mode:
mode += 'b' # we want to use binary mode, ever!
self._mode = mode # for self.close()
if self.locking:
self.lock(mode)
try:
if 'r' in mode:
filename = self._fname
self._fileobj = open(filename, mode, bufsize)
elif 'w' in mode:
# we do not write content to old inode, but to a new file
# so we don't need to lock when we just want to read the file
# (at least on POSIX, this works)
filename = None
fd, filename = tempfile.mkstemp('.tmp', self.key, self.arena_dir)
self._tmp_fname = filename
self._fileobj = os.fdopen(fd, mode, bufsize)
except IOError, err:
if 'w' in mode:
# IOerror for 'r' can be just a non-existing file, do not log that,
# but if open fails for 'w', we likely have some bigger problem:
logging.error(str(err))
raise CacheError(str(err))
def read(self, size=-1):
""" read data from cache file
@param size: how many bytes to read (default: -1 == everything)
@return: read data (str)
"""
return self._fileobj.read(size)
def write(self, data):
""" write data to cache file
@param data: write data (str)
"""
self._fileobj.write(data)
def close(self):
""" close cache file (and release lock, if any) """
try:
if self._fileobj:
self._fileobj.close()
self._fileobj = None
if 'w' in self._mode:
filesys.chmod(self._tmp_fname, 0666 & config.umask) # fix mode that mkstemp chose
# this is either atomic or happening with real locks set:
filesys.rename(self._tmp_fname, self._fname)
finally:
if self.locking:
self.unlock()
# ------------------------------------------------------------------------
def update(self, content):
try:
if hasattr(content, 'read'):
# content is file-like
assert not (self.use_pickle or self.use_encode), 'caching: use_pickle and use_encode not supported with file-like api'
try:
self.open(mode='w')
shutil.copyfileobj(content, self)
finally:
self.close()
else:
# content is a string
if self.use_pickle:
content = pickle.dumps(content, PICKLE_PROTOCOL)
elif self.use_encode:
content = content.encode(config.charset)
try:
self.open(mode='w')
self.write(content)
finally:
self.close()
except (pickle.PicklingError, OSError, IOError, ValueError), err:
raise CacheError(str(err))
def content(self):
# no file-like api yet, we implement it when we need it
try:
try:
self.open(mode='r')
data = self.read()
finally:
self.close()
if self.use_pickle:
data = pickle.loads(data)
elif self.use_encode:
data = data.decode(config.charset)
return data
except (pickle.UnpicklingError, IOError, EOFError, ValueError), err:
raise CacheError(str(err))
def remove(self):
if self.locking:
self.lock('w')
try:
try:
os.remove(self._fname)
except OSError:
pass
finally:
if self.locking:
self.unlock()
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