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# -*- coding: utf-8 -*-
# Copyright 2016-2020 Mike Fährmann
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
"""Decorators to keep function results in an in-memory and database cache"""
import sqlite3
import pickle
import time
import os
import functools
from . import config, util
class CacheDecorator():
"""Simplified in-memory cache"""
def __init__(self, func, keyarg):
self.func = func
self.cache = {}
self.keyarg = keyarg
def __get__(self, instance, cls):
return functools.partial(self.__call__, instance)
def __call__(self, *args, **kwargs):
key = "" if self.keyarg is None else args[self.keyarg]
try:
value = self.cache[key]
except KeyError:
value = self.cache[key] = self.func(*args, **kwargs)
return value
def update(self, key, value):
self.cache[key] = value
def invalidate(self, key=""):
try:
del self.cache[key]
except KeyError:
pass
class MemoryCacheDecorator(CacheDecorator):
"""In-memory cache"""
def __init__(self, func, keyarg, maxage):
CacheDecorator.__init__(self, func, keyarg)
self.maxage = maxage
def __call__(self, *args, **kwargs):
key = "" if self.keyarg is None else args[self.keyarg]
timestamp = int(time.time())
try:
value, expires = self.cache[key]
except KeyError:
expires = 0
if expires < timestamp:
value = self.func(*args, **kwargs)
expires = timestamp + self.maxage
self.cache[key] = value, expires
return value
def update(self, key, value):
self.cache[key] = value, int(time.time()) + self.maxage
class DatabaseCacheDecorator():
"""Database cache"""
db = None
_init = True
def __init__(self, func, keyarg, maxage):
self.key = "%s.%s" % (func.__module__, func.__name__)
self.func = func
self.cache = {}
self.keyarg = keyarg
self.maxage = maxage
def __get__(self, obj, objtype):
return functools.partial(self.__call__, obj)
def __call__(self, *args, **kwargs):
key = "" if self.keyarg is None else args[self.keyarg]
timestamp = int(time.time())
# in-memory cache lookup
try:
value, expires = self.cache[key]
if expires > timestamp:
return value
except KeyError:
pass
# database lookup
fullkey = "%s-%s" % (self.key, key)
with self.database() as db:
cursor = db.cursor()
try:
cursor.execute("BEGIN EXCLUSIVE")
except sqlite3.OperationalError:
pass # Silently swallow exception - workaround for Python 3.6
cursor.execute(
"SELECT value, expires FROM data WHERE key=? LIMIT 1",
(fullkey,),
)
result = cursor.fetchone()
if result and result[1] > timestamp:
value, expires = result
value = pickle.loads(value)
else:
value = self.func(*args, **kwargs)
expires = timestamp + self.maxage
cursor.execute(
"INSERT OR REPLACE INTO data VALUES (?,?,?)",
(fullkey, pickle.dumps(value), expires),
)
self.cache[key] = value, expires
return value
def update(self, key, value):
expires = int(time.time()) + self.maxage
self.cache[key] = value, expires
with self.database() as db:
db.execute(
"INSERT OR REPLACE INTO data VALUES (?,?,?)",
("%s-%s" % (self.key, key), pickle.dumps(value), expires),
)
def invalidate(self, key):
try:
del self.cache[key]
except KeyError:
pass
with self.database() as db:
db.execute(
"DELETE FROM data WHERE key=?",
("%s-%s" % (self.key, key),),
)
def database(self):
if self._init:
self.db.execute(
"CREATE TABLE IF NOT EXISTS data "
"(key TEXT PRIMARY KEY, value TEXT, expires INTEGER)"
)
DatabaseCacheDecorator._init = False
return self.db
def memcache(maxage=None, keyarg=None):
if maxage:
def wrap(func):
return MemoryCacheDecorator(func, keyarg, maxage)
else:
def wrap(func):
return CacheDecorator(func, keyarg)
return wrap
def cache(maxage=3600, keyarg=None):
def wrap(func):
return DatabaseCacheDecorator(func, keyarg, maxage)
return wrap
def clear():
"""Delete all database entries"""
db = DatabaseCacheDecorator.db
if db:
rowcount = 0
cursor = db.cursor()
try:
cursor.execute("DELETE FROM data")
except sqlite3.OperationalError:
pass # database is not initialized, can't be modified, etc.
else:
rowcount = cursor.rowcount
db.commit()
cursor.execute("VACUUM")
return rowcount
return None
def _path():
path = config.get(("cache",), "file", -1)
if path != -1:
return util.expand_path(path)
if os.name == "nt":
import tempfile
return os.path.join(tempfile.gettempdir(), ".gallery-dl.cache")
cachedir = util.expand_path(os.path.join(
os.environ.get("XDG_CACHE_HOME", "~/.cache"), "gallery-dl"))
os.makedirs(cachedir, exist_ok=True)
return os.path.join(cachedir, "cache.sqlite3")
try:
dbfile = _path()
if os.name != "nt":
# restrict access permissions for new db files
os.close(os.open(dbfile, os.O_CREAT | os.O_RDONLY, 0o600))
DatabaseCacheDecorator.db = sqlite3.connect(
dbfile, timeout=30, check_same_thread=False)
except (OSError, TypeError, sqlite3.OperationalError):
cache = memcache # noqa: F811
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