Typo fix.
[didex.git] / didex / cache.py
CommitLineData
b080a59c
FT
1import threading, weakref
2
3class entry(object):
4 __slots__ = ["p", "n", "id", "obj", "st", "lk"]
5 def __init__(self, id, c):
6 self.id = id
7 self.obj = None
8 self.st = None
9 self.lk = None
10 self.n = c.mru
11 self.p = None
12 if c.mru is not None:
13 c.mru.p = self
14 c.mru = self
15 else:
16 c.mru = c.lru = self
17 c.n += 1
18
19 def relink(self, c):
20 if c.mru is self:
21 return
22 if self.n is not None:
23 self.n.p = self.p
24 self.p.n = self.n
25 if c.lru is self:
26 c.lru = self.p
27 self.p = None
28 self.n = c.mru
29 c.mru.p = self
3e3af3c5 30 c.mru = self
b080a59c
FT
31
32 def remove(self, c):
33 if self.n is not None:
34 self.n.p = self.p
35 if self.p is not None:
36 self.p.n = self.n
37 if c.mru is self:
38 c.mru = self.n
39 if c.lru is self:
40 c.lru = self.p
41 c.n -= 1
42
43class cache(object):
44 def __init__(self, *, keep=1000):
45 self.keep = keep
46 self.cur = {}
47 self.mru = self.lru = None
48 self.n = 0
49 self.lk = threading.Lock()
50
51 def _trim(self, n):
52 ent = self.lru
53 for i in range(self.n - n):
54 if ent.st == "l":
55 ent.obj = weakref.ref(ent.obj)
56 ent.st = "w"
57 elif ent.st == "w" and ent.obj() is None:
58 del self.cur[ent.id]
59 ent.remove(self)
60 ent.st = "r"
61 ent = ent.p
62
63 def get(self, id, load=True):
64 while True:
65 with self.lk:
66 ent = self.cur.get(id)
67 if ent is None:
68 if not load:
69 raise KeyError(id)
70 self.cur[id] = ent = entry(id, self)
71 ent.lk = lk = threading.Lock()
72 ent.st = "ld"
73 st = None
74 self._trim(self.keep)
75 elif ent.st == "l":
76 ent.relink(self)
77 return ent.obj
78 elif ent.st == "w":
79 ret = ent.obj()
80 if ret is None:
81 del self.cur[id]
82 ent.remove(self)
83 ent.st = "r"
84 continue
85 return ret
86 elif ent.st == "ld":
87 lk = ent.lk
88 st = "ld"
89 if lk is None:
90 continue
91 elif ent.st == "r":
92 continue
93 with lk:
94 if st is None:
95 try:
96 ret = ent.obj = self.load(id)
97 ent.st = "l"
98 return ret
99 except:
100 with self.lk:
101 del self.cur[id]
102 ent.remove(self)
103 ent.st = "r"
104 raise
105 finally:
106 ent.lk = None
107 elif st == "ld":
108 continue
109
110 def put(self, id, ob):
111 while True:
112 with self.lk:
113 ent = self.cur.get(id)
114 if ent is None:
115 self.cur[id] = ent = entry(id, self)
116 ent.obj = ob
117 ent.st = "l"
118 self._trim(self.keep)
119 return
120 elif ent.st == "l":
121 ent.obj = ob
122 return
123 elif ent.st == "w":
124 ent.obj = ob
125 return
126 elif ent.st == "r":
127 continue
128 elif ent.st == "ld":
129 lk = ent.lk
130 if lk is None:
131 continue
132 with lk:
133 continue
134
135 def remove(self, id):
136 while True:
137 with self.lk:
138 ent = self.cur.get(id)
139 if ent is None:
140 return
141 elif ent.st == "ld":
142 lk = ent.lk
143 if lk is None:
144 continue
145 else:
146 del self.cur[id]
147 ent.remove(self)
148 ent.st = "r"
149 return
150 with lk:
151 continue
152
153 def load(self, id):
154 raise KeyError()