1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
(** Semaphores *)
type sem = {
mut: Mutex.t;
mutable v: int;
nonzero: Condition.t
}
module Counting = struct
type t = sem
let make v =
if v < 0 then invalid_arg "Semaphore.Counting.init: wrong initial value";
{ mut = Mutex.create(); v; nonzero = Condition.create() }
let release s =
Mutex.lock s.mut;
if s.v < max_int then begin
s.v <- s.v + 1;
Condition.signal s.nonzero;
Mutex.unlock s.mut
end else begin
Mutex.unlock s.mut;
raise (Sys_error "Semaphore.Counting.release: overflow")
end
let acquire s =
Mutex.lock s.mut;
while s.v = 0 do Condition.wait s.nonzero s.mut done;
s.v <- s.v - 1;
Mutex.unlock s.mut
let try_acquire s =
Mutex.lock s.mut;
let ret = if s.v = 0 then false else (s.v <- s.v - 1; true) in
Mutex.unlock s.mut;
ret
let get_value s = s.v
end
module Binary = struct
type t = sem
let make b =
{ mut = Mutex.create();
v = if b then 1 else 0;
nonzero = Condition.create() }
let release s =
Mutex.lock s.mut;
s.v <- 1;
Condition.signal s.nonzero;
Mutex.unlock s.mut
let acquire s =
Mutex.lock s.mut;
while s.v = 0 do Condition.wait s.nonzero s.mut done;
s.v <- 0;
Mutex.unlock s.mut
let try_acquire s =
Mutex.lock s.mut;
let ret = if s.v = 0 then false else (s.v <- 0; true) in
Mutex.unlock s.mut;
ret
end