/
flock.cr
61 lines (51 loc) · 1.44 KB
/
flock.cr
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
# TODO: use fcntl/lockf instead of flock (which doesn't lock over NFS)
# TODO: always use non-blocking locks, yield fiber until resource becomes available
lib LibC
@[Flags]
enum FlockOp
SH = 0x1
EX = 0x2
NB = 0x4
UN = 0x8
end
fun flock(fd : Int, op : FlockOp) : Int
end
class File
def flock_shared(blocking = true)
flock_shared blocking
begin
yield
ensure
flock_unlock
end
end
# Place a shared advisory lock. More than one process may hold a shared lock for a given file at a given time.
# Errno::EWOULDBLOCK is raised if *blocking* is set to `false` and an existing exclusive lock is set.
def flock_shared(blocking = true)
flock LibC::FlockOp::SH, blocking
end
def flock_exclusive(blocking = true)
flock_exclusive blocking
begin
yield
ensure
flock_unlock
end
end
# Place an exclusive advisory lock. Only one process may hold an exclusive lock for a given file at a given time.
# Errno::EWOULDBLOCK is raised if *blocking* is set to `false` and any existing lock is set.
def flock_exclusive(blocking = true)
flock LibC::FlockOp::EX, blocking
end
# Remove an existing advisory lock held by this process.
def flock_unlock
flock LibC::FlockOp::UN
end
private def flock(op : LibC::FlockOp, blocking : Bool = true)
op |= LibC::FlockOp::NB unless blocking
if LibC.flock(@fd, op) != 0
raise Errno.new("flock")
end
nil
end
end