blob: 997dc4ae203a73511653ff9623f1fdbe7e29eeb0 (
plain)
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
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
|
package main
import (
"time"
"sync"
)
const (
addAction = 0
removeAction = 1
moveUpAction = 2
moveDownAction = 3
)
type Update struct {
Song *Song
Action uint
Timestamp int64
Next *Update
}
type Listener struct {
L chan bool
Next *Listener
}
var headUpdates map[int]*Update
var tailUpdates map[int]*Update
var listeners map[int]*Listener
var updateLock sync.Mutex
func init() {
headUpdates = make(map[int]*Update)
tailUpdates = make(map[int]*Update)
listeners = make(map[int]*Listener)
}
func addUpdate(pid int, action uint, song *Song) {
update := new(Update)
update.Song = song
update.Action = action
update.Timestamp = time.Nanoseconds()
updateLock.Lock()
defer updateLock.Unlock()
// write new update
pup := tailUpdates[pid]
if pup != nil {
pup.Next = update
} else {
headUpdates[pid] = update
}
tailUpdates[pid] = update
// expire old updates
const expiryTime = 1e9 * 3 * 60 // 3 minutes
pup = headUpdates[pid]
for pup != nil && pup.Timestamp < update.Timestamp - expiryTime {
pup = pup.Next
headUpdates[pid] = pup
}
// notify listeners
listener := listeners[pid]
for listener != nil {
listener.L <- true
listener = listener.Next
}
listeners[pid] = nil
}
// assumes caller has updateLock
func checkUpdates(pid int, timestamp int64) *Update {
pup, _ := headUpdates[pid]
for pup != nil {
if pup.Timestamp > timestamp {
return pup
}
pup = pup.Next
}
return nil
}
func getUpdates(id string, timestamp int64) *Update {
db := <-dbPool
pid := getpid(db, id)
dbPool <- db
if pid == -1 {
return nil
}
updateLock.Lock()
pup := checkUpdates(pid, timestamp)
if pup != nil {
updateLock.Unlock()
return pup
}
// didn't get updates
listener := new(Listener)
listener.L = make(chan bool)
lhead := listeners[pid]
if lhead != nil {
listener.Next = lhead
}
listeners[pid] = listener
updateLock.Unlock()
<-listener.L
updateLock.Lock()
pup = checkUpdates(pid, timestamp)
updateLock.Unlock()
return pup
}
|
