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
|
/*
*------------------------------------------------------------------
* Copyright (c) 2020 Cisco and/or its affiliates.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*------------------------------------------------------------------
*/
package memif
import "fmt"
// ReadPacket reads one packet form the shared memory and
// returns the number of bytes read
func (q *Queue) ReadPacket(pkt []byte) (int, error) {
var mask int = q.ring.size - 1
var slot int
var lastSlot int
var length int
var offset int
var pktOffset int = 0
var nSlots uint16
var desc descBuf = newDescBuf()
if q.i.args.IsMaster {
slot = int(q.lastHead)
lastSlot = q.readHead()
} else {
slot = int(q.lastTail)
lastSlot = q.readTail()
}
nSlots = uint16(lastSlot - slot)
if nSlots == 0 {
goto refill
}
// copy descriptor from shm
q.getDescBuf(slot&mask, desc)
length = desc.getLength()
offset = desc.getOffset()
copy(pkt[:], q.i.regions[desc.getRegion()].data[offset:offset+length])
pktOffset += length
slot++
nSlots--
for (desc.getFlags() & descFlagNext) == descFlagNext {
if nSlots == 0 {
return 0, fmt.Errorf("Incomplete chained buffer, may suggest peer error.")
}
q.getDescBuf(slot&mask, desc)
length = desc.getLength()
offset = desc.getOffset()
copy(pkt[pktOffset:], q.i.regions[desc.getRegion()].data[offset:offset+length])
pktOffset += length
slot++
nSlots--
}
refill:
if q.i.args.IsMaster {
q.lastHead = uint16(slot)
q.writeTail(slot)
} else {
q.lastTail = uint16(slot)
head := q.readHead()
for nSlots := uint16(q.ring.size - head + int(q.lastTail)); nSlots > 0; nSlots-- {
q.setDescLength(head&mask, int(q.i.run.PacketBufferSize))
head++
}
q.writeHead(head)
}
return pktOffset, nil
}
|
