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-rw-r--r--extras/gomemif/memif/packet_reader.go91
1 files changed, 91 insertions, 0 deletions
diff --git a/extras/gomemif/memif/packet_reader.go b/extras/gomemif/memif/packet_reader.go
new file mode 100644
index 00000000000..58338f6f2ab
--- /dev/null
+++ b/extras/gomemif/memif/packet_reader.go
@@ -0,0 +1,91 @@
+/*
+ *------------------------------------------------------------------
+ * 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
+}