gomemif: introduce gomemif

[vpp.git] / extras / gomemif / memif / packet_writer.go

diff --git a/extras/gomemif/memif/packet_writer.go b/extras/gomemif/memif/packet_writer.go
new file mode 100644 (file)
index 0000000..702044f
--- /dev/null
+++ b/extras/gomemif/memif/packet_writer.go
@@ -0,0 +1,95 @@
+/*
+ *------------------------------------------------------------------
+ * 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
+
+// WritePacket writes one packet to the shared memory and
+// returns the number of bytes written
+func (q *Queue) WritePacket(pkt []byte) int {
+       var mask int = q.ring.size - 1
+       var slot int
+       var nFree uint16
+       var packetBufferSize int = int(q.i.run.PacketBufferSize)
+
+       if q.i.args.IsMaster {
+               slot = q.readTail()
+               nFree = uint16(q.readHead() - slot)
+       } else {
+               slot = q.readHead()
+               nFree = uint16(q.ring.size - slot + q.readTail())
+       }
+
+       if nFree == 0 {
+               q.interrupt()
+               return 0
+       }
+
+       // copy descriptor from shm
+       desc := newDescBuf()
+       q.getDescBuf(slot&mask, desc)
+       // reset flags
+       desc.setFlags(0)
+       // reset length
+       if q.i.args.IsMaster {
+               packetBufferSize = desc.getLength()
+       }
+       desc.setLength(0)
+       offset := desc.getOffset()
+
+       // write packet into memif buffer
+       n := copy(q.i.regions[desc.getRegion()].data[offset:offset+packetBufferSize], pkt[:])
+       desc.setLength(n)
+       for n < len(pkt) {
+               nFree--
+               if nFree == 0 {
+                       q.interrupt()
+                       return 0
+               }
+               desc.setFlags(descFlagNext)
+               q.putDescBuf(slot&mask, desc)
+               slot++
+
+               // copy descriptor from shm
+               q.getDescBuf(slot&mask, desc)
+               // reset flags
+               desc.setFlags(0)
+               // reset length
+               if q.i.args.IsMaster {
+                       packetBufferSize = desc.getLength()
+               }
+               desc.setLength(0)
+               offset := desc.getOffset()
+
+               tmp := copy(q.i.regions[desc.getRegion()].data[offset:offset+packetBufferSize], pkt[:])
+               desc.setLength(tmp)
+               n += tmp
+       }
+
+       // copy descriptor to shm
+       q.putDescBuf(slot&mask, desc)
+       slot++
+
+       if q.i.args.IsMaster {
+               q.writeTail(slot)
+       } else {
+               q.writeHead(slot)
+       }
+
+       q.interrupt()
+
+       return n
+}