Use simple Transport interface

kotlin-mbedtls/src/main/kotlin/org/opencoap/ssl/transport/DatagramChannelAdapter.kt

@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2022 kotlin-mbedtls contributors (https://github.com/open-coap/kotlin-mbedtls)
+ * SPDX-License-Identifier: Apache-2.0
+ * 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 org.opencoap.ssl.transport
+
+import java.net.InetSocketAddress
+import java.nio.ByteBuffer
+import java.nio.channels.DatagramChannel
+import java.nio.channels.SelectionKey
+import java.nio.channels.Selector
+import java.time.Duration
+import java.util.concurrent.CompletableFuture
+import java.util.concurrent.CompletableFuture.completedFuture
+import java.util.concurrent.Executors
+
+class DatagramChannelAdapter(
+    private val channel: DatagramChannel,
+    private val buffer: ByteBuffer = ByteBuffer.allocateDirect(16384)
+) : Transport<ByteBufferPacket> {
+
+    companion object {
+        fun open(port: Int = 0): Transport<ByteBufferPacket> {
+            val datagramChannel = DatagramChannel.open().bind(InetSocketAddress("0.0.0.0", port))
+            return DatagramChannelAdapter(datagramChannel)
+        }
+
+        fun connect(dest: InetSocketAddress, listenPort: Int = 0): Transport<ByteBuffer> {
+            val channel: DatagramChannel = DatagramChannel.open()
+            if (listenPort > 0) channel.bind(InetSocketAddress("0.0.0.0", listenPort))
+            channel.connect(dest)
+
+            return DatagramChannelAdapter(channel).map(ByteBufferPacket::buffer) { ByteBufferPacket(it, dest) }
+        }
+    }
+
+    private val selector: Selector = Selector.open()
+    private val port get() = (channel.localAddress as InetSocketAddress).port
+    private val executor = Executors.newSingleThreadExecutor { Thread(it, "udp-io (:$port)") }
+
+    init {
+        channel.configureBlocking(false)
+        channel.register(selector, SelectionKey.OP_READ)
+    }
+
+    override fun receive(timeout: Duration): CompletableFuture<ByteBufferPacket> {
+        return executor.supply {
+            selector.select(timeout.toMillis())
+            buffer.clear()
+
+            val sourceAddress = channel.receive(buffer)
+            if (sourceAddress == null) {
+                Packet.EmptyByteBufferPacket
+            } else {
+                buffer.flip()
+                Packet(buffer, sourceAddress as InetSocketAddress)
+            }
+        }
+    }
+
+    override fun send(packet: Packet<ByteBuffer>): CompletableFuture<Boolean> {
+        return try {
+            completedFuture(channel.send(packet.buffer, packet.peerAddress) > 0)
+        } catch (ex: Exception) {
+            CompletableFuture<Boolean>().also { it.completeExceptionally(ex) }
+        }
+    }
+
+    override fun close() {
+        channel.close()
+        selector.close()
+        executor.shutdown()
+    }
+
+    override fun localPort() = (channel.localAddress as InetSocketAddress).port
+}