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   1 /**
   2  * Copyright (c) 2010-2023 Contributors to the openHAB project
   3  *
   4  * See the NOTICE file(s) distributed with this work for additional
   5  * information.
   6  *
   7  * This program and the accompanying materials are made available under the
   8  * terms of the Eclipse Public License 2.0 which is available at
   9  * http://www.eclipse.org/legal/epl-2.0
  10  *
  11  * SPDX-License-Identifier: EPL-2.0
  12  */
  13 package org.openhab.binding.velbus.internal;
  14
  15 import java.io.IOException;
  16 import java.io.InputStream;
  17 import java.util.ArrayList;
  18
  19 import org.eclipse.jdt.annotation.NonNullByDefault;
  20 import org.eclipse.jdt.annotation.Nullable;
  21 import org.openhab.binding.velbus.internal.packets.VelbusPacket;
  22 import org.slf4j.Logger;
  23 import org.slf4j.LoggerFactory;
  24
  25 /**
  26  * The {@link VelbusPacketInputStream} is a wrapper around an InputStream that
  27  * aggregates bytes from the input stream to meaningfull packets in the Velbus system.
  28  *
  29  * @author Cedric Boon - Initial contribution
  30  */
  31 @NonNullByDefault
  32 public class VelbusPacketInputStream {
  33     private final Logger logger = LoggerFactory.getLogger(VelbusPacketInputStream.class);
  34
  35     public InputStream inputStream;
  36
  37     private ArrayList<Byte> currentData = new ArrayList<Byte>();
  38     private @Nullable Byte currentSTX = null;
  39     private @Nullable Byte currentPriority = null;
  40     private @Nullable Byte currentAddress = null;
  41     private @Nullable Byte currentDataLength = null;
  42     private @Nullable Byte currentChecksum = null;
  43
  44     public VelbusPacketInputStream(InputStream inputStream) {
  45         this.inputStream = inputStream;
  46     }
  47
  48     public byte[] readPacket() throws IOException {
  49         int currentDataByte;
  50
  51         while ((currentDataByte = inputStream.read()) > -1) {
  52             if (currentSTX == null) {
  53                 if (((byte) currentDataByte) == VelbusPacket.STX) {
  54                     currentSTX = (byte) currentDataByte;
  55                 } else {
  56                     resetCurrentState();
  57                     logger.debug("Packet with invalid start byte: {}", currentDataByte);
  58                 }
  59             } else if (currentPriority == null) {
  60                 if (((byte) currentDataByte) == VelbusPacket.PRIO_HI
  61                         || ((byte) currentDataByte) == VelbusPacket.PRIO_LOW) {
  62                     currentPriority = (byte) currentDataByte;
  63                 } else {
  64                     resetCurrentState();
  65                     logger.debug("Packet with invalid priority received: {}", currentDataByte);
  66                 }
  67             } else if (currentAddress == null) {
  68                 currentAddress = (byte) currentDataByte;
  69             } else if (currentDataLength == null && currentDataByte <= 8) {
  70                 currentDataLength = (byte) currentDataByte;
  71             } else if (currentDataLength == null) {
  72                 currentDataLength = 1;
  73                 currentData.add((byte) currentDataByte);
  74             } else if (currentDataLength != null && (currentData.size() < currentDataLength)) {
  75                 currentData.add((byte) currentDataByte);
  76             } else if (currentChecksum == null) {
  77                 currentChecksum = (byte) currentDataByte;
  78                 byte[] packet = getCurrentPacket();
  79                 byte expectedChecksum = VelbusPacket.computeCRCByte(packet);
  80
  81                 if (currentChecksum != expectedChecksum) {
  82                     resetCurrentState();
  83                     logger.debug("Packet with invalid checksum received: {} instead of {}", currentChecksum,
  84                             expectedChecksum);
  85                 }
  86             } else if (((byte) currentDataByte) == VelbusPacket.ETX) {
  87                 byte[] packet = getCurrentPacket();
  88
  89                 resetCurrentState();
  90
  91                 return packet;
  92             } else {
  93                 resetCurrentState();
  94                 logger.debug("Packet with invalid ETX received: {}", currentDataByte);
  95             }
  96         }
  97
  98         return new byte[0];
  99     }
 100
 101     public void close() throws IOException {
 102         inputStream.close();
 103     }
 104
 105     protected byte[] getCurrentPacket() {
 106         if (currentDataLength != null && currentSTX != null && currentPriority != null && currentAddress != null
 107                 && currentChecksum != null) {
 108             byte[] packet = new byte[6 + currentDataLength];
 109             packet[0] = currentSTX;
 110             packet[1] = currentPriority;
 111             packet[2] = currentAddress;
 112             packet[3] = currentDataLength;
 113
 114             for (int i = 0; i < currentDataLength; i++) {
 115                 packet[4 + i] = currentData.get(i);
 116             }
 117
 118             packet[4 + currentDataLength] = currentChecksum;
 119             packet[5 + currentDataLength] = VelbusPacket.ETX;
 120
 121             return packet;
 122         }
 123
 124         return new byte[0];
 125     }
 126
 127     protected void resetCurrentState() {
 128         currentSTX = null;
 129         currentPriority = null;
 130         currentAddress = null;
 131         currentDataLength = null;
 132         currentData = new ArrayList<>();
 133         currentChecksum = null;
 134     }
 135 }