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| Rev | Author | Line No. | Line |
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| 15 | arune | 1 | /** |
| 2 | * File created by Jimmy |
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| 3 | * at 2003-dec-28 19:50:12 |
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| 4 | */ |
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| 5 | package Macbeth.System; |
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| 6 | |||
| 7 | import java.io.PrintStream; |
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| 8 | |||
| 9 | /** |
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| 10 | * A packet transport plugs directly into the kernel and helps |
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| 11 | * it delivering packets via different transports. For instance, |
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| 12 | * a local transport might deliver a packet directly to the |
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| 13 | * destination module within the local kernel, while an internet |
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| 14 | * transport might send the packet to a kernel on a remote location. |
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| 15 | * Packet transports primarily send packets, but they can of |
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| 16 | * course also receive packets on their own, and when they do, they |
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| 17 | * can simply tell the kernel to put the new, received, packet onto |
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| 18 | * the standard packet queue by calling the packetReceived-method |
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| 19 | * declared in this class. |
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| 20 | */ |
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| 21 | public abstract class MbPacketTransport { |
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| 22 | //reference to our parent kernel object |
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| 23 | protected MbKernel parentKernel; |
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| 24 | //references to output streams |
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| 25 | protected PrintStream _debug,_info,_errors; |
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| 26 | |||
| 27 | //counts how many packets this transport has sent/received |
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| 28 | public int packetsSent = 0; |
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| 29 | public int packetsReceived = 0; |
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| 30 | |||
| 31 | /** |
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| 32 | * Creates a new instance of MbPacketTransport. |
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| 33 | * @param parentKernel Reference to the parent kernel object. |
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| 34 | */ |
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| 35 | public MbPacketTransport(MbKernel parentKernel) { |
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| 36 | this.parentKernel = parentKernel; |
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| 37 | } |
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| 38 | |||
| 39 | /** |
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| 40 | * Will be called by the kernel when it has a new packet that |
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| 41 | * needs to be delivered. The kernel has a list of packet |
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| 42 | * transport systems, and typically it will try to invoke them |
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| 43 | * in the same order as they were added to that list. In other |
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| 44 | * words, there is no way you can tell whether one packet |
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| 45 | * transport will be invoked before another one. Therefore, it is |
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| 46 | * very important that you return false here if you cannot deliver |
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| 47 | * the current packet. The kernel will then try with the next |
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| 48 | * transport in list. If, and only if, none of the transports |
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| 49 | * could deliver the packet, the kernel will drop it. |
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| 50 | * @param p The packet that needs to be delivered. |
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| 51 | * @return False if this packet transport cannot perform delivery |
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| 52 | * on the specified packet. True if the packets has been delivered |
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| 53 | * successfully. When you return true, the packet is considered |
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| 54 | * delivered, and no further transports will be invoked. |
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| 55 | * @throws MbPacketDeliveryException if an error occured while trying |
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| 56 | * to deliver the packet. |
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| 57 | */ |
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| 58 | public abstract boolean deliverPacket(MbPacket p) throws MbPacketDeliveryException; |
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| 59 | |||
| 60 | /** |
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| 61 | * Override this if you need to perform anything particular |
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| 62 | * during kernel startup. |
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| 63 | */ |
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| 64 | public void startup() { |
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| 65 | //keep references to output streams |
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| 66 | _debug = parentKernel._debug; |
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| 67 | _info = parentKernel._info; |
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| 68 | _errors = parentKernel._errors; |
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| 69 | } |
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| 70 | |||
| 71 | /** |
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| 72 | * Override this if you need to perform anything particular |
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| 73 | * during kernel shutdown. |
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| 74 | */ |
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| 75 | public void shutdown() {} |
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| 76 | |||
| 77 | /** |
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| 78 | * Returns the name of this transport. This is only used by |
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| 79 | * kernel to show user-friendly information. |
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| 80 | * @return The name of this transport. |
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| 81 | */ |
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| 82 | public abstract String getName(); |
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| 83 | |||
| 84 | /** |
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| 85 | * Call this method if you have received a new, incoming, |
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| 86 | * packet via your transport and need to handle it over to |
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| 87 | * the kernel. This is useful for bidirectional delivery |
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| 88 | * systems. |
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| 89 | * @param p The new packet that you have received. |
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| 90 | */ |
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| 91 | protected void packetReceived(MbPacket p) { |
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| 92 | //put this packet onto the kernel packet queue |
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| 93 | parentKernel.packetReceived(p); |
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| 94 | //increase packets received-counter |
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| 95 | packetsReceived++; |
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| 96 | } |
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| 97 | |||
| 98 | /** |
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| 99 | * Thrown when a packet couldn't be delivered properly. |
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| 100 | */ |
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| 101 | public class MbPacketDeliveryException extends Exception { |
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| 102 | /** |
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| 103 | * Creates a new instance of MbPacketDeliveryException |
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| 104 | * @param s The reason of this exception. |
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| 105 | */ |
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| 106 | public MbPacketDeliveryException(String s) { |
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| 107 | super(s); |
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| 108 | } |
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| 109 | } |
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| 110 | } |