liblttng-ust-java-agent/java/lttng-ust-agent-common/org/lttng/ust/agent/client/SessiondListLoggersCommand.java

   1 /*
   2  * SPDX-License-Identifier: LGPL-2.1-only
   3  *
   4  * Copyright (C) 2015 EfficiOS Inc.
   5  * Copyright (C) 2015 Alexandre Montplaisir <alexmonthy@efficios.com>
   6  * Copyright (C) 2013 David Goulet <dgoulet@efficios.com>
   7  */
   8
   9 package org.lttng.ust.agent.client;
  10
  11 import java.nio.ByteBuffer;
  12 import java.nio.ByteOrder;
  13 import java.util.Collection;
  14
  15 /**
  16  * Session daemon command asking the Java agent to list its registered loggers,
  17  * which corresponds to event names in the tracing session.
  18  *
  19  * @author Alexandre Montplaisir
  20  * @author David Goulet
  21  */
  22 class SessiondListLoggersCommand extends SessiondCommand {
  23
  24         @Override
  25         public LttngAgentResponse execute(ILttngTcpClientListener agent) {
  26                 final Collection<String> loggerList = agent.listAvailableEvents();
  27                 return new SessiondListLoggersResponse(loggerList);
  28         }
  29
  30         private static class SessiondListLoggersResponse extends LttngAgentResponse {
  31
  32                 private final static int SIZE = 12;
  33
  34                 private final Collection<String> loggers;
  35
  36                 public SessiondListLoggersResponse(Collection<String> loggers) {
  37                         this.loggers = loggers;
  38                 }
  39
  40                 @Override
  41                 public ReturnCode getReturnCode() {
  42                         /* This command can't really fail */
  43                         return ReturnCode.CODE_SUCCESS_CMD;
  44                 }
  45
  46                 @Override
  47                 public byte[] getBytes() {
  48                         /*
  49                          * Compute the data size, which is the number of bytes of each
  50                          * encoded string, +1 per string for the \0
  51                          */
  52                         int dataSize = 0;
  53                         for (String logger : loggers) {
  54                                 dataSize += logger.getBytes(SESSIOND_PROTOCOL_CHARSET).length + 1;
  55                         }
  56
  57                         /* Prepare the buffer */
  58                         byte data[] = new byte[SIZE + dataSize];
  59                         ByteBuffer buf = ByteBuffer.wrap(data);
  60                         buf.order(ByteOrder.BIG_ENDIAN);
  61
  62                         /* Write the header section of the response */
  63                         buf.putInt(getReturnCode().getCode());
  64                         buf.putInt(dataSize);
  65                         buf.putInt(loggers.size());
  66
  67                         /* Write the payload */
  68                         for (String logger : loggers) {
  69                                 buf.put(logger.getBytes(SESSIOND_PROTOCOL_CHARSET));
  70                                 /* NULL terminated byte after the logger name. */
  71                                 buf.put((byte) 0x0);
  72                         }
  73                         return data;
  74                 }
  75         }
  76
  77 }