| 1 | /* |
| 2 | * SPDX-License-Identifier: LGPL-2.1-only |
| 3 | * |
| 4 | * Copyright (C) 2015-2016 EfficiOS Inc. |
| 5 | * Copyright (C) 2015-2016 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.charset.Charset; |
| 13 | |
| 14 | /** |
| 15 | * Base class to represent all commands sent from the session daemon to the Java |
| 16 | * agent. The agent is then expected to execute the command and provide a |
| 17 | * response. |
| 18 | * |
| 19 | * @author Alexandre Montplaisir |
| 20 | */ |
| 21 | abstract class SessiondCommand { |
| 22 | |
| 23 | /** |
| 24 | * Encoding that should be used for the strings in the sessiond agent |
| 25 | * protocol on the socket. |
| 26 | */ |
| 27 | protected static final Charset SESSIOND_PROTOCOL_CHARSET = Charset.forName("UTF-8"); |
| 28 | |
| 29 | enum CommandType { |
| 30 | /** List logger(s). */ |
| 31 | CMD_LIST(1), |
| 32 | /** Enable logger by name. */ |
| 33 | CMD_EVENT_ENABLE(2), |
| 34 | /** Disable logger by name. */ |
| 35 | CMD_EVENT_DISABLE(3), |
| 36 | /** Registration done */ |
| 37 | CMD_REG_DONE(4), |
| 38 | /** Enable application context */ |
| 39 | CMD_APP_CTX_ENABLE(5), |
| 40 | /** Disable application context */ |
| 41 | CMD_APP_CTX_DISABLE(6); |
| 42 | |
| 43 | private int code; |
| 44 | |
| 45 | private CommandType(int c) { |
| 46 | code = c; |
| 47 | } |
| 48 | |
| 49 | public int getCommandType() { |
| 50 | return code; |
| 51 | } |
| 52 | } |
| 53 | |
| 54 | /** |
| 55 | * Execute the command handler's action on the specified tracing agent. |
| 56 | * |
| 57 | * @param agent |
| 58 | * The agent on which to execute the command |
| 59 | * @return If the command completed successfully or not |
| 60 | */ |
| 61 | public abstract LttngAgentResponse execute(ILttngTcpClientListener agent); |
| 62 | |
| 63 | /** |
| 64 | * Utility method to read agent-protocol strings passed on the socket. The |
| 65 | * buffer will contain a 32-bit integer representing the length, immediately |
| 66 | * followed by the string itself. |
| 67 | * |
| 68 | * @param buffer |
| 69 | * The ByteBuffer from which to read. It should already be setup |
| 70 | * and positioned where the read should begin. |
| 71 | * @return The string that was read, or <code>null</code> if it was badly |
| 72 | * formatted. |
| 73 | */ |
| 74 | protected static String readNextString(ByteBuffer buffer) { |
| 75 | int nbBytes = buffer.getInt(); |
| 76 | if (nbBytes < 0) { |
| 77 | /* The string length should be positive */ |
| 78 | return null; |
| 79 | } |
| 80 | if (nbBytes == 0) { |
| 81 | /* The string is explicitly an empty string */ |
| 82 | return ""; |
| 83 | } |
| 84 | |
| 85 | byte[] stringBytes = new byte[nbBytes]; |
| 86 | buffer.get(stringBytes); |
| 87 | return new String(stringBytes, SESSIOND_PROTOCOL_CHARSET).trim(); |
| 88 | } |
| 89 | } |