DLT：dlt-daemon示例解析

dlt-daemon中带有一些示例程序，路径为dlt-daemon/examples/，这里对example1进行解析。

这个示例展示了怎样创建dlt程序，包括注册和取消注册，发送log等。log的值可通过dlt-viewer查看。

dlt对一些函数用宏进行了封装，这样可以减少开发的代码量。

示例1：

//example1.cpp
#include <stdio.h>      /* for printf() and fprintf() */
#include <stdlib.h>     /* for atoi() and exit() */

#include <dlt.h>

DLT_DECLARE_CONTEXT(con_exa1);

int main()
{
    struct timespec ts;

    DLT_REGISTER_APP("app1", "First Example");

    DLT_REGISTER_CONTEXT(con_exa1, "con1", "First context");

    DLT_LOG(con_exa1, DLT_LOG_INFO, DLT_STRING("Hello world! This is first example"));

    ts.tv_sec = 1;
    ts.tv_nsec = 1000000;
    nanosleep(&ts, NULL);

    DLT_UNREGISTER_CONTEXT(con_exa1);

  //CMakeLists.txt
#######
# SPDX license identifier: MPL-2.0
#
# Copyright (C) 2011-2015, BMW AG
#
# This file is part of GENIVI Project DLT - Diagnostic Log and Trace.
#
# This Source Code Form is subject to the terms of the
# Mozilla Public License (MPL), v. 2.0.
# If a copy of the MPL was not distributed with this file,
# You can obtain one at http://mozilla.org/MPL/2.0/.
#
# For further information see http://www.genivi.org/.
#######

#
# DLT example implementation
#

cmake_minimum_required( VERSION 2.6 )
project( automotive-dlt-example1 )

#
# find dependency packages
#

find_package(PkgConfig)
pkg_check_modules(DLT REQUIRED automotive-dlt)

#
# include directories
#

include_directories(
    ${DLT_INCLUDE_DIRS}
)

#
# build project
#

set(dlt_example1_SRCS example1.c)
add_executable(dlt-example1 ${dlt_example1_SRCS})
target_link_libraries(dlt-example1 ${DLT_LIBRARIES})
set_target_properties(dlt-example1 PROPERTIES LINKER_LANGUAGE C)

install(TARGETS dlt-example1
	RUNTIME DESTINATION bin
	COMPONENT base)

运行步骤：

1. 运行dlt-daemon

2. 运行dlt-viewer

3. 运行example1，在dlt-viewer中查看结果

DLT_DECLARE_CONTEXT

dlt-daemon/include/dlt/dlt_user_macros.h

/**

* Create an object for a new context.

* This macro has to be called first for every.

* @param CONTEXT object containing information about one special logging context

* @note To avoid the MISRA warning "Null statement is located close to other code or comments"

* remove the semicolon when using the macro.

* Example: DLT_DECLARE_CONTEXT(hContext)

*/

声明 DltContext对象，每个dlt程序都需要新建 DltContext对象。

#define DLT_DECLARE_CONTEXT(CONTEXT) \

DltContext CONTEXT;

DLT_REGISTER_APP

dlt-daemon/include/dlt/dlt_user_macros.h

/**

* Register application.

* @param APPID application id with maximal four characters

* @param DESCRIPTION ASCII string containing description

*/

#define DLT_REGISTER_APP(APPID, DESCRIPTION) do { \

(void)dlt_check_library_version(_DLT_PACKAGE_MAJOR_VERSION, _DLT_PACKAGE_MINOR_VERSION); \

(void)dlt_register_app(APPID, DESCRIPTION); } while(false)

DLT_REGISTER_APP是一个注册函数的宏，展开后是这样的：

do{

(void)dlt_check_library_version(_DLT_PACKAGE_MAJOR_VERSION, _DLT_PACKAGE_MINOR_VERSION); //(1)

(void)dlt_register_app(APPID, DESCRIPTION);

}while(false)

(1)此句虽然是用来检测版本，但是没有它的处理返回值，相当于没判断。可以用dlt_register_app(APPID, DESCRIPTION)代替此宏。

DLT_REGISTER_CONTEXT

/**

* Register context (with default log level and default trace status)

* @param CONTEXT object containing information about one special logging context

* @param CONTEXTID context id with maximal four characters

* @param DESCRIPTION ASCII string containing description

*/

#define DLT_REGISTER_CONTEXT(CONTEXT, CONTEXTID, DESCRIPTION) do { \

(void)dlt_register_context(&(CONTEXT), CONTEXTID, DESCRIPTION); } while (false)

调用 dlt_register_context函数注册context

DLT_LOG

/**

* Send log message with variable list of messages (intended for verbose mode)

* @param CONTEXT object containing information about one special logging context

* @param LOGLEVEL the log level of the log message

* @param ... variable list of arguments

* @note To avoid the MISRA warning "The comma operator has been used outside a for statement"

* use a semicolon instead of a comma to separate the __VA_ARGS__.

* Example: DLT_LOG(hContext, DLT_LOG_INFO, DLT_STRING("Hello world"); DLT_INT(123));

*/

#ifdef _MSC_VER

/* DLT_LOG is not supported by MS Visual C++ */

/* use function interface instead */

#else

# define DLT_LOG(CONTEXT, LOGLEVEL, ...) \

do { \

DltContextData log_local; \

int dlt_local; \

dlt_local = dlt_user_log_write_start(&CONTEXT, &log_local, LOGLEVEL); \

if (dlt_local == DLT_RETURN_TRUE) \

{ \

__VA_ARGS__; \

(void)dlt_user_log_write_finish(&log_local); \

} \

} while

发送一个带有可变消息列表的日志

参数CONTEXT：CONTEXT 对象，其中包含有关一个特殊日志记录上下文的信息。

参数LOGLEVEL： 日志消息的等级。

log等级划分：

/**

* Definitions of DLT log level

*/

typedef enum

{

DLT_LOG_DEFAULT = -1, /**< Default log level */

DLT_LOG_OFF = 0x00, /**< Log level off */

DLT_LOG_FATAL = 0x01, /**< fatal system error */

DLT_LOG_ERROR = 0x02, /**< error with impact to correct functionality */

DLT_LOG_WARN = 0x03, /**< warning, correct behaviour could not be ensured */

DLT_LOG_INFO = 0x04, /**< informational */

DLT_LOG_DEBUG = 0x05, /**< debug */

DLT_LOG_VERBOSE = 0x06, /**< highest grade of information */

DLT_LOG_MAX /**< maximum value, used for range check */

} DltLogLevelType;

DLT_UNREGISTER_CONTEXT

/**

* Unregister context.

* @param CONTEXT object containing information about one special logging context

*/

#define DLT_UNREGISTER_CONTEXT(CONTEXT) do { \

(void)dlt_unregister_context(&(CONTEXT)); } while(false)

在dlt-daemon中注销context

DLT_UNREGISTER_APP

/**

* Unregister application.

*/

#define DLT_UNREGISTER_APP() do { \

(void)dlt_unregister_app(); } while(false)

在dlt-daemon中注销app

运行结果，可以在dlt-viewer中看到打印的log