Litos

这篇文章主要描述我们如何在litos工程中，自定义一个demo出来。

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前言

1.环境及MCU 小熊派(IOT开发板)+linux环境+litos

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提示：以下是本篇文章正文内容，下面案例可供参考

一、前期准备

1.如果你想完成自定义demo，首先你需要去看一下其它demo中是如何定义这个demo的。比如说Kconfig，makefile，需要什么文件等等。
2.你需要对makefile，Kconfig这种文件语法懂一些。
3.自己要会编译下载。(不会的话，参考我的一篇环境搭建的文章，里面包含了如何下载程序)

二、使用步骤

1.查看其它demos文件

• 建议你用source insight建立一个工程，查看方便。
• 上述图片是我写好的调用cjson库的demo，后面我就以这个讲解
• json-c.mk文件是增加一个当前的头文件路径

DEMOS_JSON_INCLUDE := \
    -I $(LITEOSTOPDIR)/demos/utility/cjson

• Kconfig文件是增加一个编译选项

config LOSCFG_DEMOS_CJSON
    bool "Enable cJson Demo"
    default n
    help
      Answer y to enable json demo.

• Makefile 提供一些编译文件名，统计头文件路径称等等，可以细细看看

include $(LITEOSTOPDIR)/config.mk
include $(LITEOSTOPDIR)/demos/utility/cjson/json-c.mk

MODULE_NAME := cjson_demo

JSON_DEMO_SRCS = $(wildcard *.c)

JSON_DEMO_INCLUDE := \
    -I $(LITEOSTOPDIR)/lib/libc/include \
    -I $(LITEOSTOPDIR)/components/lib/cjson/$(CJSON_VERSION)\
    -I $(LITEOSTOPDIR)/demos/utility/cjson

LOCAL_INCLUDE := $(JSON_DEMO_INCLUDE) $(COMPONENTS_JSON_INCLUDE) 

LOCAL_SRCS := $(subst $(CURDIR)/,, $(JSON_DEMO_SRCS))

LOCAL_EXT_FLAG := -Wno-error -fstack-protector-strong

LOCAL_FLAGS := $(LOCAL_EXT_FLAG) $(LOCAL_INCLUDE)

include $(MODULE)

2.修改上层目录的Kconfig和mk

（1）找到utility目录下的Makefile

（2）Makefile添加这条数据

（3）同理，此目录中找到Kconfig文件，并添加如下箭头数据

（3）找到utility.mk文件，添加如下箭头数据

3.执行make menuconfig选择库和新加demo

（1）使能cjson库



（2）使能cjson_demo

4.修改cjson_demo.c和.h文件

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "cJSON.h"
#include "los_task.h"

#define CJSON_TASK_PRIORITY        3
#define CJSON_TASK_STACK_SIZE     0x1000
STATIC UINT32 g_demoTaskId;

/* Used by some code below as an example datatype. */
struct record
{
    
    const char *precision;
    double lat;
    double lon;
    const char *address;
    const char *city;
    const char *state;
    const char *zip;
    const char *country;
};

/* Create a bunch of objects as demonstration. */
static int print_preallocated(cJSON *root)
{
    
    /* declarations */
    char *out = NULL;
    char *buf = NULL;
    char *buf_fail = NULL;
    size_t len = 0;
    size_t len_fail = 0;

    /* formatted print */
    out = cJSON_Print(root);

    /* create buffer to succeed */
    /* the extra 5 bytes are because of inaccuracies when reserving memory */
    len = strlen(out) + 5;
    buf = (char*)malloc(len);
    if (buf == NULL)
    {
    
        printf("Failed to allocate memory.\n");
        exit(1);
    }

    /* create buffer to fail */
    len_fail = strlen(out);
    buf_fail = (char*)malloc(len_fail);
    if (buf_fail == NULL)
    {
    
        printf("Failed to allocate memory.\n");
        exit(1);
    }

    /* Print to buffer */
    if (!cJSON_PrintPreallocated(root, buf, (int)len, 1)) {
    
        printf("cJSON_PrintPreallocated failed!\n");
        if (strcmp(out, buf) != 0) {
    
            printf("cJSON_PrintPreallocated not the same as cJSON_Print!\n");
            printf("cJSON_Print result:\n%s\n", out);
            printf("cJSON_PrintPreallocated result:\n%s\n", buf);
        }
        free(out);
        free(buf_fail);
        free(buf);
        return -1;
    }

    /* success */
    printf("%s\n", buf);

    /* force it to fail */
    if (cJSON_PrintPreallocated(root, buf_fail, (int)len_fail, 1)) {
    
        printf("cJSON_PrintPreallocated failed to show error with insufficient memory!\n");
        printf("cJSON_Print result:\n%s\n", out);
        printf("cJSON_PrintPreallocated result:\n%s\n", buf_fail);
        free(out);
        free(buf_fail);
        free(buf);
        return -1;
    }

    free(out);
    free(buf_fail);
    free(buf);
    return 0;
}

/* Create a bunch of objects as demonstration. */
static void create_objects(void)
{
    
    /* declare a few. */
    cJSON *root = NULL;
    cJSON *fmt = NULL;
    cJSON *img = NULL;
    cJSON *thm = NULL;
    cJSON *fld = NULL;
    int i = 0;

    /* Our "days of the week" array: */
    const char *strings[7] =
    {
    
        "Sunday",
        "Monday",
        "Tuesday",
        "Wednesday",
        "Thursday",
        "Friday",
        "Saturday"
    };
    /* Our matrix: */
    int numbers[3][3] =
    {
    
        {
    0, -1, 0},
        {
    1, 0, 0},
        {
    0 ,0, 1}
    };
    /* Our "gallery" item: */
    int ids[4] = {
     116, 943, 234, 38793 };
    /* Our array of "records": */
    struct record fields[2] =
    {
    
        {
    
            "zip",
            37.7668,
            -1.223959e+2,
            "",
            "SAN FRANCISCO",
            "CA",
            "94107",
            "US"
        },
        {
    
            "zip",
            37.371991,
            -1.22026e+2,
            "",
            "SUNNYVALE",
            "CA",
            "94085",
            "US"
        }
    };
    volatile double zero = 0.0;
	 
    /* Here we construct some JSON standards, from the JSON site. */
    printf("Version: %s\n", cJSON_Version());
    /* Our "Video" datatype: */
    root = cJSON_CreateObject();
    cJSON_AddItemToObject(root, "name", cJSON_CreateString("Jack (\"Bee\") Nimble"));
    cJSON_AddItemToObject(root, "format", fmt = cJSON_CreateObject());
    cJSON_AddStringToObject(fmt, "type", "rect");
    cJSON_AddNumberToObject(fmt, "width", 1920);
    cJSON_AddNumberToObject(fmt, "height", 1080);
    cJSON_AddFalseToObject (fmt, "interlace");
    cJSON_AddNumberToObject(fmt, "frame rate", 24);
    
    /* Print to text */
    if (print_preallocated(root) != 0) {
    
        cJSON_Delete(root);
        exit(EXIT_FAILURE);
    }
    cJSON_Delete(root);
    printf("1333331111\n");
    /* Our "days of the week" array: */
    root = cJSON_CreateStringArray(strings, 7);

    if (print_preallocated(root) != 0) {
    
        cJSON_Delete(root);
        exit(EXIT_FAILURE);
    }
    cJSON_Delete(root);

    /* Our matrix: */
    root = cJSON_CreateArray();
    for (i = 0; i < 3; i++)
    {
    
        cJSON_AddItemToArray(root, cJSON_CreateIntArray(numbers[i], 3));
    }

    /* cJSON_ReplaceItemInArray(root, 1, cJSON_CreateString("Replacement")); */

    if (print_preallocated(root) != 0) {
    
        cJSON_Delete(root);
        exit(EXIT_FAILURE);
    }
    cJSON_Delete(root);

    /* Our "gallery" item: */
    root = cJSON_CreateObject();
    cJSON_AddItemToObject(root, "Image", img = cJSON_CreateObject());
    cJSON_AddNumberToObject(img, "Width", 800);
    cJSON_AddNumberToObject(img, "Height", 600);
    cJSON_AddStringToObject(img, "Title", "View from 15th Floor");
    cJSON_AddItemToObject(img, "Thumbnail", thm = cJSON_CreateObject());
    cJSON_AddStringToObject(thm, "Url", "http:/*www.example.com/image/481989943");
    cJSON_AddNumberToObject(thm, "Height", 125);
    cJSON_AddStringToObject(thm, "Width", "100");
    cJSON_AddItemToObject(img, "IDs", cJSON_CreateIntArray(ids, 4));

    if (print_preallocated(root) != 0) {
    
        cJSON_Delete(root);
        exit(EXIT_FAILURE);
    }
    cJSON_Delete(root);

    /* Our array of "records": */
    root = cJSON_CreateArray();
    for (i = 0; i < 2; i++)
    {
    
        cJSON_AddItemToArray(root, fld = cJSON_CreateObject());
        cJSON_AddStringToObject(fld, "precision", fields[i].precision);
        cJSON_AddNumberToObject(fld, "Latitude", fields[i].lat);
        cJSON_AddNumberToObject(fld, "Longitude", fields[i].lon);
        cJSON_AddStringToObject(fld, "Address", fields[i].address);
        cJSON_AddStringToObject(fld, "City", fields[i].city);
        cJSON_AddStringToObject(fld, "State", fields[i].state);
        cJSON_AddStringToObject(fld, "Zip", fields[i].zip);
        cJSON_AddStringToObject(fld, "Country", fields[i].country);
    }

    /* cJSON_ReplaceItemInObject(cJSON_GetArrayItem(root, 1), "City", cJSON_CreateIntArray(ids, 4)); */

    if (print_preallocated(root) != 0) {
    
        cJSON_Delete(root);
        exit(EXIT_FAILURE);
    }
    cJSON_Delete(root);

    root = cJSON_CreateObject();
    cJSON_AddNumberToObject(root, "number", 1.0 / zero);

    if (print_preallocated(root) != 0) {
    
        cJSON_Delete(root);
        exit(EXIT_FAILURE);
    }
    cJSON_Delete(root);
}

int CJSON_CDECL cjson_test(void)
{
    
    /* print the version */
	UINT32 ret;
    TSK_INIT_PARAM_S taskInitParam = {
    0};
    taskInitParam.usTaskPrio = CJSON_TASK_PRIORITY;
    taskInitParam.pcName = "CJSONTask";
    taskInitParam.pfnTaskEntry = (TSK_ENTRY_FUNC)create_objects;
    taskInitParam.uwStackSize = CJSON_TASK_STACK_SIZE;
    taskInitParam.uwResved = LOS_TASK_STATUS_DETACHED;
    ret = LOS_TaskCreate(&g_demoTaskId, &taskInitParam);
    if (ret != LOS_OK) {
    
        printf("Create libevent demo task failed.\n");
    }
    /* Now some samplecode for building objects concisely: */
   // create_objects();

    return 0;
}

#ifndef _CJSON_DEMO_H
#define _CJSON_DEMO_H

#include "los_typedef.h"

#ifdef __cplusplus
#if __cplusplus
extern "C" {
    
#endif /* __cplusplus */
#endif /* __cplusplus */

int  cjson_test(void);


#ifdef __cplusplus
#if __cplusplus
}
#endif /* __cplusplus */
#endif /* __cplusplus */

#endif /* _CJSON_DEMO_H */

5.修改demo_entry.c文件

添加头文件

添加调用demo的入口

6.执行Make编译

（1）编译后现象

（2）下载 ，不会下载的看我上一篇关于litos文章

7.程序运行现象

我只截取了一部分内容，如果有什么不会的，留言，我会回复。觉得ok，点个赞吧。

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