C language exercise: esp32 ble Low Power Bluetooth server data packaging and client data analysis

Problem description ：

BLE Low power Bluetooth consists of server and client , The existing server obtains PWM data 、 Power Supply ADC The data is packaged and transmitted to the client through Bluetooth for data analysis , Finally, the parsed pwm and adc Data to int Type to deal with , And display the information on the screen of the client .

Why Package data ？

Because of the low power consumption BLE Bluetooth a service has multiple tags , Also known as eigenvalue , A label can ( read 、 Write 、 Notice, etc ) Serial communication is transmitted to the client device , Save the resources of Bluetooth transmission channel .

Parsing character data

#include <stdio.h>
#include <string.h>
#include <stdlib.h>


/** * @brief  Parsing character data  ： Parse the expected string from a string   Explain  * @param pBuff:  The string address to parse  * @param pLeft:  The string to the left of the target string  * @param pRight:  The string to the right of the target string  * @param pRes:  Address to receive character data  * @retval 0: success  -1: Failure  */

int DataParsingChar(const char *pBuff, const char *pLeft, const char *pRight,char *pRes)
{
    
    char *pBegin = NULL;
    char *pEnd = NULL;
    pBegin = strstr(pBuff, pLeft);
    pEnd = strstr(pBegin + strlen(pLeft), pRight);
    if (pEnd == NULL || pBegin == NULL || pBegin > pEnd) {
    
        return -1;
    } else {
    
        pBegin += strlen(pLeft);
        memcpy(pRes, pBegin, pEnd - pBegin);
        return 0;
    }
}

int main(int argc, char **argv)
{
    
    /*  Raw data  */
    char *name = "LiHua";
    int age = 20;
    int number = 10086;

    char buff[100] = {
    0};
    char re_name[10] = {
    0};
    char re_age[10] = {
    0};
    char re_number[10] = {
    0};

    /*  Data packaging  */
    sprintf(buff,"name:%s, age:%d, number:%d.",name, age, number);
    
    /*  Data analysis  */
    DataParsingChar(buff, "name:", ",", re_name);
    DataParsingChar(buff, "age:", ",", re_age);
    DataParsingChar(buff, "number:", ".", re_number);

    printf("buff : %s\n", buff);
    printf("re_name : %s\n", re_name);
    printf("re_age : %s\n", re_age);
    printf("re_number : %s\n", re_number);

    return 0; 
}

The results are as follows ：

---

Parsing integer data

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

/** * @brief  Extract integer data from a string  * @param pBuff:  The string address to parse  * @param pLeft:  The string to the left of the target data  * @param pRight:  The string to the right of the target data  * @param pRes:  Address to receive integer data  * @retval 0: success  -1: Failure  */

int DataParsingInt(const char *pBuff, const char *pLeft, const char *pRight, int *pRes)
{
    
    char *pBegin = NULL;
    char *pEnd = NULL;
    char *pTemp = NULL;
    pBegin = strstr(pBuff, pLeft); //  character string  pBuff Find the first occurrence of the string  pLeft The location of , Does not contain Terminator  '\0'
    pEnd = strstr(pBegin + strlen(pLeft), pRight); //  Compute string  str  The length of , Until the empty end character , But does not include the null end character 
    if (pEnd == NULL || pBegin == NULL || pBegin > pEnd) {
    
        return -1;
    } else {
    
        pBegin += strlen(pLeft);
        pTemp = (char *)malloc(pEnd - pBegin); // malloc  Dynamic memory allocation  ( The length of the transmitted string is unknown )
        memcpy(pTemp, pBegin, pEnd - pBegin); //  From the storage area  pBegin Copy  pEnd - pBegin  Bytes to storage  pTemp
        *pRes = atoi(pTemp);                 //  String to integer variable  int type 
        free(pTemp);
        return 0;
    }
}

int main(int argc, char **argv)
{
    
    /*  Raw data  */
    int left = 123;
    int right = 456;

    char buff[100] = {
    0};
    int re_left = 0;
    int re_right = 0;

    /*  Data packaging  */
    sprintf(buff, "[%d,%d]", left, right);
    
    /*  Data analysis  */
    DataParsingInt(buff, "[", ",", &re_left);
    DataParsingInt(buff, ",", "]", &re_right);

    printf("buff : %s\n", buff);
    printf("re_left : %d\n", re_left);
    printf("re_right : %d\n", re_right);
    printf("re_right - re_left = %d\n", re_right - re_left);

    return 0; 
}

---

Reference material ：

• [1] C Language simple data analysis : https://blog.csdn.net/weixin_45861321/article/details/114632122
• [2] C Library function - strstr()
• [3] C Library function - strlen()
• [4] C Library function - memcpy()
• [5] C Library function - malloc()