问用C语言中的strok解析NMEA字符串
EN

Stack Overflow用户

提问于 2018-01-28 05:37:58

回答 2查看 3.5K关注 0票数 0

我正试图使用带有分隔符的strtok函数来解析一个GNRMC字符串，"，当我注意到一些我没有预料到的不同的事情时，一切都进行得很顺利。如果字符串包含连续的"，"然后strtok超调和打印函数错误地放置真实的数据，我的目标是打印数字当在连续的之间没有可用的数据“，"

我该怎么做呢？

这是我的密码

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


int main()
{
 char str[] = "$GPRMC,105954.000,A,3150.6731,N,11711.9399,E,0.00,96.10,250313,,,A*53";
 char* Message_ID = strtok(str,",");
 char* Time = strtok(NULL,",");
 char* Data_Valid = strtok(NULL,",");
 char* Raw_Latitude = strtok(NULL,",");
 char* N_S = strtok(NULL,",");
 char* Raw_Longitude = strtok(NULL,",");
 char* E_W = strtok(NULL,",");
 char* Speed = strtok(NULL,",");
 char* COG = strtok(NULL,",");
 char* Date = strtok(NULL,",");
 char* Magnetic_Variation = strtok(NULL,",");
 char* M_E_W = strtok(NULL,",");
 char* Positioning_Mode = strtok(NULL,",");

 double Latitude = atof(Raw_Latitude);
 double Longitude = atof(Raw_Longitude);

  printf("The Message ID is : %s\n", Message_ID);
  printf("The Time is : %s\n", Time);
  printf("The data valid is : %s\n", Data_Valid);
  printf("The Latitude is : %f\n", Latitude);
  printf("The N_S is : %s\n", N_S);
  printf("The Longitude is : %f\n", Longitude);
  printf("The E_W is : %s\n", E_W);
  printf("The Speed is : %s\n", Speed);
  printf("The COG is : %s\n", COG);
  printf("The Date is : %s\n", Date);
  printf("The Magnetic_Variation is : %s\n", Magnetic_Variation);
  printf("The M_E_W is : %s\n", M_E_W);
  printf("The Positioning_Mode is : %s\n", Positioning_Mode);

    return 0;
}

输出窗口

string

parsing

delimiter

回答 2

Stack Overflow用户

回答已采纳

发布于 2018-01-28 06:26:17

如果您只检测到一个特定的字符(如',')，那么直接前进的方法将是使用好的旧strchr()。

 char str[] = 
   "$GPRMC,105954.000,A,3150.6731,N,11711.9399,E,0.00,96.10,250313,,,A*53";

 char* message_id = str;

 char* time = strchr(message_id, ','); *time = '\0'; ++time;
 char* data_valid = strchr(time,","); *data_valid = '\0'; ++data_valid;
 char* raw_latitude = strchr(data_valid,","); *raw_latitude = '\0'; ++raw_latitude;
 ...

一个复杂的宏可以简化使用：

#define FIND_AND_NUL(s, p, c) ( \
   (p) = strchr(s, c), \
   *(p) = '\0', \
   ++(p), \
   (p))

像这样使用它：

 char str[] = 
   "$GPRMC,105954.000,A,3150.6731,N,11711.9399,E,0.00,96.10,250313,,,A*53";

 char* message_id = str;

 char* time = FIND_AND_NUL(message_id, time, ',');
 char* data_valid = FIND_AND_NUL(time, data_valid, ',');
 char* raw_latitude = FIND_AND_NUL(data_valid, raw_latitude, ',');
 ...

票数 3

Stack Overflow用户

发布于 2020-01-25 16:46:34

我使用我自己的strtok函数，它非常简单，但与原始函数有两个不同之处：(1)分隔符只是一个字符，而不是字符串(2)如果要解析的字符串有两个连续的分隔符，则该函数返回一个空的非空标记“。这对于解析NMEA消息非常方便。

char *strtok_fr (char *s, char delim, char **save_ptr)
{
    char *tail;
    char c;

    if (s == NULL) {
        s = *save_ptr;
    }
    tail = s;
    if ((c = *tail) == '\0') {
        s = NULL;
    }
    else {
        do {
            if (c == delim) {
                *tail++ = '\0';
                break;
           }
        }while ((c = *++tail) != '\0');
    }
    *save_ptr = tail;
    return s;
}

非递归版本：

char *strtok_f (char *s, char delim)
{
    static char *save_ptr;

    return strtok_fr (s, delim, &save_ptr);
}

因此，您的示例(注意'，‘而不是"，“分隔符和strtok_f而不是strtok函数)：

int main (int argc, char *argv[])
{
    char str[] = "$GPRMC,105954.000,A,3150.6731,N,11711.9399,E,0.00,96.10,250313,,,A*53";
    char* Message_ID = strtok_f(str,',');
    char* Time = strtok_f(NULL,',');
    char* Data_Valid = strtok_f(NULL,',');
    char* Raw_Latitude = strtok_f(NULL,',');
    char* N_S = strtok_f(NULL,',');
    char* Raw_Longitude = strtok_f(NULL,',');
    char* E_W = strtok_f(NULL,',');
    char* Speed = strtok_f(NULL,',');
    char* COG = strtok_f(NULL,',');
    char* Date = strtok_f(NULL,',');
    char* Magnetic_Variation = strtok_f(NULL,',');
    char* M_E_W = strtok_f(NULL,',');
    char* Positioning_Mode = strtok_f(NULL,',');

    double Latitude = atof(Raw_Latitude);
    double Longitude = atof(Raw_Longitude);

    printf("The Message ID is : %s\n", Message_ID);
    printf("The Time is : %s\n", Time);
    printf("The data valid is : %s\n", Data_Valid);
    printf("The Latitude is : %f\n", Latitude);
    printf("The N_S is : %s\n", N_S);
    printf("The Longitude is : %f\n", Longitude);
    printf("The E_W is : %s\n", E_W);
    printf("The Speed is : %s\n", Speed);
    printf("The COG is : %s\n", COG);
    printf("The Date is : %s\n", Date);
    printf("The Magnetic_Variation is : %s\n", Magnetic_Variation);
    printf("The M_E_W is : %s\n", M_E_W);
    printf("The Positioning_Mode is : %s\n", Positioning_Mode);

    return 0;
}

现在的结果：

消息ID是：$GPRMC 时间是: 105954.000 有效的数据是：纬度是: 3150.673100 N_S是:n 经度是: 11711.939900 E_W是:e 速度是: 0.00 组委会为: 96.10 日期是: 250313 Magnetic_Variation是： M_E_W是： Positioning_Mode是: A*53 C:\Users\froca\Desktop\strtok>

请注意，“磁性变化”和"M_E_W“现在是空标记。那才是关键。

票数 1

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原文链接：

https://stackoverflow.com/questions/48486952

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