逗号分隔字符串的解析函数 [英] Parsing function for comma-delimited string

问题描述

假设我有一个这样的字符串 "cmd,param1,param2".String 是 Arduino String 类型.https://www.arduino.cc/en/Reference/String

Suppose I have a string like this "cmd,param1,param2". The String is the Arduino String type. https://www.arduino.cc/en/Reference/String

我想提取以逗号分隔的每个子字符串.我已经成功地为这样的特定案例编写了代码.这是代码;

I want to extract each of the substrings separated by commas. I have successfully written the code for a specific case like this. Here's the code;

String = str_data('cmd,param1,param2');
int firstCommaIndex = str_data.indexOf(',');
int secondCommaIndex = str_data.indexOf(',', firstCommaIndex+1);
String cmd = str_data.substring(0, firstCommaIndex);
String param1 = str_data.substring(firstCommaIndex+1, secondCommaIndex);
String param2 = str_data.substring(secondCommaIndex+1);

我的问题是有一个解决一般情况的函数.字符串可以用任意数量的逗号分隔.我想要一个看起来像这样的函数；

My problem is to have a function that solves the general case. The string can be delimited with any number of commas. I would like to have a function that looks like this;

String parserCommaDelimited(String input_delimited_str, int nth_param_num)
{
    //implementation
}

假设 input_delimited_str="cmd,param1,param2,param3,param4"

parserCommaDelimited(input_delimited_str, 1) 返回 "cmd".parserCommaDelimited(input_delimited_str, 5) 返回 "param4".

推荐答案

以下是基本的CSV解析器:

The following is a basic CSV parser:

void readCSVline(char *line);
char *readCSVfield(char *line, char *buf);
void readCSVdemo(void)
{
    char line[]= "0,,10004,10004,\"Albany Hwy After Galliers Av\",\"\",-32.13649428,116.0176090070,3";
    readCSVline(line);

}
/* readCSVline is where you put your "intelligence" about fields to read
 * and what to do with them
 */
void readCSVline(char *line)
{
    char field1[80], *lineptr=line;
    int nfields=0;

    while (*lineptr) {
        lineptr= readCSVfield(lineptr, field1);
        printf("%s\n", field1);
        nfields++;
    }
    printf("%d fields read.\n", nfields);
}
/* readCSVfield reads a field from a CSV line until the next comma or end-of-line.
 * It returns where the reading stopped.
 */
char *readCSVfield(char *line, char *buf)
{
    int instr= FALSE;   // track whether we are in a string
    char *cptr= line;

    while (*cptr)
    {
        if (instr) {
            if (*cptr=='"') {
                char cc= *++cptr;
                if (cc=='"')        // escaped double quote
                    *buf++ = '"';
                else {
                    *buf='\0';
                    cptr--;
                    instr= FALSE;
                }
            }
            else *buf++ = *cptr;
        }
        else switch (*cptr) {
        case '"': instr= TRUE; break;
        case ',': cptr++; *buf= '\0'; return(cptr);
        case ' ': case '\t': case '\n': case '\r': break;
        default: *buf++ = *cptr;
        }
        cptr++;
    }
    *buf= '\0';
    return(cptr);
}

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