convert_timestamp.c

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

#define MAX_STR_LEN 20

char strbuf[16];
char str[] = "10000:12:34";

int convertTimestampToSeconds(char* ts) {
	char* p = ts;
	while (*(p++) != '\0') {
	    if ((p - ts) > MAX_STR_LEN) {
	        return -1;
	    }
	}
	int radix = 0;
	int total = 0;
	while(p >= ts) {
	    while(*p != ':' && p >= ts) {
	        p--;
	    }
	    int val = atoi(p+1);
	    // handle atoi parse failure
	    if (val < 0) {
	        return -1;
	    }
	    //convert to seconds
        val *= pow(60, radix);
	    total += val;
	    radix++;
	    
	    *p = '\0';
	    p--;
	}
	
	return total;
}

int main()
{
    strcpy(strbuf, str);
    int val = convertTimestampToSeconds(strbuf);
    printf("%d\n", val);
    return 0;
}