convert csv string to array of floats - c

Question

Can anyone advise on a simple way of converting a csv string to an array of floats in C?
e.g.
char my_string[] = "1.0,2.0,3.0";
to:
my_array = [1.0, 2.0, 3.0]
where my_array is of type float[]
I would use sscanf as a quick and easy solution but I don't know how many values are contained in the string in advance
Is there some existing library function that could do this without me having to resort to looping over every char looking for a ","?

Answer 1

You could use strtok():
float my_array[N]; // if you don't know how many there are, use the heap
int i = 0;
char *tok = strtok(my_string, ",");
while (tok != NULL) {
my_array[i++] = atof(tok);
tok = strtok(NULL, ",");
}

Answer 2

There's a library you could use - LibCSV
From their description:
libcsv is a small, simple and fast CSV library written in pure ANSI
C89 that can read and write CSV data. It provides a straight-forward
interface using callback functions to handle parsed fields and rows
and can parse improperly formatted CSV files

Answer 3

Use a while() loop that reads only one float at a time with sscanf(). As soon as sscanf() returns 0, you know you're at the end of the list.

Answer 4

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char** split(const char *str, const char *delimiter, size_t *len){
char *text, *p, *first, **array;
int c;
char** ret;
*len = 0;
text=strdup(str);
if(text==NULL) return NULL;
for(c=0,p=text;NULL!=(p=strtok(p, delimiter));p=NULL, c++)//count item
if(c==0) first=p; //first token top
ret=(char**)malloc(sizeof(char*)*c+1);//+1 for NULL
if(ret==NULL){
free(text);
return NULL;
}
strcpy(text, str+(first-text));//skip until top token
array=ret;
for(p=text;NULL!=(p=strtok(p, delimiter));p=NULL){
*array++=strdup(p);
}
*array=NULL;
*len=c;
free(text);
return ret;
}
void free4split(char** sa){
char **array=sa;
if(sa!=NULL){
while(*sa)
free(*sa++);//for string
free(array); //for array
}
}
int main(){
char my_string[] = "1.0,2.0,3.0";
float *my_array;
char **strs;
size_t count;
strs=split(my_string, ", \t", &count);
my_array=(float*)malloc(sizeof(float)*count);
{ //convert
int i;
for(i=0;i<count;++i)
my_array[i]=(float)atof(strs[i]);
free4split(strs);
}
{ //test print
int i;
for(i=0;i<count;++i)
printf("%f\n", my_array[i]);
}
return 0;
}

Answer 5

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char* getToken(char **p, const char delimiter){
char *word, *top=*p;
int len;
if(*p == NULL || **p == '\0') return NULL;
while(**p && **p != delimiter)
++(*p);
if(**p != delimiter) return strdup(top);
len = *p - top;
++(*p);
word=(char*)malloc(sizeof(char)*(len+1));
strncpy(word, top, len);
word[len]='\0';
return word;
}
int main(){
char my_string[] = "1.0,2.0,3.0";
float *my_array=NULL;
char *word, *p=my_string;
int count=0;
while(NULL!=(word=getToken(&p, ','))){
my_array=(float*)realloc(my_array, sizeof(float)*(++count));
my_array[count-1]=(float)atof(word);
free(word);
}
{ //test print
int i;
for(i=0;i<count;++i)
printf("%f\n", my_array[i]);
}
return 0;
}

Answer 6

You might want to look into using the strchr family of functions.
STRCHR(3) Linux Programmer's Manual STRCHR(3)
NAME
strchr, strrchr - locate character in string
SYNOPSIS
#include <string.h>
char *strchr(const char *s, int c);
char *strrchr(const char *s, int c);
DESCRIPTION
The strchr() function returns a pointer to the first
occurrence of the character c in the string s.
The strrchr() function returns a pointer to the last
occurrence of the character c in the string s.
RETURN VALUE
The strchr() and strrchr() functions return a pointer to
the matched character or NULL if the character is not
found.
CONFORMING TO
SVID 3, POSIX, BSD 4.3, ISO 9899
SEE ALSO
index(3), memchr(3), rindex(3), strpbrk(3), strsep(3),
strspn(3), strstr(3), strtok(3)