tools.c

int thousandsep(double in, char* out_str, size_t out_len, unsigned int precision) {
char in_str[128], int_str[128], format[32];
size_t dlen, mod, i, j;
int c;
snprintf(format, sizeof format, "%%.%df", precision);
snprintf(in_str, sizeof in_str, format, in);
snprintf(int_str, sizeof int_str, "%d", (int) in);
dlen = strlen(in_str);
mod = strlen(int_str) % 3;
c = (mod == 0) ? 3 : mod;
for (i = 0, j = 0; i < dlen; i++, j++, c--) {
if (j >= out_len - 1) {
/* out_str is too small */
return -1;
}
if (in_str[i] == '.') {
c = -1;
} else if (c == 0) {
out_str[j++] = ',';
c = 3;
}
out_str[j] = in_str[i];
}
out_str[j] = '\0';
return 0;
}