small converter for string decimal numbers integers for microcontoller. Numbers can be negeative and starting spaces are ignored.

atoi.c

int atoi(const char *c) {
   int result = 0;
   int sign   = 1;
   if (!c)
       return 0;
   while (*c == ' ') 
       c++;
   if (*c == '-') {
       sign = -1;
       c++;
   }
   while (*c >= '0' && *c <= '9') {
       result *= 10;
       result += *c++ - '0';
   }
   return result * sign;
}