ref: ae0d87a19f53e5e8690e4a41536b5a825a3d9787
dir: /src/libc/stdlib/_dtoi.c/
#include <ctype.h>
#include <limits.h>
#include <string.h>
int
_dtoi(char c)
{
static const char digits[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char *p;
if (p = strchr(digits, toupper(c)))
return p - digits;
return INT_MAX;
}