readint.c (mrb_int_read): new function.

We no longer use `mrb_read_int` which is kinda compatible with `strtol`.

src/readint.c

@@ -1,16 +1,15 @@
 #include <mruby.h>
 #include <mruby/numeric.h>
-#include <errno.h>
 
-/* mrb_int_read(): read mrb_int from a string (base 10 only) */
+/* mrb_read_int(): read mrb_int from a string (base 10 only) */
 /* const char *p - string to read                            */
 /* const char *e - end of string                             */
 /* char **endp   - end of parsed integer                     */
-
-/* if integer overflows, errno will be set to ERANGE         */
-/* also endp will be set to NULL on overflow                 */
-MRB_API mrb_int
-mrb_int_read(const char *p, const char *e, char **endp)
+/* mrb_int *np   - variable to save the result               */
+/* returns TRUE if read succeeded                            */
+/* if integer overflows, returns FALSE                       */
+MRB_API mrb_bool
+mrb_read_int(const char *p, const char *e, char **endp, mrb_int *np)
 {
   mrb_int n = 0;
   int ch;
@@ -19,12 +18,11 @@ mrb_int_read(const char *p, const char *e, char **endp)
     ch = *p - '0';
     if (mrb_int_mul_overflow(n, 10, &n) ||
         mrb_int_add_overflow(n, ch, &n)) {
-      if (endp) *endp = NULL;
-      errno = ERANGE;
-      return MRB_INT_MAX;
+      return FALSE;
     }
     p++;
   }
   if (endp) *endp = (char*)p;
-  return n;
+  *np = n;
+  return TRUE;
 }