* fns.c (validate_subarray): Rename from validate_substring,

since it works for vectors too.  New arg ARRAY.  Optimize for the
non-nil case.  Instead of returning bool, throw an error if out of
range, so that the caller needn't do that.  All uses changed.
Report original values if out of range.
(Fsubstring, Fsubstring_no_properties, secure_hash):
Also optimize the case where FROM is 0 or TO is the size.

src/ChangeLog

+2014-04-01  Paul Eggert  <eggert@cs.ucla.edu>
+
+	* fns.c (validate_subarray): Rename from validate_substring,
+	since it works for vectors too.  New arg ARRAY.  Optimize for the
+	non-nil case.  Instead of returning bool, throw an error if out of
+	range, so that the caller needn't do that.  All uses changed.
+	Report original values if out of range.
+	(Fsubstring, Fsubstring_no_properties, secure_hash):
+	Also optimize the case where FROM is 0 or TO is the size.
+
 2014-03-31  Dmitry Antipov  <dmantipov@yandex.ru>
 
 	* search.c (Freplace_match): Use make_specified_string.

src/fns.c

@@ -1127,36 +1127,45 @@ Elements of ALIST that are not conses are also shared.  */)
   return alist;
 }
 
-/* True if [FROM..TO) specifies a valid substring of SIZE-characters string.
-   If FROM is nil, 0 assumed.  If TO is nil, SIZE assumed.  Negative
-   values are counted from the end.  *FROM_CHAR and *TO_CHAR are updated
-   with corresponding C values of TO and FROM.  */
+/* Check that ARRAY can have a valid subarray [FROM..TO),
+   given that its size is SIZE.
+   If FROM is nil, use 0; if TO is nil, use SIZE.
+   Count negative values backwards from the end.
+   Set *IFROM and *ITO to the two indexes used.  */
 
-static bool
-validate_substring (Lisp_Object from, Lisp_Object to, ptrdiff_t size,
-		    EMACS_INT *from_char, EMACS_INT *to_char)
+static void
+validate_subarray (Lisp_Object array, Lisp_Object from, Lisp_Object to,
+		   ptrdiff_t size, EMACS_INT *ifrom, EMACS_INT *ito)
 {
-  if (NILP (from))
-    *from_char = 0;
-  else
+  EMACS_INT f, t;
+
+  if (INTEGERP (from))
     {
-      CHECK_NUMBER (from);
-      *from_char = XINT (from);
-      if (*from_char < 0)
-	*from_char += size;
+      f = XINT (from);
+      if (f < 0)
+	f += size;
     }
-
-  if (NILP (to))
-    *to_char = size;
+  else if (NILP (from))
+    f = 0;
   else
+    wrong_type_argument (Qintegerp, from);
+
+  if (INTEGERP (to))
     {
-      CHECK_NUMBER (to);
-      *to_char = XINT (to);
-      if (*to_char < 0)
-	*to_char += size;
+      t = XINT (to);
+      if (t < 0)
+	t += size;
     }
+  else if (NILP (to))
+    t = size;
+  else
+    wrong_type_argument (Qintegerp, to);
+
+  if (! (0 <= f && f <= t && t <= size))
+    args_out_of_range_3 (array, from, to);
 
-  return (0 <= *from_char && *from_char <= *to_char && *to_char <= size);
+  *ifrom = f;
+  *ito = t;
 }
 
 DEFUN ("substring", Fsubstring, Ssubstring, 1, 3, 0,
@@ -1176,7 +1185,7 @@ With one argument, just copy STRING (with properties, if any).  */)
 {
   Lisp_Object res;
   ptrdiff_t size;
-  EMACS_INT from_char, to_char;
+  EMACS_INT ifrom, ito;
 
   if (STRINGP (string))
     size = SCHARS (string);
@@ -1184,24 +1193,23 @@ With one argument, just copy STRING (with properties, if any).  */)
     size = ASIZE (string);
   else
     wrong_type_argument (Qarrayp, string);
-  
-  if (!validate_substring (from, to, size, &from_char, &to_char))
-    args_out_of_range_3 (string, make_number (from_char),
-			 make_number (to_char));
+
+  validate_subarray (string, from, to, size, &ifrom, &ito);
 
   if (STRINGP (string))
     {
-      ptrdiff_t to_byte =
-	(NILP (to) ? SBYTES (string) : string_char_to_byte (string, to_char));
-      ptrdiff_t from_byte = string_char_to_byte (string, from_char);
+      ptrdiff_t from_byte
+	= !ifrom ? 0 : string_char_to_byte (string, ifrom);
+      ptrdiff_t to_byte
+	= ito == size ? SBYTES (string) : string_char_to_byte (string, ito);
       res = make_specified_string (SSDATA (string) + from_byte,
-				   to_char - from_char, to_byte - from_byte,
+				   ito - ifrom, to_byte - from_byte,
 				   STRING_MULTIBYTE (string));
-      copy_text_properties (make_number (from_char), make_number (to_char),
+      copy_text_properties (make_number (ifrom), make_number (ito),
 			    string, make_number (0), res, Qnil);
     }
   else
-    res = Fvector (to_char - from_char, aref_addr (string, from_char));
+    res = Fvector (ito - ifrom, aref_addr (string, ifrom));
 
   return res;
 }
@@ -1224,14 +1232,11 @@ With one argument, just copy STRING without its properties.  */)
   CHECK_STRING (string);
 
   size = SCHARS (string);
+  validate_subarray (string, from, to, size, &from_char, &to_char);
 
-  if (!validate_substring (from, to, size, &from_char, &to_char))
-    args_out_of_range_3 (string, make_number (from_char),
-			 make_number (to_char));
-
-  from_byte = NILP (from) ? 0 : string_char_to_byte (string, from_char);
+  from_byte = !from_char ? 0 : string_char_to_byte (string, from_char);
   to_byte =
-    NILP (to) ? SBYTES (string) : string_char_to_byte (string, to_char);
+    to_char == size ? SBYTES (string) : string_char_to_byte (string, to_char);
   return make_specified_string (SSDATA (string) + from_byte,
 				to_char - from_char, to_byte - from_byte,
 				STRING_MULTIBYTE (string));
@@ -4612,14 +4617,12 @@ secure_hash (Lisp_Object algorithm, Lisp_Object object, Lisp_Object start, Lisp_
 	object = code_convert_string (object, coding_system, Qnil, 1, 0, 1);
 
       size = SCHARS (object);
+      validate_subarray (object, start, end, size, &start_char, &end_char);
 
-      if (!validate_substring (start, end, size, &start_char, &end_char))
-	args_out_of_range_3 (object, make_number (start_char),
-			     make_number (end_char));
-
-      start_byte = NILP (start) ? 0 : string_char_to_byte (object, start_char);
-      end_byte =
-	NILP (end) ? SBYTES (object) : string_char_to_byte (object, end_char);
+      start_byte = !start_char ? 0 : string_char_to_byte (object, start_char);
+      end_byte = (end_char == size
+		  ? SBYTES (object)
+		  : string_char_to_byte (object, end_char));
     }
   else
     {