Create generic check methods for RangeError causing checks.

sdk/lib/convert/utf.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.convert;
 
 /** The Unicode Replacement character `U+FFFD` (�). */
 const int UNICODE_REPLACEMENT_CHARACTER_RUNE = 0xFFFD;
 
 /** The Unicode Byte Order Marker (BOM) character `U+FEFF`. */
@@ skipping 71 matching lines @@
 
   /**
    * Converts [string] to its UTF-8 code units (a list of
    * unsigned 8-bit integers).
    *
    * If [start] and [end] are provided, only the substring
    * `string.substring(start, end)` is converted.
    */
   List<int> convert(String string, [int start = 0, int end]) {
     int stringLength = string.length;
-    if (start < 0 || start > stringLength) {
-      throw new RangeError.range(start, 0, stringLength, "start");
-    }
-    if (end == null) {
-      end = stringLength;
-    } else if (end < start || end > stringLength) {
-      throw new RangeError.range(end, start, stringLength, "end");
-    }
+    RangeError.checkValidRange(start, end, stringLength);
+    if (end == null) end = stringLength;
     int length = end - start;
     if (length == 0) return new Uint8List(0);
     // Create a new encoder with a length that is guaranteed to be big enough.
     // A single code unit uses at most 3 bytes, a surrogate pair at most 4.
     _Utf8Encoder encoder = new _Utf8Encoder.withBufferSize(length * 3);
     int endPosition = encoder._fillBuffer(string, start, end);
     assert(endPosition >= end - 1);
     if (endPosition != end) {
       // Encoding skipped the last code unit.
       // That can only happen if the last code unit is a leadsurrogate.
@@ skipping 221 matching lines @@
    * corresponding string.
    *
    * Uses the code units from [start] to, but no including, [end].
    * If [end] is omitted, it defaults to `codeUnits.length`.
    *
    * If the [codeUnits] start with a leading [UNICODE_BOM_CHARACTER_RUNE] this
    * character is discarded.
    */
   String convert(List<int> codeUnits, [int start = 0, int end]) {
     int length = codeUnits.length;
-    if (start < 0 || start > length) {
-      throw new RangeError.range(start, 0, length, "start");
-    }
-    if (end == null) {
-      end = length;
-    } else if (end < start || end > length) {
-      throw new RangeError.range(end, start, length, "end");
-    }
+    RangeError.checkValidRange(start, end, length);
+    if (end == null) end = length;
     StringBuffer buffer = new StringBuffer();
     _Utf8Decoder decoder = new _Utf8Decoder(buffer, _allowMalformed);
     decoder.convert(codeUnits, start, end);
     decoder.close();
     return buffer.toString();
   }
 
   /**
    * Starts a chunked conversion.
    *
@@ skipping 208 matching lines @@
       }
       break loop;
     }
     if (expectedUnits > 0) {
       _value = value;
       _expectedUnits = expectedUnits;
       _extraUnits = extraUnits;
     }
   }
 }