Create generic check methods for RangeError causing checks.

sdk/lib/convert/ascii.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;
 
 /**
  * An instance of the default implementation of the [AsciiCodec].
  *
  * This instance provides a convenient access to the most common ASCII
@@ skipping 64 matching lines @@
   const _UnicodeSubsetEncoder(this._subsetMask);
 
   /**
    * Converts the [String] into a list of its code units.
    *
    * If [start] and [end] are provided, only the substring
    * `string.substring(start, end)` is used as input to the conversion.
    */
   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;
     List result = new Uint8List(length);
     for (int i = 0; i < length; i++) {
       var codeUnit = string.codeUnitAt(start + i);
       if ((codeUnit & ~_subsetMask) != 0) {
         throw new ArgumentError("String contains invalid characters.");
       }
       result[i] = codeUnit;
     }
     return result;
@@ skipping 31 matching lines @@
   final ByteConversionSink _sink;
   final int _subsetMask;
 
   _UnicodeSubsetEncoderSink(this._subsetMask, this._sink);
 
   void close() {
     _sink.close();
   }
 
   void addSlice(String source, int start, int end, bool isLast) {
-    if (start < 0 || start > source.length) {
-      throw new RangeError.range(start, 0, source.length);
-    }
-    if (end < start || end > source.length) {
-      throw new RangeError.range(end, start, source.length);
-    }
+    RangeError.checkValidRange(start, end, source.length);
     for (int i = start; i < end; i++) {
       int codeUnit = source.codeUnitAt(i);
       if ((codeUnit & ~_subsetMask) != 0) {
         throw new ArgumentError(
             "Source contains invalid character with code point: $codeUnit.");
       }
     }
     _sink.add(source.codeUnits.sublist(start, end));
     if (isLast) {
       close();
@@ skipping 27 matching lines @@
 
   /**
    * Converts the [bytes] (a list of unsigned 7- or 8-bit integers) to the
    * corresponding string.
    *
    * If [start] and [end] are provided, only the sub-list of bytes from
    * `start` to `end` (`end` not inclusive) is used as input to the conversion.
    */
   String convert(List<int> bytes, [int start = 0, int end]) {
     int byteCount = bytes.length;
-    if (start < 0 || start > byteCount) {
-      throw new RangeError.range(start, 0, byteCount, "start");
-    }
-    if (end == null) {
-      end = byteCount;
-    } else {
-      if (end < start || end > byteCount) {
-        throw new RangeError.range(end, start, byteCount, "end");
-      }
-    }
+    RangeError.checkValidRange(start, end, byteCount);
+    if (end == null) end = byteCount;
     int length = end - start;
 
     for (int i = start; i < end; i++) {
       int byte = bytes[i];
       if ((byte & ~_subsetMask) != 0) {
         if (!_allowInvalid) {
           throw new FormatException("Invalid value in input: $byte");
         }
         return _convertInvalid(bytes, start, end);
       }
@@ skipping 58 matching lines @@
 
   void close() {
     _utf8Sink.close();
   }
 
   void add(List<int> source) {
     addSlice(source, 0, source.length, false);
   }
 
   void addSlice(List<int> source, int start, int end, bool isLast) {
-    if (start < 0 || start > source.length) {
-      throw new RangeError.range(start, 0, source.length);
-    }
-    if (end < start || end > source.length) {
-      throw new RangeError.range(end, start, source.length);
-    }
+    RangeError.checkValidRange(start, end, source.length);
     for (int i = start; i < end; i++) {
       if ((source[i] & ~_ASCII_MASK) != 0) {
         if (i > start) _utf8Sink.addSlice(source, start, i, false);
         // Add UTF-8 encoding of U+FFFD.
         _utf8Sink.add(const<int>[0xEF, 0xBF, 0xBD]);
         start = i + 1;
       }
     }
     if (start < end) {
       _utf8Sink.addSlice(source, start, end, isLast);
@@ skipping 15 matching lines @@
     for (int i = 0; i < source.length; i++) {
       if ((source[i] & ~_ASCII_MASK) != 0) {
         throw new FormatException("Source contains non-ASCII bytes.");
       }
     }
     _sink.add(new String.fromCharCodes(source));
   }
 
   void addSlice(List<int> source, int start, int end, bool isLast) {
     final int length = source.length;
-    if (start < 0 || start > length) {
-      throw new RangeError.range(start, 0, length);
-    }
-    if (end < start || end > length) {
-      throw new RangeError.range(end, start, length);
-    }
+    RangeError.checkValidRange(start, end, length);
     if (start < end) {
       if (start != 0 || end != length) {
         source = source.sublist(start, end);
       }
       add(source);
     }
     if (isLast) close();
   }
 }