Recognize and special case String.fromCharCodes for Uint8List in JavaScript.

sdk/lib/_internal/compiler/js_lib/js_helper.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.
 
 library _js_helper;
 
 import 'dart:_js_embedded_names' show
     ALL_CLASSES,
     GET_ISOLATE_TAG,
     INTERCEPTED_NAMES,
@@ skipping 42 matching lines @@
     JS_OPERATOR_AS_PREFIX,
     JS_OPERATOR_IS_PREFIX,
     JS_SIGNATURE_NAME,
     JS_STRING_CONCAT,
     RAW_DART_FUNCTION_REF;
 
 import 'dart:_interceptors';
 import 'dart:_internal' as _symbol_dev;
 import 'dart:_internal' show MappedIterable;
 
+import 'dart:_native_typed_data';
+
 import 'dart:_js_names' show
     extractKeys,
     mangledNames,
     unmangleGlobalNameIfPreservedAnyways,
     unmangleAllIdentifiersIfPreservedAnyways;
 
 part 'annotations.dart';
 part 'constant_map.dart';
 part 'native_helper.dart';
 part 'regexp_helper.dart';
@@ skipping 684 matching lines @@
     if (JS('bool', '!!self.location')) {
       return JS('String', 'self.location.href');
     }
 
     return null;
   }
 
   // This is to avoid stack overflows due to very large argument arrays in
   // apply().  It fixes http://dartbug.com/6919
   static String _fromCharCodeApply(List<int> array) {
-    String result = "";
     const kMaxApply = 500;
     int end = array.length;
-    for (var i = 0; i < end; i += kMaxApply) {
-      var subarray;
-      if (end <= kMaxApply) {
-        subarray = array;
-      } else {
-        subarray = JS('JSExtendableArray', r'#.slice(#, #)', array,
-                      i, i + kMaxApply < end ? i + kMaxApply : end);
-      }
-      result = JS('String', '# + String.fromCharCode.apply(#, #)',
-                  result, null, subarray);
+    if (end <= kMaxApply) {
+      return JS('String', r'String.fromCharCode.apply(null, #)', array);
+    }
+    String result = '';
+    for (int i = 0; i < end; i += kMaxApply) {
+      int chunkEnd = (i + kMaxApply < end) ? i + kMaxApply : end;
+      result = JS('String',
+          r'# + String.fromCharCode.apply(null, #.slice(#, #))',
+          result, array, i, chunkEnd);
     }
     return result;
   }
 
   static String stringFromCodePoints(codePoints) {
     List<int> a = <int>[];
     for (var i in codePoints) {
       if (i is !int) throw new ArgumentError(i);
       if (i <= 0xffff) {
         a.add(i);
       } else if (i <= 0x10ffff) {
         a.add(0xd800 + ((((i - 0x10000) >> 10) & 0x3ff)));
         a.add(0xdc00 + (i & 0x3ff));
       } else {
         throw new ArgumentError(i);
       }
     }
     return _fromCharCodeApply(a);
   }
 
   static String stringFromCharCodes(charCodes) {
     for (var i in charCodes) {
       if (i is !int) throw new ArgumentError(i);
       if (i < 0) throw new ArgumentError(i);
       if (i > 0xffff) return stringFromCodePoints(charCodes);
     }
     return _fromCharCodeApply(charCodes);
   }
 
+  // [start] and [end] are validated.
+  static String stringFromNativeUint8List(
+      NativeUint8List charCodes, int start, int end) {
+    const kMaxApply = 500;
+    if (end <= kMaxApply && start == 0 && end == charCodes.length) {
+      return JS('String', r'String.fromCharCode.apply(null, #)', charCodes);
+    }
+    String result = '';
+    for (int i = start; i < end; i += kMaxApply) {
+      int chunkEnd = (i + kMaxApply < end) ? i + kMaxApply : end;
+      result = JS('String',
+          r'# + String.fromCharCode.apply(null, #.subarray(#, #))',
+          result, charCodes, i, chunkEnd);
+    }
+    return result;
+  }
+
+
   static String stringFromCharCode(charCode) {
     if (0 <= charCode) {
       if (charCode <= 0xffff) {
         return JS('String', 'String.fromCharCode(#)', charCode);
       }
       if (charCode <= 0x10ffff) {
         var bits = charCode - 0x10000;
         var low = 0xDC00 | (bits & 0x3ff);
         var high = 0xD800 | (bits >> 10);
         return  JS('String', 'String.fromCharCode(#, #)', high, low);
@@ skipping 2618 matching lines @@
   throw new MainError("No top-level function named 'main'.");
 }
 
 void badMain() {
   throw new MainError("'main' is not a function.");
 }
 
 void mainHasTooManyParameters() {
   throw new MainError("'main' expects too many parameters.");
 }