Implement faster splitting with empty string as pattern. Add special native for computing substring…

runtime/vm/object.cc

 // Copyright (c) 2012, 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.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
@@ skipping 10762 matching lines @@
 
 RawOneByteString* OneByteString::New(const String& str,
                                      Heap::Space space) {
   intptr_t len = str.Length();
   const String& result = String::Handle(OneByteString::New(len, space));
   String::Copy(result, 0, str, 0, len);
   return OneByteString::raw(result);
 }
 
 
+RawOneByteString* OneByteString::New(const String& other,
+                                     intptr_t other_start_index,
+                                     intptr_t other_len,
+                                     Heap::Space space) {
+  const String& result = String::Handle(OneByteString::New(other_len, space));
+  String::Copy(result, 0, other, other_start_index, other_len);

[siva, 2012/11/29 21:42:46]

Could be written as:
ASSERT(other.IsOneByteString());
NoGCScope no_gc;
memmove(OneByteString::CharAddr(result, 0),
        OneByteString::CharAddr(other, other_start_index),
        other_len);

or

ASSERT(other.IsOneByteString());
NoGCScope no_gc;
String::Copy(result,
             0, 
             OneByteString::CharAddr(other, other_start_index),
             other_len);

This would save some additional checks as you already know
it is a OneByteString.

[srdjan, 2012/11/29 22:57:14]

Done.

+  return OneByteString::raw(result);
+}
+
+
 RawOneByteString* OneByteString::Concat(const String& str1,
                                         const String& str2,
                                         Heap::Space space) {
   intptr_t len1 = str1.Length();
   intptr_t len2 = str2.Length();
   intptr_t len = len1 + len2;
   const String& result = String::Handle(OneByteString::New(len, space));
   String::Copy(result, 0, str1, 0, len1);
   String::Copy(result, len1, str2, 0, len2);
   return OneByteString::raw(result);
@@ skipping 1379 matching lines @@
   }
   return result.raw();
 }
 
 
 const char* WeakProperty::ToCString() const {
   return "_WeakProperty";
 }
 
 }  // namespace dart