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

runtime/vm/object.cc

Index: runtime/vm/object.cc
===================================================================
--- runtime/vm/object.cc	(revision 15528)
+++ runtime/vm/object.cc	(working copy)
@@ -10780,6 +10780,16 @@
 }
 
 
+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) {