Change VM's string-buffer patch to use a Uin16Array as backing buffer.

runtime/lib/string.cc

Index: runtime/lib/string.cc
diff --git a/runtime/lib/string.cc b/runtime/lib/string.cc
index 3b5b633a9e9802114463d9bfd90b71426f257511..2e72aadb0cf3cb5e4e88df5b74ab161026e26626 100644
--- a/runtime/lib/string.cc
+++ b/runtime/lib/string.cc
@@ -49,7 +49,6 @@ DEFINE_NATIVE_ENTRY(StringBase_createFromCodePoints, 1) {
   return TwoByteString::New(utf16_len, utf32_array, array_len, Heap::kNew);
 }
 
-

[srdjan, 2013/03/07 17:58:34]

Please restore line

[Lasse Reichstein Nielsen, 2013/03/08 07:18:44]

Done. *And* saving the buffer this time.

 DEFINE_NATIVE_ENTRY(StringBase_substringUnchecked, 3) {
   const String& receiver = String::CheckedHandle(arguments->NativeArgAt(0));
   GET_NON_NULL_NATIVE_ARGUMENT(Smi, start_obj, arguments->NativeArgAt(1));
@@ -197,4 +196,26 @@ DEFINE_NATIVE_ENTRY(Strings_concatAll, 1) {
   return String::ConcatAll(strings);
 }
 
+DEFINE_NATIVE_ENTRY(StringBuffer_createStringFromUint16Array, 3) {
+  GET_NON_NULL_NATIVE_ARGUMENT(Uint16Array, a, arguments->NativeArgAt(0));

[Vyacheslav Egorov (Google), 2013/03/07 13:50:52]

I'd give a longer name to a.

[Lasse Reichstein Nielsen, 2013/03/08 07:18:44]

Done.

+  GET_NON_NULL_NATIVE_ARGUMENT(Smi, smiLength, arguments->NativeArgAt(1));

[Vyacheslav Egorov (Google), 2013/03/07 13:50:52]

smiLength -> length

[Lasse Reichstein Nielsen, 2013/03/08 07:18:44]

Done.

+  GET_NON_NULL_NATIVE_ARGUMENT(Bool, isLatin1, arguments->NativeArgAt(2));
+  intptr_t array_len = a.Length();
+  int32_t length = smiLength.Value();

[Vyacheslav Egorov (Google), 2013/03/07 13:50:52]

length -> length_value

[srdjan, 2013/03/07 17:58:34]

intr32_t -> intptr_t; on x64 Smi is greater than int32_t.

[Lasse Reichstein Nielsen, 2013/03/08 07:18:44]

Done.

+  if (length < 0 || length > array_len) {
+    const Array& args = Array::Handle(Array::New(1));
+    args.SetAt(0, smiLength);
+    Exceptions::ThrowByType(Exceptions::kRange, args);
+  }
+  const String& result = isLatin1.value()
+      ? String::Handle(OneByteString::New(length, Heap::kNew))
+      : String::Handle(TwoByteString::New(length, Heap::kNew));
+  NoGCScope no_gc;
+  uint16_t* data_position = reinterpret_cast<uint16_t*>(

[Vyacheslav Egorov (Google), 2013/03/07 13:50:52]

consider a.ByteAddr(0)

[Lasse Reichstein Nielsen, 2013/03/08 07:18:44]

I already tried that, but it seems to be private on Uint16Array. Could I somehow
cast it to a ByteArray, where ByteAddr is public?

[Ivan Posva, 2013/03/08 09:15:41]

I told Lasse to make the ByteAddr public. This is all changing with TypedData
anyway, we will have to properly deal with it then.

[Lasse Reichstein Nielsen, 2013/03/08 10:19:37]

And it works with a public ByteAddr.

+      reinterpret_cast<char*>(a.raw()) +
+      Uint16Array::data_offset() - kHeapObjectTag);
+  String::Copy(result, 0, data_position, length);
+  return result.raw();
+}
+
 }  // namespace dart