Avoid unnecessary copying when parsing doubles.

runtime/lib/double.cc

 // Copyright (c) 2011, 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/bootstrap_natives.h"
 
 #include "platform/math.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/code_generator.h"  // DartModulo.
@@ skipping 164 matching lines @@
 // MAC OSX math library produces old style cast warning.
 #pragma GCC diagnostic ignored "-Wold-style-cast"
 #endif
 
 DEFINE_NATIVE_ENTRY(Double_toInt, 1) {
   const Double& arg = Double::CheckedHandle(arguments->NativeArgAt(0));
   return DoubleToInteger(arg.value(), "Infinity or NaN toInt");
 }
 
 
-DEFINE_NATIVE_ENTRY(Double_parse, 1) {
+DEFINE_NATIVE_ENTRY(Double_parse, 3) {
   GET_NON_NULL_NATIVE_ARGUMENT(String, value, arguments->NativeArgAt(0));
+  GET_NON_NULL_NATIVE_ARGUMENT(Integer, startValue, arguments->NativeArgAt(1));
+  GET_NON_NULL_NATIVE_ARGUMENT(Integer, endValue, arguments->NativeArgAt(2));
 
+  const intptr_t start = startValue.AsTruncatedUint32Value();
+  const intptr_t end = endValue.AsTruncatedUint32Value();
   const intptr_t len = value.Length();
 
+  // Indices should be inside the string, and 0 <= start < end <= len.
   // The native function only accepts one-byte strings. The Dart side converts

[Vyacheslav Egorov (Google), 2014/07/01 11:36:18]

This comment does not seem to be valid anymore.

[Lasse Reichstein Nielsen, 2014/07/01 11:54:18]

Well spotted.

   // other types of strings to one-byte strings, if necessary.
-  if ((!value.IsOneByteString() && !value.IsExternalOneByteString())
-      || (len == 0)) {
-    return Object::null();
+  if (0 <= start && start < end && end <= len) {
+    double double_value;
+    if (String::ParseDouble(value, start, end, &double_value)) {
+      return Double::New(double_value);
+    }
   }
-
-  double double_value;
-  const char* cstr = value.ToCString();
-  ASSERT(cstr != NULL);
-  if (CStringToDouble(cstr, len, &double_value)) {
-    return Double::New(double_value);
-  } else {
-    return Object::null();
-  }
+  return Object::null();
 }
 
 
 DEFINE_NATIVE_ENTRY(Double_toStringAsFixed, 2) {
   // The boundaries are exclusive.
   static const double kLowerBoundary = -1e21;
   static const double kUpperBoundary = 1e21;
 
   const Double& arg = Double::CheckedHandle(arguments->NativeArgAt(0));
   GET_NON_NULL_NATIVE_ARGUMENT(Smi, fraction_digits, arguments->NativeArgAt(1));
@@ skipping 56 matching lines @@
 DEFINE_NATIVE_ENTRY(Double_getIsNegative, 1) {
   const Double& arg = Double::CheckedHandle(arguments->NativeArgAt(0));
   // Include negative zero, infinity.
   double dval = arg.value();
   return Bool::Get(signbit(dval) && !isnan(dval)).raw();
 }
 
 // Add here only functions using/referring to old-style casts.
 
 }  // namespace dart