Don't create a Bigint object first for every integer while parsing the sources, instead first check…

vm/os.h

 // 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.
 
 #ifndef VM_OS_H_
 #define VM_OS_H_
 
 #include "vm/globals.h"
 
 // Forward declarations.
@@ skipping 64 matching lines @@
   //
   // This specification conforms to C99 standard which is implemented
   // by glibc 2.1+ with one exception: the C99 standard allows a
   // negative return value.  We will terminate the vm rather than let
   // that occur.
   static int SNPrint(char* str, size_t size, const char* format, ...);
   static int VSNPrint(char* str, size_t size,
                       const char* format,
                       va_list args);
 
+  // Converts a C string which represents a valid dart integer into a 64 bit
+  // value.
+  // Returns false if it is unable to convert the string to a 64 bit value,
+  // the failure could be because of underflow/overflow or invalid characters.
+  // On success the function returns true and 'value' contains the converted
+  // value.
+  static bool StringToInteger(const char* str, int64_t* value);
+
   // Initialize the OS class.
   static void InitOnce();
 
   // Shut down the OS class.
   static void Shutdown();
 
   static void Abort();
 
   static void Exit(int code);
 };
 
 }  // namespace dart
 
 #endif  // VM_OS_H_