Write the magic number 0xf5f5dcdc into a script snapshot file and use this to distinguish whether a…

runtime/bin/dartutils.h

 // 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.
 
 #ifndef BIN_DARTUTILS_H_
 #define BIN_DARTUTILS_H_
 
 #include "bin/builtin.h"
 #include "bin/utils.h"
 #include "include/dart_api.h"
 #include "platform/globals.h"
 
+// Forward declarations.
+class File;
+
 /* Handles error handles returned from Dart API functions.  If a value
  * is an error, uses Dart_PropagateError to throw it to the enclosing
  * Dart activation.  Otherwise, returns the original handle.
  *
  * This function can be used to wrap most API functions, but API
  * functions can also be nested without this error check, since all
  * API functions return any error handles passed in as arguments, unchanged.
  */
 static inline Dart_Handle ThrowIfError(Dart_Handle handle) {
   if (Dart_IsError(handle)) Dart_PropagateError(handle);
@@ skipping 127 matching lines @@
   static Dart_Handle ResolveScriptUri(Dart_Handle script_uri,
                                       Dart_Handle builtin_lib);
 
   static Dart_Handle FilePathFromUri(Dart_Handle script_uri,
                                      Dart_Handle builtin_lib);
 
   static Dart_Handle ResolveUri(Dart_Handle library_url,
                                 Dart_Handle url,
                                 Dart_Handle builtin_lib);
 
+  // Sniffs the specified text_buffer to see if it contains the magic number
+  // representing a script snapshot. If the text_buffer is a script snapshot
+  // the return value is an updated pointer to the text_buffer pointing past
+  // the magic number value.
+  static const uint8_t* SniffForMagicNumber(const uint8_t* text_buffer,
+                                            bool* is_snapshot);
+
+  // Write a magic number to indicate a script snapshot file.
+  static void WriteMagicNumber(File* file);
+
   // Global state that stores the original working directory..
   static const char* original_working_directory;
 
   static const char* kDartScheme;
   static const char* kDartExtensionScheme;
   static const char* kAsyncLibURL;
   static const char* kBuiltinLibURL;
   static const char* kCoreLibURL;
   static const char* kIOLibURL;
   static const char* kIOLibPatchURL;
   static const char* kUriLibURL;
   static const char* kUtfLibURL;
   static const char* kIsolateLibURL;
   static const char* kScalarlistLibURL;
   static const char* kWebLibURL;
 
   static const char* kIdFieldName;
 
+  static uint8_t magic_number[];
+
  private:
   static const char* GetCanonicalPath(const char* reference_dir,
                                       const char* filename);
 
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(DartUtils);
 };
 
 
 class CObject {
@@ skipping 223 matching lines @@
   void* Peer() const { return cobject_->value.as_external_byte_array.peer; }
   Dart_WeakPersistentHandleFinalizer Callback() const {
     return cobject_->value.as_external_byte_array.callback;
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(CObjectExternalUint8Array);
 };
 
 #endif  // BIN_DARTUTILS_H_