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

runtime/vm/dart_api_impl.cc

 // Copyright (c) 2013, 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 "include/dart_api.h"
 
 #include "platform/assert.h"
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
@@ skipping 4274 matching lines @@
 
   const Script& script = Script::Handle(
       isolate, Script::New(url_str, source_str, RawScript::kScriptTag));
   script.SetLocationOffset(line_offset, col_offset);
   Dart_Handle result;
   CompileSource(isolate, library, script, &result);
   return result;
 }
 
 
-DART_EXPORT Dart_Handle Dart_LoadScriptFromSnapshot(const uint8_t* buffer) {
+DART_EXPORT Dart_Handle Dart_LoadScriptFromSnapshot(const uint8_t* buffer,
+                                                    intptr_t buffer_len) {
   Isolate* isolate = Isolate::Current();
   DARTSCOPE(isolate);
   TIMERSCOPE(time_script_loading);
   if (buffer == NULL) {
     RETURN_NULL_ERROR(buffer);
   }
   const Snapshot* snapshot = Snapshot::SetupFromBuffer(buffer);
   if (!snapshot->IsScriptSnapshot()) {
     return Api::NewError("%s expects parameter 'buffer' to be a script type"
                          " snapshot.", CURRENT_FUNC);
   }
+  if (snapshot->length() != buffer_len) {
+    return Api::NewError("%s: 'buffer_len' of %"Pd" is not equal to %d which"
+                         " is the expected length in the snapshot.",
+                         CURRENT_FUNC, buffer_len, snapshot->length());
+  }
   Library& library =
       Library::Handle(isolate, isolate->object_store()->root_library());
   if (!library.IsNull()) {
     const String& library_url = String::Handle(isolate, library.url());
     return Api::NewError("%s: A script has already been loaded from '%s'.",
                          CURRENT_FUNC, library_url.ToCString());
   }
   CHECK_CALLBACK_STATE(isolate);
 
   SnapshotReader reader(snapshot->content(),
@@ skipping 357 matching lines @@
   }
   {
     NoGCScope no_gc;
     RawObject* raw_obj = obj.raw();
     isolate->heap()->SetPeer(raw_obj, peer);
   }
   return Api::Success(isolate);
 }
 
 }  // namespace dart