Add a version number for full and script snapshots.

runtime/vm/snapshot.cc

 // 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.
 
 #include "vm/snapshot.h"
 
 #include "platform/assert.h"
 #include "vm/bigint_operations.h"
 #include "vm/bootstrap.h"
 #include "vm/class_finalizer.h"
 #include "vm/exceptions.h"
 #include "vm/heap.h"
 #include "vm/longjump.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
 #include "vm/snapshot_ids.h"
 #include "vm/symbols.h"
+#include "vm/version.h"
 
 namespace dart {
 
 static const int kNumInitialReferencesInFullSnapshot = 160 * KB;
 static const int kNumInitialReferences = 64;
 
 
 static bool IsSingletonClassId(intptr_t class_id) {
   // Check if this is a singleton object class which is shared by all isolates.
   return ((class_id >= kClassCid && class_id <= kUnwindErrorCid) ||
@@ skipping 368 matching lines @@
   }
   ~HeapLocker() {
     page_space_->ReleaseDataLock();
   }
 
  private:
   PageSpace* page_space_;
 };
 
 
-void SnapshotReader::ReadFullSnapshot() {
+RawApiError* SnapshotReader::ReadFullSnapshot() {
   ASSERT(kind_ == Snapshot::kFull);
   Isolate* isolate = Isolate::Current();
   ASSERT(isolate != NULL);
   ObjectStore* object_store = isolate->object_store();
   ASSERT(object_store != NULL);
-  NoGCScope no_gc;
 
   // TODO(asiva): Add a check here to ensure we have the right heap
   // size for the full snapshot being read.
 
   {
+    NoGCScope no_gc;
     HeapLocker hl(isolate, old_space());
+
+    // First read the version string, and check that it matches.
+    obj_ = ReadObject();
+
+    // If the version string doesn't match, return an error.
+    // NB: New things are allocated only if we're going to return an error.
+    if (!obj_.IsString() || !String::Cast(obj_).Equals(Version::String())) {
+      const intptr_t kMessageBufferSize = 128;
+      char message_buffer[kMessageBufferSize];
+      OS::SNPrint(message_buffer,
+                  kMessageBufferSize,
+                  "Wrong full snapshot version. Found %s Expected %s",

[Ivan Posva, 2014/08/26 23:52:43]

Strange capitalization of Expected.

[siva, 2014/08/27 18:25:08]

Fixed.

+                  obj_.ToCString(),
+                  Version::String());
+      const String& msg = String::Handle(String::New(message_buffer));
+      return ApiError::New(msg);
+    }
+
+    // The version string matches. Read the rest of the snapshot.
+
     // Read in all the objects stored in the object store.
     intptr_t num_flds = (object_store->to() - object_store->from());
     for (intptr_t i = 0; i <= num_flds; i++) {
       *(object_store->from() + i) = ReadObjectImpl();
     }
     for (intptr_t i = 0; i < backward_references_.length(); i++) {
       if (!backward_references_[i].is_deserialized()) {
         ReadObjectImpl();
         backward_references_[i].set_state(kIsDeserialized);
       }
     }
+
+    // Validate the class table.
+#if defined(DEBUG)
+    isolate->ValidateClassTable();
+#endif
+
+    // Setup native resolver for bootstrap impl.
+    Bootstrap::SetupNativeResolver();
+    return ApiError::null();
+  }
+}
+
+
+RawObject* SnapshotReader::ReadScriptSnapshot() {
+  ASSERT(kind_ == Snapshot::kScript);
+
+  // First read the version string, and check that it matches.
+  obj_ = ReadObject();
+
+  // If the version string doesn't match, return an error.
+  // NB: New things are allocated only if we're going to return an error.
+  if (!obj_.IsString() || !String::Cast(obj_).Equals(Version::String())) {
+    const intptr_t kMessageBufferSize = 128;
+    char message_buffer[kMessageBufferSize];
+    OS::SNPrint(message_buffer,
+                kMessageBufferSize,
+                "Wrong script snapshot version. Found %s Expected %s",
+                obj_.ToCString(),
+                Version::String());
+    const String& msg = String::Handle(String::New(message_buffer));
+    return ApiError::New(msg);
   }
 
-  // Validate the class table.
-#if defined(DEBUG)
-  isolate->ValidateClassTable();
-#endif
-
-  // Setup native resolver for bootstrap impl.
-  Bootstrap::SetupNativeResolver();
+  // The version string matches. Read the rest of the snapshot.
+  return ReadObject();

[Ivan Posva, 2014/08/26 23:52:43]

Alternatively you could do the test for library in this function and either
return the library object or an error object.

[siva, 2014/08/27 18:25:07]

Done.

 }
 
 
 #define ALLOC_NEW_OBJECT_WITH_LEN(type, length)                                \
   ASSERT(kind_ == Snapshot::kFull);                                            \
   ASSERT(isolate()->no_gc_scope_depth() != 0);                                 \
   Raw##type* obj = reinterpret_cast<Raw##type*>(                               \
       AllocateUninitialized(k##type##Cid, type::InstanceSize(length)));        \
   obj->ptr()->length_ = Smi::New(length);                                      \
   return obj;                                                                  \
@@ skipping 723 matching lines @@
   ASSERT(isolate != NULL);
   ObjectStore* object_store = isolate->object_store();
   ASSERT(object_store != NULL);
   ASSERT(ClassFinalizer::AllClassesFinalized());
 
   // Ensure the class table is valid.
 #if defined(DEBUG)
   isolate->ValidateClassTable();
 #endif
 
-
   // Setup for long jump in case there is an exception while writing
   // the snapshot.
   LongJumpScope jump;
   if (setjmp(*jump.Set()) == 0) {
-    NoGCScope no_gc;
-
     // Reserve space in the output buffer for a snapshot header.
     ReserveHeader();
 
-    // Write out all the objects in the object store of the isolate which
-    // is the root set for all dart allocated objects at this point.
-    SnapshotWriterVisitor visitor(this, false);
-    object_store->VisitObjectPointers(&visitor);
+    // Write out the version string.
+    WriteObject(String::New(Version::String()));
 
-    // Write out all forwarded objects.
-    WriteForwardedObjects();
+    // Write out the full snapshot.
+    {
+      NoGCScope no_gc;
 
-    FillHeader(kind());
-    UnmarkAll();
+      // Write out all the objects in the object store of the isolate which
+      // is the root set for all dart allocated objects at this point.
+      SnapshotWriterVisitor visitor(this, false);
+      object_store->VisitObjectPointers(&visitor);
+
+      // Write out all forwarded objects.
+      WriteForwardedObjects();
+
+      FillHeader(kind());
+      UnmarkAll();
+    }
   } else {
     ThrowException(exception_type(), exception_msg());
   }
 }
 
 
 uword SnapshotWriter::GetObjectTags(RawObject* raw) {
   uword tags = raw->ptr()->tags_;
   if (SerializedHeaderTag::decode(tags) == kObjectId) {
     intptr_t id = SerializedHeaderData::decode(tags);
@@ skipping 395 matching lines @@
 void ScriptSnapshotWriter::WriteScriptSnapshot(const Library& lib) {
   ASSERT(kind() == Snapshot::kScript);
   Isolate* isolate = Isolate::Current();
   ASSERT(isolate != NULL);
   ASSERT(ClassFinalizer::AllClassesFinalized());
 
   // Setup for long jump in case there is an exception while writing
   // the snapshot.
   LongJumpScope jump;
   if (setjmp(*jump.Set()) == 0) {
+    // Reserve space in the output buffer for a snapshot header.
+    ReserveHeader();
+
+    // Write out the version string.
+    WriteObject(String::New(Version::String()));
+
     // Write out the library object.
-    NoGCScope no_gc;
-    ReserveHeader();
-    WriteObject(lib.raw());
-    FillHeader(kind());
-    UnmarkAll();
+    {
+      NoGCScope no_gc;
+
+      // Write out the library object.
+      WriteObject(lib.raw());
+
+      FillHeader(kind());
+      UnmarkAll();
+    }
   } else {
     ThrowException(exception_type(), exception_msg());
   }
 }
 
 
 void SnapshotWriterVisitor::VisitPointers(RawObject** first, RawObject** last) {
   for (RawObject** current = first; current <= last; current++) {
     RawObject* raw_obj = *current;
     if (as_references_) {
@@ skipping 17 matching lines @@
     NoGCScope no_gc;
     WriteObject(obj.raw());
     UnmarkAll();
   } else {
     ThrowException(exception_type(), exception_msg());
   }
 }
 
 
 }  // namespace dart