[web snapshot] Make ValueSerializer an inline member

We can avoid a pointer deref if the ValueSerializer is inlined in
WebSnapshotDeserializer.

Bug: v8:11525
Change-Id: I92d8cac37af3fdbe04a66465f97761bf5a9fd705
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3417433Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78830}

src/api/api.cc

@@ -2087,8 +2087,10 @@ MaybeLocal<Value> Script::Run(Local<Context> context,
         handle(fun->shared().script(), isolate);
     if (maybe_script->IsScript() &&
         i::Script::cast(*maybe_script).type() == i::Script::TYPE_WEB_SNAPSHOT) {
-      i::WebSnapshotDeserializer deserializer(v8_isolate);
-      deserializer.UseWebSnapshot(i::Handle<i::Script>::cast(maybe_script));
+      i::WebSnapshotDeserializer deserializer(
+          reinterpret_cast<i::Isolate*>(v8_isolate),
+          i::Handle<i::Script>::cast(maybe_script));
+      deserializer.Deserialize();
       RETURN_ON_FAILED_EXECUTION(Value);
       Local<Value> result = v8::Undefined(v8_isolate);
       RETURN_ESCAPED(result);

src/d8/d8.cc

@@ -1443,9 +1443,9 @@ bool Shell::ExecuteWebSnapshot(Isolate* isolate, const char* file_name) {
   if (length == 0) {
     isolate->ThrowError("Could not read the web snapshot file");
   } else {
-    i::WebSnapshotDeserializer deserializer(isolate);
-    success = deserializer.UseWebSnapshot(snapshot_data.get(),
+    i::WebSnapshotDeserializer deserializer(isolate, snapshot_data.get(),
                                             static_cast<size_t>(length));
+    success = deserializer.Deserialize();
   }
   if (!success) {
     CHECK(try_catch.HasCaught());
@@ -2003,9 +2003,10 @@ void Shell::RealmUseWebSnapshot(
   // Deserialize the snapshot in the specified Realm.
   {
     PerIsolateData::ExplicitRealmScope realm_scope(data, index);
-    i::WebSnapshotDeserializer deserializer(isolate);
-    bool success = deserializer.UseWebSnapshot(
-        snapshot_data_shared->buffer, snapshot_data_shared->buffer_size);
+    i::WebSnapshotDeserializer deserializer(isolate,
+                                            snapshot_data_shared->buffer,
+                                            snapshot_data_shared->buffer_size);
+    bool success = deserializer.Deserialize();
     args.GetReturnValue().Set(success);
   }
 }

src/web-snapshot/web-snapshot.cc

@@ -1028,63 +1028,51 @@ uint32_t WebSnapshotSerializer::GetObjectId(JSObject object) {
   return static_cast<uint32_t>(id);
 }
 
-WebSnapshotDeserializer::WebSnapshotDeserializer(v8::Isolate* isolate)
-    : WebSnapshotSerializerDeserializer(
-          reinterpret_cast<v8::internal::Isolate*>(isolate)) {}
-
-WebSnapshotDeserializer::~WebSnapshotDeserializer() {}
-
-void WebSnapshotDeserializer::Throw(const char* message) {
-  string_count_ = 0;
-  map_count_ = 0;
-  context_count_ = 0;
-  class_count_ = 0;
-  function_count_ = 0;
-  object_count_ = 0;
-  deferred_references_->SetLength(0);
-
-  // Make sure we don't read any more data
-  deserializer_->position_ = deserializer_->end_;
-
-  WebSnapshotSerializerDeserializer::Throw(message);
-}
-
-bool WebSnapshotDeserializer::UseWebSnapshot(const uint8_t* data,
-                                             size_t buffer_size) {
-  deserializer_.reset(new ValueDeserializer(isolate_, data, buffer_size));
-  return Deserialize();
-}
-
-bool WebSnapshotDeserializer::UseWebSnapshot(
-    Handle<Script> snapshot_as_script) {
+WebSnapshotDeserializer::WebSnapshotDeserializer(v8::Isolate* isolate,
+                                                 const uint8_t* data,
+                                                 size_t buffer_size)
+    : WebSnapshotDeserializer(reinterpret_cast<i::Isolate*>(isolate),
+                              Handle<Object>(), {data, buffer_size}) {}
+
+WebSnapshotDeserializer::WebSnapshotDeserializer(
+    Isolate* isolate, Handle<Script> snapshot_as_script)
+    : WebSnapshotDeserializer(
+          isolate, handle(snapshot_as_script->name(), isolate),
+          ExtractScriptBuffer(isolate, snapshot_as_script)) {}
+
+WebSnapshotDeserializer::WebSnapshotDeserializer(
+    Isolate* isolate, Handle<Object> script_name,
+    base::Vector<const uint8_t> buffer)
+    : WebSnapshotSerializerDeserializer(isolate),
+      script_name_(script_name),
+      deserializer_(isolate_, buffer.data(), buffer.length()) {}
+
+// static
+base::Vector<const uint8_t> WebSnapshotDeserializer::ExtractScriptBuffer(
+    Isolate* isolate, Handle<Script> snapshot_as_script) {
   Handle<String> source =
-      handle(String::cast(snapshot_as_script->source()), isolate_);
-  script_name_ = handle(snapshot_as_script->name(), isolate_);
+      handle(String::cast(snapshot_as_script->source()), isolate);
   if (source->IsExternalOneByteString()) {
     const v8::String::ExternalOneByteStringResource* resource =
         ExternalOneByteString::cast(*source).resource();
-    deserializer_.reset(new ValueDeserializer(
-        isolate_, reinterpret_cast<const uint8_t*>(resource->data()),
-        resource->length()));
-    return Deserialize();
+    return {reinterpret_cast<const uint8_t*>(resource->data()),
+            resource->length()};
   } else if (source->IsSeqOneByteString()) {
     SeqOneByteString source_as_seq = SeqOneByteString::cast(*source);
-    auto length = source_as_seq.length();
+    size_t length = source_as_seq.length();
     std::unique_ptr<uint8_t[]> data_copy(new uint8_t[length]);
     {
       DisallowGarbageCollection no_gc;
       uint8_t* data = source_as_seq.GetChars(no_gc);
       memcpy(data_copy.get(), data, length);
     }
-    deserializer_.reset(
-        new ValueDeserializer(isolate_, data_copy.get(), length));
-    return Deserialize();
+    return {data_copy.get(), length};
   } else if (source->IsExternalTwoByteString()) {
     // TODO(v8:11525): Implement end-to-end snapshot processing which gets rid
     // of the need to copy the data here.
     const v8::String::ExternalStringResource* resource =
         ExternalTwoByteString::cast(*source).resource();
-    auto length = resource->length();
+    size_t length = resource->length();
     std::unique_ptr<uint8_t[]> data_copy(new uint8_t[length]);
     {
       DisallowGarbageCollection no_gc;
@@ -1094,27 +1082,39 @@ bool WebSnapshotDeserializer::UseWebSnapshot(
         data_copy_ptr[i] = static_cast<uint8_t>(data[i]);
       }
     }
-    deserializer_.reset(
-        new ValueDeserializer(isolate_, data_copy.get(), length));
-    return Deserialize();
+    return {data_copy.get(), length};
   } else if (source->IsSeqTwoByteString()) {
     SeqTwoByteString source_as_seq = SeqTwoByteString::cast(*source);
-    auto length = source_as_seq.length();
+    size_t length = source_as_seq.length();
     std::unique_ptr<uint8_t[]> data_copy(new uint8_t[length]);
     {
       DisallowGarbageCollection no_gc;
       uint16_t* data = source_as_seq.GetChars(no_gc);
       uint8_t* data_copy_ptr = data_copy.get();
-      for (int i = 0; i < length; ++i) {
+      for (size_t i = 0; i < length; ++i) {
         data_copy_ptr[i] = static_cast<uint8_t>(data[i]);
       }
     }
-    deserializer_.reset(
-        new ValueDeserializer(isolate_, data_copy.get(), length));
-    return Deserialize();
+    return {data_copy.get(), length};
   }
   UNREACHABLE();
 }
+WebSnapshotDeserializer::~WebSnapshotDeserializer() {}
+
+void WebSnapshotDeserializer::Throw(const char* message) {
+  string_count_ = 0;
+  map_count_ = 0;
+  context_count_ = 0;
+  class_count_ = 0;
+  function_count_ = 0;
+  object_count_ = 0;
+  deferred_references_->SetLength(0);
+
+  // Make sure we don't read any more data
+  deserializer_.position_ = deserializer_.end_;
+
+  WebSnapshotSerializerDeserializer::Throw(message);
+}
 
 bool WebSnapshotDeserializer::Deserialize() {
   RCS_SCOPE(isolate_, RuntimeCallCounterId::kWebSnapshotDeserialize);
@@ -1123,7 +1123,7 @@ bool WebSnapshotDeserializer::Deserialize() {
     return false;
   }
   deserialized_ = true;
-  auto buffer_size = deserializer_->end_ - deserializer_->position_;
+  auto buffer_size = deserializer_.end_ - deserializer_.position_;
 
   base::ElapsedTimer timer;
   if (FLAG_trace_web_snapshot) {
@@ -1148,7 +1148,7 @@ bool WebSnapshotDeserializer::DeserializeSnapshot() {
   deferred_references_ = ArrayList::New(isolate_, 30);
 
   const void* magic_bytes;
-  if (!deserializer_->ReadRawBytes(sizeof(kMagicNumber), &magic_bytes) ||
+  if (!deserializer_.ReadRawBytes(sizeof(kMagicNumber), &magic_bytes) ||
       memcmp(magic_bytes, kMagicNumber, sizeof(kMagicNumber)) != 0) {
     Throw("Invalid magic number");
     return false;
@@ -1170,13 +1170,13 @@ bool WebSnapshotDeserializer::DeserializeSnapshot() {
 
 bool WebSnapshotDeserializer::DeserializeScript() {
   // If there is more data, treat it as normal JavaScript.
-  DCHECK_LE(deserializer_->position_, deserializer_->end_);
-  auto remaining_bytes = deserializer_->end_ - deserializer_->position_;
+  DCHECK_LE(deserializer_.position_, deserializer_.end_);
+  auto remaining_bytes = deserializer_.end_ - deserializer_.position_;
   if (remaining_bytes > 0 && remaining_bytes < v8::String::kMaxLength) {
     v8::Isolate* v8_isolate = reinterpret_cast<v8::Isolate*>(isolate_);
     v8::Local<v8::String> source =
         v8::String::NewFromUtf8(
-            v8_isolate, reinterpret_cast<const char*>(deserializer_->position_),
+            v8_isolate, reinterpret_cast<const char*>(deserializer_.position_),
             NewStringType::kNormal, static_cast<int>(remaining_bytes))
             .ToLocalChecked();
 
@@ -1206,7 +1206,7 @@ bool WebSnapshotDeserializer::DeserializeScript() {
 
 void WebSnapshotDeserializer::DeserializeStrings() {
   RCS_SCOPE(isolate_, RuntimeCallCounterId::kWebSnapshotDeserialize_Strings);
-  if (!deserializer_->ReadUint32(&string_count_) ||
+  if (!deserializer_.ReadUint32(&string_count_) ||
       string_count_ > kMaxItemCount) {
     Throw("Malformed string table");
     return;
@@ -1214,7 +1214,7 @@ void WebSnapshotDeserializer::DeserializeStrings() {
   STATIC_ASSERT(kMaxItemCount <= FixedArray::kMaxLength);
   strings_ = isolate_->factory()->NewFixedArray(string_count_);
   for (uint32_t i = 0; i < string_count_; ++i) {
-    MaybeHandle<String> maybe_string = deserializer_->ReadUtf8String();
+    MaybeHandle<String> maybe_string = deserializer_.ReadUtf8String();
     Handle<String> string;
     if (!maybe_string.ToHandle(&string)) {
       Throw("Malformed string");
@@ -1227,7 +1227,7 @@ void WebSnapshotDeserializer::DeserializeStrings() {
 Handle<String> WebSnapshotDeserializer::ReadString(bool internalize) {
   DCHECK(!strings_->is_null());
   uint32_t string_id;
-  if (!deserializer_->ReadUint32(&string_id) || string_id >= string_count_) {
+  if (!deserializer_.ReadUint32(&string_id) || string_id >= string_count_) {
     Throw("malformed string id\n");
     return isolate_->factory()->empty_string();
   }
@@ -1242,7 +1242,7 @@ Handle<String> WebSnapshotDeserializer::ReadString(bool internalize) {
 
 void WebSnapshotDeserializer::DeserializeMaps() {
   RCS_SCOPE(isolate_, RuntimeCallCounterId::kWebSnapshotDeserialize_Maps);
-  if (!deserializer_->ReadUint32(&map_count_) || map_count_ > kMaxItemCount) {
+  if (!deserializer_.ReadUint32(&map_count_) || map_count_ > kMaxItemCount) {
     Throw("Malformed shape table");
     return;
   }
@@ -1250,7 +1250,7 @@ void WebSnapshotDeserializer::DeserializeMaps() {
   maps_ = isolate_->factory()->NewFixedArray(map_count_);
   for (uint32_t i = 0; i < map_count_; ++i) {
     uint32_t map_type;
-    if (!deserializer_->ReadUint32(&map_type)) {
+    if (!deserializer_.ReadUint32(&map_type)) {
       Throw("Malformed shape");
       return;
     }
@@ -1268,14 +1268,14 @@ void WebSnapshotDeserializer::DeserializeMaps() {
     }
 
     uint32_t prototype_id;
-    if (!deserializer_->ReadUint32(&prototype_id) ||
+    if (!deserializer_.ReadUint32(&prototype_id) ||
         prototype_id > kMaxItemCount) {
       Throw("Malformed shape");
       return;
     }
 
     uint32_t property_count;
-    if (!deserializer_->ReadUint32(&property_count)) {
+    if (!deserializer_.ReadUint32(&property_count)) {
       Throw("Malformed shape");
       return;
     }
@@ -1301,7 +1301,7 @@ void WebSnapshotDeserializer::DeserializeMaps() {
       PropertyAttributes attributes = PropertyAttributes::NONE;
       if (has_custom_property_attributes) {
         uint32_t flags;
-        if (!deserializer_->ReadUint32(&flags)) {
+        if (!deserializer_.ReadUint32(&flags)) {
           Throw("Malformed shape");
           return;
         }
@@ -1345,7 +1345,7 @@ void WebSnapshotDeserializer::DeserializeMaps() {
 
 void WebSnapshotDeserializer::DeserializeContexts() {
   RCS_SCOPE(isolate_, RuntimeCallCounterId::kWebSnapshotDeserialize_Contexts);
-  if (!deserializer_->ReadUint32(&context_count_) ||
+  if (!deserializer_.ReadUint32(&context_count_) ||
       context_count_ > kMaxItemCount) {
     Throw("Malformed context table");
     return;
@@ -1354,7 +1354,7 @@ void WebSnapshotDeserializer::DeserializeContexts() {
   contexts_ = isolate_->factory()->NewFixedArray(context_count_);
   for (uint32_t i = 0; i < context_count_; ++i) {
     uint32_t context_type;
-    if (!deserializer_->ReadUint32(&context_type)) {
+    if (!deserializer_.ReadUint32(&context_type)) {
       Throw("Malformed context type");
       return;
     }
@@ -1362,14 +1362,14 @@ void WebSnapshotDeserializer::DeserializeContexts() {
     uint32_t parent_context_id;
     // Parent context is serialized before child context. Note: not >= on
     // purpose, we're going to subtract 1 later.
-    if (!deserializer_->ReadUint32(&parent_context_id) ||
+    if (!deserializer_.ReadUint32(&parent_context_id) ||
         parent_context_id > i) {
       Throw("Malformed context");
       return;
     }
 
     uint32_t variable_count;
-    if (!deserializer_->ReadUint32(&variable_count)) {
+    if (!deserializer_.ReadUint32(&variable_count)) {
       Throw("Malformed context");
       return;
     }
@@ -1551,7 +1551,7 @@ Handle<JSFunction> WebSnapshotDeserializer::CreateJSFunction(
 
 void WebSnapshotDeserializer::DeserializeFunctions() {
   RCS_SCOPE(isolate_, RuntimeCallCounterId::kWebSnapshotDeserialize_Functions);
-  if (!deserializer_->ReadUint32(&function_count_) ||
+  if (!deserializer_.ReadUint32(&function_count_) ||
       function_count_ > kMaxItemCount) {
     Throw("Malformed function table");
     return;
@@ -1576,8 +1576,7 @@ void WebSnapshotDeserializer::DeserializeFunctions() {
   for (; current_function_count_ < function_count_; ++current_function_count_) {
     uint32_t context_id;
     // Note: > (not >= on purpose, we will subtract 1).
-    if (!deserializer_->ReadUint32(&context_id) ||
-        context_id > context_count_) {
+    if (!deserializer_.ReadUint32(&context_id) || context_id > context_count_) {
       Throw("Malformed function");
       return;
     }
@@ -1594,10 +1593,10 @@ void WebSnapshotDeserializer::DeserializeFunctions() {
     uint32_t length;
     uint32_t parameter_count;
     uint32_t flags;
-    if (!deserializer_->ReadUint32(&start_position) ||
-        !deserializer_->ReadUint32(&length) ||
-        !deserializer_->ReadUint32(&parameter_count) ||
-        !deserializer_->ReadUint32(&flags)) {
+    if (!deserializer_.ReadUint32(&start_position) ||
+        !deserializer_.ReadUint32(&length) ||
+        !deserializer_.ReadUint32(&parameter_count) ||
+        !deserializer_.ReadUint32(&flags)) {
       Throw("Malformed function");
       return;
     }
@@ -1615,7 +1614,7 @@ void WebSnapshotDeserializer::DeserializeFunctions() {
 
 void WebSnapshotDeserializer::DeserializeClasses() {
   RCS_SCOPE(isolate_, RuntimeCallCounterId::kWebSnapshotDeserialize_Classes);
-  if (!deserializer_->ReadUint32(&class_count_) ||
+  if (!deserializer_.ReadUint32(&class_count_) ||
       class_count_ > kMaxItemCount) {
     Throw("Malformed class table");
     return;
@@ -1632,8 +1631,7 @@ void WebSnapshotDeserializer::DeserializeClasses() {
   for (; current_class_count_ < class_count_; ++current_class_count_) {
     uint32_t context_id;
     // Note: > (not >= on purpose, we will subtract 1).
-    if (!deserializer_->ReadUint32(&context_id) ||
-        context_id > context_count_) {
+    if (!deserializer_.ReadUint32(&context_id) || context_id > context_count_) {
       Throw("Malformed class");
       return;
     }
@@ -1650,10 +1648,10 @@ void WebSnapshotDeserializer::DeserializeClasses() {
     uint32_t length;
     uint32_t parameter_count;
     uint32_t flags;
-    if (!deserializer_->ReadUint32(&start_position) ||
-        !deserializer_->ReadUint32(&length) ||
-        !deserializer_->ReadUint32(&parameter_count) ||
-        !deserializer_->ReadUint32(&flags)) {
+    if (!deserializer_.ReadUint32(&start_position) ||
+        !deserializer_.ReadUint32(&length) ||
+        !deserializer_.ReadUint32(&parameter_count) ||
+        !deserializer_.ReadUint32(&flags)) {
       Throw("Malformed class");
       return;
     }
@@ -1671,7 +1669,7 @@ void WebSnapshotDeserializer::DeserializeClasses() {
 
 void WebSnapshotDeserializer::DeserializeObjects() {
   RCS_SCOPE(isolate_, RuntimeCallCounterId::kWebSnapshotDeserialize_Objects);
-  if (!deserializer_->ReadUint32(&object_count_) ||
+  if (!deserializer_.ReadUint32(&object_count_) ||
       object_count_ > kMaxItemCount) {
     Throw("Malformed objects table");
     return;
@@ -1680,7 +1678,7 @@ void WebSnapshotDeserializer::DeserializeObjects() {
   objects_ = isolate_->factory()->NewFixedArray(object_count_);
   for (; current_object_count_ < object_count_; ++current_object_count_) {
     uint32_t map_id;
-    if (!deserializer_->ReadUint32(&map_id) || map_id >= map_count_) {
+    if (!deserializer_.ReadUint32(&map_id) || map_id >= map_count_) {
       Throw("Malformed object");
       return;
     }
@@ -1718,7 +1716,7 @@ void WebSnapshotDeserializer::DeserializeObjects() {
 
 void WebSnapshotDeserializer::DeserializeArrays() {
   RCS_SCOPE(isolate_, RuntimeCallCounterId::kWebSnapshotDeserialize_Arrays);
-  if (!deserializer_->ReadUint32(&array_count_) ||
+  if (!deserializer_.ReadUint32(&array_count_) ||
       object_count_ > kMaxItemCount) {
     Throw("Malformed array table");
     return;
@@ -1727,7 +1725,7 @@ void WebSnapshotDeserializer::DeserializeArrays() {
   arrays_ = isolate_->factory()->NewFixedArray(array_count_);
   for (; current_array_count_ < array_count_; ++current_array_count_) {
     uint32_t length;
-    if (!deserializer_->ReadUint32(&length) || length > kMaxItemCount) {
+    if (!deserializer_.ReadUint32(&length) || length > kMaxItemCount) {
       Throw("Malformed array");
       return;
     }
@@ -1752,7 +1750,7 @@ void WebSnapshotDeserializer::DeserializeArrays() {
 void WebSnapshotDeserializer::DeserializeExports() {
   RCS_SCOPE(isolate_, RuntimeCallCounterId::kWebSnapshotDeserialize_Exports);
   uint32_t count;
-  if (!deserializer_->ReadUint32(&count) || count > kMaxItemCount) {
+  if (!deserializer_.ReadUint32(&count) || count > kMaxItemCount) {
     Throw("Malformed export table");
     return;
   }
@@ -1808,7 +1806,7 @@ void WebSnapshotDeserializer::ReadValue(
   uint32_t value_type;
   Factory* factory = isolate_->factory();
   // TODO(v8:11525): Consider adding a ReadByte.
-  if (!deserializer_->ReadUint32(&value_type)) {
+  if (!deserializer_.ReadUint32(&value_type)) {
     Throw("Malformed variable");
     // Set "value" here so that the "keep on trucking" error handling won't fail
     // when dereferencing the handle.
@@ -1838,7 +1836,7 @@ void WebSnapshotDeserializer::ReadValue(
       break;
     }
     case ValueType::INTEGER: {
-      Maybe<int32_t> number = deserializer_->ReadZigZag<int32_t>();
+      Maybe<int32_t> number = deserializer_.ReadZigZag<int32_t>();
       if (number.IsNothing()) {
         Throw("Malformed integer");
         return;
@@ -1849,7 +1847,7 @@ void WebSnapshotDeserializer::ReadValue(
     }
     case ValueType::DOUBLE: {
       double number;
-      if (!deserializer_->ReadDouble(&number)) {
+      if (!deserializer_.ReadDouble(&number)) {
         Throw("Malformed double");
         return;
       }
@@ -1864,7 +1862,7 @@ void WebSnapshotDeserializer::ReadValue(
     }
     case ValueType::ARRAY_ID:
       uint32_t array_id;
-      if (!deserializer_->ReadUint32(&array_id) || array_id >= kMaxItemCount) {
+      if (!deserializer_.ReadUint32(&array_id) || array_id >= kMaxItemCount) {
         Throw("Malformed variable");
         return;
       }
@@ -1884,7 +1882,7 @@ void WebSnapshotDeserializer::ReadValue(
       break;
     case ValueType::OBJECT_ID:
       uint32_t object_id;
-      if (!deserializer_->ReadUint32(&object_id) || object_id > kMaxItemCount) {
+      if (!deserializer_.ReadUint32(&object_id) || object_id > kMaxItemCount) {
         Throw("Malformed variable");
         return;
       }
@@ -1905,7 +1903,7 @@ void WebSnapshotDeserializer::ReadValue(
       break;
     case ValueType::FUNCTION_ID: {
       uint32_t function_id;
-      if (!deserializer_->ReadUint32(&function_id) ||
+      if (!deserializer_.ReadUint32(&function_id) ||
           function_id >= function_count_) {
         Throw("Malformed object property");
         return;
@@ -1928,7 +1926,7 @@ void WebSnapshotDeserializer::ReadValue(
     }
     case ValueType::CLASS_ID: {
       uint32_t class_id;
-      if (!deserializer_->ReadUint32(&class_id) || class_id >= kMaxItemCount) {
+      if (!deserializer_.ReadUint32(&class_id) || class_id >= kMaxItemCount) {
         Throw("Malformed object property");
         return;
       }
@@ -1976,7 +1974,7 @@ void WebSnapshotDeserializer::ReadFunctionPrototype(
     Handle<JSFunction> function) {
   uint32_t object_id;
 
-  if (!deserializer_->ReadUint32(&object_id) || object_id > kMaxItemCount + 1) {
+  if (!deserializer_.ReadUint32(&object_id) || object_id > kMaxItemCount + 1) {
     Throw("Malformed class / function");
     return;
   }

src/web-snapshot/web-snapshot.h

@@ -228,10 +228,11 @@ class V8_EXPORT WebSnapshotSerializer
 class V8_EXPORT WebSnapshotDeserializer
     : public WebSnapshotSerializerDeserializer {
  public:
-  explicit WebSnapshotDeserializer(v8::Isolate* v8_isolate);
+  WebSnapshotDeserializer(v8::Isolate* v8_isolate, const uint8_t* data,
+                          size_t buffer_size);
+  WebSnapshotDeserializer(Isolate* isolate, Handle<Script> snapshot_as_script);
   ~WebSnapshotDeserializer();
-  bool UseWebSnapshot(const uint8_t* data, size_t buffer_size);
-  bool UseWebSnapshot(Handle<Script> snapshot_as_script);
+  bool Deserialize();
 
   // For inspecting the state after deserializing a snapshot.
   uint32_t string_count() const { return string_count_; }
@@ -243,7 +244,10 @@ class V8_EXPORT WebSnapshotDeserializer
   uint32_t object_count() const { return object_count_; }
 
  private:
-  bool Deserialize();
+  WebSnapshotDeserializer(Isolate* isolate, Handle<Object> script_name,
+                          base::Vector<const uint8_t> buffer);
+  base::Vector<const uint8_t> ExtractScriptBuffer(
+      Isolate* isolate, Handle<Script> snapshot_as_script);
   bool DeserializeSnapshot();
   bool DeserializeScript();
 
@@ -305,7 +309,7 @@ class V8_EXPORT WebSnapshotDeserializer
   uint32_t object_count_ = 0;
   uint32_t current_object_count_ = 0;
 
-  std::unique_ptr<ValueDeserializer> deserializer_;
+  ValueDeserializer deserializer_;
 
   bool deserialized_ = false;
 };

test/cctest/test-web-snapshots.cc

@@ -47,9 +47,9 @@ void TestWebSnapshotExtensive(
     v8::HandleScope scope(isolate);
     v8::Local<v8::Context> new_context = CcTest::NewContext();
     v8::Context::Scope context_scope(new_context);
-    WebSnapshotDeserializer deserializer(isolate);
-    CHECK(deserializer.UseWebSnapshot(snapshot_data.buffer,
-                                      snapshot_data.buffer_size));
+    WebSnapshotDeserializer deserializer(isolate, snapshot_data.buffer,
+                                         snapshot_data.buffer_size);
+    CHECK(deserializer.Deserialize());
     CHECK(!deserializer.has_error());
     tester(isolate, new_context);
     CHECK_EQ(string_count, deserializer.string_count());
@@ -343,9 +343,9 @@ TEST(SFIDeduplication) {
   {
     v8::Local<v8::Context> new_context = CcTest::NewContext();
     v8::Context::Scope context_scope(new_context);
-    WebSnapshotDeserializer deserializer(isolate);
-    CHECK(deserializer.UseWebSnapshot(snapshot_data.buffer,
-                                      snapshot_data.buffer_size));
+    WebSnapshotDeserializer deserializer(isolate, snapshot_data.buffer,
+                                         snapshot_data.buffer_size);
+    CHECK(deserializer.Deserialize());
     CHECK(!deserializer.has_error());
 
     const char* get_inner = "foo.inner";
@@ -399,9 +399,9 @@ TEST(SFIDeduplicationClasses) {
   {
     v8::Local<v8::Context> new_context = CcTest::NewContext();
     v8::Context::Scope context_scope(new_context);
-    WebSnapshotDeserializer deserializer(isolate);
-    CHECK(deserializer.UseWebSnapshot(snapshot_data.buffer,
-                                      snapshot_data.buffer_size));
+    WebSnapshotDeserializer deserializer(isolate, snapshot_data.buffer,
+                                         snapshot_data.buffer_size);
+    CHECK(deserializer.Deserialize());
     CHECK(!deserializer.has_error());
 
     const char* get_class = "foo.class";
@@ -464,9 +464,9 @@ TEST(SFIDeduplicationAfterBytecodeFlushing) {
     v8::HandleScope scope(isolate);
     v8::Local<v8::Context> new_context = CcTest::NewContext();
     v8::Context::Scope context_scope(new_context);
-    WebSnapshotDeserializer deserializer(isolate);
-    CHECK(deserializer.UseWebSnapshot(snapshot_data.buffer,
-                                      snapshot_data.buffer_size));
+    WebSnapshotDeserializer deserializer(isolate, snapshot_data.buffer,
+                                         snapshot_data.buffer_size);
+    CHECK(deserializer.Deserialize());
     CHECK(!deserializer.has_error());
 
     const char* get_outer = "foo.outer";
@@ -549,9 +549,9 @@ TEST(SFIDeduplicationAfterBytecodeFlushingClasses) {
     v8::HandleScope scope(isolate);
     v8::Local<v8::Context> new_context = CcTest::NewContext();
     v8::Context::Scope context_scope(new_context);
-    WebSnapshotDeserializer deserializer(isolate);
-    CHECK(deserializer.UseWebSnapshot(snapshot_data.buffer,
-                                      snapshot_data.buffer_size));
+    WebSnapshotDeserializer deserializer(isolate, snapshot_data.buffer,
+                                         snapshot_data.buffer_size);
+    CHECK(deserializer.Deserialize());
     CHECK(!deserializer.has_error());
 
     const char* get_create = "foo.create";
@@ -626,9 +626,9 @@ TEST(SFIDeduplicationOfFunctionsNotInSnapshot) {
   {
     v8::Local<v8::Context> new_context = CcTest::NewContext();
     v8::Context::Scope context_scope(new_context);
-    WebSnapshotDeserializer deserializer(isolate);
-    CHECK(deserializer.UseWebSnapshot(snapshot_data.buffer,
-                                      snapshot_data.buffer_size));
+    WebSnapshotDeserializer deserializer(isolate, snapshot_data.buffer,
+                                         snapshot_data.buffer_size);
+    CHECK(deserializer.Deserialize());
     CHECK(!deserializer.has_error());
 
     const char* create_new_inner = "foo.outer()";
@@ -738,8 +738,8 @@ TEST(Concatenation) {
     v8::HandleScope scope(isolate);
     v8::Local<v8::Context> new_context = CcTest::NewContext();
     v8::Context::Scope context_scope(new_context);
-    WebSnapshotDeserializer deserializer(isolate);
-    CHECK(deserializer.UseWebSnapshot(buffer.get(), buffer_size));
+    WebSnapshotDeserializer deserializer(isolate, buffer.get(), buffer_size);
+    CHECK(deserializer.Deserialize());
     CHECK(!deserializer.has_error());
     CHECK_EQ(kObjectCount, deserializer.object_count());
 
@@ -785,8 +785,8 @@ TEST(ConcatenationErrors) {
     v8::HandleScope scope(isolate);
     v8::Local<v8::Context> new_context = CcTest::NewContext();
     v8::Context::Scope context_scope(new_context);
-    WebSnapshotDeserializer deserializer(isolate);
-    CHECK(!deserializer.UseWebSnapshot(buffer.get(), buffer_size));
+    WebSnapshotDeserializer deserializer(isolate, buffer.get(), buffer_size);
+    CHECK(!deserializer.Deserialize());
   }
 }
 
@@ -819,9 +819,9 @@ TEST(CompactedSourceCode) {
   {
     v8::Local<v8::Context> new_context = CcTest::NewContext();
     v8::Context::Scope context_scope(new_context);
-    WebSnapshotDeserializer deserializer(isolate);
-    CHECK(deserializer.UseWebSnapshot(snapshot_data.buffer,
-                                      snapshot_data.buffer_size));
+    WebSnapshotDeserializer deserializer(isolate, snapshot_data.buffer,
+                                         snapshot_data.buffer_size);
+    CHECK(deserializer.Deserialize());
     CHECK(!deserializer.has_error());
 
     const char* get_function = "e[0]";