[wasm] Transferrable modules

src/value-serializer.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_VALUE_SERIALIZER_H_
 #define V8_VALUE_SERIALIZER_H_
 
 #include <cstdint>
 #include <vector>
 
@@ skipping 13 matching lines @@
 class JSArrayBuffer;
 class JSArrayBufferView;
 class JSDate;
 class JSMap;
 class JSRegExp;
 class JSSet;
 class JSValue;
 class Object;
 class Oddball;
 class Smi;
+class WasmModuleObject;
 
 enum class SerializationTag : uint8_t;
 
 /**
  * Writes V8 objects in a binary format that allows the objects to be cloned
  * according to the HTML structured clone algorithm.
  *
  * Format is based on Blink's previous serialization logic.
  */
 class ValueSerializer {
@@ skipping 160 matching lines @@
       WARN_UNUSED_RESULT;
 
   /*
    * Accepts the array buffer corresponding to the one passed previously to
    * ValueSerializer::TransferArrayBuffer.
    */
   void TransferArrayBuffer(uint32_t transfer_id,
                            Handle<JSArrayBuffer> array_buffer);
 
   /*
+   * Accepts the WasmModuleObject corresponding to the one having transfer_id
+   * produced by v8::ValueSerializer::GetWasmCompiledModuleId().
+   * See issue v8:6106.
+   */
+  void TransferWasmModule(uint32_t transfer_id,
+                          Handle<WasmModuleObject> module);
+  /*
    * Publicly exposed wire format writing methods.
    * These are intended for use within the delegate's WriteHostObject method.
    */
   bool ReadUint32(uint32_t* value) WARN_UNUSED_RESULT;
   bool ReadUint64(uint64_t* value) WARN_UNUSED_RESULT;
   bool ReadDouble(double* value) WARN_UNUSED_RESULT;
   bool ReadRawBytes(size_t length, const void** data) WARN_UNUSED_RESULT;
+  void set_allow_inline_wasm(bool allow_inline_wasm) {
+    allow_inline_wasm_ = allow_inline_wasm;
+  }
 
  private:
   // Reading the wire format.
   Maybe<SerializationTag> PeekTag() const WARN_UNUSED_RESULT;
   void ConsumeTag(SerializationTag peeked_tag);
   Maybe<SerializationTag> ReadTag() WARN_UNUSED_RESULT;
   template <typename T>
   Maybe<T> ReadVarint() WARN_UNUSED_RESULT;
   template <typename T>
   Maybe<T> ReadZigZag() WARN_UNUSED_RESULT;
   Maybe<double> ReadDouble() WARN_UNUSED_RESULT;
   Maybe<Vector<const uint8_t>> ReadRawBytes(int size) WARN_UNUSED_RESULT;
+  bool allow_inline_wasm() const { return allow_inline_wasm_; }
 
   // Reads a string if it matches the one provided.
   // Returns true if this was the case. Otherwise, nothing is consumed.
   bool ReadExpectedString(Handle<String> expected) WARN_UNUSED_RESULT;
 
   // Like ReadObject, but skips logic for special cases in simulating the
   // "stack machine".
   MaybeHandle<Object> ReadObjectInternal() WARN_UNUSED_RESULT;
 
   // Reads a string intended to be part of a more complicated object.
@@ skipping 13 matching lines @@
   MaybeHandle<JSValue> ReadJSValue(SerializationTag tag) WARN_UNUSED_RESULT;
   MaybeHandle<JSRegExp> ReadJSRegExp() WARN_UNUSED_RESULT;
   MaybeHandle<JSMap> ReadJSMap() WARN_UNUSED_RESULT;
   MaybeHandle<JSSet> ReadJSSet() WARN_UNUSED_RESULT;
   MaybeHandle<JSArrayBuffer> ReadJSArrayBuffer() WARN_UNUSED_RESULT;
   MaybeHandle<JSArrayBuffer> ReadTransferredJSArrayBuffer(bool is_shared)
       WARN_UNUSED_RESULT;
   MaybeHandle<JSArrayBufferView> ReadJSArrayBufferView(
       Handle<JSArrayBuffer> buffer) WARN_UNUSED_RESULT;
   MaybeHandle<JSObject> ReadWasmModule() WARN_UNUSED_RESULT;
+  MaybeHandle<JSObject> ReadWasmModuleTransfer() WARN_UNUSED_RESULT;
   MaybeHandle<JSObject> ReadHostObject() WARN_UNUSED_RESULT;
 
   /*
    * Reads key-value pairs into the object until the specified end tag is
    * encountered. If successful, returns the number of properties read.
    */
   Maybe<uint32_t> ReadJSObjectProperties(Handle<JSObject> object,
                                          SerializationTag end_tag,
                                          bool can_use_transitions);
 
   // Manipulating the map from IDs to reified objects.
   bool HasObjectWithID(uint32_t id);
   MaybeHandle<JSReceiver> GetObjectWithID(uint32_t id);
   void AddObjectWithID(uint32_t id, Handle<JSReceiver> object);
 
   Isolate* const isolate_;
   v8::ValueDeserializer::Delegate* const delegate_;
   const uint8_t* position_;
   const uint8_t* const end_;
   PretenureFlag pretenure_;
   uint32_t version_ = 0;
   uint32_t next_id_ = 0;
+  bool allow_inline_wasm_ = false;
 
   // Always global handles.
   Handle<FixedArray> id_map_;
   MaybeHandle<SeededNumberDictionary> array_buffer_transfer_map_;
+  std::vector<Handle<WasmModuleObject>> transferred_wasm_modules_;

[jbroman, 2017/03/17 14:44:37]

Hmm. This seems to require that the handles remain valid long after they are
passed in, which depends on HandleScope lifetime. The way
|array_buffer_transfer_map_| (and, for that matter, |id_map_|) works is that the
(optional) lookup table is held as a heap object by one global handle, and the
map then holds the objects.

Put another way, as a user I'd have expected this to be a legitimate use of the
API:

{
  v8::HandleScope handleScope(isolate);
  v8::Local<v8::WasmCompiledModule> module = ...;
  deserializer.TransferWasmCompiledModule(0, module);
}
deserializer.ReadValue(...);

[Mircea Trofin, 2017/03/17 16:55:31]

As discussed offline - this alternative appears to introduce more complexity
than the previous solution, even considering the difference with SABs. We agreed
to go back to the delegate-based mechanism, and address quickly thereafter
v8:6106.

 
   DISALLOW_COPY_AND_ASSIGN(ValueDeserializer);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_VALUE_SERIALIZER_H_