Add an experimental public API for value serialization.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 6858a325c40a86dea6b2fa130591d36c4ac09ff5..f832b3071fc82d27a706013735b6f34aa0c30ca2 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -24,6 +24,7 @@
 #include "src/base/functional.h"
 #include "src/base/platform/platform.h"
 #include "src/base/platform/time.h"
+#include "src/base/safe_conversions.h"
 #include "src/base/utils/random-number-generator.h"
 #include "src/bootstrapper.h"
 #include "src/char-predicates-inl.h"
@@ -68,6 +69,7 @@
 #include "src/unicode-inl.h"
 #include "src/v8.h"
 #include "src/v8threads.h"
+#include "src/value-serializer.h"
 #include "src/version.h"
 #include "src/vm-state-inl.h"
 #include "src/wasm/wasm-module.h"
@@ -2832,6 +2834,104 @@ MaybeLocal<String> JSON::Stringify(Local<Context> context,
   RETURN_ESCAPED(result);
 }
 
+// --- V a l u e   S e r i a l i z a t i o n ---
+
+struct ValueSerializer::PrivateData {
+  explicit PrivateData(i::Isolate* i) : isolate(i), serializer(i) {}
+  i::Isolate* isolate;
+  i::ValueSerializer serializer;
+};
+
+ValueSerializer::ValueSerializer(Isolate* isolate)
+    : private_(new PrivateData(reinterpret_cast<i::Isolate*>(isolate))) {}
+
+ValueSerializer::~ValueSerializer() { delete private_; }
+
+void ValueSerializer::WriteHeader() {
+  CHECK(private_);

[Jakob Kummerow, 2016/08/24 17:41:04]

What does this guard against? A future constructor that forgets to initialize
|private_|? Maybe make it a DCHECK then.

[jbroman, 2016/08/24 21:26:36]

Fair enough, it's probably premature since there's no actual way for this to
fail as yet. Removed.

I considered having failure of WriteHeader/WriteValue delete private_ to make it
failing to respect the error a more aggressive failure, but didn't end up doing
that.

+  private_->serializer.WriteHeader();
+}
+
+Maybe<bool> ValueSerializer::WriteValue(Local<Context> context,
+                                        Local<Value> value) {
+  CHECK(private_);
+  PREPARE_FOR_EXECUTION_PRIMITIVE(context, ValueSerializer, WriteValue, bool);
+  i::Handle<i::Object> object = Utils::OpenHandle(*value);
+  Maybe<bool> result = private_->serializer.WriteObject(object);
+  if (result.IsNothing()) {
+    has_pending_exception = private_->isolate->has_pending_exception();
+    RETURN_ON_FAILED_EXECUTION_PRIMITIVE(bool);
+  }
+  return result;
+}
+
+std::vector<uint8_t> ValueSerializer::ReleaseBuffer() {
+  CHECK(private_);
+  return private_->serializer.ReleaseBuffer();
+}
+
+struct ValueDeserializer::PrivateData {
+  PrivateData(i::Isolate* i, i::Vector<const uint8_t> data)
+      : isolate(i), deserializer(i, data) {}
+  i::Isolate* isolate;
+  i::ValueDeserializer deserializer;
+  bool supports_legacy_wire_format;

[Jakob Kummerow, 2016/08/24 17:41:03]

How about initializing this?

[jbroman, 2016/08/24 21:26:36]

Done.

+};
+
+ValueDeserializer::ValueDeserializer(Isolate* isolate, const uint8_t* data,
+                                     size_t size) {
+  if (base::IsValueInRangeForNumericType<int>(size)) {
+    private_ =
+        new PrivateData(reinterpret_cast<i::Isolate*>(isolate),
+                        i::Vector<const uint8_t>(data, static_cast<int>(size)));
+  }

[Jakob Kummerow, 2016/08/24 17:41:04]

how about: else { private_ = nullptr; } ?

[jbroman, 2016/08/24 21:26:36]

Not one, but two uninitialized variables in one small CL.

/me hangs his head in shame.

Done.

+}
+
+ValueDeserializer::~ValueDeserializer() { delete private_; }
+
+Maybe<bool> ValueDeserializer::ReadHeader() {
+  // TODO(jbroman): Today, all wire formats are "legacy". When a more supported
+  // format is added, compare the version of the internal serializer to the
+  // minimum non-legacy version number.
+  if (!private_ || !private_->deserializer.ReadHeader().FromMaybe(false) ||
+      !private_->supports_legacy_wire_format) {
+    delete private_;
+    private_ = nullptr;
+    return Nothing<bool>();
+  }
+  return Just(true);
+}
+
+void ValueDeserializer::SetSupportsLegacyWireFormat(
+    bool supports_legacy_wire_format) {
+  CHECK(private_);

[Jakob Kummerow, 2016/08/24 17:41:04]

Presumably this needs to be called before ReadHeader (which checks for
private_->supports_legacy_wire_format), but it doesn't allow the embedder to
check for successful initialization without crashing.

[jbroman, 2016/08/24 21:26:36]

Added a comment to clarify usage, and made it just return if private_ is null
(since the embedder will notice the failure shortly when they try to
ReadHeader). Seemed nicer than adding two-phase initialization or an
easy-to-forget "is it OK to proceed" getter.

+  private_->supports_legacy_wire_format = supports_legacy_wire_format;
+}
+
+uint32_t ValueDeserializer::GetWireFormatVersion() const {
+  CHECK(private_);
+  return private_->deserializer.GetWireFormatVersion();
+}
+
+MaybeLocal<Value> ValueDeserializer::ReadValue(Local<Context> context) {
+  CHECK(private_);
+  PREPARE_FOR_EXECUTION(context, ValueDeserializer, ReadValue, Value);
+  i::MaybeHandle<i::Object> result;
+  if (GetWireFormatVersion() > 0) {
+    result = private_->deserializer.ReadObject();
+  } else {
+    result =
+        private_->deserializer.ReadObjectUsingEntireBufferForLegacyFormat();
+  }
+  Local<Value> value;
+  if (!ToLocal(result, &value)) {
+    has_pending_exception = private_->isolate->has_pending_exception();
+    RETURN_ON_FAILED_EXECUTION(Value);
+    return MaybeLocal<Value>();
+  }
+  RETURN_ESCAPED(value);
+}
+
 // --- D a t a ---
 
 bool Value::FullIsUndefined() const {