1 files changed, 466 insertions, 0 deletions
diff --git a/dom/ipc/SharedMap.cpp b/dom/ipc/SharedMap.cpp
new file mode 100644
index 0000000000..70e12784e9
--- /dev/null
+++ b/dom/ipc/SharedMap.cpp
@@ -0,0 +1,466 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SharedMap.h"
+#include "SharedMapChangeEvent.h"
+
+#include "MemMapSnapshot.h"
+#include "ScriptPreloader-inl.h"
+
+#include "mozilla/dom/AutoEntryScript.h"
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/ContentProcessMessageManager.h"
+#include "mozilla/dom/IPCBlobUtils.h"
+#include "mozilla/dom/RootedDictionary.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/IOBuffers.h"
+#include "mozilla/ScriptPreloader.h"
+
+using namespace mozilla::loader;
+
+namespace mozilla {
+
+using namespace ipc;
+
+namespace dom::ipc {
+
+// Align to size of uintptr_t here, to be safe. It's probably not strictly
+// necessary, though.
+constexpr size_t kStructuredCloneAlign = sizeof(uintptr_t);
+
+static inline void AlignTo(size_t* aOffset, size_t aAlign) {
+  if (auto mod = *aOffset % aAlign) {
+    *aOffset += aAlign - mod;
+  }
+}
+
+SharedMap::SharedMap() : DOMEventTargetHelper() {}
+
+SharedMap::SharedMap(nsIGlobalObject* aGlobal, const FileDescriptor& aMapFile,
+                     size_t aMapSize, nsTArray<RefPtr<BlobImpl>>&& aBlobs)
+    : DOMEventTargetHelper(aGlobal), mBlobImpls(std::move(aBlobs)) {
+  mMapFile.reset(new FileDescriptor(aMapFile));
+  mMapSize = aMapSize;
+}
+
+bool SharedMap::Has(const nsACString& aName) {
+  Unused << MaybeRebuild();
+  return mEntries.Contains(aName);
+}
+
+void SharedMap::Get(JSContext* aCx, const nsACString& aName,
+                    JS::MutableHandle<JS::Value> aRetVal, ErrorResult& aRv) {
+  auto res = MaybeRebuild();
+  if (res.isErr()) {
+    aRv.Throw(res.unwrapErr());
+    return;
+  }
+
+  Entry* entry = mEntries.Get(aName);
+  if (!entry) {
+    aRetVal.setNull();
+    return;
+  }
+
+  entry->Read(aCx, aRetVal, aRv);
+}
+
+void SharedMap::Entry::Read(JSContext* aCx,
+                            JS::MutableHandle<JS::Value> aRetVal,
+                            ErrorResult& aRv) {
+  if (mData.is<StructuredCloneData>()) {
+    // We have a temporary buffer for a key that was changed after the last
+    // snapshot. Just decode it directly.
+    auto& holder = mData.as<StructuredCloneData>();
+    holder.Read(aCx, aRetVal, aRv);
+    return;
+  }
+
+  // We have a pointer to a shared memory region containing our structured
+  // clone data. Create a temporary buffer to decode that data, and then
+  // discard it so that we don't keep a separate process-local copy around any
+  // longer than necessary.
+  StructuredCloneData holder;
+  if (!holder.CopyExternalData(Data(), Size())) {
+    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    return;
+  }
+  if (mBlobCount) {
+    holder.BlobImpls().AppendElements(Blobs());
+  }
+  holder.Read(aCx, aRetVal, aRv);
+}
+
+FileDescriptor SharedMap::CloneMapFile() const {
+  if (mMap.initialized()) {
+    return mMap.cloneHandle();
+  }
+  return *mMapFile;
+}
+
+void SharedMap::Update(const FileDescriptor& aMapFile, size_t aMapSize,
+                       nsTArray<RefPtr<BlobImpl>>&& aBlobs,
+                       nsTArray<nsCString>&& aChangedKeys) {
+  MOZ_DIAGNOSTIC_ASSERT(!mWritable);
+
+  mMap.reset();
+  if (mMapFile) {
+    *mMapFile = aMapFile;
+  } else {
+    mMapFile.reset(new FileDescriptor(aMapFile));
+  }
+  mMapSize = aMapSize;
+  mEntries.Clear();
+  mEntryArray.reset();
+
+  mBlobImpls = std::move(aBlobs);
+
+  AutoEntryScript aes(GetParentObject(), "SharedMap change event");
+  JSContext* cx = aes.cx();
+
+  RootedDictionary<MozSharedMapChangeEventInit> init(cx);
+  if (!init.mChangedKeys.SetCapacity(aChangedKeys.Length(), fallible)) {
+    NS_WARNING("Failed to dispatch SharedMap change event");
+    return;
+  }
+  for (auto& key : aChangedKeys) {
+    Unused << init.mChangedKeys.AppendElement(NS_ConvertUTF8toUTF16(key),
+                                              fallible);
+  }
+
+  RefPtr<SharedMapChangeEvent> event =
+      SharedMapChangeEvent::Constructor(this, u"change"_ns, init);
+  event->SetTrusted(true);
+
+  DispatchEvent(*event);
+}
+
+const nsTArray<SharedMap::Entry*>& SharedMap::EntryArray() const {
+  if (mEntryArray.isNothing()) {
+    MaybeRebuild();
+
+    mEntryArray.emplace(mEntries.Count());
+    auto& array = mEntryArray.ref();
+    for (auto& entry : mEntries) {
+      array.AppendElement(entry.GetWeak());
+    }
+  }
+
+  return mEntryArray.ref();
+}
+
+const nsString SharedMap::GetKeyAtIndex(uint32_t aIndex) const {
+  return NS_ConvertUTF8toUTF16(EntryArray()[aIndex]->Name());
+}
+
+bool SharedMap::GetValueAtIndex(JSContext* aCx, uint32_t aIndex,
+                                JS::MutableHandle<JS::Value> aResult) const {
+  ErrorResult rv;
+  EntryArray()[aIndex]->Read(aCx, aResult, rv);
+  if (rv.MaybeSetPendingException(aCx)) {
+    return false;
+  }
+  return true;
+}
+
+void SharedMap::Entry::TakeData(StructuredCloneData&& aHolder) {
+  mData = AsVariant(std::move(aHolder));
+
+  mSize = Holder().Data().Size();
+  mBlobCount = Holder().BlobImpls().Length();
+}
+
+void SharedMap::Entry::ExtractData(char* aDestPtr, uint32_t aNewOffset,
+                                   uint16_t aNewBlobOffset) {
+  if (mData.is<StructuredCloneData>()) {
+    char* ptr = aDestPtr;
+    Holder().Data().ForEachDataChunk([&](const char* aData, size_t aSize) {
+      memcpy(ptr, aData, aSize);
+      ptr += aSize;
+      return true;
+    });
+    MOZ_ASSERT(uint32_t(ptr - aDestPtr) == mSize);
+  } else {
+    memcpy(aDestPtr, Data(), mSize);
+  }
+
+  mData = AsVariant(aNewOffset);
+  mBlobOffset = aNewBlobOffset;
+}
+
+Result<Ok, nsresult> SharedMap::MaybeRebuild() {
+  if (!mMapFile) {
+    return Ok();
+  }
+
+  // This function maps a shared memory region created by Serialize() and reads
+  // its header block to build a new mEntries hashtable of its contents.
+  //
+  // The entries created by this function contain a pointer to this SharedMap
+  // instance, and the offsets and sizes of their structured clone data within
+  // its shared memory region. When needed, that structured clone data is
+  // retrieved directly as indexes into the SharedMap's shared memory region.
+
+  MOZ_TRY(mMap.initWithHandle(*mMapFile, mMapSize));
+  mMapFile.reset();
+
+  // We should be able to pass this range as an initializer list or an immediate
+  // param, but gcc currently chokes on that if optimization is enabled, and
+  // initializes everything to 0.
+  Range<uint8_t> range(&mMap.get<uint8_t>()[0], mMap.size());
+  InputBuffer buffer(range);
+
+  uint32_t count;
+  buffer.codeUint32(count);
+
+  for (uint32_t i = 0; i < count; i++) {
+    auto entry = MakeUnique<Entry>(*this);
+    entry->Code(buffer);
+
+    // This buffer was created at runtime, during this session, so any errors
+    // indicate memory corruption, and are fatal.
+    MOZ_RELEASE_ASSERT(!buffer.error());
+
+    // Note: While the order of evaluation of the arguments to Put doesn't
+    // matter for this (the actual move will only happen within Put), to be
+    // clear about this, we call entry->Name() before calling Put.
+    const auto& name = entry->Name();
+    mEntries.InsertOrUpdate(name, std::move(entry));
+  }
+
+  return Ok();
+}
+
+void SharedMap::MaybeRebuild() const {
+  Unused << const_cast<SharedMap*>(this)->MaybeRebuild();
+}
+
+WritableSharedMap::WritableSharedMap() : SharedMap() {
+  mWritable = true;
+  // Serialize the initial empty contents of the map immediately so that we
+  // always have a file descriptor to send to callers of CloneMapFile().
+  Unused << Serialize();
+  MOZ_RELEASE_ASSERT(mMap.initialized());
+}
+
+SharedMap* WritableSharedMap::GetReadOnly() {
+  if (!mReadOnly) {
+    nsTArray<RefPtr<BlobImpl>> blobs(mBlobImpls.Clone());
+    mReadOnly =
+        new SharedMap(ContentProcessMessageManager::Get()->GetParentObject(),
+                      CloneMapFile(), MapSize(), std::move(blobs));
+  }
+  return mReadOnly;
+}
+
+Result<Ok, nsresult> WritableSharedMap::Serialize() {
+  // Serializes a new snapshot of the map, initializes a new read-only shared
+  // memory region with its contents, and updates all entries to point to that
+  // new snapshot.
+  //
+  // The layout of the snapshot is as follows:
+  //
+  // - A header containing a uint32 count field containing the number of
+  //   entries in the map, followed by that number of serialized entry headers,
+  //   as produced by Entry::Code.
+  //
+  // - A data block containing structured clone data for each of the entries'
+  //   values. This data is referenced by absolute byte offsets from the start
+  //   of the shared memory region, encoded in each of the entry header values.
+  //   Each entry's data is aligned to kStructuredCloneAlign, and therefore may
+  //   have alignment padding before it.
+  //
+  // This serialization format is decoded by the MaybeRebuild() method of
+  // read-only SharedMap() instances, and used to populate their mEntries
+  // hashtables.
+  //
+  // Writable instances never read the header blocks, but instead directly
+  // update their Entry instances to point to the appropriate offsets in the
+  // shared memory region created by this function.
+
+  uint32_t count = mEntries.Count();
+
+  size_t dataSize = 0;
+  size_t headerSize = sizeof(count);
+  size_t blobCount = 0;
+
+  for (const auto& entry : mEntries.Values()) {
+    headerSize += entry->HeaderSize();
+    blobCount += entry->BlobCount();
+
+    dataSize += entry->Size();
+    AlignTo(&dataSize, kStructuredCloneAlign);
+  }
+
+  size_t offset = headerSize;
+  AlignTo(&offset, kStructuredCloneAlign);
+
+  OutputBuffer header;
+  header.codeUint32(count);
+
+  MemMapSnapshot mem;
+  MOZ_TRY(mem.Init(offset + dataSize));
+
+  auto ptr = mem.Get<char>();
+
+  // We need to build the new array of blobs before we overwrite the existing
+  // one, since previously-serialized entries will store their blob references
+  // as indexes into our blobs array.
+  nsTArray<RefPtr<BlobImpl>> blobImpls(blobCount);
+
+  for (const auto& entry : mEntries.Values()) {
+    AlignTo(&offset, kStructuredCloneAlign);
+
+    size_t blobOffset = blobImpls.Length();
+    if (entry->BlobCount()) {
+      blobImpls.AppendElements(entry->Blobs());
+    }
+
+    entry->ExtractData(&ptr[offset], offset, blobOffset);
+    entry->Code(header);
+
+    offset += entry->Size();
+  }
+
+  mBlobImpls = std::move(blobImpls);
+
+  // FIXME: We should create a separate OutputBuffer class which can encode to
+  // a static memory region rather than dynamically allocating and then
+  // copying.
+  MOZ_ASSERT(header.cursor() == headerSize);
+  memcpy(ptr.get(), header.Get(), header.cursor());
+
+  // We've already updated offsets at this point. We need this to succeed.
+  mMap.reset();
+  MOZ_RELEASE_ASSERT(mem.Finalize(mMap).isOk());
+
+  return Ok();
+}
+
+void WritableSharedMap::SendTo(ContentParent* aParent) const {
+  nsTArray<IPCBlob> blobs(mBlobImpls.Length());
+
+  for (auto& blobImpl : mBlobImpls) {
+    nsresult rv = IPCBlobUtils::Serialize(blobImpl, *blobs.AppendElement());
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      continue;
+    }
+  }
+
+  Unused << aParent->SendUpdateSharedData(CloneMapFile(), mMap.size(), blobs,
+                                          mChangedKeys);
+}
+
+void WritableSharedMap::BroadcastChanges() {
+  if (mChangedKeys.IsEmpty()) {
+    return;
+  }
+
+  if (!Serialize().isOk()) {
+    return;
+  }
+
+  nsTArray<ContentParent*> parents;
+  ContentParent::GetAll(parents);
+  for (auto& parent : parents) {
+    SendTo(parent);
+  }
+
+  if (mReadOnly) {
+    nsTArray<RefPtr<BlobImpl>> blobImpls(mBlobImpls.Clone());
+    mReadOnly->Update(CloneMapFile(), mMap.size(), std::move(blobImpls),
+                      std::move(mChangedKeys));
+  }
+
+  mChangedKeys.Clear();
+}
+
+void WritableSharedMap::Delete(const nsACString& aName) {
+  if (mEntries.Remove(aName)) {
+    KeyChanged(aName);
+  }
+}
+
+void WritableSharedMap::Set(JSContext* aCx, const nsACString& aName,
+                            JS::Handle<JS::Value> aValue, ErrorResult& aRv) {
+  StructuredCloneData holder;
+
+  holder.Write(aCx, aValue, aRv);
+  if (aRv.Failed()) {
+    return;
+  }
+
+  if (!holder.InputStreams().IsEmpty()) {
+    aRv.Throw(NS_ERROR_INVALID_ARG);
+    return;
+  }
+
+  Entry* entry = mEntries.GetOrInsertNew(aName, *this, aName);
+  entry->TakeData(std::move(holder));
+
+  KeyChanged(aName);
+}
+
+void WritableSharedMap::Flush() { BroadcastChanges(); }
+
+void WritableSharedMap::IdleFlush() {
+  mPendingFlush = false;
+  Flush();
+}
+
+nsresult WritableSharedMap::KeyChanged(const nsACString& aName) {
+  if (!mChangedKeys.ContainsSorted(aName)) {
+    mChangedKeys.InsertElementSorted(aName);
+  }
+  mEntryArray.reset();
+
+  if (!mPendingFlush) {
+    MOZ_TRY(NS_DispatchToCurrentThreadQueue(
+        NewRunnableMethod("WritableSharedMap::IdleFlush", this,
+                          &WritableSharedMap::IdleFlush),
+        EventQueuePriority::Idle));
+    mPendingFlush = true;
+  }
+  return NS_OK;
+}
+
+JSObject* SharedMap::WrapObject(JSContext* aCx,
+                                JS::Handle<JSObject*> aGivenProto) {
+  return MozSharedMap_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+JSObject* WritableSharedMap::WrapObject(JSContext* aCx,
+                                        JS::Handle<JSObject*> aGivenProto) {
+  return MozWritableSharedMap_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+/* static */
+already_AddRefed<SharedMapChangeEvent> SharedMapChangeEvent::Constructor(
+    EventTarget* aEventTarget, const nsAString& aType,
+    const MozSharedMapChangeEventInit& aInit) {
+  RefPtr<SharedMapChangeEvent> event = new SharedMapChangeEvent(aEventTarget);
+
+  bool trusted = event->Init(aEventTarget);
+  event->InitEvent(aType, aInit.mBubbles, aInit.mCancelable);
+  event->SetTrusted(trusted);
+  event->SetComposed(aInit.mComposed);
+
+  event->mChangedKeys = aInit.mChangedKeys;
+
+  return event.forget();
+}
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(WritableSharedMap, SharedMap, mReadOnly)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(WritableSharedMap)
+NS_INTERFACE_MAP_END_INHERITING(SharedMap)
+
+NS_IMPL_ADDREF_INHERITED(WritableSharedMap, SharedMap)
+NS_IMPL_RELEASE_INHERITED(WritableSharedMap, SharedMap)
+
+}  // namespace dom::ipc
+}  // namespace mozilla