1 files changed, 140 insertions, 0 deletions
diff --git a/dom/ipc/SharedStringMap.cpp b/dom/ipc/SharedStringMap.cpp
new file mode 100644
index 0000000000..8d50de6863
--- /dev/null
+++ b/dom/ipc/SharedStringMap.cpp
@@ -0,0 +1,140 @@
+/* -*- 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 "SharedStringMap.h"
+
+#include "MemMapSnapshot.h"
+#include "ScriptPreloader-inl.h"
+
+#include "mozilla/BinarySearch.h"
+#include "mozilla/Try.h"
+#include "mozilla/ipc/FileDescriptor.h"
+
+using namespace mozilla::loader;
+
+namespace mozilla {
+
+using namespace ipc;
+
+namespace dom::ipc {
+
+static constexpr uint32_t kSharedStringMapMagic = 0x9e3779b9;
+
+static inline size_t GetAlignmentOffset(size_t aOffset, size_t aAlign) {
+  auto mod = aOffset % aAlign;
+  return mod ? aAlign - mod : 0;
+}
+
+SharedStringMap::SharedStringMap(const FileDescriptor& aMapFile,
+                                 size_t aMapSize) {
+  auto result = mMap.initWithHandle(aMapFile, aMapSize);
+  MOZ_RELEASE_ASSERT(result.isOk());
+  MOZ_RELEASE_ASSERT(GetHeader().mMagic == kSharedStringMapMagic);
+  // We return literal nsStrings and nsCStrings pointing to the mapped data,
+  // which means that we may still have references to the mapped data even
+  // after this instance is destroyed. That means that we need to keep the
+  // mapping alive until process shutdown, in order to be safe.
+  mMap.setPersistent();
+}
+
+SharedStringMap::SharedStringMap(SharedStringMapBuilder&& aBuilder) {
+  auto result = aBuilder.Finalize(mMap);
+  MOZ_RELEASE_ASSERT(result.isOk());
+  MOZ_RELEASE_ASSERT(GetHeader().mMagic == kSharedStringMapMagic);
+  mMap.setPersistent();
+}
+
+mozilla::ipc::FileDescriptor SharedStringMap::CloneFileDescriptor() const {
+  return mMap.cloneHandle();
+}
+
+bool SharedStringMap::Has(const nsCString& aKey) {
+  size_t index;
+  return Find(aKey, &index);
+}
+
+bool SharedStringMap::Get(const nsCString& aKey, nsAString& aValue) {
+  const auto& entries = Entries();
+
+  size_t index;
+  if (!Find(aKey, &index)) {
+    return false;
+  }
+
+  aValue.Assign(ValueTable().Get(entries[index].mValue));
+  return true;
+}
+
+bool SharedStringMap::Find(const nsCString& aKey, size_t* aIndex) {
+  const auto& keys = KeyTable();
+
+  return BinarySearchIf(
+      Entries(), 0, EntryCount(),
+      [&](const Entry& aEntry) { return Compare(aKey, keys.Get(aEntry.mKey)); },
+      aIndex);
+}
+
+void SharedStringMapBuilder::Add(const nsCString& aKey,
+                                 const nsString& aValue) {
+  mEntries.InsertOrUpdate(aKey,
+                          Entry{mKeyTable.Add(aKey), mValueTable.Add(aValue)});
+}
+
+Result<Ok, nsresult> SharedStringMapBuilder::Finalize(
+    loader::AutoMemMap& aMap) {
+  using Header = SharedStringMap::Header;
+
+  MOZ_ASSERT(mEntries.Count() == mKeyTable.Count());
+
+  auto keys = ToTArray<nsTArray<nsCString>>(mEntries.Keys());
+  keys.Sort();
+
+  Header header = {kSharedStringMapMagic, uint32_t(keys.Length())};
+
+  size_t offset = sizeof(header);
+  offset += GetAlignmentOffset(offset, alignof(Header));
+
+  offset += keys.Length() * sizeof(SharedStringMap::Entry);
+
+  header.mKeyStringsOffset = offset;
+  header.mKeyStringsSize = mKeyTable.Size();
+
+  offset += header.mKeyStringsSize;
+  offset +=
+      GetAlignmentOffset(offset, alignof(decltype(mValueTable)::ElemType));
+
+  header.mValueStringsOffset = offset;
+  header.mValueStringsSize = mValueTable.Size();
+
+  offset += header.mValueStringsSize;
+
+  MemMapSnapshot mem;
+  MOZ_TRY(mem.Init(offset));
+
+  auto headerPtr = mem.Get<Header>();
+  headerPtr[0] = header;
+
+  auto* entry = reinterpret_cast<Entry*>(&headerPtr[1]);
+  for (auto& key : keys) {
+    *entry++ = mEntries.Get(key);
+  }
+
+  auto ptr = mem.Get<uint8_t>();
+
+  mKeyTable.Write({&ptr[header.mKeyStringsOffset], header.mKeyStringsSize});
+
+  mValueTable.Write(
+      {&ptr[header.mValueStringsOffset], header.mValueStringsSize});
+
+  mKeyTable.Clear();
+  mValueTable.Clear();
+  mEntries.Clear();
+
+  return mem.Finalize(aMap);
+}
+
+}  // namespace dom::ipc
+}  // namespace mozilla