1 files changed, 237 insertions, 0 deletions
diff --git a/modules/libpref/SharedPrefMap.cpp b/modules/libpref/SharedPrefMap.cpp
new file mode 100644
index 0000000000..7782ffdcbf
--- /dev/null
+++ b/modules/libpref/SharedPrefMap.cpp
@@ -0,0 +1,237 @@
+/* -*- 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 "SharedPrefMap.h"
+
+#include "mozilla/dom/ipc/MemMapSnapshot.h"
+
+#include "mozilla/BinarySearch.h"
+#include "mozilla/ResultExtensions.h"
+#include "mozilla/Try.h"
+#include "mozilla/ipc/FileDescriptor.h"
+
+using namespace mozilla::loader;
+
+namespace mozilla {
+
+using namespace ipc;
+
+static inline size_t GetAlignmentOffset(size_t aOffset, size_t aAlign) {
+  auto mod = aOffset % aAlign;
+  return mod ? aAlign - mod : 0;
+}
+
+SharedPrefMap::SharedPrefMap(const FileDescriptor& aMapFile, size_t aMapSize) {
+  auto result = mMap.initWithHandle(aMapFile, aMapSize);
+  MOZ_RELEASE_ASSERT(result.isOk());
+  // We return literal nsCStrings pointing to the mapped data for preference
+  // names and string values, 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();
+}
+
+SharedPrefMap::SharedPrefMap(SharedPrefMapBuilder&& aBuilder) {
+  auto result = aBuilder.Finalize(mMap);
+  MOZ_RELEASE_ASSERT(result.isOk());
+  mMap.setPersistent();
+}
+
+mozilla::ipc::FileDescriptor SharedPrefMap::CloneFileDescriptor() const {
+  return mMap.cloneHandle();
+}
+
+bool SharedPrefMap::Has(const char* aKey) const {
+  size_t index;
+  return Find(aKey, &index);
+}
+
+Maybe<const SharedPrefMap::Pref> SharedPrefMap::Get(const char* aKey) const {
+  Maybe<const Pref> result;
+
+  size_t index;
+  if (Find(aKey, &index)) {
+    result.emplace(Pref{this, &Entries()[index]});
+  }
+
+  return result;
+}
+
+bool SharedPrefMap::Find(const char* aKey, size_t* aIndex) const {
+  const auto& keys = KeyTable();
+
+  return BinarySearchIf(
+      Entries(), 0, EntryCount(),
+      [&](const Entry& aEntry) {
+        return strcmp(aKey, keys.GetBare(aEntry.mKey));
+      },
+      aIndex);
+}
+
+void SharedPrefMapBuilder::Add(const nsCString& aKey, const Flags& aFlags,
+                               bool aDefaultValue, bool aUserValue) {
+  mEntries.AppendElement(Entry{
+      aKey.get(),
+      mKeyTable.Add(aKey),
+      {aDefaultValue, aUserValue},
+      uint8_t(PrefType::Bool),
+      aFlags.mHasDefaultValue,
+      aFlags.mHasUserValue,
+      aFlags.mIsSticky,
+      aFlags.mIsLocked,
+      aFlags.mIsSanitized,
+      aFlags.mIsSkippedByIteration,
+  });
+}
+
+void SharedPrefMapBuilder::Add(const nsCString& aKey, const Flags& aFlags,
+                               int32_t aDefaultValue, int32_t aUserValue) {
+  ValueIdx index;
+  if (aFlags.mHasUserValue) {
+    index = mIntValueTable.Add(aDefaultValue, aUserValue);
+  } else {
+    index = mIntValueTable.Add(aDefaultValue);
+  }
+
+  mEntries.AppendElement(Entry{
+      aKey.get(),
+      mKeyTable.Add(aKey),
+      {index},
+      uint8_t(PrefType::Int),
+      aFlags.mHasDefaultValue,
+      aFlags.mHasUserValue,
+      aFlags.mIsSticky,
+      aFlags.mIsLocked,
+      aFlags.mIsSanitized,
+      aFlags.mIsSkippedByIteration,
+  });
+}
+
+void SharedPrefMapBuilder::Add(const nsCString& aKey, const Flags& aFlags,
+                               const nsCString& aDefaultValue,
+                               const nsCString& aUserValue) {
+  ValueIdx index;
+  StringTableEntry defaultVal = mValueStringTable.Add(aDefaultValue);
+  if (aFlags.mHasUserValue) {
+    StringTableEntry userVal = mValueStringTable.Add(aUserValue);
+    index = mStringValueTable.Add(defaultVal, userVal);
+  } else {
+    index = mStringValueTable.Add(defaultVal);
+  }
+
+  mEntries.AppendElement(Entry{
+      aKey.get(),
+      mKeyTable.Add(aKey),
+      {index},
+      uint8_t(PrefType::String),
+      aFlags.mHasDefaultValue,
+      aFlags.mHasUserValue,
+      aFlags.mIsSticky,
+      aFlags.mIsLocked,
+      aFlags.mIsSanitized,
+      aFlags.mIsSkippedByIteration,
+  });
+}
+
+Result<Ok, nsresult> SharedPrefMapBuilder::Finalize(loader::AutoMemMap& aMap) {
+  using Header = SharedPrefMap::Header;
+
+  // Create an array of entry pointers for the entry array, and sort it by
+  // preference name prior to serialization, so that entries can be looked up
+  // using binary search.
+  nsTArray<Entry*> entries(mEntries.Length());
+  for (auto& entry : mEntries) {
+    entries.AppendElement(&entry);
+  }
+  entries.Sort([](const Entry* aA, const Entry* aB) {
+    return strcmp(aA->mKeyString, aB->mKeyString);
+  });
+
+  Header header = {uint32_t(entries.Length())};
+
+  size_t offset = sizeof(header);
+  offset += GetAlignmentOffset(offset, alignof(Header));
+
+  offset += entries.Length() * sizeof(SharedPrefMap::Entry);
+
+  header.mKeyStrings.mOffset = offset;
+  header.mKeyStrings.mSize = mKeyTable.Size();
+  offset += header.mKeyStrings.mSize;
+
+  offset += GetAlignmentOffset(offset, mIntValueTable.Alignment());
+  header.mUserIntValues.mOffset = offset;
+  header.mUserIntValues.mSize = mIntValueTable.UserSize();
+  offset += header.mUserIntValues.mSize;
+
+  offset += GetAlignmentOffset(offset, mIntValueTable.Alignment());
+  header.mDefaultIntValues.mOffset = offset;
+  header.mDefaultIntValues.mSize = mIntValueTable.DefaultSize();
+  offset += header.mDefaultIntValues.mSize;
+
+  offset += GetAlignmentOffset(offset, mStringValueTable.Alignment());
+  header.mUserStringValues.mOffset = offset;
+  header.mUserStringValues.mSize = mStringValueTable.UserSize();
+  offset += header.mUserStringValues.mSize;
+
+  offset += GetAlignmentOffset(offset, mStringValueTable.Alignment());
+  header.mDefaultStringValues.mOffset = offset;
+  header.mDefaultStringValues.mSize = mStringValueTable.DefaultSize();
+  offset += header.mDefaultStringValues.mSize;
+
+  header.mValueStrings.mOffset = offset;
+  header.mValueStrings.mSize = mValueStringTable.Size();
+  offset += header.mValueStrings.mSize;
+
+  MemMapSnapshot mem;
+  MOZ_TRY(mem.Init(offset));
+
+  auto headerPtr = mem.Get<Header>();
+  headerPtr[0] = header;
+
+  auto* entryPtr = reinterpret_cast<SharedPrefMap::Entry*>(&headerPtr[1]);
+  for (auto* entry : entries) {
+    *entryPtr = {
+        entry->mKey,
+        GetValue(*entry),
+        entry->mType,
+        entry->mHasDefaultValue,
+        entry->mHasUserValue,
+        entry->mIsSticky,
+        entry->mIsLocked,
+        entry->mIsSanitized,
+        entry->mIsSkippedByIteration,
+    };
+    entryPtr++;
+  }
+
+  auto ptr = mem.Get<uint8_t>();
+
+  mKeyTable.Write({&ptr[header.mKeyStrings.mOffset], header.mKeyStrings.mSize});
+
+  mValueStringTable.Write(
+      {&ptr[header.mValueStrings.mOffset], header.mValueStrings.mSize});
+
+  mIntValueTable.WriteDefaultValues(
+      {&ptr[header.mDefaultIntValues.mOffset], header.mDefaultIntValues.mSize});
+  mIntValueTable.WriteUserValues(
+      {&ptr[header.mUserIntValues.mOffset], header.mUserIntValues.mSize});
+
+  mStringValueTable.WriteDefaultValues(
+      {&ptr[header.mDefaultStringValues.mOffset],
+       header.mDefaultStringValues.mSize});
+  mStringValueTable.WriteUserValues(
+      {&ptr[header.mUserStringValues.mOffset], header.mUserStringValues.mSize});
+
+  mKeyTable.Clear();
+  mValueStringTable.Clear();
+  mIntValueTable.Clear();
+  mStringValueTable.Clear();
+  mEntries.Clear();
+
+  return mem.Finalize(aMap);
+}
+
+}  // namespace mozilla