/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
 * 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 "nsThreadUtils.h"
#include "nsIFile.h"
#include "nsIFileURL.h"
#include "nsIXPConnect.h"
#include "mozilla/AppShutdown.h"
#include "mozilla/Telemetry.h"
#include "mozilla/Mutex.h"
#include "mozilla/CondVar.h"
#include "mozilla/Attributes.h"
#include "mozilla/ErrorNames.h"
#include "mozilla/Unused.h"
#include "mozilla/dom/quota/QuotaObject.h"
#include "mozilla/ScopeExit.h"
#include "mozilla/SpinEventLoopUntil.h"
#include "mozilla/StaticPrefs_storage.h"

#include "mozIStorageCompletionCallback.h"
#include "mozIStorageFunction.h"

#include "mozStorageAsyncStatementExecution.h"
#include "mozStorageSQLFunctions.h"
#include "mozStorageConnection.h"
#include "mozStorageService.h"
#include "mozStorageStatement.h"
#include "mozStorageAsyncStatement.h"
#include "mozStorageArgValueArray.h"
#include "mozStoragePrivateHelpers.h"
#include "mozStorageStatementData.h"
#include "StorageBaseStatementInternal.h"
#include "SQLCollations.h"
#include "FileSystemModule.h"
#include "mozStorageHelper.h"

#include "mozilla/Logging.h"
#include "mozilla/Printf.h"
#include "mozilla/ProfilerLabels.h"
#include "nsProxyRelease.h"
#include "nsURLHelper.h"

#define MIN_AVAILABLE_BYTES_PER_CHUNKED_GROWTH 524288000  // 500 MiB

// Maximum size of the pages cache per connection.
#define MAX_CACHE_SIZE_KIBIBYTES 2048  // 2 MiB

mozilla::LazyLogModule gStorageLog("mozStorage");

// Checks that the protected code is running on the main-thread only if the
// connection was also opened on it.
#ifdef DEBUG
#  define CHECK_MAINTHREAD_ABUSE()                                   \
    do {                                                             \
      NS_WARNING_ASSERTION(                                          \
          eventTargetOpenedOn == GetMainThreadSerialEventTarget() || \
              !NS_IsMainThread(),                                    \
          "Using Storage synchronous API on main-thread, but "       \
          "the connection was opened on another thread.");           \
    } while (0)
#else
#  define CHECK_MAINTHREAD_ABUSE() \
    do { /* Nothing */             \
    } while (0)
#endif

namespace mozilla::storage {

using mozilla::dom::quota::QuotaObject;
using mozilla::Telemetry::AccumulateCategoricalKeyed;
using mozilla::Telemetry::LABELS_SQLITE_STORE_OPEN;
using mozilla::Telemetry::LABELS_SQLITE_STORE_QUERY;

const char* GetBaseVFSName(bool);
const char* GetQuotaVFSName();
const char* GetObfuscatingVFSName();

namespace {

int nsresultToSQLiteResult(nsresult aXPCOMResultCode) {
  if (NS_SUCCEEDED(aXPCOMResultCode)) {
    return SQLITE_OK;
  }

  switch (aXPCOMResultCode) {
    case NS_ERROR_FILE_CORRUPTED:
      return SQLITE_CORRUPT;
    case NS_ERROR_FILE_ACCESS_DENIED:
      return SQLITE_CANTOPEN;
    case NS_ERROR_STORAGE_BUSY:
      return SQLITE_BUSY;
    case NS_ERROR_FILE_IS_LOCKED:
      return SQLITE_LOCKED;
    case NS_ERROR_FILE_READ_ONLY:
      return SQLITE_READONLY;
    case NS_ERROR_STORAGE_IOERR:
      return SQLITE_IOERR;
    case NS_ERROR_FILE_NO_DEVICE_SPACE:
      return SQLITE_FULL;
    case NS_ERROR_OUT_OF_MEMORY:
      return SQLITE_NOMEM;
    case NS_ERROR_UNEXPECTED:
      return SQLITE_MISUSE;
    case NS_ERROR_ABORT:
      return SQLITE_ABORT;
    case NS_ERROR_STORAGE_CONSTRAINT:
      return SQLITE_CONSTRAINT;
    default:
      return SQLITE_ERROR;
  }

  MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Must return in switch above!");
}

////////////////////////////////////////////////////////////////////////////////
//// Variant Specialization Functions (variantToSQLiteT)

int sqlite3_T_int(sqlite3_context* aCtx, int aValue) {
  ::sqlite3_result_int(aCtx, aValue);
  return SQLITE_OK;
}

int sqlite3_T_int64(sqlite3_context* aCtx, sqlite3_int64 aValue) {
  ::sqlite3_result_int64(aCtx, aValue);
  return SQLITE_OK;
}

int sqlite3_T_double(sqlite3_context* aCtx, double aValue) {
  ::sqlite3_result_double(aCtx, aValue);
  return SQLITE_OK;
}

int sqlite3_T_text(sqlite3_context* aCtx, const nsCString& aValue) {
  ::sqlite3_result_text(aCtx, aValue.get(), aValue.Length(), SQLITE_TRANSIENT);
  return SQLITE_OK;
}

int sqlite3_T_text16(sqlite3_context* aCtx, const nsString& aValue) {
  ::sqlite3_result_text16(
      aCtx, aValue.get(),
      aValue.Length() * sizeof(char16_t),  // Number of bytes.
      SQLITE_TRANSIENT);
  return SQLITE_OK;
}

int sqlite3_T_null(sqlite3_context* aCtx) {
  ::sqlite3_result_null(aCtx);
  return SQLITE_OK;
}

int sqlite3_T_blob(sqlite3_context* aCtx, const void* aData, int aSize) {
  ::sqlite3_result_blob(aCtx, aData, aSize, free);
  return SQLITE_OK;
}

#include "variantToSQLiteT_impl.h"

////////////////////////////////////////////////////////////////////////////////
//// Modules

struct Module {
  const char* name;
  int (*registerFunc)(sqlite3*, const char*);
};

Module gModules[] = {{"filesystem", RegisterFileSystemModule}};

////////////////////////////////////////////////////////////////////////////////
//// Local Functions

int tracefunc(unsigned aReason, void* aClosure, void* aP, void* aX) {
  switch (aReason) {
    case SQLITE_TRACE_STMT: {
      // aP is a pointer to the prepared statement.
      sqlite3_stmt* stmt = static_cast<sqlite3_stmt*>(aP);
      // aX is a pointer to a string containing the unexpanded SQL or a comment,
      // starting with "--"" in case of a trigger.
      char* expanded = static_cast<char*>(aX);
      // Simulate what sqlite_trace was doing.
      if (!::strncmp(expanded, "--", 2)) {
        MOZ_LOG(gStorageLog, LogLevel::Debug,
                ("TRACE_STMT on %p: '%s'", aClosure, expanded));
      } else {
        char* sql = ::sqlite3_expanded_sql(stmt);
        MOZ_LOG(gStorageLog, LogLevel::Debug,
                ("TRACE_STMT on %p: '%s'", aClosure, sql));
        ::sqlite3_free(sql);
      }
      break;
    }
    case SQLITE_TRACE_PROFILE: {
      // aX is pointer to a 64bit integer containing nanoseconds it took to
      // execute the last command.
      sqlite_int64 time = *(static_cast<sqlite_int64*>(aX)) / 1000000;
      if (time > 0) {
        MOZ_LOG(gStorageLog, LogLevel::Debug,
                ("TRACE_TIME on %p: %lldms", aClosure, time));
      }
      break;
    }
  }
  return 0;
}

void basicFunctionHelper(sqlite3_context* aCtx, int aArgc,
                         sqlite3_value** aArgv) {
  void* userData = ::sqlite3_user_data(aCtx);

  mozIStorageFunction* func = static_cast<mozIStorageFunction*>(userData);

  RefPtr<ArgValueArray> arguments(new ArgValueArray(aArgc, aArgv));
  if (!arguments) return;

  nsCOMPtr<nsIVariant> result;
  nsresult rv = func->OnFunctionCall(arguments, getter_AddRefs(result));
  if (NS_FAILED(rv)) {
    nsAutoCString errorMessage;
    GetErrorName(rv, errorMessage);
    errorMessage.InsertLiteral("User function returned ", 0);
    errorMessage.Append('!');

    NS_WARNING(errorMessage.get());

    ::sqlite3_result_error(aCtx, errorMessage.get(), -1);
    ::sqlite3_result_error_code(aCtx, nsresultToSQLiteResult(rv));
    return;
  }
  int retcode = variantToSQLiteT(aCtx, result);
  if (retcode != SQLITE_OK) {
    NS_WARNING("User function returned invalid data type!");
    ::sqlite3_result_error(aCtx, "User function returned invalid data type",
                           -1);
  }
}

/**
 * This code is heavily based on the sample at:
 *   http://www.sqlite.org/unlock_notify.html
 */
class UnlockNotification {
 public:
  UnlockNotification()
      : mMutex("UnlockNotification mMutex"),
        mCondVar(mMutex, "UnlockNotification condVar"),
        mSignaled(false) {}

  void Wait() {
    MutexAutoLock lock(mMutex);
    while (!mSignaled) {
      (void)mCondVar.Wait();
    }
  }

  void Signal() {
    MutexAutoLock lock(mMutex);
    mSignaled = true;
    (void)mCondVar.Notify();
  }

 private:
  Mutex mMutex MOZ_UNANNOTATED;
  CondVar mCondVar;
  bool mSignaled;
};

void UnlockNotifyCallback(void** aArgs, int aArgsSize) {
  for (int i = 0; i < aArgsSize; i++) {
    UnlockNotification* notification =
        static_cast<UnlockNotification*>(aArgs[i]);
    notification->Signal();
  }
}

int WaitForUnlockNotify(sqlite3* aDatabase) {
  UnlockNotification notification;
  int srv =
      ::sqlite3_unlock_notify(aDatabase, UnlockNotifyCallback, &notification);
  MOZ_ASSERT(srv == SQLITE_LOCKED || srv == SQLITE_OK);
  if (srv == SQLITE_OK) {
    notification.Wait();
  }

  return srv;
}

////////////////////////////////////////////////////////////////////////////////
//// Local Classes

class AsyncCloseConnection final : public Runnable {
 public:
  AsyncCloseConnection(Connection* aConnection, sqlite3* aNativeConnection,
                       nsIRunnable* aCallbackEvent)
      : Runnable("storage::AsyncCloseConnection"),
        mConnection(aConnection),
        mNativeConnection(aNativeConnection),
        mCallbackEvent(aCallbackEvent) {}

  NS_IMETHOD Run() override {
    // Make sure we don't dispatch to the current thread.
    MOZ_ASSERT(!IsOnCurrentSerialEventTarget(mConnection->eventTargetOpenedOn));

    nsCOMPtr<nsIRunnable> event =
        NewRunnableMethod("storage::Connection::shutdownAsyncThread",
                          mConnection, &Connection::shutdownAsyncThread);
    MOZ_ALWAYS_SUCCEEDS(NS_DispatchToMainThread(event));

    // Internal close.
    (void)mConnection->internalClose(mNativeConnection);

    // Callback
    if (mCallbackEvent) {
      nsCOMPtr<nsIThread> thread;
      (void)NS_GetMainThread(getter_AddRefs(thread));
      (void)thread->Dispatch(mCallbackEvent, NS_DISPATCH_NORMAL);
    }

    return NS_OK;
  }

  ~AsyncCloseConnection() override {
    NS_ReleaseOnMainThread("AsyncCloseConnection::mConnection",
                           mConnection.forget());
    NS_ReleaseOnMainThread("AsyncCloseConnection::mCallbackEvent",
                           mCallbackEvent.forget());
  }

 private:
  RefPtr<Connection> mConnection;
  sqlite3* mNativeConnection;
  nsCOMPtr<nsIRunnable> mCallbackEvent;
};

/**
 * An event used to initialize the clone of a connection.
 *
 * Must be executed on the clone's async execution thread.
 */
class AsyncInitializeClone final : public Runnable {
 public:
  /**
   * @param aConnection The connection being cloned.
   * @param aClone The clone.
   * @param aReadOnly If |true|, the clone is read only.
   * @param aCallback A callback to trigger once initialization
   *                  is complete. This event will be called on
   *                  aClone->eventTargetOpenedOn.
   */
  AsyncInitializeClone(Connection* aConnection, Connection* aClone,
                       const bool aReadOnly,
                       mozIStorageCompletionCallback* aCallback)
      : Runnable("storage::AsyncInitializeClone"),
        mConnection(aConnection),
        mClone(aClone),
        mReadOnly(aReadOnly),
        mCallback(aCallback) {
    MOZ_ASSERT(NS_IsMainThread());
  }

  NS_IMETHOD Run() override {
    MOZ_ASSERT(!NS_IsMainThread());
    nsresult rv = mConnection->initializeClone(mClone, mReadOnly);
    if (NS_FAILED(rv)) {
      return Dispatch(rv, nullptr);
    }
    return Dispatch(NS_OK,
                    NS_ISUPPORTS_CAST(mozIStorageAsyncConnection*, mClone));
  }

 private:
  nsresult Dispatch(nsresult aResult, nsISupports* aValue) {
    RefPtr<CallbackComplete> event =
        new CallbackComplete(aResult, aValue, mCallback.forget());
    return mClone->eventTargetOpenedOn->Dispatch(event, NS_DISPATCH_NORMAL);
  }

  ~AsyncInitializeClone() override {
    nsCOMPtr<nsIThread> thread;
    DebugOnly<nsresult> rv = NS_GetMainThread(getter_AddRefs(thread));
    MOZ_ASSERT(NS_SUCCEEDED(rv));

    // Handle ambiguous nsISupports inheritance.
    NS_ProxyRelease("AsyncInitializeClone::mConnection", thread,
                    mConnection.forget());
    NS_ProxyRelease("AsyncInitializeClone::mClone", thread, mClone.forget());

    // Generally, the callback will be released by CallbackComplete.
    // However, if for some reason Run() is not executed, we still
    // need to ensure that it is released here.
    NS_ProxyRelease("AsyncInitializeClone::mCallback", thread,
                    mCallback.forget());
  }

  RefPtr<Connection> mConnection;
  RefPtr<Connection> mClone;
  const bool mReadOnly;
  nsCOMPtr<mozIStorageCompletionCallback> mCallback;
};

/**
 * A listener for async connection closing.
 */
class CloseListener final : public mozIStorageCompletionCallback {
 public:
  NS_DECL_ISUPPORTS
  CloseListener() : mClosed(false) {}

  NS_IMETHOD Complete(nsresult, nsISupports*) override {
    mClosed = true;
    return NS_OK;
  }

  bool mClosed;

 private:
  ~CloseListener() = default;
};

NS_IMPL_ISUPPORTS(CloseListener, mozIStorageCompletionCallback)

class AsyncVacuumEvent final : public Runnable {
 public:
  AsyncVacuumEvent(Connection* aConnection,
                   mozIStorageCompletionCallback* aCallback,
                   bool aUseIncremental, int32_t aSetPageSize)
      : Runnable("storage::AsyncVacuum"),
        mConnection(aConnection),
        mCallback(aCallback),
        mUseIncremental(aUseIncremental),
        mSetPageSize(aSetPageSize),
        mStatus(NS_ERROR_UNEXPECTED) {}

  NS_IMETHOD Run() override {
    // This is initially dispatched to the helper thread, then re-dispatched
    // to the opener thread, where it will callback.
    if (IsOnCurrentSerialEventTarget(mConnection->eventTargetOpenedOn)) {
      // Send the completion event.
      if (mCallback) {
        mozilla::Unused << mCallback->Complete(mStatus, nullptr);
      }
      return NS_OK;
    }

    // Ensure to invoke the callback regardless of errors.
    auto guard = MakeScopeExit([&]() {
      mConnection->mIsStatementOnHelperThreadInterruptible = false;
      mozilla::Unused << mConnection->eventTargetOpenedOn->Dispatch(
          this, NS_DISPATCH_NORMAL);
    });

    // Get list of attached databases.
    nsCOMPtr<mozIStorageStatement> stmt;
    nsresult rv = mConnection->CreateStatement(MOZ_STORAGE_UNIQUIFY_QUERY_STR
                                               "PRAGMA database_list"_ns,
                                               getter_AddRefs(stmt));
    NS_ENSURE_SUCCESS(rv, rv);
    // We must accumulate names and loop through them later, otherwise VACUUM
    // will see an ongoing statement and bail out.
    nsTArray<nsCString> schemaNames;
    bool hasResult = false;
    while (stmt && NS_SUCCEEDED(stmt->ExecuteStep(&hasResult)) && hasResult) {
      nsAutoCString name;
      rv = stmt->GetUTF8String(1, name);
      if (NS_SUCCEEDED(rv) && !name.EqualsLiteral("temp")) {
        schemaNames.AppendElement(name);
      }
    }
    mStatus = NS_OK;
    // Mark this vacuum as an interruptible operation, so it can be interrupted
    // if the connection closes during shutdown.
    mConnection->mIsStatementOnHelperThreadInterruptible = true;
    for (const nsCString& schemaName : schemaNames) {
      rv = this->Vacuum(schemaName);
      if (NS_FAILED(rv)) {
        // This is sub-optimal since it's only keeping the last error reason,
        // but it will do for now.
        mStatus = rv;
      }
    }
    return mStatus;
  }

  nsresult Vacuum(const nsACString& aSchemaName) {
    // Abort if we're in shutdown.
    if (AppShutdown::IsInOrBeyond(ShutdownPhase::AppShutdownConfirmed)) {
      return NS_ERROR_ABORT;
    }
    int32_t removablePages = mConnection->RemovablePagesInFreeList(aSchemaName);
    if (!removablePages) {
      // There's no empty pages to remove, so skip this vacuum for now.
      return NS_OK;
    }
    nsresult rv;
    bool needsFullVacuum = true;

    if (mSetPageSize) {
      nsAutoCString query(MOZ_STORAGE_UNIQUIFY_QUERY_STR "PRAGMA ");
      query.Append(aSchemaName);
      query.AppendLiteral(".page_size = ");
      query.AppendInt(mSetPageSize);
      nsCOMPtr<mozIStorageStatement> stmt;
      rv = mConnection->ExecuteSimpleSQL(query);
      NS_ENSURE_SUCCESS(rv, rv);
    }

    // Check auto_vacuum.
    {
      nsAutoCString query(MOZ_STORAGE_UNIQUIFY_QUERY_STR "PRAGMA ");
      query.Append(aSchemaName);
      query.AppendLiteral(".auto_vacuum");
      nsCOMPtr<mozIStorageStatement> stmt;
      rv = mConnection->CreateStatement(query, getter_AddRefs(stmt));
      NS_ENSURE_SUCCESS(rv, rv);
      bool hasResult = false;
      bool changeAutoVacuum = false;
      if (stmt && NS_SUCCEEDED(stmt->ExecuteStep(&hasResult)) && hasResult) {
        bool isIncrementalVacuum = stmt->AsInt32(0) == 2;
        changeAutoVacuum = isIncrementalVacuum != mUseIncremental;
        if (isIncrementalVacuum && !changeAutoVacuum) {
          needsFullVacuum = false;
        }
      }
      // Changing auto_vacuum is only supported on the main schema.
      if (aSchemaName.EqualsLiteral("main") && changeAutoVacuum) {
        nsAutoCString query(MOZ_STORAGE_UNIQUIFY_QUERY_STR "PRAGMA ");
        query.Append(aSchemaName);
        query.AppendLiteral(".auto_vacuum = ");
        query.AppendInt(mUseIncremental ? 2 : 0);
        rv = mConnection->ExecuteSimpleSQL(query);
        NS_ENSURE_SUCCESS(rv, rv);
      }
    }

    if (needsFullVacuum) {
      nsAutoCString query(MOZ_STORAGE_UNIQUIFY_QUERY_STR "VACUUM ");
      query.Append(aSchemaName);
      rv = mConnection->ExecuteSimpleSQL(query);
      // TODO (Bug 1818039): Report failed vacuum telemetry.
      NS_ENSURE_SUCCESS(rv, rv);
    } else {
      nsAutoCString query(MOZ_STORAGE_UNIQUIFY_QUERY_STR "PRAGMA ");
      query.Append(aSchemaName);
      query.AppendLiteral(".incremental_vacuum(");
      query.AppendInt(removablePages);
      query.AppendLiteral(")");
      rv = mConnection->ExecuteSimpleSQL(query);
      NS_ENSURE_SUCCESS(rv, rv);
    }

    return NS_OK;
  }

  ~AsyncVacuumEvent() override {
    NS_ReleaseOnMainThread("AsyncVacuum::mConnection", mConnection.forget());
    NS_ReleaseOnMainThread("AsyncVacuum::mCallback", mCallback.forget());
  }

 private:
  RefPtr<Connection> mConnection;
  nsCOMPtr<mozIStorageCompletionCallback> mCallback;
  bool mUseIncremental;
  int32_t mSetPageSize;
  Atomic<nsresult> mStatus;
};

}  // namespace

////////////////////////////////////////////////////////////////////////////////
//// Connection

Connection::Connection(Service* aService, int aFlags,
                       ConnectionOperation aSupportedOperations,
                       bool aInterruptible, bool aIgnoreLockingMode)
    : sharedAsyncExecutionMutex("Connection::sharedAsyncExecutionMutex"),
      sharedDBMutex("Connection::sharedDBMutex"),
      eventTargetOpenedOn(WrapNotNull(GetCurrentSerialEventTarget())),
      mIsStatementOnHelperThreadInterruptible(false),
      mDBConn(nullptr),
      mDefaultTransactionType(mozIStorageConnection::TRANSACTION_DEFERRED),
      mDestroying(false),
      mProgressHandler(nullptr),
      mStorageService(aService),
      mFlags(aFlags),
      mTransactionNestingLevel(0),
      mSupportedOperations(aSupportedOperations),
      mInterruptible(aSupportedOperations == Connection::ASYNCHRONOUS ||
                     aInterruptible),
      mIgnoreLockingMode(aIgnoreLockingMode),
      mAsyncExecutionThreadShuttingDown(false),
      mConnectionClosed(false),
      mGrowthChunkSize(0) {
  MOZ_ASSERT(!mIgnoreLockingMode || mFlags & SQLITE_OPEN_READONLY,
             "Can't ignore locking for a non-readonly connection!");
  mStorageService->registerConnection(this);
}

Connection::~Connection() {
  // Failsafe Close() occurs in our custom Release method because of
  // complications related to Close() potentially invoking AsyncClose() which
  // will increment our refcount.
  MOZ_ASSERT(!mAsyncExecutionThread,
             "The async thread has not been shutdown properly!");
}

NS_IMPL_ADDREF(Connection)

NS_INTERFACE_MAP_BEGIN(Connection)
  NS_INTERFACE_MAP_ENTRY(mozIStorageAsyncConnection)
  NS_INTERFACE_MAP_ENTRY(nsIInterfaceRequestor)
  NS_INTERFACE_MAP_ENTRY(mozIStorageConnection)
  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, mozIStorageConnection)
NS_INTERFACE_MAP_END

// This is identical to what NS_IMPL_RELEASE provides, but with the
// extra |1 == count| case.
NS_IMETHODIMP_(MozExternalRefCountType) Connection::Release(void) {
  MOZ_ASSERT(0 != mRefCnt, "dup release");
  nsrefcnt count = --mRefCnt;
  NS_LOG_RELEASE(this, count, "Connection");
  if (1 == count) {
    // If the refcount went to 1, the single reference must be from
    // gService->mConnections (in class |Service|).  And the code calling
    // Release is either:
    // - The "user" code that had created the connection, releasing on any
    //   thread.
    // - One of Service's getConnections() callers had acquired a strong
    //   reference to the Connection that out-lived the last "user" reference,
    //   and now that just got dropped.  Note that this reference could be
    //   getting dropped on the main thread or Connection->eventTargetOpenedOn
    //   (because of the NewRunnableMethod used by minimizeMemory).
    //
    // Either way, we should now perform our failsafe Close() and unregister.
    // However, we only want to do this once, and the reality is that our
    // refcount could go back up above 1 and down again at any time if we are
    // off the main thread and getConnections() gets called on the main thread,
    // so we use an atomic here to do this exactly once.
    if (mDestroying.compareExchange(false, true)) {
      // Close the connection, dispatching to the opening event target if we're
      // not on that event target already and that event target is still
      // accepting runnables. We do this because it's possible we're on the main
      // thread because of getConnections(), and we REALLY don't want to
      // transfer I/O to the main thread if we can avoid it.
      if (IsOnCurrentSerialEventTarget(eventTargetOpenedOn)) {
        // This could cause SpinningSynchronousClose() to be invoked and AddRef
        // triggered for AsyncCloseConnection's strong ref if the conn was ever
        // use for async purposes.  (Main-thread only, though.)
        Unused << synchronousClose();
      } else {
        nsCOMPtr<nsIRunnable> event =
            NewRunnableMethod("storage::Connection::synchronousClose", this,
                              &Connection::synchronousClose);
        if (NS_FAILED(eventTargetOpenedOn->Dispatch(event.forget(),
                                                    NS_DISPATCH_NORMAL))) {
          // The event target was dead and so we've just leaked our runnable.
          // This should not happen because our non-main-thread consumers should
          // be explicitly closing their connections, not relying on us to close
          // them for them.  (It's okay to let a statement go out of scope for
          // automatic cleanup, but not a Connection.)
          MOZ_ASSERT(false,
                     "Leaked Connection::synchronousClose(), ownership fail.");
          Unused << synchronousClose();
        }
      }

      // This will drop its strong reference right here, right now.
      mStorageService->unregisterConnection(this);
    }
  } else if (0 == count) {
    mRefCnt = 1; /* stabilize */
#if 0            /* enable this to find non-threadsafe destructors: */
    NS_ASSERT_OWNINGTHREAD(Connection);
#endif
    delete (this);
    return 0;
  }
  return count;
}

int32_t Connection::getSqliteRuntimeStatus(int32_t aStatusOption,
                                           int32_t* aMaxValue) {
  MOZ_ASSERT(connectionReady(), "A connection must exist at this point");
  int curr = 0, max = 0;
  DebugOnly<int> rc =
      ::sqlite3_db_status(mDBConn, aStatusOption, &curr, &max, 0);
  MOZ_ASSERT(NS_SUCCEEDED(convertResultCode(rc)));
  if (aMaxValue) *aMaxValue = max;
  return curr;
}

nsIEventTarget* Connection::getAsyncExecutionTarget() {
  NS_ENSURE_TRUE(IsOnCurrentSerialEventTarget(eventTargetOpenedOn), nullptr);

  // Don't return the asynchronous event target if we are shutting down.
  if (mAsyncExecutionThreadShuttingDown) {
    return nullptr;
  }

  // Create the async event target if there's none yet.
  if (!mAsyncExecutionThread) {
    static nsThreadPoolNaming naming;
    nsresult rv = NS_NewNamedThread(naming.GetNextThreadName("mozStorage"),
                                    getter_AddRefs(mAsyncExecutionThread));
    if (NS_FAILED(rv)) {
      NS_WARNING("Failed to create async thread.");
      return nullptr;
    }
    mAsyncExecutionThread->SetNameForWakeupTelemetry("mozStorage (all)"_ns);
  }

  return mAsyncExecutionThread;
}

void Connection::RecordOpenStatus(nsresult rv) {
  nsCString histogramKey = mTelemetryFilename;

  if (histogramKey.IsEmpty()) {
    histogramKey.AssignLiteral("unknown");
  }

  if (NS_SUCCEEDED(rv)) {
    AccumulateCategoricalKeyed(histogramKey, LABELS_SQLITE_STORE_OPEN::success);
    return;
  }

  switch (rv) {
    case NS_ERROR_FILE_CORRUPTED:
      AccumulateCategoricalKeyed(histogramKey,
                                 LABELS_SQLITE_STORE_OPEN::corrupt);
      break;
    case NS_ERROR_STORAGE_IOERR:
      AccumulateCategoricalKeyed(histogramKey,
                                 LABELS_SQLITE_STORE_OPEN::diskio);
      break;
    case NS_ERROR_FILE_ACCESS_DENIED:
    case NS_ERROR_FILE_IS_LOCKED:
    case NS_ERROR_FILE_READ_ONLY:
      AccumulateCategoricalKeyed(histogramKey,
                                 LABELS_SQLITE_STORE_OPEN::access);
      break;
    case NS_ERROR_FILE_NO_DEVICE_SPACE:
      AccumulateCategoricalKeyed(histogramKey,
                                 LABELS_SQLITE_STORE_OPEN::diskspace);
      break;
    default:
      AccumulateCategoricalKeyed(histogramKey,
                                 LABELS_SQLITE_STORE_OPEN::failure);
  }
}

void Connection::RecordQueryStatus(int srv) {
  nsCString histogramKey = mTelemetryFilename;

  if (histogramKey.IsEmpty()) {
    histogramKey.AssignLiteral("unknown");
  }

  switch (srv) {
    case SQLITE_OK:
    case SQLITE_ROW:
    case SQLITE_DONE:

    // Note that these are returned when we intentionally cancel a statement so
    // they aren't indicating a failure.
    case SQLITE_ABORT:
    case SQLITE_INTERRUPT:
      AccumulateCategoricalKeyed(histogramKey,
                                 LABELS_SQLITE_STORE_QUERY::success);
      break;
    case SQLITE_CORRUPT:
    case SQLITE_NOTADB:
      AccumulateCategoricalKeyed(histogramKey,
                                 LABELS_SQLITE_STORE_QUERY::corrupt);
      break;
    case SQLITE_PERM:
    case SQLITE_CANTOPEN:
    case SQLITE_LOCKED:
    case SQLITE_READONLY:
      AccumulateCategoricalKeyed(histogramKey,
                                 LABELS_SQLITE_STORE_QUERY::access);
      break;
    case SQLITE_IOERR:
    case SQLITE_NOLFS:
      AccumulateCategoricalKeyed(histogramKey,
                                 LABELS_SQLITE_STORE_QUERY::diskio);
      break;
    case SQLITE_FULL:
    case SQLITE_TOOBIG:
      AccumulateCategoricalKeyed(histogramKey,
                                 LABELS_SQLITE_STORE_QUERY::diskspace);
      break;
    case SQLITE_CONSTRAINT:
    case SQLITE_RANGE:
    case SQLITE_MISMATCH:
    case SQLITE_MISUSE:
      AccumulateCategoricalKeyed(histogramKey,
                                 LABELS_SQLITE_STORE_QUERY::misuse);
      break;
    case SQLITE_BUSY:
      AccumulateCategoricalKeyed(histogramKey, LABELS_SQLITE_STORE_QUERY::busy);
      break;
    default:
      AccumulateCategoricalKeyed(histogramKey,
                                 LABELS_SQLITE_STORE_QUERY::failure);
  }
}

nsresult Connection::initialize(const nsACString& aStorageKey,
                                const nsACString& aName) {
  MOZ_ASSERT(aStorageKey.Equals(kMozStorageMemoryStorageKey));
  NS_ASSERTION(!connectionReady(),
               "Initialize called on already opened database!");
  MOZ_ASSERT(!mIgnoreLockingMode, "Can't ignore locking on an in-memory db.");
  AUTO_PROFILER_LABEL("Connection::initialize", OTHER);

  mStorageKey = aStorageKey;
  mName = aName;

  // in memory database requested, sqlite uses a magic file name

  const nsAutoCString path =
      mName.IsEmpty() ? nsAutoCString(":memory:"_ns)
                      : "file:"_ns + mName + "?mode=memory&cache=shared"_ns;

  mTelemetryFilename.AssignLiteral(":memory:");

  int srv =
      ::sqlite3_open_v2(path.get(), &mDBConn, mFlags, GetBaseVFSName(true));
  if (srv != SQLITE_OK) {
    mDBConn = nullptr;
    nsresult rv = convertResultCode(srv);
    RecordOpenStatus(rv);
    return rv;
  }

#ifdef MOZ_SQLITE_FTS3_TOKENIZER
  srv =
      ::sqlite3_db_config(mDBConn, SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER, 1, 0);
  MOZ_ASSERT(srv == SQLITE_OK,
             "SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER should be enabled");
#endif

  // Do not set mDatabaseFile or mFileURL here since this is a "memory"
  // database.

  nsresult rv = initializeInternal();
  RecordOpenStatus(rv);
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;
}

nsresult Connection::initialize(nsIFile* aDatabaseFile) {
  NS_ASSERTION(aDatabaseFile, "Passed null file!");
  NS_ASSERTION(!connectionReady(),
               "Initialize called on already opened database!");
  AUTO_PROFILER_LABEL("Connection::initialize", OTHER);

  // Do not set mFileURL here since this is database does not have an associated
  // URL.
  mDatabaseFile = aDatabaseFile;
  aDatabaseFile->GetNativeLeafName(mTelemetryFilename);

  nsAutoString path;
  nsresult rv = aDatabaseFile->GetPath(path);
  NS_ENSURE_SUCCESS(rv, rv);

  bool exclusive = StaticPrefs::storage_sqlite_exclusiveLock_enabled();
  int srv;
  if (mIgnoreLockingMode) {
    exclusive = false;
    srv = ::sqlite3_open_v2(NS_ConvertUTF16toUTF8(path).get(), &mDBConn, mFlags,
                            "readonly-immutable-nolock");
  } else {
    srv = ::sqlite3_open_v2(NS_ConvertUTF16toUTF8(path).get(), &mDBConn, mFlags,
                            GetBaseVFSName(exclusive));
    if (exclusive && (srv == SQLITE_LOCKED || srv == SQLITE_BUSY)) {
      // Retry without trying to get an exclusive lock.
      exclusive = false;
      srv = ::sqlite3_open_v2(NS_ConvertUTF16toUTF8(path).get(), &mDBConn,
                              mFlags, GetBaseVFSName(false));
    }
  }
  if (srv != SQLITE_OK) {
    mDBConn = nullptr;
    rv = convertResultCode(srv);
    RecordOpenStatus(rv);
    return rv;
  }

  rv = initializeInternal();
  if (exclusive &&
      (rv == NS_ERROR_STORAGE_BUSY || rv == NS_ERROR_FILE_IS_LOCKED)) {
    // Usually SQLite will fail to acquire an exclusive lock on opening, but in
    // some cases it may successfully open the database and then lock on the
    // first query execution. When initializeInternal fails it closes the
    // connection, so we can try to restart it in non-exclusive mode.
    srv = ::sqlite3_open_v2(NS_ConvertUTF16toUTF8(path).get(), &mDBConn, mFlags,
                            GetBaseVFSName(false));
    if (srv == SQLITE_OK) {
      rv = initializeInternal();
    }
  }

  RecordOpenStatus(rv);
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;
}

nsresult Connection::initialize(nsIFileURL* aFileURL,
                                const nsACString& aTelemetryFilename) {
  NS_ASSERTION(aFileURL, "Passed null file URL!");
  NS_ASSERTION(!connectionReady(),
               "Initialize called on already opened database!");
  AUTO_PROFILER_LABEL("Connection::initialize", OTHER);

  nsCOMPtr<nsIFile> databaseFile;
  nsresult rv = aFileURL->GetFile(getter_AddRefs(databaseFile));
  NS_ENSURE_SUCCESS(rv, rv);

  // Set both mDatabaseFile and mFileURL here.
  mFileURL = aFileURL;
  mDatabaseFile = databaseFile;

  if (!aTelemetryFilename.IsEmpty()) {
    mTelemetryFilename = aTelemetryFilename;
  } else {
    databaseFile->GetNativeLeafName(mTelemetryFilename);
  }

  nsAutoCString spec;
  rv = aFileURL->GetSpec(spec);
  NS_ENSURE_SUCCESS(rv, rv);

  // If there is a key specified, we need to use the obfuscating VFS.
  nsAutoCString query;
  rv = aFileURL->GetQuery(query);
  NS_ENSURE_SUCCESS(rv, rv);

  bool hasKey = false;
  bool hasDirectoryLockId = false;

  MOZ_ALWAYS_TRUE(URLParams::Parse(
      query, [&hasKey, &hasDirectoryLockId](const nsAString& aName,
                                            const nsAString& aValue) {
        if (aName.EqualsLiteral("key")) {
          hasKey = true;
          return true;
        }
        if (aName.EqualsLiteral("directoryLockId")) {
          hasDirectoryLockId = true;
          return true;
        }
        return true;
      }));

  bool exclusive = StaticPrefs::storage_sqlite_exclusiveLock_enabled();

  const char* const vfs = hasKey               ? GetObfuscatingVFSName()
                          : hasDirectoryLockId ? GetQuotaVFSName()
                                               : GetBaseVFSName(exclusive);

  int srv = ::sqlite3_open_v2(spec.get(), &mDBConn, mFlags, vfs);
  if (srv != SQLITE_OK) {
    mDBConn = nullptr;
    rv = convertResultCode(srv);
    RecordOpenStatus(rv);
    return rv;
  }

  rv = initializeInternal();
  RecordOpenStatus(rv);
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;
}

nsresult Connection::initializeInternal() {
  MOZ_ASSERT(mDBConn);
  auto guard = MakeScopeExit([&]() { initializeFailed(); });

  mConnectionClosed = false;

#ifdef MOZ_SQLITE_FTS3_TOKENIZER
  DebugOnly<int> srv2 =
      ::sqlite3_db_config(mDBConn, SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER, 1, 0);
  MOZ_ASSERT(srv2 == SQLITE_OK,
             "SQLITE_DBCONFIG_ENABLE_FTS3_TOKENIZER should be enabled");
#endif

  MOZ_ASSERT(!mTelemetryFilename.IsEmpty(),
             "A telemetry filename should have been set by now.");

  // Properly wrap the database handle's mutex.
  sharedDBMutex.initWithMutex(sqlite3_db_mutex(mDBConn));

  // SQLite tracing can slow down queries (especially long queries)
  // significantly. Don't trace unless the user is actively monitoring SQLite.
  if (MOZ_LOG_TEST(gStorageLog, LogLevel::Debug)) {
    ::sqlite3_trace_v2(mDBConn, SQLITE_TRACE_STMT | SQLITE_TRACE_PROFILE,
                       tracefunc, this);

    MOZ_LOG(
        gStorageLog, LogLevel::Debug,
        ("Opening connection to '%s' (%p)", mTelemetryFilename.get(), this));
  }

  int64_t pageSize = Service::kDefaultPageSize;

  // Set page_size to the preferred default value.  This is effective only if
  // the database has just been created, otherwise, if the database does not
  // use WAL journal mode, a VACUUM operation will updated its page_size.
  nsAutoCString pageSizeQuery(MOZ_STORAGE_UNIQUIFY_QUERY_STR
                              "PRAGMA page_size = ");
  pageSizeQuery.AppendInt(pageSize);
  int srv = executeSql(mDBConn, pageSizeQuery.get());
  if (srv != SQLITE_OK) {
    return convertResultCode(srv);
  }

  // Setting the cache_size forces the database open, verifying if it is valid
  // or corrupt.  So this is executed regardless it being actually needed.
  // The cache_size is calculated from the actual page_size, to save memory.
  nsAutoCString cacheSizeQuery(MOZ_STORAGE_UNIQUIFY_QUERY_STR
                               "PRAGMA cache_size = ");
  cacheSizeQuery.AppendInt(-MAX_CACHE_SIZE_KIBIBYTES);
  srv = executeSql(mDBConn, cacheSizeQuery.get());
  if (srv != SQLITE_OK) {
    return convertResultCode(srv);
  }

  // Register our built-in SQL functions.
  srv = registerFunctions(mDBConn);
  if (srv != SQLITE_OK) {
    return convertResultCode(srv);
  }

  // Register our built-in SQL collating sequences.
  srv = registerCollations(mDBConn, mStorageService);
  if (srv != SQLITE_OK) {
    return convertResultCode(srv);
  }

  // Set the default synchronous value. Each consumer can switch this
  // accordingly to their needs.
#if defined(ANDROID)
  // Android prefers synchronous = OFF for performance reasons.
  Unused << ExecuteSimpleSQL("PRAGMA synchronous = OFF;"_ns);
#else
  // Normal is the suggested value for WAL journals.
  Unused << ExecuteSimpleSQL("PRAGMA synchronous = NORMAL;"_ns);
#endif

  // Initialization succeeded, we can stop guarding for failures.
  guard.release();
  return NS_OK;
}

nsresult Connection::initializeOnAsyncThread(nsIFile* aStorageFile) {
  MOZ_ASSERT(!IsOnCurrentSerialEventTarget(eventTargetOpenedOn));
  nsresult rv = aStorageFile
                    ? initialize(aStorageFile)
                    : initialize(kMozStorageMemoryStorageKey, VoidCString());
  if (NS_FAILED(rv)) {
    // Shutdown the async thread, since initialization failed.
    MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
    mAsyncExecutionThreadShuttingDown = true;
    nsCOMPtr<nsIRunnable> event =
        NewRunnableMethod("Connection::shutdownAsyncThread", this,
                          &Connection::shutdownAsyncThread);
    Unused << NS_DispatchToMainThread(event);
  }
  return rv;
}

void Connection::initializeFailed() {
  {
    MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
    mConnectionClosed = true;
  }
  MOZ_ALWAYS_TRUE(::sqlite3_close(mDBConn) == SQLITE_OK);
  mDBConn = nullptr;
  sharedDBMutex.destroy();
}

nsresult Connection::databaseElementExists(
    enum DatabaseElementType aElementType, const nsACString& aElementName,
    bool* _exists) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_AVAILABLE;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // When constructing the query, make sure to SELECT the correct db's
  // sqlite_master if the user is prefixing the element with a specific db. ex:
  // sample.test
  nsCString query("SELECT name FROM (SELECT * FROM ");
  nsDependentCSubstring element;
  int32_t ind = aElementName.FindChar('.');
  if (ind == kNotFound) {
    element.Assign(aElementName);
  } else {
    nsDependentCSubstring db(Substring(aElementName, 0, ind + 1));
    element.Assign(Substring(aElementName, ind + 1, aElementName.Length()));
    query.Append(db);
  }
  query.AppendLiteral(
      "sqlite_master UNION ALL SELECT * FROM sqlite_temp_master) WHERE type = "
      "'");

  switch (aElementType) {
    case INDEX:
      query.AppendLiteral("index");
      break;
    case TABLE:
      query.AppendLiteral("table");
      break;
  }
  query.AppendLiteral("' AND name ='");
  query.Append(element);
  query.Append('\'');

  sqlite3_stmt* stmt;
  int srv = prepareStatement(mDBConn, query, &stmt);
  if (srv != SQLITE_OK) {
    RecordQueryStatus(srv);
    return convertResultCode(srv);
  }

  srv = stepStatement(mDBConn, stmt);
  // we just care about the return value from step
  (void)::sqlite3_finalize(stmt);

  RecordQueryStatus(srv);

  if (srv == SQLITE_ROW) {
    *_exists = true;
    return NS_OK;
  }
  if (srv == SQLITE_DONE) {
    *_exists = false;
    return NS_OK;
  }

  return convertResultCode(srv);
}

bool Connection::findFunctionByInstance(mozIStorageFunction* aInstance) {
  sharedDBMutex.assertCurrentThreadOwns();

  for (const auto& data : mFunctions.Values()) {
    if (data.function == aInstance) {
      return true;
    }
  }
  return false;
}

/* static */
int Connection::sProgressHelper(void* aArg) {
  Connection* _this = static_cast<Connection*>(aArg);
  return _this->progressHandler();
}

int Connection::progressHandler() {
  sharedDBMutex.assertCurrentThreadOwns();
  if (mProgressHandler) {
    bool result;
    nsresult rv = mProgressHandler->OnProgress(this, &result);
    if (NS_FAILED(rv)) return 0;  // Don't break request
    return result ? 1 : 0;
  }
  return 0;
}

nsresult Connection::setClosedState() {
  // Flag that we are shutting down the async thread, so that
  // getAsyncExecutionTarget knows not to expose/create the async thread.
  MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
  NS_ENSURE_FALSE(mAsyncExecutionThreadShuttingDown, NS_ERROR_UNEXPECTED);

  mAsyncExecutionThreadShuttingDown = true;

  // Set the property to null before closing the connection, otherwise the
  // other functions in the module may try to use the connection after it is
  // closed.
  mDBConn = nullptr;

  return NS_OK;
}

bool Connection::operationSupported(ConnectionOperation aOperationType) {
  if (aOperationType == ASYNCHRONOUS) {
    // Async operations are supported for all connections, on any thread.
    return true;
  }
  // Sync operations are supported for sync connections (on any thread), and
  // async connections on a background thread.
  MOZ_ASSERT(aOperationType == SYNCHRONOUS);
  return mSupportedOperations == SYNCHRONOUS || !NS_IsMainThread();
}

nsresult Connection::ensureOperationSupported(
    ConnectionOperation aOperationType) {
  if (NS_WARN_IF(!operationSupported(aOperationType))) {
#ifdef DEBUG
    if (NS_IsMainThread()) {
      nsCOMPtr<nsIXPConnect> xpc = nsIXPConnect::XPConnect();
      Unused << xpc->DebugDumpJSStack(false, false, false);
    }
#endif
    MOZ_ASSERT(false,
               "Don't use async connections synchronously on the main thread");
    return NS_ERROR_NOT_AVAILABLE;
  }
  return NS_OK;
}

bool Connection::isConnectionReadyOnThisThread() {
  MOZ_ASSERT_IF(connectionReady(), !mConnectionClosed);
  if (mAsyncExecutionThread && mAsyncExecutionThread->IsOnCurrentThread()) {
    return true;
  }
  return connectionReady();
}

bool Connection::isClosing() {
  MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
  return mAsyncExecutionThreadShuttingDown && !mConnectionClosed;
}

bool Connection::isClosed() {
  MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
  return mConnectionClosed;
}

bool Connection::isClosed(MutexAutoLock& lock) { return mConnectionClosed; }

bool Connection::isAsyncExecutionThreadAvailable() {
  MOZ_ASSERT(IsOnCurrentSerialEventTarget(eventTargetOpenedOn));
  return mAsyncExecutionThread && !mAsyncExecutionThreadShuttingDown;
}

void Connection::shutdownAsyncThread() {
  MOZ_ASSERT(IsOnCurrentSerialEventTarget(eventTargetOpenedOn));
  MOZ_ASSERT(mAsyncExecutionThread);
  MOZ_ASSERT(mAsyncExecutionThreadShuttingDown);

  MOZ_ALWAYS_SUCCEEDS(mAsyncExecutionThread->Shutdown());
  mAsyncExecutionThread = nullptr;
}

nsresult Connection::internalClose(sqlite3* aNativeConnection) {
#ifdef DEBUG
  {  // Make sure we have marked our async thread as shutting down.
    MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
    MOZ_ASSERT(mAsyncExecutionThreadShuttingDown,
               "Did not call setClosedState!");
    MOZ_ASSERT(!isClosed(lockedScope), "Unexpected closed state");
  }
#endif  // DEBUG

  if (MOZ_LOG_TEST(gStorageLog, LogLevel::Debug)) {
    nsAutoCString leafName(":memory");
    if (mDatabaseFile) (void)mDatabaseFile->GetNativeLeafName(leafName);
    MOZ_LOG(gStorageLog, LogLevel::Debug,
            ("Closing connection to '%s'", leafName.get()));
  }

  // At this stage, we may still have statements that need to be
  // finalized. Attempt to close the database connection. This will
  // always disconnect any virtual tables and cleanly finalize their
  // internal statements. Once this is done, closing may fail due to
  // unfinalized client statements, in which case we need to finalize
  // these statements and close again.
  {
    MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
    mConnectionClosed = true;
  }

  // Nothing else needs to be done if we don't have a connection here.
  if (!aNativeConnection) return NS_OK;

  int srv = ::sqlite3_close(aNativeConnection);

  if (srv == SQLITE_BUSY) {
    {
      // Nothing else should change the connection or statements status until we
      // are done here.
      SQLiteMutexAutoLock lockedScope(sharedDBMutex);
      // We still have non-finalized statements. Finalize them.
      sqlite3_stmt* stmt = nullptr;
      while ((stmt = ::sqlite3_next_stmt(aNativeConnection, stmt))) {
        MOZ_LOG(gStorageLog, LogLevel::Debug,
                ("Auto-finalizing SQL statement '%s' (%p)", ::sqlite3_sql(stmt),
                 stmt));

#ifdef DEBUG
        SmprintfPointer msg = ::mozilla::Smprintf(
            "SQL statement '%s' (%p) should have been finalized before closing "
            "the connection",
            ::sqlite3_sql(stmt), stmt);
        NS_WARNING(msg.get());
#endif  // DEBUG

        srv = ::sqlite3_finalize(stmt);

#ifdef DEBUG
        if (srv != SQLITE_OK) {
          SmprintfPointer msg = ::mozilla::Smprintf(
              "Could not finalize SQL statement (%p)", stmt);
          NS_WARNING(msg.get());
        }
#endif  // DEBUG

        // Ensure that the loop continues properly, whether closing has
        // succeeded or not.
        if (srv == SQLITE_OK) {
          stmt = nullptr;
        }
      }
      // Scope exiting will unlock the mutex before we invoke sqlite3_close()
      // again, since Sqlite will try to acquire it.
    }

    // Now that all statements have been finalized, we
    // should be able to close.
    srv = ::sqlite3_close(aNativeConnection);
    MOZ_ASSERT(false,
               "Had to forcibly close the database connection because not all "
               "the statements have been finalized.");
  }

  if (srv == SQLITE_OK) {
    sharedDBMutex.destroy();
  } else {
    MOZ_ASSERT(false,
               "sqlite3_close failed. There are probably outstanding "
               "statements that are listed above!");
  }

  return convertResultCode(srv);
}

nsCString Connection::getFilename() { return mTelemetryFilename; }

int Connection::stepStatement(sqlite3* aNativeConnection,
                              sqlite3_stmt* aStatement) {
  MOZ_ASSERT(aStatement);

  AUTO_PROFILER_LABEL_DYNAMIC_CSTR("Connection::stepStatement", OTHER,
                                   ::sqlite3_sql(aStatement));

  bool checkedMainThread = false;
  TimeStamp startTime = TimeStamp::Now();

  // The connection may have been closed if the executing statement has been
  // created and cached after a call to asyncClose() but before the actual
  // sqlite3_close().  This usually happens when other tasks using cached
  // statements are asynchronously scheduled for execution and any of them ends
  // up after asyncClose. See bug 728653 for details.
  if (!isConnectionReadyOnThisThread()) return SQLITE_MISUSE;

  (void)::sqlite3_extended_result_codes(aNativeConnection, 1);

  int srv;
  while ((srv = ::sqlite3_step(aStatement)) == SQLITE_LOCKED_SHAREDCACHE) {
    if (!checkedMainThread) {
      checkedMainThread = true;
      if (::NS_IsMainThread()) {
        NS_WARNING("We won't allow blocking on the main thread!");
        break;
      }
    }

    srv = WaitForUnlockNotify(aNativeConnection);
    if (srv != SQLITE_OK) {
      break;
    }

    ::sqlite3_reset(aStatement);
  }

  // Report very slow SQL statements to Telemetry
  TimeDuration duration = TimeStamp::Now() - startTime;
  const uint32_t threshold = NS_IsMainThread()
                                 ? Telemetry::kSlowSQLThresholdForMainThread
                                 : Telemetry::kSlowSQLThresholdForHelperThreads;
  if (duration.ToMilliseconds() >= threshold) {
    nsDependentCString statementString(::sqlite3_sql(aStatement));
    Telemetry::RecordSlowSQLStatement(statementString, mTelemetryFilename,
                                      duration.ToMilliseconds());
  }

  (void)::sqlite3_extended_result_codes(aNativeConnection, 0);
  // Drop off the extended result bits of the result code.
  return srv & 0xFF;
}

int Connection::prepareStatement(sqlite3* aNativeConnection,
                                 const nsCString& aSQL, sqlite3_stmt** _stmt) {
  // We should not even try to prepare statements after the connection has
  // been closed.
  if (!isConnectionReadyOnThisThread()) return SQLITE_MISUSE;

  bool checkedMainThread = false;

  (void)::sqlite3_extended_result_codes(aNativeConnection, 1);

  int srv;
  while ((srv = ::sqlite3_prepare_v2(aNativeConnection, aSQL.get(), -1, _stmt,
                                     nullptr)) == SQLITE_LOCKED_SHAREDCACHE) {
    if (!checkedMainThread) {
      checkedMainThread = true;
      if (::NS_IsMainThread()) {
        NS_WARNING("We won't allow blocking on the main thread!");
        break;
      }
    }

    srv = WaitForUnlockNotify(aNativeConnection);
    if (srv != SQLITE_OK) {
      break;
    }
  }

  if (srv != SQLITE_OK) {
    nsCString warnMsg;
    warnMsg.AppendLiteral("The SQL statement '");
    warnMsg.Append(aSQL);
    warnMsg.AppendLiteral("' could not be compiled due to an error: ");
    warnMsg.Append(::sqlite3_errmsg(aNativeConnection));

#ifdef DEBUG
    NS_WARNING(warnMsg.get());
#endif
    MOZ_LOG(gStorageLog, LogLevel::Error, ("%s", warnMsg.get()));
  }

  (void)::sqlite3_extended_result_codes(aNativeConnection, 0);
  // Drop off the extended result bits of the result code.
  int rc = srv & 0xFF;
  // sqlite will return OK on a comment only string and set _stmt to nullptr.
  // The callers of this function are used to only checking the return value,
  // so it is safer to return an error code.
  if (rc == SQLITE_OK && *_stmt == nullptr) {
    return SQLITE_MISUSE;
  }

  return rc;
}

int Connection::executeSql(sqlite3* aNativeConnection, const char* aSqlString) {
  if (!isConnectionReadyOnThisThread()) return SQLITE_MISUSE;

  AUTO_PROFILER_LABEL_DYNAMIC_CSTR("Connection::executeSql", OTHER, aSqlString);

  TimeStamp startTime = TimeStamp::Now();
  int srv =
      ::sqlite3_exec(aNativeConnection, aSqlString, nullptr, nullptr, nullptr);
  RecordQueryStatus(srv);

  // Report very slow SQL statements to Telemetry
  TimeDuration duration = TimeStamp::Now() - startTime;
  const uint32_t threshold = NS_IsMainThread()
                                 ? Telemetry::kSlowSQLThresholdForMainThread
                                 : Telemetry::kSlowSQLThresholdForHelperThreads;
  if (duration.ToMilliseconds() >= threshold) {
    nsDependentCString statementString(aSqlString);
    Telemetry::RecordSlowSQLStatement(statementString, mTelemetryFilename,
                                      duration.ToMilliseconds());
  }

  return srv;
}

////////////////////////////////////////////////////////////////////////////////
//// nsIInterfaceRequestor

NS_IMETHODIMP
Connection::GetInterface(const nsIID& aIID, void** _result) {
  if (aIID.Equals(NS_GET_IID(nsIEventTarget))) {
    nsIEventTarget* background = getAsyncExecutionTarget();
    NS_IF_ADDREF(background);
    *_result = background;
    return NS_OK;
  }
  return NS_ERROR_NO_INTERFACE;
}

////////////////////////////////////////////////////////////////////////////////
//// mozIStorageConnection

NS_IMETHODIMP
Connection::Close() {
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }
  return synchronousClose();
}

nsresult Connection::synchronousClose() {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }

#ifdef DEBUG
  // Since we're accessing mAsyncExecutionThread, we need to be on the opener
  // event target. We make this check outside of debug code below in
  // setClosedState, but this is here to be explicit.
  MOZ_ASSERT(IsOnCurrentSerialEventTarget(eventTargetOpenedOn));
#endif  // DEBUG

  // Make sure we have not executed any asynchronous statements.
  // If this fails, the mDBConn may be left open, resulting in a leak.
  // We'll try to finalize the pending statements and close the connection.
  if (isAsyncExecutionThreadAvailable()) {
#ifdef DEBUG
    if (NS_IsMainThread()) {
      nsCOMPtr<nsIXPConnect> xpc = nsIXPConnect::XPConnect();
      Unused << xpc->DebugDumpJSStack(false, false, false);
    }
#endif
    MOZ_ASSERT(false,
               "Close() was invoked on a connection that executed asynchronous "
               "statements. "
               "Should have used asyncClose().");
    // Try to close the database regardless, to free up resources.
    Unused << SpinningSynchronousClose();
    return NS_ERROR_UNEXPECTED;
  }

  // setClosedState nullifies our connection pointer, so we take a raw pointer
  // off it, to pass it through the close procedure.
  sqlite3* nativeConn = mDBConn;
  nsresult rv = setClosedState();
  NS_ENSURE_SUCCESS(rv, rv);

  return internalClose(nativeConn);
}

NS_IMETHODIMP
Connection::SpinningSynchronousClose() {
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }
  if (!IsOnCurrentSerialEventTarget(eventTargetOpenedOn)) {
    return NS_ERROR_NOT_SAME_THREAD;
  }

  // As currently implemented, we can't spin to wait for an existing AsyncClose.
  // Our only existing caller will never have called close; assert if misused
  // so that no new callers assume this works after an AsyncClose.
  MOZ_DIAGNOSTIC_ASSERT(connectionReady());
  if (!connectionReady()) {
    return NS_ERROR_UNEXPECTED;
  }

  RefPtr<CloseListener> listener = new CloseListener();
  rv = AsyncClose(listener);
  NS_ENSURE_SUCCESS(rv, rv);
  MOZ_ALWAYS_TRUE(
      SpinEventLoopUntil("storage::Connection::SpinningSynchronousClose"_ns,
                         [&]() { return listener->mClosed; }));
  MOZ_ASSERT(isClosed(), "The connection should be closed at this point");

  return rv;
}

NS_IMETHODIMP
Connection::AsyncClose(mozIStorageCompletionCallback* aCallback) {
  NS_ENSURE_TRUE(NS_IsMainThread(), NS_ERROR_NOT_SAME_THREAD);
  // Check if AsyncClose or Close were already invoked.
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(ASYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // The two relevant factors at this point are whether we have a database
  // connection and whether we have an async execution thread.  Here's what the
  // states mean and how we handle them:
  //
  // - (mDBConn && asyncThread): The expected case where we are either an
  //   async connection or a sync connection that has been used asynchronously.
  //   Either way the caller must call us and not Close().  Nothing surprising
  //   about this.  We'll dispatch AsyncCloseConnection to the already-existing
  //   async thread.
  //
  // - (mDBConn && !asyncThread): A somewhat unusual case where the caller
  //   opened the connection synchronously and was planning to use it
  //   asynchronously, but never got around to using it asynchronously before
  //   needing to shutdown.  This has been observed to happen for the cookie
  //   service in a case where Firefox shuts itself down almost immediately
  //   after startup (for unknown reasons).  In the Firefox shutdown case,
  //   we may also fail to create a new async execution thread if one does not
  //   already exist.  (nsThreadManager will refuse to create new threads when
  //   it has already been told to shutdown.)  As such, we need to handle a
  //   failure to create the async execution thread by falling back to
  //   synchronous Close() and also dispatching the completion callback because
  //   at least Places likes to spin a nested event loop that depends on the
  //   callback being invoked.
  //
  //   Note that we have considered not trying to spin up the async execution
  //   thread in this case if it does not already exist, but the overhead of
  //   thread startup (if successful) is significantly less expensive than the
  //   worst-case potential I/O hit of synchronously closing a database when we
  //   could close it asynchronously.
  //
  // - (!mDBConn && asyncThread): This happens in some but not all cases where
  //   OpenAsyncDatabase encountered a problem opening the database.  If it
  //   happened in all cases AsyncInitDatabase would just shut down the thread
  //   directly and we would avoid this case.  But it doesn't, so for simplicity
  //   and consistency AsyncCloseConnection knows how to handle this and we
  //   act like this was the (mDBConn && asyncThread) case in this method.
  //
  // - (!mDBConn && !asyncThread): The database was never successfully opened or
  //   Close() or AsyncClose() has already been called (at least) once.  This is
  //   undeniably a misuse case by the caller.  We could optimize for this
  //   case by adding an additional check of mAsyncExecutionThread without using
  //   getAsyncExecutionTarget() to avoid wastefully creating a thread just to
  //   shut it down.  But this complicates the method for broken caller code
  //   whereas we're still correct and safe without the special-case.
  nsIEventTarget* asyncThread = getAsyncExecutionTarget();

  // Create our callback event if we were given a callback.  This will
  // eventually be dispatched in all cases, even if we fall back to Close() and
  // the database wasn't open and we return an error.  The rationale is that
  // no existing consumer checks our return value and several of them like to
  // spin nested event loops until the callback fires.  Given that, it seems
  // preferable for us to dispatch the callback in all cases.  (Except the
  // wrong thread misuse case we bailed on up above.  But that's okay because
  // that is statically wrong whereas these edge cases are dynamic.)
  nsCOMPtr<nsIRunnable> completeEvent;
  if (aCallback) {
    completeEvent = newCompletionEvent(aCallback);
  }

  if (!asyncThread) {
    // We were unable to create an async thread, so we need to fall back to
    // using normal Close().  Since there is no async thread, Close() will
    // not complain about that.  (Close() may, however, complain if the
    // connection is closed, but that's okay.)
    if (completeEvent) {
      // Closing the database is more important than returning an error code
      // about a failure to dispatch, especially because all existing native
      // callers ignore our return value.
      Unused << NS_DispatchToMainThread(completeEvent.forget());
    }
    MOZ_ALWAYS_SUCCEEDS(synchronousClose());
    // Return a success inconditionally here, since Close() is unlikely to fail
    // and we want to reassure the consumer that its callback will be invoked.
    return NS_OK;
  }

  // If we're closing the connection during shutdown, and there is an
  // interruptible statement running on the helper thread, issue a
  // sqlite3_interrupt() to avoid crashing when that statement takes a long
  // time (for example a vacuum).
  if (AppShutdown::IsInOrBeyond(ShutdownPhase::AppShutdownConfirmed) &&
      mInterruptible && mIsStatementOnHelperThreadInterruptible) {
    MOZ_ASSERT(!isClosing(), "Must not be closing, see Interrupt()");
    DebugOnly<nsresult> rv2 = Interrupt();
    MOZ_ASSERT(NS_SUCCEEDED(rv2));
  }

  // setClosedState nullifies our connection pointer, so we take a raw pointer
  // off it, to pass it through the close procedure.
  sqlite3* nativeConn = mDBConn;
  rv = setClosedState();
  NS_ENSURE_SUCCESS(rv, rv);

  // Create and dispatch our close event to the background thread.
  nsCOMPtr<nsIRunnable> closeEvent =
      new AsyncCloseConnection(this, nativeConn, completeEvent);
  rv = asyncThread->Dispatch(closeEvent, NS_DISPATCH_NORMAL);
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;
}

NS_IMETHODIMP
Connection::AsyncClone(bool aReadOnly,
                       mozIStorageCompletionCallback* aCallback) {
  AUTO_PROFILER_LABEL("Connection::AsyncClone", OTHER);

  NS_ENSURE_TRUE(NS_IsMainThread(), NS_ERROR_NOT_SAME_THREAD);
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(ASYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }
  if (!mDatabaseFile) return NS_ERROR_UNEXPECTED;

  int flags = mFlags;
  if (aReadOnly) {
    // Turn off SQLITE_OPEN_READWRITE, and set SQLITE_OPEN_READONLY.
    flags = (~SQLITE_OPEN_READWRITE & flags) | SQLITE_OPEN_READONLY;
    // Turn off SQLITE_OPEN_CREATE.
    flags = (~SQLITE_OPEN_CREATE & flags);
  }

  // The cloned connection will still implement the synchronous API, but throw
  // if any synchronous methods are called on the main thread.
  RefPtr<Connection> clone =
      new Connection(mStorageService, flags, ASYNCHRONOUS);

  RefPtr<AsyncInitializeClone> initEvent =
      new AsyncInitializeClone(this, clone, aReadOnly, aCallback);
  // Dispatch to our async thread, since the originating connection must remain
  // valid and open for the whole cloning process.  This also ensures we are
  // properly serialized with a `close` operation, rather than race with it.
  nsCOMPtr<nsIEventTarget> target = getAsyncExecutionTarget();
  if (!target) {
    return NS_ERROR_UNEXPECTED;
  }
  return target->Dispatch(initEvent, NS_DISPATCH_NORMAL);
}

nsresult Connection::initializeClone(Connection* aClone, bool aReadOnly) {
  nsresult rv;
  if (!mStorageKey.IsEmpty()) {
    rv = aClone->initialize(mStorageKey, mName);
  } else if (mFileURL) {
    rv = aClone->initialize(mFileURL, mTelemetryFilename);
  } else {
    rv = aClone->initialize(mDatabaseFile);
  }
  if (NS_FAILED(rv)) {
    return rv;
  }

  auto guard = MakeScopeExit([&]() { aClone->initializeFailed(); });

  rv = aClone->SetDefaultTransactionType(mDefaultTransactionType);
  NS_ENSURE_SUCCESS(rv, rv);

  // Re-attach on-disk databases that were attached to the original connection.
  {
    nsCOMPtr<mozIStorageStatement> stmt;
    rv = CreateStatement("PRAGMA database_list"_ns, getter_AddRefs(stmt));
    NS_ENSURE_SUCCESS(rv, rv);
    bool hasResult = false;
    while (stmt && NS_SUCCEEDED(stmt->ExecuteStep(&hasResult)) && hasResult) {
      nsAutoCString name;
      rv = stmt->GetUTF8String(1, name);
      if (NS_SUCCEEDED(rv) && !name.EqualsLiteral("main") &&
          !name.EqualsLiteral("temp")) {
        nsCString path;
        rv = stmt->GetUTF8String(2, path);
        if (NS_SUCCEEDED(rv) && !path.IsEmpty()) {
          nsCOMPtr<mozIStorageStatement> attachStmt;
          rv = aClone->CreateStatement("ATTACH DATABASE :path AS "_ns + name,
                                       getter_AddRefs(attachStmt));
          NS_ENSURE_SUCCESS(rv, rv);
          rv = attachStmt->BindUTF8StringByName("path"_ns, path);
          NS_ENSURE_SUCCESS(rv, rv);
          rv = attachStmt->Execute();
          NS_ENSURE_SUCCESS(rv, rv);
        }
      }
    }
  }

  // Copy over pragmas from the original connection.
  // LIMITATION WARNING!  Many of these pragmas are actually scoped to the
  // schema ("main" and any other attached databases), and this implmentation
  // fails to propagate them.  This is being addressed on trunk.
  static const char* pragmas[] = {
      "cache_size",  "temp_store",         "foreign_keys", "journal_size_limit",
      "synchronous", "wal_autocheckpoint", "busy_timeout"};
  for (auto& pragma : pragmas) {
    // Read-only connections just need cache_size and temp_store pragmas.
    if (aReadOnly && ::strcmp(pragma, "cache_size") != 0 &&
        ::strcmp(pragma, "temp_store") != 0) {
      continue;
    }

    nsAutoCString pragmaQuery("PRAGMA ");
    pragmaQuery.Append(pragma);
    nsCOMPtr<mozIStorageStatement> stmt;
    rv = CreateStatement(pragmaQuery, getter_AddRefs(stmt));
    NS_ENSURE_SUCCESS(rv, rv);
    bool hasResult = false;
    if (stmt && NS_SUCCEEDED(stmt->ExecuteStep(&hasResult)) && hasResult) {
      pragmaQuery.AppendLiteral(" = ");
      pragmaQuery.AppendInt(stmt->AsInt32(0));
      rv = aClone->ExecuteSimpleSQL(pragmaQuery);
      NS_ENSURE_SUCCESS(rv, rv);
    }
  }

  // Copy over temporary tables, triggers, and views from the original
  // connections. Entities in `sqlite_temp_master` are only visible to the
  // connection that created them.
  if (!aReadOnly) {
    rv = aClone->ExecuteSimpleSQL("BEGIN TRANSACTION"_ns);
    NS_ENSURE_SUCCESS(rv, rv);

    nsCOMPtr<mozIStorageStatement> stmt;
    rv = CreateStatement(nsLiteralCString("SELECT sql FROM sqlite_temp_master "
                                          "WHERE type IN ('table', 'view', "
                                          "'index', 'trigger')"),
                         getter_AddRefs(stmt));
    // Propagate errors, because failing to copy triggers might cause schema
    // coherency issues when writing to the database from the cloned connection.
    NS_ENSURE_SUCCESS(rv, rv);
    bool hasResult = false;
    while (stmt && NS_SUCCEEDED(stmt->ExecuteStep(&hasResult)) && hasResult) {
      nsAutoCString query;
      rv = stmt->GetUTF8String(0, query);
      NS_ENSURE_SUCCESS(rv, rv);

      // The `CREATE` SQL statements in `sqlite_temp_master` omit the `TEMP`
      // keyword. We need to add it back, or we'll recreate temporary entities
      // as persistent ones. `sqlite_temp_master` also holds `CREATE INDEX`
      // statements, but those don't need `TEMP` keywords.
      if (StringBeginsWith(query, "CREATE TABLE "_ns) ||
          StringBeginsWith(query, "CREATE TRIGGER "_ns) ||
          StringBeginsWith(query, "CREATE VIEW "_ns)) {
        query.Replace(0, 6, "CREATE TEMP");
      }

      rv = aClone->ExecuteSimpleSQL(query);
      NS_ENSURE_SUCCESS(rv, rv);
    }

    rv = aClone->ExecuteSimpleSQL("COMMIT"_ns);
    NS_ENSURE_SUCCESS(rv, rv);
  }

  // Copy any functions that have been added to this connection.
  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  for (const auto& entry : mFunctions) {
    const nsACString& key = entry.GetKey();
    Connection::FunctionInfo data = entry.GetData();

    rv = aClone->CreateFunction(key, data.numArgs, data.function);
    if (NS_FAILED(rv)) {
      NS_WARNING("Failed to copy function to cloned connection");
    }
  }

  guard.release();
  return NS_OK;
}

NS_IMETHODIMP
Connection::Clone(bool aReadOnly, mozIStorageConnection** _connection) {
  MOZ_ASSERT(IsOnCurrentSerialEventTarget(eventTargetOpenedOn));

  AUTO_PROFILER_LABEL("Connection::Clone", OTHER);

  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  int flags = mFlags;
  if (aReadOnly) {
    // Turn off SQLITE_OPEN_READWRITE, and set SQLITE_OPEN_READONLY.
    flags = (~SQLITE_OPEN_READWRITE & flags) | SQLITE_OPEN_READONLY;
    // Turn off SQLITE_OPEN_CREATE.
    flags = (~SQLITE_OPEN_CREATE & flags);
  }

  RefPtr<Connection> clone = new Connection(
      mStorageService, flags, mSupportedOperations, mInterruptible);

  rv = initializeClone(clone, aReadOnly);
  if (NS_FAILED(rv)) {
    return rv;
  }

  NS_IF_ADDREF(*_connection = clone);
  return NS_OK;
}

NS_IMETHODIMP
Connection::Interrupt() {
  MOZ_ASSERT(mInterruptible, "Interrupt method not allowed");
  MOZ_ASSERT_IF(SYNCHRONOUS == mSupportedOperations,
                !IsOnCurrentSerialEventTarget(eventTargetOpenedOn));
  MOZ_ASSERT_IF(ASYNCHRONOUS == mSupportedOperations,
                IsOnCurrentSerialEventTarget(eventTargetOpenedOn));

  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }

  if (isClosing()) {  // Closing already in asynchronous case
    return NS_OK;
  }

  {
    // As stated on https://www.sqlite.org/c3ref/interrupt.html,
    // it is not safe to call sqlite3_interrupt() when
    // database connection is closed or might close before
    // sqlite3_interrupt() returns.
    MutexAutoLock lockedScope(sharedAsyncExecutionMutex);
    if (!isClosed(lockedScope)) {
      MOZ_ASSERT(mDBConn);
      ::sqlite3_interrupt(mDBConn);
    }
  }

  return NS_OK;
}

NS_IMETHODIMP
Connection::AsyncVacuum(mozIStorageCompletionCallback* aCallback,
                        bool aUseIncremental, int32_t aSetPageSize) {
  NS_ENSURE_TRUE(NS_IsMainThread(), NS_ERROR_NOT_SAME_THREAD);
  // Abort if we're shutting down.
  if (AppShutdown::IsInOrBeyond(ShutdownPhase::AppShutdownConfirmed)) {
    return NS_ERROR_ABORT;
  }
  // Check if AsyncClose or Close were already invoked.
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(ASYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }
  nsIEventTarget* asyncThread = getAsyncExecutionTarget();
  if (!asyncThread) {
    return NS_ERROR_NOT_INITIALIZED;
  }

  // Create and dispatch our vacuum event to the background thread.
  nsCOMPtr<nsIRunnable> vacuumEvent =
      new AsyncVacuumEvent(this, aCallback, aUseIncremental, aSetPageSize);
  rv = asyncThread->Dispatch(vacuumEvent, NS_DISPATCH_NORMAL);
  NS_ENSURE_SUCCESS(rv, rv);

  return NS_OK;
}

NS_IMETHODIMP
Connection::GetDefaultPageSize(int32_t* _defaultPageSize) {
  *_defaultPageSize = Service::kDefaultPageSize;
  return NS_OK;
}

NS_IMETHODIMP
Connection::GetConnectionReady(bool* _ready) {
  MOZ_ASSERT(IsOnCurrentSerialEventTarget(eventTargetOpenedOn));
  *_ready = connectionReady();
  return NS_OK;
}

NS_IMETHODIMP
Connection::GetDatabaseFile(nsIFile** _dbFile) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(ASYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  NS_IF_ADDREF(*_dbFile = mDatabaseFile);

  return NS_OK;
}

NS_IMETHODIMP
Connection::GetLastInsertRowID(int64_t* _id) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  sqlite_int64 id = ::sqlite3_last_insert_rowid(mDBConn);
  *_id = id;

  return NS_OK;
}

NS_IMETHODIMP
Connection::GetAffectedRows(int32_t* _rows) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  *_rows = ::sqlite3_changes(mDBConn);

  return NS_OK;
}

NS_IMETHODIMP
Connection::GetLastError(int32_t* _error) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  *_error = ::sqlite3_errcode(mDBConn);

  return NS_OK;
}

NS_IMETHODIMP
Connection::GetLastErrorString(nsACString& _errorString) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  const char* serr = ::sqlite3_errmsg(mDBConn);
  _errorString.Assign(serr);

  return NS_OK;
}

NS_IMETHODIMP
Connection::GetSchemaVersion(int32_t* _version) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  nsCOMPtr<mozIStorageStatement> stmt;
  (void)CreateStatement("PRAGMA user_version"_ns, getter_AddRefs(stmt));
  NS_ENSURE_TRUE(stmt, NS_ERROR_OUT_OF_MEMORY);

  *_version = 0;
  bool hasResult;
  if (NS_SUCCEEDED(stmt->ExecuteStep(&hasResult)) && hasResult)
    *_version = stmt->AsInt32(0);

  return NS_OK;
}

NS_IMETHODIMP
Connection::SetSchemaVersion(int32_t aVersion) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  nsAutoCString stmt("PRAGMA user_version = "_ns);
  stmt.AppendInt(aVersion);

  return ExecuteSimpleSQL(stmt);
}

NS_IMETHODIMP
Connection::CreateStatement(const nsACString& aSQLStatement,
                            mozIStorageStatement** _stmt) {
  NS_ENSURE_ARG_POINTER(_stmt);
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  RefPtr<Statement> statement(new Statement());
  NS_ENSURE_TRUE(statement, NS_ERROR_OUT_OF_MEMORY);

  rv = statement->initialize(this, mDBConn, aSQLStatement);
  NS_ENSURE_SUCCESS(rv, rv);

  Statement* rawPtr;
  statement.forget(&rawPtr);
  *_stmt = rawPtr;
  return NS_OK;
}

NS_IMETHODIMP
Connection::CreateAsyncStatement(const nsACString& aSQLStatement,
                                 mozIStorageAsyncStatement** _stmt) {
  NS_ENSURE_ARG_POINTER(_stmt);
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(ASYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  RefPtr<AsyncStatement> statement(new AsyncStatement());
  NS_ENSURE_TRUE(statement, NS_ERROR_OUT_OF_MEMORY);

  rv = statement->initialize(this, mDBConn, aSQLStatement);
  NS_ENSURE_SUCCESS(rv, rv);

  AsyncStatement* rawPtr;
  statement.forget(&rawPtr);
  *_stmt = rawPtr;
  return NS_OK;
}

NS_IMETHODIMP
Connection::ExecuteSimpleSQL(const nsACString& aSQLStatement) {
  CHECK_MAINTHREAD_ABUSE();
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  int srv = executeSql(mDBConn, PromiseFlatCString(aSQLStatement).get());
  return convertResultCode(srv);
}

NS_IMETHODIMP
Connection::ExecuteAsync(
    const nsTArray<RefPtr<mozIStorageBaseStatement>>& aStatements,
    mozIStorageStatementCallback* aCallback,
    mozIStoragePendingStatement** _handle) {
  nsTArray<StatementData> stmts(aStatements.Length());
  for (uint32_t i = 0; i < aStatements.Length(); i++) {
    nsCOMPtr<StorageBaseStatementInternal> stmt =
        do_QueryInterface(aStatements[i]);
    NS_ENSURE_STATE(stmt);

    // Obtain our StatementData.
    StatementData data;
    nsresult rv = stmt->getAsynchronousStatementData(data);
    NS_ENSURE_SUCCESS(rv, rv);

    NS_ASSERTION(stmt->getOwner() == this,
                 "Statement must be from this database connection!");

    // Now append it to our array.
    stmts.AppendElement(data);
  }

  // Dispatch to the background
  return AsyncExecuteStatements::execute(std::move(stmts), this, mDBConn,
                                         aCallback, _handle);
}

NS_IMETHODIMP
Connection::ExecuteSimpleSQLAsync(const nsACString& aSQLStatement,
                                  mozIStorageStatementCallback* aCallback,
                                  mozIStoragePendingStatement** _handle) {
  NS_ENSURE_TRUE(NS_IsMainThread(), NS_ERROR_NOT_SAME_THREAD);

  nsCOMPtr<mozIStorageAsyncStatement> stmt;
  nsresult rv = CreateAsyncStatement(aSQLStatement, getter_AddRefs(stmt));
  if (NS_FAILED(rv)) {
    return rv;
  }

  nsCOMPtr<mozIStoragePendingStatement> pendingStatement;
  rv = stmt->ExecuteAsync(aCallback, getter_AddRefs(pendingStatement));
  if (NS_FAILED(rv)) {
    return rv;
  }

  pendingStatement.forget(_handle);
  return rv;
}

NS_IMETHODIMP
Connection::TableExists(const nsACString& aTableName, bool* _exists) {
  return databaseElementExists(TABLE, aTableName, _exists);
}

NS_IMETHODIMP
Connection::IndexExists(const nsACString& aIndexName, bool* _exists) {
  return databaseElementExists(INDEX, aIndexName, _exists);
}

NS_IMETHODIMP
Connection::GetTransactionInProgress(bool* _inProgress) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(ASYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  *_inProgress = transactionInProgress(lockedScope);
  return NS_OK;
}

NS_IMETHODIMP
Connection::GetDefaultTransactionType(int32_t* _type) {
  *_type = mDefaultTransactionType;
  return NS_OK;
}

NS_IMETHODIMP
Connection::SetDefaultTransactionType(int32_t aType) {
  NS_ENSURE_ARG_RANGE(aType, TRANSACTION_DEFERRED, TRANSACTION_EXCLUSIVE);
  mDefaultTransactionType = aType;
  return NS_OK;
}

NS_IMETHODIMP
Connection::GetVariableLimit(int32_t* _limit) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  int limit = ::sqlite3_limit(mDBConn, SQLITE_LIMIT_VARIABLE_NUMBER, -1);
  if (limit < 0) {
    return NS_ERROR_UNEXPECTED;
  }
  *_limit = limit;
  return NS_OK;
}

NS_IMETHODIMP
Connection::BeginTransaction() {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  return beginTransactionInternal(lockedScope, mDBConn,
                                  mDefaultTransactionType);
}

nsresult Connection::beginTransactionInternal(
    const SQLiteMutexAutoLock& aProofOfLock, sqlite3* aNativeConnection,
    int32_t aTransactionType) {
  if (transactionInProgress(aProofOfLock)) {
    return NS_ERROR_FAILURE;
  }
  nsresult rv;
  switch (aTransactionType) {
    case TRANSACTION_DEFERRED:
      rv = convertResultCode(executeSql(aNativeConnection, "BEGIN DEFERRED"));
      break;
    case TRANSACTION_IMMEDIATE:
      rv = convertResultCode(executeSql(aNativeConnection, "BEGIN IMMEDIATE"));
      break;
    case TRANSACTION_EXCLUSIVE:
      rv = convertResultCode(executeSql(aNativeConnection, "BEGIN EXCLUSIVE"));
      break;
    default:
      return NS_ERROR_ILLEGAL_VALUE;
  }
  return rv;
}

NS_IMETHODIMP
Connection::CommitTransaction() {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  return commitTransactionInternal(lockedScope, mDBConn);
}

nsresult Connection::commitTransactionInternal(
    const SQLiteMutexAutoLock& aProofOfLock, sqlite3* aNativeConnection) {
  if (!transactionInProgress(aProofOfLock)) {
    return NS_ERROR_UNEXPECTED;
  }
  nsresult rv =
      convertResultCode(executeSql(aNativeConnection, "COMMIT TRANSACTION"));
  return rv;
}

NS_IMETHODIMP
Connection::RollbackTransaction() {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  return rollbackTransactionInternal(lockedScope, mDBConn);
}

nsresult Connection::rollbackTransactionInternal(
    const SQLiteMutexAutoLock& aProofOfLock, sqlite3* aNativeConnection) {
  if (!transactionInProgress(aProofOfLock)) {
    return NS_ERROR_UNEXPECTED;
  }

  nsresult rv =
      convertResultCode(executeSql(aNativeConnection, "ROLLBACK TRANSACTION"));
  return rv;
}

NS_IMETHODIMP
Connection::CreateTable(const char* aTableName, const char* aTableSchema) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  SmprintfPointer buf =
      ::mozilla::Smprintf("CREATE TABLE %s (%s)", aTableName, aTableSchema);
  if (!buf) return NS_ERROR_OUT_OF_MEMORY;

  int srv = executeSql(mDBConn, buf.get());

  return convertResultCode(srv);
}

NS_IMETHODIMP
Connection::CreateFunction(const nsACString& aFunctionName,
                           int32_t aNumArguments,
                           mozIStorageFunction* aFunction) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(ASYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // Check to see if this function is already defined.  We only check the name
  // because a function can be defined with the same body but different names.
  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  NS_ENSURE_FALSE(mFunctions.Contains(aFunctionName), NS_ERROR_FAILURE);

  int srv = ::sqlite3_create_function(
      mDBConn, nsPromiseFlatCString(aFunctionName).get(), aNumArguments,
      SQLITE_ANY, aFunction, basicFunctionHelper, nullptr, nullptr);
  if (srv != SQLITE_OK) return convertResultCode(srv);

  FunctionInfo info = {aFunction, aNumArguments};
  mFunctions.InsertOrUpdate(aFunctionName, info);

  return NS_OK;
}

NS_IMETHODIMP
Connection::RemoveFunction(const nsACString& aFunctionName) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(ASYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  NS_ENSURE_TRUE(mFunctions.Get(aFunctionName, nullptr), NS_ERROR_FAILURE);

  int srv = ::sqlite3_create_function(
      mDBConn, nsPromiseFlatCString(aFunctionName).get(), 0, SQLITE_ANY,
      nullptr, nullptr, nullptr, nullptr);
  if (srv != SQLITE_OK) return convertResultCode(srv);

  mFunctions.Remove(aFunctionName);

  return NS_OK;
}

NS_IMETHODIMP
Connection::SetProgressHandler(int32_t aGranularity,
                               mozIStorageProgressHandler* aHandler,
                               mozIStorageProgressHandler** _oldHandler) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(ASYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // Return previous one
  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  NS_IF_ADDREF(*_oldHandler = mProgressHandler);

  if (!aHandler || aGranularity <= 0) {
    aHandler = nullptr;
    aGranularity = 0;
  }
  mProgressHandler = aHandler;
  ::sqlite3_progress_handler(mDBConn, aGranularity, sProgressHelper, this);

  return NS_OK;
}

NS_IMETHODIMP
Connection::RemoveProgressHandler(mozIStorageProgressHandler** _oldHandler) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(ASYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // Return previous one
  SQLiteMutexAutoLock lockedScope(sharedDBMutex);
  NS_IF_ADDREF(*_oldHandler = mProgressHandler);

  mProgressHandler = nullptr;
  ::sqlite3_progress_handler(mDBConn, 0, nullptr, nullptr);

  return NS_OK;
}

NS_IMETHODIMP
Connection::SetGrowthIncrement(int32_t aChunkSize,
                               const nsACString& aDatabaseName) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  // Bug 597215: Disk space is extremely limited on Android
  // so don't preallocate space. This is also not effective
  // on log structured file systems used by Android devices
#if !defined(ANDROID) && !defined(MOZ_PLATFORM_MAEMO)
  // Don't preallocate if less than 500MiB is available.
  int64_t bytesAvailable;
  rv = mDatabaseFile->GetDiskSpaceAvailable(&bytesAvailable);
  NS_ENSURE_SUCCESS(rv, rv);
  if (bytesAvailable < MIN_AVAILABLE_BYTES_PER_CHUNKED_GROWTH) {
    return NS_ERROR_FILE_TOO_BIG;
  }

  int srv = ::sqlite3_file_control(
      mDBConn,
      aDatabaseName.Length() ? nsPromiseFlatCString(aDatabaseName).get()
                             : nullptr,
      SQLITE_FCNTL_CHUNK_SIZE, &aChunkSize);
  if (srv == SQLITE_OK) {
    mGrowthChunkSize = aChunkSize;
  }
#endif
  return NS_OK;
}

int32_t Connection::RemovablePagesInFreeList(const nsACString& aSchemaName) {
  int32_t freeListPagesCount = 0;
  if (!isConnectionReadyOnThisThread()) {
    MOZ_ASSERT(false, "Database connection is not ready");
    return freeListPagesCount;
  }
  {
    nsAutoCString query(MOZ_STORAGE_UNIQUIFY_QUERY_STR "PRAGMA ");
    query.Append(aSchemaName);
    query.AppendLiteral(".freelist_count");
    nsCOMPtr<mozIStorageStatement> stmt;
    DebugOnly<nsresult> rv = CreateStatement(query, getter_AddRefs(stmt));
    MOZ_ASSERT(NS_SUCCEEDED(rv));
    bool hasResult = false;
    if (stmt && NS_SUCCEEDED(stmt->ExecuteStep(&hasResult)) && hasResult) {
      freeListPagesCount = stmt->AsInt32(0);
    }
  }
  // If there's no chunk size set, any page is good to be removed.
  if (mGrowthChunkSize == 0 || freeListPagesCount == 0) {
    return freeListPagesCount;
  }
  int32_t pageSize;
  {
    nsAutoCString query(MOZ_STORAGE_UNIQUIFY_QUERY_STR "PRAGMA ");
    query.Append(aSchemaName);
    query.AppendLiteral(".page_size");
    nsCOMPtr<mozIStorageStatement> stmt;
    DebugOnly<nsresult> rv = CreateStatement(query, getter_AddRefs(stmt));
    MOZ_ASSERT(NS_SUCCEEDED(rv));
    bool hasResult = false;
    if (stmt && NS_SUCCEEDED(stmt->ExecuteStep(&hasResult)) && hasResult) {
      pageSize = stmt->AsInt32(0);
    } else {
      MOZ_ASSERT(false, "Couldn't get page_size");
      return 0;
    }
  }
  return std::max(0, freeListPagesCount - (mGrowthChunkSize / pageSize));
}

NS_IMETHODIMP
Connection::EnableModule(const nsACString& aModuleName) {
  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  for (auto& gModule : gModules) {
    struct Module* m = &gModule;
    if (aModuleName.Equals(m->name)) {
      int srv = m->registerFunc(mDBConn, m->name);
      if (srv != SQLITE_OK) return convertResultCode(srv);

      return NS_OK;
    }
  }

  return NS_ERROR_FAILURE;
}

// Implemented in QuotaVFS.cpp
already_AddRefed<QuotaObject> GetQuotaObjectForFile(sqlite3_file* pFile);

NS_IMETHODIMP
Connection::GetQuotaObjects(QuotaObject** aDatabaseQuotaObject,
                            QuotaObject** aJournalQuotaObject) {
  MOZ_ASSERT(aDatabaseQuotaObject);
  MOZ_ASSERT(aJournalQuotaObject);

  if (!connectionReady()) {
    return NS_ERROR_NOT_INITIALIZED;
  }
  nsresult rv = ensureOperationSupported(SYNCHRONOUS);
  if (NS_FAILED(rv)) {
    return rv;
  }

  sqlite3_file* file;
  int srv = ::sqlite3_file_control(mDBConn, nullptr, SQLITE_FCNTL_FILE_POINTER,
                                   &file);
  if (srv != SQLITE_OK) {
    return convertResultCode(srv);
  }

  RefPtr<QuotaObject> databaseQuotaObject = GetQuotaObjectForFile(file);
  if (NS_WARN_IF(!databaseQuotaObject)) {
    return NS_ERROR_FAILURE;
  }

  srv = ::sqlite3_file_control(mDBConn, nullptr, SQLITE_FCNTL_JOURNAL_POINTER,
                               &file);
  if (srv != SQLITE_OK) {
    return convertResultCode(srv);
  }

  RefPtr<QuotaObject> journalQuotaObject = GetQuotaObjectForFile(file);
  if (NS_WARN_IF(!journalQuotaObject)) {
    return NS_ERROR_FAILURE;
  }

  databaseQuotaObject.forget(aDatabaseQuotaObject);
  journalQuotaObject.forget(aJournalQuotaObject);
  return NS_OK;
}

SQLiteMutex& Connection::GetSharedDBMutex() { return sharedDBMutex; }

uint32_t Connection::GetTransactionNestingLevel(
    const mozilla::storage::SQLiteMutexAutoLock& aProofOfLock) {
  return mTransactionNestingLevel;
}

uint32_t Connection::IncreaseTransactionNestingLevel(
    const mozilla::storage::SQLiteMutexAutoLock& aProofOfLock) {
  return ++mTransactionNestingLevel;
}

uint32_t Connection::DecreaseTransactionNestingLevel(
    const mozilla::storage::SQLiteMutexAutoLock& aProofOfLock) {
  return --mTransactionNestingLevel;
}

}  // namespace mozilla::storage