gecko-dev/xpcom/io/InputStreamLengthHelper.h

/* -*- 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/. */

#ifndef mozilla_InputStreamLengthHelper_h
#define mozilla_InputStreamLengthHelper_h

#include <functional>

#include "nsISupportsImpl.h"
#include "nsIInputStreamLength.h"
#include "nsThreadUtils.h"

class nsIInputStream;

namespace mozilla {

// This class helps to retrieve the stream's length.

class InputStreamLengthHelper final : public Runnable,
                                      public nsIInputStreamLengthCallback {
 public:
  NS_DECL_ISUPPORTS_INHERITED

  // This is one of the 2 entry points of this class. It returns false if the
  // length cannot be taken synchronously.
  static bool GetSyncLength(nsIInputStream* aStream, int64_t* aLength);

  // This is one of the 2 entry points of this class. The callback is executed
  // asynchronously when the length is known.
  static void GetAsyncLength(
      nsIInputStream* aStream,
      const std::function<void(int64_t aLength)>& aCallback);

 private:
  NS_DECL_NSIINPUTSTREAMLENGTHCALLBACK

  InputStreamLengthHelper(
      nsIInputStream* aStream,
      const std::function<void(int64_t aLength)>& aCallback);

  ~InputStreamLengthHelper();

  NS_IMETHOD
  Run() override;

  void ExecCallback(int64_t aLength);

  nsCOMPtr<nsIInputStream> mStream;
  std::function<void(int64_t aLength)> mCallback;
};

}  // namespace mozilla

#endif  // mozilla_InputStreamLengthHelper_h