ZeroCopyNSIOutputStream.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */

/* 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_devtools_ZeroCopyNSIOutputStream__

#define mozilla_devtools_ZeroCopyNSIOutputStream__

#include <google/protobuf/io/zero_copy_stream.h>

#include <google/protobuf/stubs/common.h>

#include "nsCOMPtr.h"

#include "nsIOutputStream.h"

namespace mozilla {

namespace devtools {

// A `google::protobuf::io::ZeroCopyOutputStream` implementation that uses an

// `nsIOutputStream` under the covers.

//

// This class will automatically write and flush its data to the

// `nsIOutputStream` in its destructor, but if you care whether that call

// succeeds or fails, then you should call the `flush` method yourself. Errors

// will be logged, however.

class MOZ_STACK_CLASS ZeroCopyNSIOutputStream

    : public ::google::protobuf::io::ZeroCopyOutputStream {

  static const int BUFFER_SIZE = 8192;

  // The nsIOutputStream we are streaming to.

  nsCOMPtr<nsIOutputStream>& out;

  // The buffer we write data to before passing it to the output stream.

  char buffer[BUFFER_SIZE];

  // The status of writing to the underlying output stream.

  nsresult result_;

  // The number of bytes in the buffer that have been used thus far.

  int amountUsed;

  // Excluding the amount of the buffer currently used (which hasn't been

  // written and flushed yet), this is the number of bytes written to the output

  // stream.

  int64_t writtenCount;

  // Write the internal buffer to the output stream and flush it.

  nsresult writeBuffer();

 public:

  explicit ZeroCopyNSIOutputStream(nsCOMPtr<nsIOutputStream>& out);

  nsresult flush() { return writeBuffer(); }

  // Return true if writing to the underlying output stream ever failed.

  bool failed() const { return NS_FAILED(result_); }

  nsresult result() const { return result_; }

  // ZeroCopyOutputStream Interface

  virtual ~ZeroCopyNSIOutputStream() override;

  virtual bool Next(void** data, int* size) override;

  virtual void BackUp(int count) override;

  virtual ::google::protobuf::int64 ByteCount() const override;

};

}  // namespace devtools

}  // namespace mozilla

#endif  // mozilla_devtools_ZeroCopyNSIOutputStream__