Stanford CS144: Computer Network check0

实现一个 stream。

byte_stream.hh 处的修改。

class ByteStream
{
public:
  explicit ByteStream( uint64_t capacity );

  // Helper functions (provided) to access the ByteStream's Reader and Writer interfaces
  Reader& reader();
  const Reader& reader() const;
  Writer& writer();
  const Writer& writer() const;

  void set_error() { error_ = true; };       // Signal that the stream suffered an error.
  bool has_error() const { return error_; }; // Has the stream had an error?

protected:
  // Please add any additional state to the ByteStream here, and not to the Writer and Reader interfaces.
  uint64_t count_ = 0; // data buffed
  std::queue<std::string> buffer_ {};
  uint64_t total_bytes_pushed_ = 0;
  uint64_t prefix_ = 0;
  bool closed_ {};

  uint64_t capacity_;
  bool error_ {};
};

byte_stream.cc 处的修改。

void Writer::push( string data )
{
  if (is_closed() || available_capacity() == 0 || data.empty()) {
    return;
  } 

  if (data.size() > available_capacity()) {
    data.resize(available_capacity());
  }

  count_ += data.size();
  total_bytes_pushed_ += data.size();

  buffer_.push(std::move(data));
}

void Writer::close()
{
  closed_ = true;
}

bool Writer::is_closed() const
{
  return closed_;
}

uint64_t Writer::available_capacity() const
{
  return capacity_ - count_;
}

uint64_t Writer::bytes_pushed() const
{
  return total_bytes_pushed_;
}

string_view Reader::peek() const
{
  if (buffer_.empty()) {
    return {};
  }

  return string_view(buffer_.front()).substr(prefix_);
}

void Reader::pop( uint64_t len )
{
  while (not buffer_.empty()) {
    if (len + prefix_ >= buffer_.front().size()) {
      len -= buffer_.front().size() - prefix_;
      count_ -= buffer_.front().size() - prefix_;
      prefix_ = 0;
      buffer_.pop();
    } else {
      prefix_ += len;
      count_ -= len;
      break;
    }
  }
}

bool Reader::is_finished() const
{
  return closed_ and count_ == 0;
}

uint64_t Reader::bytes_buffered() const
{
  return count_;
}

uint64_t Reader::bytes_popped() const
{
  return total_bytes_pushed_ - count_;
}