Re: [Boost-users] [circular_buffer] About overwriting elements

Subject: Re: [Boost-users] [circular_buffer] About overwriting elements
From: Jan Gaspar (jano_gaspar_at_[hidden])
Date: 2010-04-19 06:55:02

Yes, that behaviour is expected. When the circular buffer is empty read_pos points to the end. After you put some items into it read_pos will point to the begining.

In your case I would recommend you not to rely on iterators as they may get invalidated. Instead, in you read operation rely on array_one() and after that clear the whole circular buffer.

Jan



----- Original Message ----
From: Daniele Barzotti <daniele.barzotti_at_[hidden]>
To: boost-users_at_[hidden]
Sent: Mon, 19 April, 2010 11:44:14
Subject: Re: [Boost-users] [circular_buffer] About overwriting elements

Il 16/04/2010 17:28, Jan Gaspar ha scritto:
> Hi Daniele,
> 
> The circular_buffer behaves like a sliding window - 
> which is what you don't want apparently.
> If you want the behaviour you described have a look at array_one()
> and array_two() methods.

Hi,
in my code I have this struct:

template<typename T>
struct TBuffer
{
  boost::circular_buffer<T>  data;
  iterator                   write_pos;
  iterator                   read_pos;

  TBuffer(){ write_pos = data.begin(); read_pos = data.begin(); };
};

Then, when I write to it *(when it's still empty!)*:

size_type Write(const T* pData, size_type items)
{
...

  buffer_.read_pos = buffer_.data.begin();

  if (buffer_.read_pos == buffer_.data.begin())
    cout << endl << "THIS IS TRUE.." << endl;

  std::copy(pData,
            pData + items,
            back_inserter(buffer_.data));

  // Move the write cursor to the next position
  buffer_.write_pos = buffer_.data.begin() + items;

  if (buffer_.read_pos == buffer_.data.begin())
    cout << endl << "THIS IS NO MORE TRUE!!!" << endl
...
}

After inserting the elements, the begin() iterator changes and is no
more equal to the buffer_.read_pos iterator!
Is it normal?!

Regards,
Daniele.
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