[asio-users] Expected behavior of read with a streambuf and a completion routine

[Philippe Leuba]

Hi,

I have encountered a strange behavior when reading on a TCP stream with a streambuf and a completion routine.

Imagine that I'm receiving in a single chunk: "Welcome\n".

Then the following code:
streambuf buf;
read(sock, buf, at_least(2));
buf.consume(2);
read(sock, buf, at_least(2)); // Blocks

The documentation says that read() results in zero or n call to read_some. In this case, the data are already in the buf, but the completion routine is called with total_transferred = 0, resulting in a new call to read_some that blocks even if the data are already present.
Same behavior for async_read, but async/read_until returns directly with the data already in the buffer.

I was expecting that the data already in the streambuf was counted in the total_transferred parameter of the completion routine.

Is it a bug ?

Philippe Leuba

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