Re: Howto read line from a stream

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Sun, 31 May 2009 03:41:46 -0700 (PDT), Tomek Walkuski wrote:

> I have a stream, which is defined as:
> Channel : Stream_Access;
>
> This stream is associated with a socket. If I knew how long is input
> message I could do:
> Msg : String (1 .. Known_Length);
> String'Read (Channel, Msg);

One potential problem with using Streams as an interface to sockets is that
there is nothing in the Ada standard that mandates Stream_Element to be an
octet of bits, as socket I/O demands.

> Is there any smart solution?

If you know the size of packets you can read it as a whole. Typically
protocols deploy some headers determining the length of a packet body. The
header is usually read octet by octet, and the rest in bigger chunks.

However, String'Read is not necessarily mapped into one single socket's
read. Quite possible is that it will be split into separate Character'Read
implemented by independent reads.

(I assume that you are using TCP/IP rather than UDP)

> Or should I read character by character
> from a stream until I get CR & LF ?

No. There is no any CR's or LF's in the stream unless the protocol defines
them as a part of the content.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de