Re: Asynchronous I/O on a serial device

["Yannick Duchêne (Hibou57)" <yannick_duchene@yahoo.fr>]

Le Sat, 11 Jun 2011 23:46:47 +0200, Kim Rostgaard Christensen  
<krc@retrospekt.dk> a écrit:

> Hi there
Hi you :)

> I am desperately trying to implement a protocol on top of a serial  
> transport.
>
> I am running Debian, and for the moment using /dev/ttyACM0 for reading.  
> This works fine using standard the Text_IO package
Not good in my opinion (see later)

> and In_File.
> Only, when I need to write to the device It fails because It is in  
> In_File mode - Obviously.
> Reset on the file handle gives me a USE_ERROR exception, probably due to  
> it being a special file - please correct me if I am wrong.
I do not know about your device node, so I could not say if its writable  
or not, but note you also have Inout_File in Ada (do not know what it  
named Inout_File instead of In_Out_File, but that's another story) beside  
of In_File, so could perfectly have input and output on the file.

> Do I need to implement this more system-near/specific, or is there some  
> way I can do bi-directional communication like, for instance two file  
> handles. (I tried Form => "shared=yes", and it also failed).
I would not say more system specific, but rather more close to some  
implicit specifications here: I am not sure you have good reasons [*] to  
use Text_IO, and you may better have a file of some basic type, like bytes  
or characters (well, a file of the more atomic type your protocol defines).

[*] If something is missing we do not know, tell us.

-- 
“Syntactic sugar causes cancer of the semi-colons.”  [Epigrams on  
Programming — Alan J. — P. Yale University]
“Structured Programming supports the law of the excluded muddle.” [Idem]
“c++; /* this makes c bigger but returns the old value */” [Anonymous]