Re: [f-cpu] binary streams

[Michael Riepe <michael@stud.uni-hannover.de>]

On Thu, Sep 13, 2001 at 03:38:54AM +0200, Yann Guidon wrote:
[...]
> > but I don't know what to do in VHDL.  Perhaps you can do something like
> >         type octet is 0 to 255;
> >         type octet_stream is file of octet;
> i think i tried this already, however i presume that this "subset"
> for the "integer" type keeps the 4-byte encoding (the range is only restricted)
> so if i read a "byte" i will increment the file counter by four.
> i'll try anyway because i better prove it, but it's a gut feeling.

There's a fundamental difference between the declarations

	type octet is range 0 to 255;	-- i forgot the `range'...
	subtype other_octet is integer range 0 to 255;

`other_octet' is a subtype of `integer', and must use the same (4-byte)
encoding, IIRC, while `octet' is a new type that may use a single-byte
representation (vanilla doesn't, unfortunately).

> > If it still stops at a ^Z, I would consider that a bug in Simili.
> simili and vanilla definitely differ !

As well as the underlying OSes.

> > But you'll probably have to write a completely new set of I/O routines
> > for the `octet' type.
> not necessarily, but if it's necessary, i'll do it.

Seems like there are predefined read and write procedures...

> > On the other hand, binary files are evil anyway because they're not
> > portable (imagine you had to transfer them to a big-endian box, like
> > SPARC).
> in this case (random numbers coming from /dev/random or .tgz files)
> it is irrevelant.

In that case, you could also try a `file of integer' or something like
that, and read larger quantities.  I've attached an example (works
with vanilla; please try simili yourself, I can't reboot while I'm
writing e-mails ;).

-- 
 Michael "Tired" Riepe <Michael.Riepe@stud.uni-hannover.de>
 "All I wanna do is have a little fun before I die"
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_textio.all;
library std;
use std.textio.all;

entity blah is
end blah;

architecture blah of blah is
	type int_stream is file of integer;
	file x : int_stream open read_mode is "random";
begin
	process
		variable y : integer;
		variable lout : line;
	begin
		while not endfile(x) loop
			read(x, y);
			write(lout, y);
			writeline(output, lout);
		end loop;
		wait;
	end process;
end blah;