Re: KI_FILE count precondition

Bernd Schoeller wrote:
> On Thu, 18 Jan 2007 17:30:19 +0100, Eric Bezault <ericb-D6Qt/9opevxWk0Htik3J/[email protected]>  
> wrote:
> 
>> Bernd Schoeller wrote:
>>> Can anybody motivate for me the reason of the 'is_closed' precondition  
>>> in
>>> KI_FILE?
>> If the file is not closed, then we might be writing
>> to it. The new characters may still be in the buffer
>> or already on disk. What does `count' means in that
>> case?
> 
> Well - on an open file, the count should be exactly what is visible  
> through the open file handle. 

What do you mean by "visible" if the file is write-only?

> The code in question reads the content of file into a string, a common  
> task that should be reasonably easy to implement.
> 
> Currently, it looks as follows:
> 
> file.reset(filename)
> filesize := file.count
> file.open_read
> if file.is_open_read then
>    file.read_string(filesize)
>    s := file.last_string
>    file.close
> end

If this code is in Gobo then it needs to be fixed. Indeed there
is no guarantee that `read_string' will read `filesize' characters.
It could well be implemented to read only one character even if
the file is much bigger. So we need a loop until the end of file
is reached. Therefore the value of `filesize' that you provide is
arbitrary. Even more under Windows with the %R%N end-of-line.

> This looks a little complex to me and still has problems. I am a little  
> afraid to just call
> 
>    file.read_string(Platform.Maximum_integer)
> 
> as, looking at the implementation in KL_TEXT_INPUT_FILE, this might create  
> a buffer of that size.
> 
> It would be best if there was a 'read_string(-1)' that would just read in  
> everything available.

This -1 is very ugly. This might be common practice in
other languages, but in Eiffel I would prefer to have a new
feature `read_all' or `read_to_end' or something like that.
Then I wonder whether this routine should write to `last_string'
or to a string given as argument (like `read_to_string').

-- 
Eric Bezault
mailto:ericb-D6Qt/9opevxWk0Htik3J/[email protected]
http://www.gobosoft.com