[Alephmodular-devel] Random rumblings on files and errors

[Br'fin <br...@ma...>]

I've been mucking with a spare copy of AM, actually trying to implement 
what I have described in my draft so far. Which is of course turning up 
more areas to work upon.

Like, most files are going to be opened in binary mode. So this makes a 
reasonable default, however, some files in the future are going to be 
text based, so we should support that as well. I was thinking of 
exposing the iostream openmode flags as part of the 
open_file_for_reading/writing business. And just have it default to 
binary. You could clear it of course by passing 0 for the mode (or a 
suitably equivalent definition)


The other two aspects I found myself leaning towards were calling 
conventions and error feedback.

By calling conventions I was thinking of calls like this:

	virtual bool get_named_child(const char *name, IFileSystemDesc* 
&out_desc) const = 0;

This is a method to specify a file or directory within a directory. The 
name of that desc would be the string name.

If the function was successful, then it would return true, and the 
IFileSystemDesc* would point to a newly acquired class. (Which the 
caller would need to free currently)

If the function failed, then it would return false, and the 
IFileSystemDesc* would remain untouched.

And the reason for failure? Well, after a little bit of thinking, I 
realized that there should be an IError interface with three methods. A 
protected set_state, a public get_state and a public clear_state. And 
in thinking of it, it's possible that the state itself could be verbose 
enough to display/log when dumped to a stream.


Why not exceptions? I have not been sold on exception handling in C++ 
under some warnings of exception handling being there, but less than 
optimal under C++ (Less practical in terms of speed, doing extra work 
with stuff too low level for me really to be thinking about :) ) and a 
simple lack of knowledge on how one is supposed to do it in C++. (Java 
is at least clear on what things you should be throwing around) 
Admittedly a nice clear document that counters these perceptions as 
myth might change my mind.

-Jeremy Parsons