Re: implementation question about writing and reading from files

[Ted Dennison<dennison@telepath.com>]

In article <9kv5rs$6hosn$2@ID-102190.news.dfncis.de>, Francis Crick says...
>And also, if I want to use a stream for keeping data in memory, how do i
>that?  How do i instantiate a stream that I can just write to and read from
>at my leisure? 

The only language-defined streams are in Ada.Streams.Stream_IO,
Ada.Text_IO.Text_Streams, and Ada.Wide_Text_IO.Text_Streams. I believe they all
deal with files. If you want to use one to make yourself a buffer, you will have
to code it yourself by deriving it from Ada.Streams.Root_Stream_Type and
overriding "Read" and "Write". 

>               Also, the data I'm moving is large, and chances are I won't
>be using it for much else other than writing back to other file streams, so
>how can i make the reading and writing as fast as possible?  Could I make it
>read a whole mb in one go as a single unit?

The easiest way to do that is to unchecked_conversion your data (or better yet,
a pointer to it) into a Ada.Streams.Stream_Element_Array, then call
Ada.Streams.Write directly. If you just use the stream attributes, it will
perform one write for each element, which I've found to be significantly slower
(even when the target is a memory-based stream).

A good Ada book should go over the basics of this. Stream use is a complicated
enough topic that you really ought to have such a resource to learn the basics
from.

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