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Subject: Re: Any examples of Byte Ordering Functions
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Date: Sun, 19 Oct 2003 18:52:58 +0100
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Date: 2003-10-19T18:52:58+01:00
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Martin Dowie wrote:

> You don't need to look up the RM (Annex B.2) wrt the
> predefined modular types in package "Interfaces" and there
> you will find Shift_Left/Shift_Right/etc routines. These are
> defined as "Intrinsic", which means they are "built in" to the
> compiler - i.e. it should have a blinking good idea of a good
> representation of this on the target h/w.

Didn't know about that, thanks!  That means if we want to output any 
word to a stream in big endian we can do:

    procedure Write_Big_Endian
          (Stream : access Root_Stream_Type'Class;
           W      : in Word) is
       A, B : Byte;
    begin
       A := Byte (Shift_Right (Unsigned_32(W), 8));
       B := Byte (W and 16#00FF#);

       Byte'Write (Stream, A);
       Byte'Write (Stream, B);
    end Write_Big_Endian;


and for little endian we can do:

    procedure Write_Little_Endian
          (Stream : access Root_Stream_Type'Class;
           W      : in Word) is
       A, B : Byte;
    begin
       A := Byte (W and 16#00FF#);
       B := Byte (Shift_Right (Unsigned_32(W), 8));
       Byte'Write (Stream, B);
       Byte'Write (Stream, A);
    end Write_Little_Endian;

and this will work whatever the platform we compile on?