Re: int vs. struct

[Dan Stromberg <strombrg@xxxxxxxxxxxxxxx>]

Yes, any ADT that is to be saved on disk or transmitted over the net (or
given any other external form) should have a conversion from host byte
order (and FP format, &c) to network byte order (&c).

This problem also exists with non-struct/non-OOP interfaces.

Dave Dyer wrote:
> 
>  I should point out that in C, any "standard interface" based on structs
> is fraught with peril unless it is rigourously adhered to, and that if
> the interface includes a networking substrate, it is essential that the
> exact byte sequences be specified.
> 
> For example:
> 
>         struct point { short x;short y; };
> 
> will, in byte terms, store x and y in multiple different ways, depending
> on the endian class of the machine, and on the whim of the C compiler.
> 
> defining
>         #define x_from_point(i) ((short)(i>>16))
>         #define y_from_point(i) ((short)(i&0xffff))
>         #define point(x,y)              ((x<<16)|(y&0xffff))
> 
> is safe locally
> 
> both possible definitions will be non-portable across networks and file
> systems unless the protocol for transmitting a point is specified (and
> adhered to) as a sequence of bytes.  For example, writing an array of
> "points", or a "point" embedded in a larger struct, will not be portable
> using simple code such as:
> 
>         write(stream,&a_point,4);