Re: [xine-devel] big endian - little endian

[Mike M. <mel...@pc...>]

On Wed, 16 Apr 2003, wg - drs wrote:

> Hi Mike,
> 
> Thanks for the quick response.   When I'm looking through the header files I
> noticed that all of the conversion macros go from the endian type to Machine
> Endian.  I guess the ./configure script must have detected the machine type
> and defined the flags accordingly so i can build correctly?

	The ./configure script determines the machine endian-ness and
#define's WORDS_BIGENDIAN in config.h if the machine is big endian or
leaves it un-#define'd if the machine is little endian. Thus, if you code
absolutely must include endian-specific code:

#ifdef WORDS_BIGENDIAN
  /* this is big endian specific */
#else
  /* this is little endian specific */
#endif

Endian-ness is determined at compile time, not run time, since a binary
program should never have to figure this out at run time (if you know
otherwise, I would sure like to hear about it).

	I stress the point that *IF* you must include endian-specific code
in your program. For the most part, all you will want to do is load big or
little endian numbers from a bytestream. I use the LE_* and BE_* macros in
a lot of my code to handle this. For example:
  x = BE_16(&bytestream[2])
will take the 2 bytes at bytestream[2] and bytestream[3] and load them
into x as a 16-bit big endian number.

	Hope this helps...
--
        -Mike Melanson