Mac Forum / Programming / Perl / June 2005

John Mercer said:

Well, I can answer this part of the question...

"endian.h" looks to be a fairly general file, that GLT just happens to
include.  It defines some macros for dealing with endian issues.  Now the
question is what are endian issues.  ;)

Endian issues (and endian in general) are computer terms dealing with how
numbers are stored/worked with on a computer.  Just about every computer
knows what a 'byte' is, but then you have numbers which are two, or four,
or___ bytes long.  The question is: What order are the bytes in?  There
are two possbile (Well, with longer numbers there are more, but only two
good ones.), and good reasons for each.  So, of course, people do it both
ways.

Normally you don't have to think about this that much, but when you have
complicated, optimized, number crunching you often want to remove the
levels of abstraction that mean most programmers don't have to think about
this.  Graphics processing and encryption are prime candidates for such,
so them both using the same routines to handle it isn't suprising.

Short version: It's a number-handling header, that they both happen to
use.  You'll need to find something that has or will install a copy for
you, most likely.

Daniel T. Staal

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Looks to me that _idea.c is assuming that all system have /usr/
include/endian.h, which is false (it's probably a Linux assumption).  
You can probably get this to work by changing line 8 to:

#include <machine/endian.h>

for Mac OS X anyways.

Edward Moy
Apple