[sac-dev] byte order and swapping

[George Helffrich]

The byte-swapping/header rewriting issue highlights a problem that SAC 
still has, to wit:
there is no specification as to what the byte order in SAC files is.

By accident, there is a reliable way to tell the endianness of a SAC 
data file due to the known format of the data file header.  However, 
there is no analogous way to tell what the endianness of a SAC SGF file 
is reliably.  So the present situation provides a workable, yet 
complicated solution for SAC data, but none for SGF.

If we decide, as a community, this endianness issue, then the issues 
with byte-swapped headers vs data disappears.  The only reason it 
exists is because we never have answered the endianness question.

So why not specify it?

Based on the historical fact that SAC was developed on Ridge and Sun 
machines -- both big-endian -- there is an argument for files being 
big-endian.  However, both Macs and PCs are converging towards 
little-endian order, so a more practical choice might be little.

Does anybody object to or disagree with the need to specify a byte 
order?

                                                                         
      George Helffrich