From help-octave-request at bevo dot che dot wisc dot edu Fri Jan 16 11:49:16 2004
Subject: Testing endianness
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Jean-Francois Cardoso <cardoso at tsi dot enst dot fr>
Cc: help-octave at bevo dot che dot wisc dot edu
Date: Fri, 16 Jan 2004 09:49:06 -0800

On 16-Jan-2004, Jean-Francois Cardoso <cardoso at tsi dot enst dot fr> wrote:

| I am porting some code from matlab to octave which needs to determine
| the endianness of the machine, as shown below in the original matlab
| version.  Some adjustments are needed because octave's computer() does
| not return the same strings.  I could make these changes on an ad hoc
| basis, adding new tests each time I want to run the code on a
| different machine.  BUT, maybe someone knows of a clean way to test
| for endianness.  Is there a simpler/more robust way to find out?
| 
| Could jwe think of adding a function (like isieee() for instance)
| which would return the endianness of the machine?  I did not see
| anything related.  That would be better than letting the user parse
| strings.
| 
| Thanks, JFC
| 
| % First try to figure out if we need to swap bytes. 
| %
| friend = computer;
| if     strmatch(friend,'PCWIN')    bswap = 'b';
| elseif strmatch(friend,'LNX86')    bswap = 'b';
| elseif strmatch(friend,'GLNX86')   bswap = 'b';
| elseif strmatch(friend,'ALPHA')    bswap = 'b';
| else   bswap = 'l';
| end

How about the following patch?  With it

  octave_config_info ("words_big_endian")

and

  octave_config_info ("words_little_endian")

return TRUE or FALSE, and

  octave_config_info ("float_format")

will return a string (either ieee_big_endian or ieee_little_endian on
most current systems where Octave can actually run, the notable
exception being the Cray SV1).

jwe


src/ChangeLog:

2004-01-16  John W. Eaton  <jwe at bevo dot che dot wisc dot edu>

	* toplev.cc (octave_config_info): Add float_format,
	words_big_endian, and words_little_endian to the struct.


Index: src/toplev.cc
===================================================================
RCS file: /usr/local/cvsroot/octave/src/toplev.cc,v
retrieving revision 1.148
diff -u -r1.148 toplev.cc
--- src/toplev.cc	10 Jan 2004 18:16:03 -0000	1.148
+++ src/toplev.cc	16 Jan 2004 17:45:24 -0000
 at @ -743,6 +743,16 @@
     {
       m.assign ("dld", octave_value (octave_supports_dynamic_linking));
 
+      oct_mach_info::float_format ff = oct_mach_info::native_float_format ();
+      m.assign ("float_format",
+		octave_value (oct_mach_info::float_format_as_string (ff)));
+
+      m.assign ("words_big_endian",
+		octave_value (oct_mach_info::words_big_endian ()));
+
+      m.assign ("words_little_endian",
+		octave_value (oct_mach_info::words_little_endian ()));
+
       int i = 0;
 
       while (true)



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