[Bug fortran/23815] New: Add -byteswapio flag

["rrr6399 at futuretek dot com" <gcc-bugzilla at gcc dot gnu dot org>]

It is pretty typical that aero engineers involved in CFD (computational
fluid dynamics) need to ship around large (50-1000 MB) binary files between
various big-endian and little-endian machines without having to reformat them. 

Typically they generate files that are all big-endian using a compiler switch to
avoid having to byte swap as well. So it'd be great to have a compiler switch
that reversed the byte order of integers (2, 4, 8 byte) and floating point
numbers (4, 8 byte) when they are read from or written to an unformatted file.

For instance if you had an 4 byte int stored as an array of chars,
you might swap it using this simple approach:
 for (i = 0; i < 4; i++ ) {
   swappedBytes[i] = bytes[3-i];
 }

or if you want to do the bit shifting thing, you do do it this way:

    return (((buf [ 3 ] & 0xff) << 24) | ((buf [ 2 ] & 0xff) << 16) |
           ((buf [ 1 ] & 0xff) << 8) | (buf [ 0 ] & 0xff));

(I grabbed this code from converToInt() in: 
gcc-4.1-20050909/libjava/classpath/gnu/CORBA/CDR/LittleEndianInputStream.java)

-- 
           Summary: Add -byteswapio flag
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P1
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rrr6399 at futuretek dot com
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23815