[Discuss-gnuradio] byteswapping problems in usrp code

[Greg Troxel]

gnuradio/trunk/usrp/host/lib/legacy/usrp_bytesex.h includes byteswap.h,
which appears to be a Linux-specific header file.  I looked briefly, and
didn't see any POSIX/SUSv3 definitions of these macros.  I just fixed
this to build on NetBSD, which I suspect also fixes it on several other
non-Linux systems.

NetBSD has bswap macros, in machine/bswap.h:

 BSWAP(3)                NetBSD Library Functions Manual               BSWAP(3)

 NAME
      bswap16, bswap32, bswap64 -- byte-order swapping functions

 LIBRARY
      Standard C Library (libc, -lc)

 SYNOPSIS
      #include <sys/types.h>
      #include <machine/bswap.h>

      uint16_t
      bswap16(uint16_t);

      uint32_t
      bswap32(uint32_t);

      uint64_t
      bswap64(uint64_t);

 DESCRIPTION
      The bswap16(), bswap32(), and bswap64() functions return the value of
      their argument with the bytes inverted.  They can be used to convert 16,
      32 or 64 bits integers from little to big endian, or vice-versa.

 SEE ALSO
      byteorder(3)

 NetBSD 4.0_BETA2                March 17, 1998                NetBSD 4.0_BETA2

Berndt sent a patch to the list to look for this; it seems equally
reasonable as the Linux header, neither being defined by a standard.



Also, the code uses 'short int' and 'int', which is nonportable.  It
should be using the POSIX fixed-width types.

I wonder if the use of swap is really right - this seems to be about
host to USRP, but perhaps the USRP is always little endian?  It
definitely needs more comments if that's what's going on.