Re: glibc related porting questions

[Marcus Brinkmann]

On Mon, Jul 23, 2001 at 07:32:10PM -0400, Roland McGrath wrote:
> > 2. There is a READ_DATA_PENDING macro to determine the available bytes
> >    for reading(?) on various systems.  Seems to be a highly inofficial 
> >    thing.  Anyways, the GLibC support there relies on _STDIO_USES_IOSTREAM,
> >    which we don't define.  What will work for us with our stdio?
> 
> Add a configure check for stdio_ext.h and use those interfaces.  They exist
> in libio since glibc-2.2, and it so happens I just added them for stdio
> this weekend (you need to test the new code because I haven't).

I don't see anything there that returns how much (or if) can be read.
The closest thing is __fpending, but this returns the number of pending
bytes in the output buffer, not input buffer.

Here is the relevant code from icon, which has a similar issue:

FILE *f;

   /* check for data already in buffer */
   /* there's no legal way to do this in C; we cheat */
#ifdef __linux
   if (f->_IO_read_ptr < f->_IO_read_end)
      RetArg(1);
#elif __bsdi__ || __FreeBSD__ || __NetBSD__ || __OpenBSD__
   if (f->_r > 0)
      RetArg(1);
#else
   if (f->_cnt > 0)
      RetArg(1);
#endif

Thanks,
Marcus

-- 
`Rhubarb is no Egyptian god.' Debian http://www.debian.org brinkmd@debian.org
Marcus Brinkmann              GNU    http://www.gnu.org    marcus@gnu.org
Marcus.Brinkmann@ruhr-uni-bochum.de
http://www.marcus-brinkmann.de