8 <<funopen>>, <<fropen>>, <<fwopen>>---open a stream with custom callbacks
35 <[readfn]> should return -1 on failure, or else the number of bytes
41 <[writefn]> should return -1 on failure, or else the number of bytes
47 <[seekfn]> should return (fpos_t)-1 on failure, or else the current
54 <[closefn]> should return -1 on failure, or 0 on success.  It is
78 It is not portable.  See also the <<fopencookie>> interface from Linux.
116   if ((result = c->readfn (c->cookie, buf, n)) < 0 && errno)  in funreader()
130   if ((result = c->writefn (c->cookie, buf, n)) < 0 && errno)  in funwriter()
145   if ((result = c->seekfn (c->cookie, (fpos_t) off, whence)) < 0 && errno)  in funseeker()
150   if ((result = c->seekfn (c->cookie, (_fpos64_t) off, whence)) < 0 && errno)  in funseeker()
155       result = -1;  in funseeker()
171   if ((result = c->seekfn (c->cookie, off, whence)) < 0 && errno)  in funseeker64()
183   if (c->closefn)  in funcloser()
186       if ((result = c->closefn (c->cookie)) < 0 && errno)  in funcloser()
214       fp->_flags = 0;		/* release */  in funopen()
216       __lock_close_recursive (fp->_lock);  in funopen()
223   fp->_file = -1;  in funopen()
224   c->cookie = (void *) cookie; /* cast away const */  in funopen()
225   fp->_cookie = c;  in funopen()
228       c->readfn = readfn;  in funopen()
229       fp->_read = funreader;  in funopen()
232 	  fp->_flags = __SRW;  in funopen()
233 	  c->writefn = writefn;  in funopen()
234 	  fp->_write = funwriter;  in funopen()
238 	  fp->_flags = __SRD;  in funopen()
239 	  c->writefn = NULL;  in funopen()
240 	  fp->_write = NULL;  in funopen()
245       fp->_flags = __SWR;  in funopen()
246       c->writefn = writefn;  in funopen()
247       fp->_write = funwriter;  in funopen()
248       c->readfn = NULL;  in funopen()
249       fp->_read = NULL;  in funopen()
251   c->seekfn = seekfn;  in funopen()
252   fp->_seek = seekfn ? funseeker : NULL;  in funopen()
254   fp->_seek64 = seekfn ? funseeker64 : NULL;  in funopen()
255   fp->_flags |= __SL64;  in funopen()
257   c->closefn = closefn;  in funopen()
258   fp->_close = funcloser;  in funopen()