workbench/network/stacks/AROSTCP/netlib/_dup.c

   1 /* $Id$
   2  *
   3  *      _dup.c - duplicate a file descriptor (SAS/C)
   4  *
   5  *      Copyright © 1994 AmiTCP/IP Group,
   6  *                       Network Solutions Development Inc.
   7  *                       All rights reserved.
   8  */
   9
  10 #include <ios1.h>
  11 #include <fcntl.h>
  12 #include <stdlib.h>
  13 #include <dos.h>
  14 #define USE_BUILTIN_MATH
  15 #include <string.h>
  16 #include <errno.h>
  17 #include <dos/dos.h>
  18 #include <proto/dos.h>
  19
  20 #include <bsdsocket.h>
  21
  22 /****** net.lib/dup ***********************************************************
  23
  24     NAME
  25         dup, dup2 - duplicate an existing file descriptor
  26
  27     SYNOPSIS
  28         #include <unistd.h>
  29
  30         int dup(int oldd)
  31
  32         int dup2(int oldd, int newd)
  33
  34     FUNCTION
  35         Dup() duplicates an existing object descriptor and returns its value
  36         to the calling program (newd = dup(oldd)). The argument oldd is a
  37         small nonnegative integer index in the program's descriptor table.
  38         The value must be less than the size of the table, which is returned
  39         by getdtablesize().  The new descriptor returned by the call is the
  40         lowest numbered descriptor currently not in use by the program.
  41
  42         The object referenced by the descriptor does not distinguish between
  43         oldd and newd in any way.  Thus if newd and oldd are duplicate
  44         references to an open file, read() and write() calls all move a single
  45         pointer into the file, and append mode, non-blocking I/O and
  46         asynchronous I/O options are shared between the references.  If a
  47         separate pointer into the file is desired, a different object
  48         reference to the file must be obtained by issuing an additional open()
  49         call.  The close-on-exec flag on the new file descriptor is unset.
  50
  51         In dup2(), the value of the new descriptor newd is specified.  If this
  52         descriptor is already in use, the descriptor is first deallocated as
  53         if a close() call had been done first.
  54
  55     RETURN VALUES
  56         The value -1 is returned if an error occurs in either call.  The
  57         external variable errno indicates the cause of the error.
  58
  59     BUGS
  60         The current UFB implementation for SAS C allows only sockets to be
  61         duplicated.
  62
  63     ERRORS
  64         Dup() and dup2() fail if:
  65
  66         [EBADF]       Oldd or newd is not a valid active descriptor
  67
  68         [EMFILE]      Too many descriptors are active.
  69
  70     SEE ALSO
  71         accept(),  open(),  close(),  socket(),  getdtablesize()
  72
  73     STANDARDS
  74         Dup() and dup2() are expected to conform to IEEE Std 1003.1-1988
  75         (``POSIX'').
  76
  77     COPYRIGHT
  78         This manual page is copyright © 1980, 1991 Regents of the
  79         University of California.  All rights reserved.
  80
  81 *******************************************************************************
  82 */
  83
  84
  85 int
  86 dup(int old_fd)
  87 {
  88   struct UFB *ufb;
  89   int ufbflg;
  90   /*
  91    * Check for the break signals
  92    */
  93   __chkabort();
  94
  95   /*
  96    * Find the ufb * for the given FD
  97    */
  98   if ((ufb = __chkufb(old_fd)) == NULL) {
  99     errno = EBADF;
 100     return -1;
 101   }
 102
 103   ufbflg = ufb->ufbflg;
 104
 105   /*
 106    * The brain dead UFB system won't allow duplicating ordinary files
 107    */
 108   if ((ufbflg & UFB_SOCK) == UFB_SOCK) {
 109     return Dup2Socket(old_fd, -1);
 110   } else {
 111     errno = EBADF;
 112     return -1;
 113   }
 114 }