compiler/posixc/dup2.c

   1 /*
   2     Copyright © 1995-2014, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     POSIX.1-2008 function dup2().
   6 */
   7
   8 #include <stdlib.h>
   9 #include <errno.h>
  10 #include "__fdesc.h"
  11
  12 /*****************************************************************************
  13
  14     NAME */
  15 #include <unistd.h>
  16
  17         int dup2(
  18
  19 /*  SYNOPSIS */
  20         int oldfd,
  21         int newfd
  22         )
  23
  24 /*  FUNCTION
  25         Duplicates a file descriptor.
  26
  27         The object referenced by the descriptor does not distinguish between
  28         oldfd and newfd in any way. Thus if newfd and oldfd are duplicate
  29         references to an open file, read(), write() and lseek() calls all
  30         move a single pointer into the file, and append mode, non-blocking
  31         I/O and asynchronous I/O options are shared between the references.
  32         If a separate pointer into the file is desired, a different object
  33         reference to the file must be obtained by issuing an additional
  34         open(2) call.
  35
  36         The close-on-exec flag on the new file descriptor is unset.
  37
  38         If oldfd is valid and has the same integer value as newfd, nothing is
  39         done, and newfd is returned unchanged.
  40
  41         If newfd is already valid when this function is called, its old
  42         descriptor is deallocated before this function returns.
  43
  44         This function fails gracefully if oldfd is invalid.
  45
  46     INPUTS
  47         oldfd - The file descriptor to be duplicated
  48         newfd - The value of the new descriptor we want the old one to be
  49             duplicated in
  50
  51     RESULT
  52         -1 for error or newfd on success
  53
  54     NOTES
  55         This function must not be used in a shared library or
  56         in a threaded application.
  57
  58     EXAMPLE
  59
  60     BUGS
  61
  62     SEE ALSO
  63         bsdsocket.library/accept(),  open(),  close(),  fcntl(),  pipe()
  64         bsdsocket.library/socket()
  65
  66     INTERNALS
  67
  68 ******************************************************************************/
  69 {
  70     fdesc *oldfdesc, *newfdesc;
  71
  72     /* Fail if old FD is invalid */
  73     oldfdesc = __getfdesc(oldfd);
  74     if (!oldfdesc)
  75     {
  76         errno = EBADF;
  77         return -1;
  78     }
  79
  80     /* Do nothing if FDs are identical */
  81     if (oldfd == newfd)
  82         return newfd;
  83
  84     /* Allocate new FD or fail */
  85     newfdesc = __alloc_fdesc();
  86     if (!newfdesc)
  87     {
  88         errno = ENOMEM;
  89         return -1;
  90     }
  91
  92     /* Initialise new FD */
  93     newfdesc->fdflags = 0;
  94     newfdesc->fcb = oldfdesc->fcb;
  95
  96     /* Put new FD into its slot (and deallocate any FD previously there) */
  97     newfd =__getfdslot(newfd);
  98     if (newfd != -1)
  99     {
 100         newfdesc->fcb->opencount++;
 101         __setfdesc(newfd, newfdesc);
 102     }
 103
 104     return newfd;
 105 }
 106