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/* Copy a file descriptor, applying specific flags.
Copyright (C) 2009-2021 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 3 of the
License, or (at your option) any later version.
This file is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
/* Specification. */
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include "binary-io.h"
int
dup3 (int oldfd, int newfd, int flags)
{
#if HAVE_DUP3
# undef dup3
# if HAVE_SETDTABLESIZE
/* Avoid a cygwin crasher. */
setdtablesize (newfd + 1);
# endif
/* Try the system call first, if it exists. (We may be running with a glibc
that has the function but with an older kernel that lacks it.) */
{
/* Cache the information whether the system call really exists. */
static int have_dup3_really; /* 0 = unknown, 1 = yes, -1 = no */
if (have_dup3_really >= 0)
{
int result = dup3 (oldfd, newfd, flags);
if (!(result < 0 && errno == ENOSYS))
{
have_dup3_really = 1;
# if REPLACE_FCHDIR
if (0 <= result)
result = _gl_register_dup (oldfd, newfd);
# endif
return result;
}
have_dup3_really = -1;
}
}
#endif
if (newfd < 0 || newfd >= getdtablesize () || fcntl (oldfd, F_GETFD) == -1)
{
errno = EBADF;
return -1;
}
if (newfd == oldfd)
{
errno = EINVAL;
return -1;
}
/* Check the supported flags.
Note that O_NONBLOCK is not supported, because setting it on newfd
would implicitly also set it on oldfd. */
if ((flags & ~(O_CLOEXEC | O_BINARY | O_TEXT)) != 0)
{
errno = EINVAL;
return -1;
}
if (flags & O_CLOEXEC)
{
int result;
close (newfd);
result = fcntl (oldfd, F_DUPFD_CLOEXEC, newfd);
if (newfd < result)
{
close (result);
errno = EIO;
result = -1;
}
if (result < 0)
return -1;
}
else if (dup2 (oldfd, newfd) < 0)
return -1;
#if O_BINARY
if (flags & O_BINARY)
set_binary_mode (newfd, O_BINARY);
else if (flags & O_TEXT)
set_binary_mode (newfd, O_TEXT);
#endif
return newfd;
}
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