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/* $Id: fdflags.c 4740 2001-05-14 03:52:34Z rra $
**
** Set or clear file descriptor flags.
**
** Simple functions (wrappers around fcntl) to set or clear file descriptor
** flags like close on exec or nonblocking I/O.
*/
#include "config.h"
#include "clibrary.h"
#include "libinn.h"
#include <errno.h>
#include <fcntl.h>
/*
** Set a file to close on exec.
**
** One is supposed to retrieve the flags, add FD_CLOEXEC, and then set
** them, although I've never seen a system with any flags other than
** close-on-exec. Do it right anyway; it's not that expensive. Avoid
** changing errno. Errors are ignored, since it generally doesn't cause
** significant harm to fail.
*/
void
close_on_exec(int fd, bool flag)
{
int oerrno;
int oflag;
oerrno = errno;
oflag = fcntl(fd, F_GETFD, 0);
if (oflag < 0) {
errno = oerrno;
return;
}
fcntl(fd, F_SETFD, flag ? (oflag | FD_CLOEXEC) : (oflag & ~FD_CLOEXEC));
errno = oerrno;
}
/*
** Set a file descriptor to nonblocking (or clear the nonblocking flag if
** flag is false).
**
** Always use O_NONBLOCK; O_NDELAY is *not* the same thing historically.
** The semantics of O_NDELAY are that if the read would block, it returns 0
** instead. This is indistinguishable from an end of file condition.
** POSIX added O_NONBLOCK, which requires read to return -1 and set errno
** to EAGAIN, which is what we want.
**
** FNDELAY (4.3BSD) originally did the correct thing, although it has a
** different incompatibility (affecting all users of a socket rather than
** just a file descriptor and returning EWOULDBLOCK instead of EAGAIN) that
** we don't care about in INN. Using it is *probably* safe, but BSD should
** also have the ioctl, and at least on Solaris FNDELAY does the same thing
** as O_NDELAY, not O_NONBLOCK. So if we don't have O_NONBLOCK, fall back
** to the ioctl instead.
**
** Reference: Stevens, Advanced Unix Programming, pg. 364.
**
** Note that O_NONBLOCK is known not to work on earlier versions of ULTRIX,
** SunOS, and AIX, possibly not setting the socket nonblocking at all,
** despite the fact that they do define it. It works in later SunOS and,
** current AIX, however, and a 1999-10-25 survey of current operating
** systems failed to turn up any that didn't handle it correctly (as
** required by POSIX), while HP-UX 11.00 did use the broken return-zero
** semantics of O_NDELAY (most other operating systems surveyed treated
** O_NDELAY as synonymous with O_NONBLOCK). Accordingly, we currently
** unconditionally use O_NONBLOCK. If this causes too many problems, an
** autoconf test may be required.
*/
#ifdef O_NONBLOCK
int
nonblocking(int fd, bool flag)
{
int mode;
mode = fcntl(fd, F_GETFL, 0);
if (mode < 0)
return -1;
mode = (flag ? (mode | O_NONBLOCK) : (mode & ~O_NONBLOCK));
return fcntl(fd, F_SETFL, mode);
}
#else /* !O_NONBLOCK */
#include <sys/ioctl.h>
#if HAVE_SYS_FILIO_H
# include <sys/filio.h>
#endif
int
nonblocking(int fd, bool flag)
{
int state;
state = flag ? 1 : 0;
return ioctl(fd, FIONBIO, &state);
}
#endif /* !O_NONBLOCK */
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