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/*++
/* NAME
/* non_blocking 3
/* SUMMARY
/* set/clear non-blocking flag
/* SYNOPSIS
/* #include <iostuff.h>
/*
/* int non_blocking(int fd, int on)
/* DESCRIPTION
/* the \fInon_blocking\fR() function manipulates the non-blocking
/* flag for the specified open file, and returns the old setting.
/*
/* Arguments:
/* .IP fd
/* A file descriptor.
/* .IP on
/* For non-blocking I/O, specify a non-zero value (or use the
/* NON_BLOCKING constant); for blocking I/O, specify zero
/* (or use the BLOCKING constant).
/*
/* The result is non-zero when the non-blocking flag was enabled.
/* DIAGNOSTICS
/* All errors are fatal.
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/*--*/
/* System interfaces. */
#include "sys_defs.h"
#include <fcntl.h>
/* Utility library. */
#include "msg.h"
#include "iostuff.h"
/* Backwards compatibility */
#ifndef O_NONBLOCK
#define PATTERN FNDELAY
#else
#define PATTERN O_NONBLOCK
#endif
/* non_blocking - set/clear non-blocking flag */
int non_blocking(fd, on)
int fd;
int on;
{
int flags;
if ((flags = fcntl(fd, F_GETFL, 0)) < 0)
msg_fatal("fcntl: get flags: %m");
if (fcntl(fd, F_SETFL, on ? flags | PATTERN : flags & ~PATTERN) < 0)
msg_fatal("fcntl: set non-blocking flag %s: %m", on ? "on" : "off");
return ((flags & PATTERN) != 0);
}
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