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/*++
/* NAME
/* peekfd 3
/* SUMMARY
/* determine amount of data ready to read
/* SYNOPSIS
/* #include <iostuff.h>
/*
/* ssize_t peekfd(fd)
/* int fd;
/* DESCRIPTION
/* peekfd() attempts to find out how many bytes are available to
/* be read from the named file descriptor. The result value is
/* the number of available bytes.
/* DIAGNOSTICS
/* peekfd() returns -1 in case of trouble. The global \fIerrno\fR
/* variable reflects the nature of the problem.
/* BUGS
/* On some systems, non-blocking read() may fail even after a
/* positive return from peekfd(). The smtp-sink program works
/* around this by using the readable() function instead.
/* 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
/*
/* Wietse Venema
/* Google, Inc.
/* 111 8th Avenue
/* New York, NY 10011, USA
/*--*/
/* System library. */
#include <sys_defs.h>
#include <sys/ioctl.h>
#ifdef FIONREAD_IN_SYS_FILIO_H
#include <sys/filio.h>
#endif
#ifdef FIONREAD_IN_TERMIOS_H
#include <termios.h>
#endif
#include <unistd.h>
#ifndef SHUT_RDWR
#define SHUT_RDWR 2
#endif
/* Utility library. */
#include "iostuff.h"
/* peekfd - return amount of data ready to read */
ssize_t peekfd(int fd)
{
/*
* Anticipate a series of system-dependent code fragments.
*/
#ifdef FIONREAD
int count;
#ifdef SUNOS5
/*
* With Solaris10, write_wait() hangs in poll() until timeout, when
* invoked after peekfd() has received an ECONNRESET error indication.
* This happens when a client sends QUIT and closes the connection
* immediately.
*/
if (ioctl(fd, FIONREAD, (char *) &count) < 0) {
(void) shutdown(fd, SHUT_RDWR);
return (-1);
} else {
return (count);
}
#else /* SUNOS5 */
return (ioctl(fd, FIONREAD, (char *) &count) < 0 ? -1 : count);
#endif /* SUNOS5 */
#else
#error "don't know how to look ahead"
#endif
}
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