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/*++
/* NAME
/* poll_fd 3
/* SUMMARY
/* wait until file descriptor becomes readable or writable
/* SYNOPSIS
/* #include <iostuff.h>
/*
/* int readable(fd)
/* int fd;
/*
/* int writable(fd)
/* int fd;
/*
/* int read_wait(fd, time_limit)
/* int fd;
/* int time_limit;
/*
/* int write_wait(fd, time_limit)
/* int fd;
/* int time_limit;
/*
/* int poll_fd(fd, request, time_limit, true_res, false_res)
/* int fd;
/* int request;
/* int time_limit;
/* int true_res;
/* int false_res;
/* DESCRIPTION
/* The read*() and write*() functions in this module are macros
/* that provide a convenient interface to poll_fd().
/*
/* readable() asks the kernel if the specified file descriptor
/* is readable, i.e. a read operation would not block.
/*
/* writable() asks the kernel if the specified file descriptor
/* is writable, i.e. a write operation would not block.
/*
/* read_wait() waits until the specified file descriptor becomes
/* readable, or until the time limit is reached.
/*
/* write_wait() waits until the specified file descriptor
/* becomes writable, or until the time limit is reached.
/*
/* poll_fd() waits until the specified file descriptor becomes
/* readable or writable, or until the time limit is reached.
/*
/* Arguments:
/* .IP fd
/* File descriptor. With implementations based on select(), a
/* best effort is made to handle descriptors >=FD_SETSIZE.
/* .IP request
/* POLL_FD_READ (wait until readable) or POLL_FD_WRITE (wait
/* until writable).
/* .IP time_limit
/* A positive value specifies a time limit in seconds. A zero
/* value effects a poll (return immediately). A negative value
/* means wait until the requested POLL_FD_READ or POLL_FD_WRITE
/* condition becomes true.
/* .IP true_res
/* Result value when the requested POLL_FD_READ or POLL_FD_WRITE
/* condition is true.
/* .IP false_res
/* Result value when the requested POLL_FD_READ or POLL_FD_WRITE
/* condition is false.
/* DIAGNOSTICS
/* Panic: interface violation. All system call errors are fatal
/* unless specified otherwise.
/*
/* readable() and writable() return 1 when the requested
/* POLL_FD_READ or POLL_FD_WRITE condition is true, zero when
/* it is false. They never return an error indication.
/*
/* read_wait() and write_wait() return zero when the requested
/* POLL_FD_READ or POLL_FD_WRITE condition is true, -1 (with
/* errno set to ETIMEDOUT) when it is false.
/*
/* poll_fd() returns true_res when the requested POLL_FD_READ
/* or POLL_FD_WRITE condition is true, false_res when it is
/* false. When poll_fd() returns a false_res value < 0, it
/* also sets errno to ETIMEDOUT.
/* 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 library. */
#include <sys_defs.h>
#include <sys/time.h>
#include <signal.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
/*
* Use poll() with fall-back to select(). MacOSX needs this for devices.
*/
#if defined(USE_SYSV_POLL_THEN_SELECT)
#define poll_fd_sysv poll_fd
#define USE_SYSV_POLL
#define USE_BSD_SELECT
int poll_fd_bsd(int, int, int, int, int);
/*
* Use select() only.
*/
#elif defined(USE_BSD_SELECT)
#define poll_fd_bsd poll_fd
#undef USE_SYSV_POLL
/*
* Use poll() only.
*/
#elif defined(USE_SYSV_POLL)
#define poll_fd_sysv poll_fd
/*
* Sanity check.
*/
#else
#error "specify USE_SYSV_POLL, USE_BSD_SELECT or USE_SYSV_POLL_THEN_SELECT"
#endif
#ifdef USE_SYSV_POLL
#include <poll.h>
#endif
#ifdef USE_SYS_SELECT_H
#include <sys/select.h>
#endif
/* Utility library. */
#include <msg.h>
#include <iostuff.h>
#ifdef USE_BSD_SELECT
/* poll_fd_bsd - block with time_limit until file descriptor is ready */
int poll_fd_bsd(int fd, int request, int time_limit,
int true_res, int false_res)
{
fd_set req_fds;
fd_set *read_fds;
fd_set *write_fds;
fd_set except_fds;
struct timeval tv;
struct timeval *tp;
int temp_fd = -1;
/*
* Sanity checks.
*/
if (FD_SETSIZE <= fd) {
if ((temp_fd = dup(fd)) < 0 || temp_fd >= FD_SETSIZE)
msg_fatal("descriptor %d does not fit FD_SETSIZE %d", fd, FD_SETSIZE);
fd = temp_fd;
}
/*
* Use select() so we do not depend on alarm() and on signal() handlers.
* Restart select() when interrupted by some signal. Some select()
* implementations reduce the time to wait when interrupted, which is
* exactly what we want.
*/
FD_ZERO(&req_fds);
FD_SET(fd, &req_fds);
except_fds = req_fds;
if (request == POLL_FD_READ) {
read_fds = &req_fds;
write_fds = 0;
} else if (request == POLL_FD_WRITE) {
read_fds = 0;
write_fds = &req_fds;
} else {
msg_panic("poll_fd: bad request %d", request);
}
if (time_limit >= 0) {
tv.tv_usec = 0;
tv.tv_sec = time_limit;
tp = &tv;
} else {
tp = 0;
}
for (;;) {
switch (select(fd + 1, read_fds, write_fds, &except_fds, tp)) {
case -1:
if (errno != EINTR)
msg_fatal("select: %m");
continue;
case 0:
if (temp_fd != -1)
(void) close(temp_fd);
if (false_res < 0)
errno = ETIMEDOUT;
return (false_res);
default:
if (temp_fd != -1)
(void) close(temp_fd);
return (true_res);
}
}
}
#endif
#ifdef USE_SYSV_POLL
#ifdef USE_SYSV_POLL_THEN_SELECT
#define HANDLE_SYSV_POLL_ERROR(fd, req, time_limit, true_res, false_res) \
return (poll_fd_bsd((fd), (req), (time_limit), (true_res), (false_res)))
#else
#define HANDLE_SYSV_POLL_ERROR(fd, req, time_limit, true_res, false_res) \
msg_fatal("poll: %m")
#endif
/* poll_fd_sysv - block with time_limit until file descriptor is ready */
int poll_fd_sysv(int fd, int request, int time_limit,
int true_res, int false_res)
{
struct pollfd pollfd;
/*
* System-V poll() is optimal for polling a few descriptors.
*/
#define WAIT_FOR_EVENT (-1)
pollfd.fd = fd;
if (request == POLL_FD_READ) {
pollfd.events = POLLIN;
} else if (request == POLL_FD_WRITE) {
pollfd.events = POLLOUT;
} else {
msg_panic("poll_fd: bad request %d", request);
}
for (;;) {
switch (poll(&pollfd, 1, time_limit < 0 ?
WAIT_FOR_EVENT : time_limit * 1000)) {
case -1:
if (errno != EINTR)
HANDLE_SYSV_POLL_ERROR(fd, request, time_limit,
true_res, false_res);
continue;
case 0:
if (false_res < 0)
errno = ETIMEDOUT;
return (false_res);
default:
if (pollfd.revents & POLLNVAL)
HANDLE_SYSV_POLL_ERROR(fd, request, time_limit,
true_res, false_res);
return (true_res);
}
}
}
#endif
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