/*++ /* 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