/*++ /* NAME /* timed_write 3 /* SUMMARY /* write operation with pre-write timeout /* SYNOPSIS /* #include <iostuff.h> /* /* ssize_t timed_write(fd, buf, len, timeout, context) /* int fd; /* const void *buf; /* size_t len; /* int timeout; /* void *context; /* DESCRIPTION /* timed_write() performs a write() operation when the specified /* descriptor becomes writable within a user-specified deadline. /* /* Arguments: /* .IP fd /* File descriptor in the range 0..FD_SETSIZE. /* .IP buf /* Write buffer pointer. /* .IP len /* Write buffer size. /* .IP timeout /* The deadline in seconds. If this is <= 0, the deadline feature /* is disabled. /* .IP context /* Application context. This parameter is unused. It exists only /* for the sake of VSTREAM compatibility. /* DIAGNOSTICS /* When the operation does not complete within the deadline, the /* result value is -1, and errno is set to ETIMEDOUT. /* All other returns are identical to those of a write(2) operation. /* 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 <unistd.h> #include <errno.h> /* Utility library. */ #include <msg.h> #include <iostuff.h> /* timed_write - write with deadline */ ssize_t timed_write(int fd, void *buf, size_t len, int timeout, void *unused_context) { ssize_t ret; /* * Wait for a limited amount of time for something to happen. If nothing * happens, report an ETIMEDOUT error. * * XXX Solaris 8 read() fails with EAGAIN after read-select() returns * success. The code below exists just in case their write implementation * is equally broken. * * This condition may also be found on systems where select() returns * success on pipes with less than PIPE_BUF bytes of space, and with * badly designed software where multiple writers are fighting for access * to the same resource. */ for (;;) { if (timeout > 0 && write_wait(fd, timeout) < 0) return (-1); if ((ret = write(fd, buf, len)) < 0 && timeout > 0 && errno == EAGAIN) { msg_warn("write() returns EAGAIN on a writable file descriptor!"); msg_warn("pausing to avoid going into a tight select/write loop!"); sleep(1); continue; } else if (ret < 0 && errno == EINTR) { continue; } else { return (ret); } } }