103 lines
2.2 KiB
C
103 lines
2.2 KiB
C
/*++
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/* NAME
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/* read_wait 3
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/* SUMMARY
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/* wait until descriptor becomes readable
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/* SYNOPSIS
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/* #include <iostuff.h>
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/*
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/* int read_wait(fd, timeout)
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/* int fd;
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/* int timeout;
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/* DESCRIPTION
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/* read_wait() blocks the current process until the specified file
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/* descriptor becomes readable, or until the deadline is exceeded.
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/*
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/* Arguments:
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/* .IP fd
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/* File descriptor in the range 0..FD_SETSIZE.
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/* .IP timeout
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/* If positive, deadline in seconds. A zero value effects a poll.
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/* A negative value means wait until something happens.
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/* DIAGNOSTICS
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/* Panic: interface violation. All system call errors are fatal.
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/*
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/* A zero result means success. When the specified deadline is
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/* exceeded, read_wait() returns -1 and sets errno to ETIMEDOUT.
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/* LICENSE
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/* .ad
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/* .fi
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/* The Secure Mailer license must be distributed with this software.
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/* AUTHOR(S)
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/* Wietse Venema
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/* IBM T.J. Watson Research
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/* P.O. Box 704
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/* Yorktown Heights, NY 10598, USA
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/*--*/
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/* System library. */
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#include <sys_defs.h>
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#include <sys/time.h>
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#include <signal.h>
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#include <errno.h>
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#include <unistd.h>
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#include <string.h>
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#ifdef USE_SYS_SELECT_H
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#include <sys/select.h>
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#endif
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/* Utility library. */
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#include <msg.h>
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#include <iostuff.h>
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/* read_wait - block with timeout until file descriptor is readable */
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int read_wait(int fd, int timeout)
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{
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fd_set read_fds;
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fd_set except_fds;
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struct timeval tv;
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struct timeval *tp;
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/*
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* Sanity checks.
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*/
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if (FD_SETSIZE <= fd)
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msg_panic("descriptor %d does not fit FD_SETSIZE %d", fd, FD_SETSIZE);
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/*
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* Use select() so we do not depend on alarm() and on signal() handlers.
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* Restart the select when interrupted by some signal. Some select()
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* implementations reduce the time to wait when interrupted, which is
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* exactly what we want.
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*/
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FD_ZERO(&read_fds);
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FD_SET(fd, &read_fds);
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FD_ZERO(&except_fds);
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FD_SET(fd, &except_fds);
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if (timeout >= 0) {
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tv.tv_usec = 0;
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tv.tv_sec = timeout;
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tp = &tv;
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} else {
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tp = 0;
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}
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for (;;) {
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switch (select(fd + 1, &read_fds, (fd_set *) 0, &except_fds, tp)) {
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case -1:
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if (errno != EINTR)
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msg_fatal("select: %m");
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continue;
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case 0:
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errno = ETIMEDOUT;
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return (-1);
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default:
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return (0);
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}
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}
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}
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