mirror of
https://github.com/jart/cosmopolitan.git
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80 lines
4.4 KiB
C
80 lines
4.4 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/calls/struct/timespec.h"
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#include "libc/sock/struct/pollfd.h"
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/**
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* Checks status on multiple file descriptors at once.
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*
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* Servers that need to handle an unbounded number of client connections
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* should just create a separate thread for each client. poll() isn't a
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* scalable i/o solution on any platform.
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*
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* One of the use cases for poll() is to quickly check if a number of
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* file descriptors are valid. The canonical way to do this is to set
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* events to 0 which prevents blocking and causes only the invalid,
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* hangup, and error statuses to be checked.
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*
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* On XNU, the POLLHUP and POLLERR statuses aren't checked unless either
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* POLLIN, POLLOUT, or POLLPRI are specified in the events field. Cosmo
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* will however polyfill the checking of POLLNVAL on XNU with the events
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* doesn't specify any of the above i/o events.
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*
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* When XNU and BSD OSes report POLLHUP, they will always set POLLIN too
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* when POLLIN is requested, even in cases when there isn't unread data.
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*
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* Your poll() function will check the status of all file descriptors
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* before returning. This function won't block unless none of the fds
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* had had any reportable status.
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*
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* The impact shutdown() will have on poll() is a dice roll across OSes.
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*
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* @param fds[𝑖].fd should be a socket, input pipe, or conosle input
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* and if it's a negative number then the entry is ignored, plus
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* revents will be set to zero
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* @param fds[𝑖].events flags can have POLLIN, POLLOUT, POLLPRI,
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* POLLRDNORM, POLLWRNORM, POLLRDBAND, POLLWRBAND as well as
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* POLLERR, POLLHUP, and POLLNVAL although the latter are
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* always implied (assuming fd≥0) so they're ignored here
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* @param timeout_ms if 0 means don't wait and negative waits forever
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* @return number of `fds` whose revents field has been set to a nonzero
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* number, 0 if the timeout elapsed without events, or -1 w/ errno
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* @return fds[𝑖].revents is always zero initializaed and then will
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* be populated with POLL{IN,OUT,PRI,HUP,ERR,NVAL} if something
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* was determined about the file descriptor
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* @raise ECANCELED if thread was cancelled in masked mode
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* @raise EINVAL if `nfds` exceeded `RLIMIT_NOFILE`
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* @raise ENOMEM on failure to allocate memory
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* @raise EINTR if signal was delivered
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* @cancelationpoint
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* @asyncsignalsafe
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* @norestart
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*/
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int poll(struct pollfd *fds, size_t nfds, int timeout_ms) {
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struct timespec ts;
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struct timespec *tsp;
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if (timeout_ms >= 0) {
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ts.tv_sec = timeout_ms / 1000;
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ts.tv_nsec = timeout_ms % 1000 * 1000000;
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tsp = &ts;
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} else {
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tsp = 0;
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}
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return ppoll(fds, nfds, tsp, 0);
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}
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