//
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// Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
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//
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// This software is supplied under the terms of the MIT License, a
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// copy of which should be located in the distribution where this
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// file was obtained (LICENSE.txt). A copy of the license may also be
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// found online at https://opensource.org/licenses/MIT.
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//
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// POSIX pipes.
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#include "core/nng_impl.h"
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#ifdef NNG_PLATFORM_POSIX
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#include <errno.h>
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// This implementation of notification pipes works ~everywhere on POSIX,
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// as it only relies on pipe() and non-blocking I/O.
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// So as much as we would like to use eventfd, it turns out to be completely
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// busted on some systems (latest Ubuntu release for example). So we go
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// back to the old but repliable pipe() system call.
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#undef NNG_USE_EVENTFD
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#ifdef NNG_USE_EVENTFD
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// Linux eventfd. This is lighter weight than pipes, and has better semantics
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// to boot. This is far better than say epoll().
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#include <fcntl.h>
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#include <sys/eventfd.h>
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#include <unistd.h>
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#ifdef EFD_CLOEXEC
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#define NNI_EVENTFD_FLAGS EFD_CLOEXEC
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#else
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#define NNI_EVENTFD_FLAGS 0
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#endif
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int
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nni_plat_pipe_open(int *wfd, int *rfd)
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{
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int fd;
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if ((fd = eventfd(0, NNI_EVENTFD_FLAGS)) < 0) {
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return (nni_plat_errno(errno));
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}
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(void) fcntl(fd, F_SETFD, FD_CLOEXEC);
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(void) fcntl(fd, F_SETFL, O_NONBLOCK);
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*wfd = *rfd = fd;
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return (0);
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}
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void
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nni_plat_pipe_raise(int wfd)
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{
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uint64_t one = 1;
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(void) write(wfd, &one, sizeof(one));
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}
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void
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nni_plat_pipe_clear(int rfd)
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{
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uint64_t val;
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(void) read(rfd, &val, sizeof(val));
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}
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void
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nni_plat_pipe_close(int wfd, int rfd)
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{
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NNI_ASSERT(wfd == rfd);
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(void) close(wfd);
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}
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#else // NNG_USE_EVENTFD
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#include <fcntl.h>
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#include <unistd.h>
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int
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nni_plat_pipe_open(int *wfd, int *rfd)
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{
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int fds[2];
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if (pipe(fds) < 0) {
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return (nni_plat_errno(errno));
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}
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*wfd = fds[1];
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*rfd = fds[0];
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(void) fcntl(fds[0], F_SETFD, FD_CLOEXEC);
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(void) fcntl(fds[1], F_SETFD, FD_CLOEXEC);
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(void) fcntl(fds[0], F_SETFL, O_NONBLOCK);
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(void) fcntl(fds[1], F_SETFL, O_NONBLOCK);
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return (0);
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}
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void
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nni_plat_pipe_raise(int wfd)
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{
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char c = 1;
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wunused-result"
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(void) write(wfd, &c, 1);
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#pragma GCC diagnostic pop
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}
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void
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nni_plat_pipe_clear(int rfd)
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{
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char buf[32];
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for (;;) {
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// Completely drain the pipe, but don't wait. This coalesces
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// events somewhat.
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if (read(rfd, buf, sizeof(buf)) <= 0) {
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return;
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}
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}
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}
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void
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nni_plat_pipe_close(int wfd, int rfd)
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{
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close(wfd);
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close(rfd);
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}
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#endif // NNG_USE_EVENTFD
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#endif // NNG_PLATFORM_POSIX
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