Make improvements

- Clean up sigaction() code
- Add a port scanner example
- Introduce a ParseCidr() API
- Clean up our futex abstraction code
- Fix a harmless integer overflow in ParseIp()
- Use kernel semaphores on NetBSD to make threads much faster

third_party/nsync/mu_semaphore_sem.c

@@ -0,0 +1,102 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/assert.h"
+#include "libc/calls/cp.internal.h"
+#include "libc/calls/struct/timespec.internal.h"
+#include "libc/calls/syscall-sysv.internal.h"
+#include "libc/dce.h"
+#include "libc/errno.h"
+#include "libc/intrin/strace.internal.h"
+#include "libc/str/str.h"
+#include "libc/sysv/consts/f.h"
+#include "third_party/nsync/mu_semaphore.h"
+#include "third_party/nsync/time.h"
+// clang-format off
+
+#define ASSERT(x) _npassert(x)
+
+struct sem {
+	int64_t id;
+};
+
+static nsync_semaphore *sem_big_enough_for_sem = (nsync_semaphore *) (uintptr_t)(1 /
+	(sizeof (struct sem) <= sizeof (*sem_big_enough_for_sem)));
+
+/* Initialize *s; the initial value is 0. */
+void nsync_mu_semaphore_init_sem (nsync_semaphore *s) {
+	int newfd;
+	struct sem *f = (struct sem *) s;
+	f->id = 0;
+	ASSERT (!sys_sem_init (0, &f->id));
+	STRACE ("sem_init(0, [%ld]) → 0", f->id);
+	ASSERT ((newfd = __sys_fcntl (f->id, F_DUPFD_CLOEXEC, 100)) != -1);
+	ASSERT (!sys_sem_destroy (f->id));
+	f->id = newfd;
+}
+
+/* Wait until the count of *s exceeds 0, and decrement it. */
+errno_t nsync_mu_semaphore_p_sem (nsync_semaphore *s) {
+	int e, rc;
+	errno_t result;
+	struct sem *f = (struct sem *) s;
+	e = errno;
+	BEGIN_CANCELLATION_POINT;
+	rc = sys_sem_wait (f->id);
+	END_CANCELLATION_POINT;
+	STRACE ("sem_wait(%ld) → %d% m", f->id, rc);
+	if (!rc) {
+		result = 0;
+	} else {
+		result = errno;
+		errno = e;
+		ASSERT (result == ECANCELED);
+	}
+	return result;
+}
+
+/* Wait until one of:
+   the count of *s is non-zero, in which case decrement *s and return 0;
+   or abs_deadline expires, in which case return ETIMEDOUT. */
+errno_t nsync_mu_semaphore_p_with_deadline_sem (nsync_semaphore *s, nsync_time abs_deadline) {
+	int e, rc;
+	errno_t result;
+	struct sem *f = (struct sem *) s;
+	e = errno;
+	BEGIN_CANCELLATION_POINT;
+	rc = sys_sem_timedwait (f->id, &abs_deadline);
+	END_CANCELLATION_POINT;
+	STRACE ("sem_timedwait(%ld, %s) → %d% m", f->id,
+		DescribeTimespec(0, &abs_deadline), rc);
+	if (!rc) {
+		result = 0;
+	} else {
+		result = errno;
+		errno = e;
+		ASSERT (result == ETIMEDOUT ||
+			result == ECANCELED);
+	}
+	return result;
+}
+
+/* Ensure that the count of *s is at least 1. */
+void nsync_mu_semaphore_v_sem (nsync_semaphore *s) {
+	struct sem *f = (struct sem *) s;
+	ASSERT (!sys_sem_post (f->id));
+	STRACE ("sem_post(%ld) → 0% m", f->id);
+}