Initial Spring 2016 commit.

userland/testbin/schedpong/usem.c

@@ -0,0 +1,123 @@
+/*
+ * Copyright (c) 2014, 2015
+ *	The President and Fellows of Harvard College.
+ *      Written by David A. Holland.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * XXX this code is mostly copied from usemtest; it should go in a
+ * library.
+ */
+
+#include <stdio.h>
+#include <stdarg.h>
+#include <unistd.h>
+#include <err.h>
+
+#include "usem.h"
+
+void
+usem_init(struct usem *sem, const char *namefmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, namefmt);
+	vsnprintf(sem->name, sizeof(sem->name), namefmt, ap);
+	va_end(ap);
+
+	sem->fd = open(sem->name, O_RDWR|O_CREAT|O_TRUNC, 0664);
+	if (sem->fd < 0) {
+		err(1, "%s: create", sem->name);
+	}
+	close(sem->fd);
+	sem->fd = -1;
+}
+
+void
+usem_open(struct usem *sem)
+{
+	sem->fd = open(sem->name, O_RDWR);
+	if (sem->fd < 0) {
+		err(1, "%s: open", sem->name);
+	}
+}
+
+void
+usem_close(struct usem *sem)
+{
+	if (close(sem->fd) == -1) {
+		warn("%s: close", sem->name);
+	}
+}
+
+void
+usem_cleanup(struct usem *sem)
+{
+	(void)remove(sem->name);
+}
+
+void
+Pn(struct usem *sem, unsigned count)
+{
+	ssize_t r;
+	char c;
+
+	r = read(sem->fd, &c, count);
+	if (r < 0) {
+		err(1, "%s: read", sem->name);
+	}
+	if ((size_t)r < count) {
+		errx(1, "%s: read: unexpected EOF", sem->name);
+	}
+}
+
+void
+P(struct usem *sem)
+{
+	Pn(sem, 1);
+}
+
+void
+Vn(struct usem *sem, unsigned count)
+{
+	ssize_t r;
+	char c;
+
+	r = write(sem->fd, &c, count);
+	if (r < 0) {
+		err(1, "%s: write", sem->name);
+	}
+	if ((size_t)r < count) {
+		errx(1, "%s: write: Short count", sem->name);
+	}
+}
+
+void
+V(struct usem *sem)
+{
+	Vn(sem, 1);
+}