1 files changed, 144 insertions, 0 deletions
diff --git a/src/xshmfence.c b/src/xshmfence.c
new file mode 100644
index 0000000..521d3ad
--- /dev/null
+++ b/src/xshmfence.c
@@ -0,0 +1,144 @@
+/*
+ * Copyright © 2013 Keith Packard
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission.  The copyright holders make no representations
+ * about the suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, 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 "xshmfenceint.h"
+
+/**
+ * xshmfence_trigger:
+ * @f: An X fence
+ *
+ * Set @f to triggered, waking all waiters.
+ *
+ * Return value: 0 on success and -1 on error (in which case, errno
+ * will be set as appropriate).
+ **/
+int
+xshmfence_trigger(int32_t *f)
+{
+	if (__sync_val_compare_and_swap(f, 0, 1) == -1) {
+		atomic_store(f, 1);
+		if (futex_wake(f) < 0)
+			return -1;
+	}
+	return 0;
+}
+
+/**
+ * xshmfence_await:
+ * @f: An X fence
+ *
+ * Wait for @f to be triggered. If @f is already triggered, this
+ * function returns immediately.
+ *
+ * Return value: 0 on success and -1 on error (in which case, errno
+ * will be set as appropriate).
+ **/
+int
+xshmfence_await(int32_t *f)
+{
+	while (__sync_val_compare_and_swap(f, 0, -1) != 1) {
+		if (futex_wait(f, -1)) {
+			if (errno != EWOULDBLOCK)
+				return -1;
+		}
+	}
+	return 0;
+}
+
+/**
+ * xshmfence_query:
+ * @f: An X fence
+ *
+ * Return value: 1 if @f is triggered, else returns 0.
+ **/
+int
+xshmfence_query(int32_t *f)
+{
+	return atomic_fetch(f) == 1;
+}
+
+/**
+ * xshmfence_reset:
+ * @f: An X fence
+ *
+ * Reset @f to untriggered. If @f is already untriggered,
+ * this function has no effect.
+ **/
+void
+xshmfence_reset(int32_t *f)
+{
+	__sync_bool_compare_and_swap(f, 1, 0);
+}
+
+
+/**
+ * xshmfence_alloc_shm:
+ *
+ * Allocates a shared memory object large enough to hold a single
+ * fence.
+ *
+ * Return value: the file descriptor of the object, or -1 on failure
+ * (in which case, errno will be set as appropriate).
+ **/
+int
+xshmfence_alloc_shm(void)
+{
+	char	template[] = "/run/shm/shmfd-XXXXXX";
+	int	fd = mkstemp(template);
+
+	if (fd < 0)
+		return fd;
+	unlink(template);
+	ftruncate(fd, sizeof (int32_t));
+	return fd;
+}
+
+/**
+ * xshmfence_map_shm:
+ *
+ * Map a shared memory fence referenced by @fd.
+ *
+ * Return value: the fence or NULL (in which case, errno will be set
+ * as appropriate).
+ **/
+int32_t *
+xshmfence_map_shm(int fd)
+{
+	void *addr;
+	addr = mmap (NULL, sizeof (int32_t) , PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+	if (addr == MAP_FAILED) {
+		close (fd);
+		return 0;
+	}
+	return addr;
+}
+
+/**
+ * xshmfence_unmap_shm:
+ *
+ * Unap a shared memory fence @f.
+ **/
+void
+xshmfence_unmap_shm(int32_t *f)
+{
+        munmap(f, sizeof (int32_t));
+}