1 files changed, 74 insertions, 0 deletions
diff --git a/src/shared/barrier.h b/src/shared/barrier.h
new file mode 100644
index 0000000..4ee2040
--- /dev/null
+++ b/src/shared/barrier.h
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <sys/types.h>
+
+#include "macro.h"
+
+/* See source file for an API description. */
+
+typedef struct Barrier Barrier;
+
+enum {
+        BARRIER_SINGLE                  = 1LL,
+        BARRIER_ABORTION                = INT64_MAX,
+
+        /* bias values to store state; keep @WE < @THEY < @I */
+        BARRIER_BIAS                    = INT64_MIN,
+        BARRIER_WE_ABORTED              = BARRIER_BIAS + 1LL,
+        BARRIER_THEY_ABORTED            = BARRIER_BIAS + 2LL,
+        BARRIER_I_ABORTED               = BARRIER_BIAS + 3LL,
+};
+
+enum {
+        BARRIER_PARENT,
+        BARRIER_CHILD,
+};
+
+struct Barrier {
+        int me;
+        int them;
+        int pipe[2];
+        int64_t barriers;
+};
+
+#define BARRIER_NULL {-EBADF, -EBADF, {-EBADF, -EBADF}, 0}
+
+int barrier_create(Barrier *obj);
+Barrier* barrier_destroy(Barrier *b);
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(Barrier*, barrier_destroy);
+
+void barrier_set_role(Barrier *b, unsigned role);
+
+bool barrier_place(Barrier *b);
+bool barrier_abort(Barrier *b);
+
+bool barrier_wait_next(Barrier *b);
+bool barrier_wait_abortion(Barrier *b);
+bool barrier_sync_next(Barrier *b);
+bool barrier_sync(Barrier *b);
+
+static inline bool barrier_i_aborted(Barrier *b) {
+        return IN_SET(b->barriers, BARRIER_I_ABORTED, BARRIER_WE_ABORTED);
+}
+
+static inline bool barrier_they_aborted(Barrier *b) {
+        return IN_SET(b->barriers, BARRIER_THEY_ABORTED, BARRIER_WE_ABORTED);
+}
+
+static inline bool barrier_we_aborted(Barrier *b) {
+        return b->barriers == BARRIER_WE_ABORTED;
+}
+
+static inline bool barrier_is_aborted(Barrier *b) {
+        return IN_SET(b->barriers,
+                      BARRIER_I_ABORTED, BARRIER_THEY_ABORTED, BARRIER_WE_ABORTED);
+}
+
+static inline bool barrier_place_and_sync(Barrier *b) {
+        (void) barrier_place(b);
+        return barrier_sync(b);
+}