1 files changed, 85 insertions, 0 deletions
diff --git a/lib/isc/astack.c b/lib/isc/astack.c
new file mode 100644
index 0000000..484ef26
--- /dev/null
+++ b/lib/isc/astack.c
@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+#include <inttypes.h>
+#include <string.h>
+
+#include <isc/astack.h>
+#include <isc/atomic.h>
+#include <isc/mem.h>
+#include <isc/mutex.h>
+#include <isc/types.h>
+#include <isc/util.h>
+
+struct isc_astack {
+	isc_mem_t *mctx;
+	size_t size;
+	size_t pos;
+	isc_mutex_t lock;
+	uintptr_t nodes[];
+};
+
+isc_astack_t *
+isc_astack_new(isc_mem_t *mctx, size_t size) {
+	isc_astack_t *stack = isc_mem_get(
+		mctx, sizeof(isc_astack_t) + size * sizeof(uintptr_t));
+
+	*stack = (isc_astack_t){
+		.size = size,
+	};
+	isc_mem_attach(mctx, &stack->mctx);
+	memset(stack->nodes, 0, size * sizeof(uintptr_t));
+	isc_mutex_init(&stack->lock);
+	return (stack);
+}
+
+bool
+isc_astack_trypush(isc_astack_t *stack, void *obj) {
+	if (!isc_mutex_trylock(&stack->lock)) {
+		if (stack->pos >= stack->size) {
+			UNLOCK(&stack->lock);
+			return (false);
+		}
+		stack->nodes[stack->pos++] = (uintptr_t)obj;
+		UNLOCK(&stack->lock);
+		return (true);
+	} else {
+		return (false);
+	}
+}
+
+void *
+isc_astack_pop(isc_astack_t *stack) {
+	LOCK(&stack->lock);
+	uintptr_t rv;
+	if (stack->pos == 0) {
+		rv = 0;
+	} else {
+		rv = stack->nodes[--stack->pos];
+	}
+	UNLOCK(&stack->lock);
+	return ((void *)rv);
+}
+
+void
+isc_astack_destroy(isc_astack_t *stack) {
+	LOCK(&stack->lock);
+	REQUIRE(stack->pos == 0);
+	UNLOCK(&stack->lock);
+
+	isc_mutex_destroy(&stack->lock);
+
+	isc_mem_putanddetach(&stack->mctx, stack,
+			     sizeof(struct isc_astack) +
+				     stack->size * sizeof(uintptr_t));
+}