1 files changed, 72 insertions, 0 deletions
diff --git a/lib/librte_sched/rte_reciprocal.c b/lib/librte_sched/rte_reciprocal.c
new file mode 100644
index 00000000..652f0237
--- /dev/null
+++ b/lib/librte_sched/rte_reciprocal.c
@@ -0,0 +1,72 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) Hannes Frederic Sowa
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * 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.
+ *     * Neither the name of Intel Corporation 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 COPYRIGHT HOLDERS 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 COPYRIGHT
+ *   OWNER 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.
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+
+#include <rte_common.h>
+
+#include "rte_reciprocal.h"
+
+/* find largest set bit.
+ * portable and slow but does not matter for this usage.
+ */
+static inline int fls(uint32_t x)
+{
+	int b;
+
+	for (b = 31; b >= 0; --b) {
+		if (x & (1u << b))
+			return b + 1;
+	}
+
+	return 0;
+}
+
+struct rte_reciprocal rte_reciprocal_value(uint32_t d)
+{
+	struct rte_reciprocal R;
+	uint64_t m;
+	int l;
+
+	l = fls(d - 1);
+	m = ((1ULL << 32) * ((1ULL << l) - d));
+	m /= d;
+
+	++m;
+	R.m = m;
+	R.sh1 = RTE_MIN(l, 1);
+	R.sh2 = RTE_MAX(l - 1, 0);
+
+	return R;
+}