1 files changed, 76 insertions, 0 deletions
diff --git a/src/knot/zone/serial.h b/src/knot/zone/serial.h
new file mode 100644
index 0000000..effb1c6
--- /dev/null
+++ b/src/knot/zone/serial.h
@@ -0,0 +1,76 @@
+/*  Copyright (C) 2022 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#define SERIAL_MAX_INCREMENT 2147483647
+
+/*!
+ * \brief result of serial comparison. LOWER means that the first serial is lower that the second.
+ *
+ * Example: (serial_compare(a, b) & SERIAL_MASK_LEQ) means "a <= b".
+ */
+typedef enum {
+	SERIAL_INCOMPARABLE = 0x0,
+	SERIAL_LOWER = 0x1,
+	SERIAL_GREATER = 0x2,
+	SERIAL_EQUAL = 0x3,
+	SERIAL_MASK_LEQ = SERIAL_LOWER,
+	SERIAL_MASK_GEQ = SERIAL_GREATER,
+} serial_cmp_result_t;
+
+/*!
+ * \brief Compares two zone serials.
+ */
+serial_cmp_result_t serial_compare(uint32_t s1, uint32_t s2);
+
+inline static bool serial_equal(uint32_t a, uint32_t b)
+{
+	return serial_compare(a, b) == SERIAL_EQUAL;
+}
+
+/*!
+ * \brief Get (next) serial for given serial update policy.
+ *
+ * \param current  Current SOA serial.
+ * \param policy   SERIAL_POLICY_INCREMENT, SERIAL_POLICY_UNIXTIME or
+ *                 SERIAL_POLICY_DATESERIAL.
+ * \param must_increment The minimum difference to the current value.
+ *                 0 only ensures policy; 1 also increments.
+ *
+ * \return New serial.
+ */
+uint32_t serial_next(uint32_t current, int policy, uint32_t must_increment);
+
+typedef struct {
+	uint32_t serial;
+	bool valid;
+} kserial_t;
+
+/*!
+ * \brief Compares two kserials.
+ *
+ * If any of them is invalid, they are INCOMPARABLE.
+ */
+serial_cmp_result_t kserial_cmp(kserial_t a, kserial_t b);
+
+inline static bool kserial_equal(kserial_t a, kserial_t b)
+{
+	return kserial_cmp(a, b) == SERIAL_EQUAL;
+}