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+/* Copyright (C) 2023 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 <inttypes.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <time.h>
+
+#ifdef __APPLE__
+ #define st_mtim st_mtimespec
+#endif
+
+/*!
+ * \brief Specify output format for knot_time_print().
+ */
+typedef enum {
+ TIME_PRINT_UNIX, // numeric UNIX time
+ TIME_PRINT_ISO8601, // 2016-12-31T23:59:00
+ TIME_PRINT_RELSEC, // relative +6523
+ TIME_PRINT_HUMAN_MIXED, // relative with mixed-case units
+ TIME_PRINT_HUMAN_LOWER, // relative with lower-case units
+} knot_time_print_t;
+
+/*!
+ * \brief Get current time.
+ */
+struct timespec time_now(void);
+
+/*!
+ * \brief Get time elapsed between two events.
+ */
+struct timespec time_diff(const struct timespec *begin, const struct timespec *end);
+
+/*!
+ * \brief Get time elapsed between two events in milliseconds.
+ */
+double time_diff_ms(const struct timespec *begin, const struct timespec *end);
+
+/*!
+ * \brief Data type for keeping UNIX timestamps.
+ *
+ * This is because time_t can be 32-bit on some systems, which is bad.
+ * Zero value represents infinity.
+ */
+typedef uint64_t knot_time_t;
+
+/*!
+ * \brief Data type for keeping time differences.
+ */
+typedef int64_t knot_timediff_t;
+
+#define KNOT_TIMEDIFF_MIN INT64_MIN
+#define KNOT_TIMEDIFF_MAX INT64_MAX
+
+#define KNOT_TIME_PRINTF PRIu64
+#define KNOT_TIMEDIFF_PRINTF PRId64
+
+/*!
+ * \brief Returns current time sice epoch.
+ */
+inline static knot_time_t knot_time(void)
+{
+ return (knot_time_t)time(NULL);
+}
+
+/*!
+ * \brief Compare two timestamps.
+ *
+ * \return 0 if equal, -1 if the former is smaller (=earlier), 1 else.
+ */
+inline static int knot_time_cmp(knot_time_t a, knot_time_t b)
+{
+ return (a == b ? 0 : 1) * ((a && b) == 0 ? -1 : 1) * (a < b ? -1 : 1);
+}
+
+/*!
+ * \brief Return the smaller (=earlier) from given two timestamps.
+ */
+inline static knot_time_t knot_time_min(knot_time_t a, knot_time_t b)
+{
+ if ((a && b) == 0) {
+ return a + b;
+ } else {
+ return (a < b ? a : b);
+ }
+}
+
+/*!
+ * \brief Return the difference between two timestamps (to "minus" from).
+ *
+ * \note If both are zero (=infinity), KNOT_TIMEDIFF_MAX is returned.
+ */
+inline static knot_timediff_t knot_time_diff(knot_time_t to, knot_time_t from)
+{
+ if ((to && from) == 0) {
+ return (to > from ? KNOT_TIMEDIFF_MIN : KNOT_TIMEDIFF_MAX);
+ } else {
+ return (knot_timediff_t)to - (knot_timediff_t)from;
+ }
+}
+
+/*!
+ * \brief Add a time difference to timestamp.
+ */
+inline static knot_time_t knot_time_add(knot_time_t since, knot_timediff_t howlong)
+{
+ return (since != 0 ? since + howlong : since);
+}
+
+inline static knot_time_t knot_time_plus(knot_time_t a, knot_time_t b)
+{
+ return ((a && b) ? a + b : 0);
+}
+
+/*!
+ * \brief Convert uint32_t-encoded timestamp to knot_time_t.
+ *
+ * In RRSIG rdata, there are inception and expiration timestamps in uint32_t format.
+ * One shall use 'serial arithmetics' to decode them.
+ *
+ * The result of this function is a timestamp that equals to
+ * given 32-bit time in lower 32 bits, and does not differ from
+ * now by more than 2^31.
+ */
+inline static knot_time_t knot_time_from_u32(uint32_t u32time, knot_time_t now)
+{
+ if (now == 0) {
+ now = knot_time();
+ }
+
+ uint32_t now_lower32 = (uint32_t)now;
+ uint64_t now_upper32 = now >> 32;
+ if (now_lower32 > u32time && now_lower32 - u32time > INT32_MAX) {
+ now_upper32++;
+ } else if (now_lower32 < u32time && u32time - now_lower32 > INT32_MAX) {
+ now_upper32--;
+ }
+
+ return (now_upper32 << 32) + u32time;
+}
+
+/*!
+ * \brief Parse a text-formatted timestamp to knot_time_t using format specification.
+ *
+ * \param format The timestamp text format specification.
+ * \param timespec Text-formatted timestamp.
+ * \param time The parsed timestamp.
+ *
+ * The format specification basics:
+ * <format 1>|<format 2> - The pipe sign separates two time format specifications. Leftmost
+ * specification matching the timespec is used.
+ * '<a string>' - Matches exactly <a string> (not containing apostrophes) in timespec.
+ * # - Hashtag matches for a number in timespec, stands for either a UNIX timestamp,
+ * or, within a context of an unit, as a number of such units.
+ * Y, M, D, h, m, s - Matches a number, stands for a number of years, months, days, hours,
+ * minutes and seconds, respectively.
+ * +, - - The + and - signs declaring that following timespec is relative to "now".
+ * A single sign can be used to limit the timestamp being in future or in past,
+ * or both +- allow the timestamp to select any (just one) of them.
+ * U - Matches one of Y, M, D, h, m, s in the timespec standing for a time unit.
+ * u - Like U, but the unit in the timestamp is from: y, mo, d, h, mi, s.
+ *
+ * \retval -1 An error occurred, out_time has no sense.
+ * \return 0 OK, timestamp parsed successfully.
+ */
+int knot_time_parse(const char *format, const char *timespec, knot_time_t *time);
+
+/*!
+ * \brief Print the timestamp in specified format into a string buffer.
+ *
+ * \param format The timestamp text format specification.
+ * \param time The timestamp to be printed.
+ * \param dst The destination buffer pointer with text-formatted timestamp.
+ * \param dst_len The destination buffer length.
+ *
+ * \retval -1 An error occurred, the buffer may be filled with nonsense.
+ * \return 0 OK, timestamp printed successfully.
+ */
+int knot_time_print(knot_time_print_t format, knot_time_t time, char *dst, size_t dst_len);
+
+/*!
+ * \brief Print the timestamp in a predefined human format.
+ *
+ * Condensed format (zone file compatible): 1w2d3h4m5s
+ * Normal format: 1 week 2 days 3 hours 4 minutes 5 seconds
+ *
+ * \param time The timestamp to be printed.
+ * \param dst The destination buffer pointer with text-formatted timestamp.
+ * \param dst_len The destination buffer length.
+ * \param condensed Condensed format indication.
+ *
+ * \retval -1 An error occurred, the buffer may be filled with nonsense.
+ * \return >0 OK, timestamp printed successfully.
+ */
+int knot_time_print_human(knot_time_t time, char *dst, size_t dst_len, bool condensed);