Add 'corebinutils/date/' from commit 'ae4c58645a13317bb8540d47f8f7cfa768f17eb2'

git-subtree-dir: corebinutils/date
git-subtree-mainline: d12e80797cf0ae7a0bd3cd0cd7948f532f3181ac
git-subtree-split: ae4c58645a13317bb8540d47f8f7cfa768f17eb2

1 files changed, 560 insertions, 0 deletions

diff --git a/corebinutils/date/vary.c b/corebinutils/date/vary.c
new file mode 100644
index 0000000000..65440f5f64
--- /dev/null
+++ b/corebinutils/date/vary.c
@@ -0,0 +1,560 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 1997 Brian Somers <brian@Awfulhak.org>
+ * All rights reserved.
+ *
+ * Copyright (c) 2026
+ *	Project Tick. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 <ctype.h>
+#include <err.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <time.h>
+
+#include "vary.h"
+
+struct trans {
+	int64_t value;
+	const char *name;
+};
+
+static const struct trans trans_mon[] = {
+	{ 1, "january" }, { 2, "february" }, { 3, "march" }, { 4, "april" },
+	{ 5, "may" }, { 6, "june" }, { 7, "july" }, { 8, "august" },
+	{ 9, "september" }, { 10, "october" }, { 11, "november" },
+	{ 12, "december" }, { -1, NULL }
+};
+
+static const struct trans trans_wday[] = {
+	{ 0, "sunday" }, { 1, "monday" }, { 2, "tuesday" }, { 3, "wednesday" },
+	{ 4, "thursday" }, { 5, "friday" }, { 6, "saturday" }, { -1, NULL }
+};
+
+static int mdays[12] = { 31, 0, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+
+static int adjyear(struct tm *tm, char type, int64_t value, bool normalize);
+static int adjmon(struct tm *tm, char type, int64_t value, bool is_text,
+    bool normalize);
+static int adjday(struct tm *tm, char type, int64_t value, bool normalize);
+static int adjwday(struct tm *tm, char type, int64_t value, bool is_text,
+    bool normalize);
+static int adjhour(struct tm *tm, char type, int64_t value, bool normalize);
+static int adjmin(struct tm *tm, char type, int64_t value, bool normalize);
+static int adjsec(struct tm *tm, char type, int64_t value, bool normalize);
+
+static bool normalize_tm(struct tm *tm, char type);
+static int translate_token(const struct trans *table, const char *arg);
+static bool parse_decimal_component(const char *arg, size_t len, int64_t *value);
+static int daysinmonth(const struct tm *tm);
+
+static bool
+normalize_tm(struct tm *tm, char type)
+{
+	time_t converted;
+
+	tm->tm_yday = -1;
+	while ((converted = mktime(tm)) == (time_t)-1 &&
+	    tm->tm_year > 68 && tm->tm_year < 138) {
+		if (!adjhour(tm, type == '-' ? '-' : '+', 1, false))
+			return (false);
+	}
+
+	return (tm->tm_yday != -1);
+}
+
+static int
+translate_token(const struct trans *table, const char *arg)
+{
+	size_t i;
+
+	for (i = 0; table[i].value != -1; i++) {
+		if (strncasecmp(table[i].name, arg, 3) == 0 ||
+		    strcasecmp(table[i].name, arg) == 0)
+			return ((int)table[i].value);
+	}
+
+	return (-1);
+}
+
+struct vary *
+vary_append(struct vary *chain, const char *arg)
+{
+	struct vary *node;
+	struct vary **nextp;
+
+	if (chain == NULL) {
+		nextp = &chain;
+	} else {
+		nextp = &chain->next;
+		while (*nextp != NULL)
+			nextp = &(*nextp)->next;
+	}
+
+	node = malloc(sizeof(*node));
+	if (node == NULL)
+		err(1, "malloc");
+
+	node->arg = arg;
+	node->next = NULL;
+	*nextp = node;
+	return (chain);
+}
+
+static bool
+parse_decimal_component(const char *arg, size_t len, int64_t *value)
+{
+	size_t i;
+	int64_t current;
+	int digit;
+
+	if (len == 0)
+		return (false);
+
+	current = 0;
+	for (i = 0; i < len; i++) {
+		if (!isdigit((unsigned char)arg[i]))
+			return (false);
+		digit = arg[i] - '0';
+		if (current > (INT64_MAX - digit) / 10)
+			return (false);
+		current = current * 10 + digit;
+	}
+
+	*value = current;
+	return (true);
+}
+
+static int
+daysinmonth(const struct tm *tm)
+{
+	int year;
+
+	year = tm->tm_year + 1900;
+	if (tm->tm_mon == 1) {
+		if (year % 400 == 0)
+			return (29);
+		if (year % 100 == 0)
+			return (28);
+		if (year % 4 == 0)
+			return (29);
+		return (28);
+	}
+	if (tm->tm_mon >= 0 && tm->tm_mon < 12)
+		return (mdays[tm->tm_mon]);
+	return (0);
+}
+
+static int
+adjyear(struct tm *tm, char type, int64_t value, bool normalize)
+{
+	switch (type) {
+	case '+':
+		tm->tm_year += value;
+		break;
+	case '-':
+		tm->tm_year -= value;
+		break;
+	default:
+		tm->tm_year = value;
+		if (tm->tm_year < 69)
+			tm->tm_year += 100;
+		else if (tm->tm_year > 1900)
+			tm->tm_year -= 1900;
+		break;
+	}
+
+	return (!normalize || normalize_tm(tm, type));
+}
+
+static int
+adjmon(struct tm *tm, char type, int64_t value, bool is_text, bool normalize)
+{
+	int last_month_days;
+
+	if (value < 0)
+		return (0);
+
+	switch (type) {
+	case '+':
+		if (is_text) {
+			if (value <= tm->tm_mon)
+				value += 11 - tm->tm_mon;
+			else
+				value -= tm->tm_mon + 1;
+		}
+		if (value != 0) {
+			if (!adjyear(tm, '+', (tm->tm_mon + value) / 12, false))
+				return (0);
+			value %= 12;
+			tm->tm_mon += value;
+			if (tm->tm_mon > 11)
+				tm->tm_mon -= 12;
+		}
+		break;
+	case '-':
+		if (is_text) {
+			if (value - 1 > tm->tm_mon)
+				value = 13 - value + tm->tm_mon;
+			else
+				value = tm->tm_mon - value + 1;
+		}
+		if (value != 0) {
+			if (!adjyear(tm, '-', value / 12, false))
+				return (0);
+			value %= 12;
+			if (value > tm->tm_mon) {
+				if (!adjyear(tm, '-', 1, false))
+					return (0);
+				value -= 12;
+			}
+			tm->tm_mon -= value;
+		}
+		break;
+	default:
+		if (value < 1 || value > 12)
+			return (0);
+		tm->tm_mon = (int)value - 1;
+		break;
+	}
+
+	last_month_days = daysinmonth(tm);
+	if (tm->tm_mday > last_month_days)
+		tm->tm_mday = last_month_days;
+
+	return (!normalize || normalize_tm(tm, type));
+}
+
+static int
+adjday(struct tm *tm, char type, int64_t value, bool normalize)
+{
+	int last_month_days;
+
+	switch (type) {
+	case '+':
+		while (value != 0) {
+			last_month_days = daysinmonth(tm);
+			if (value > last_month_days - tm->tm_mday) {
+				value -= last_month_days - tm->tm_mday + 1;
+				tm->tm_mday = 1;
+				if (!adjmon(tm, '+', 1, false, false))
+					return (0);
+			} else {
+				tm->tm_mday += value;
+				value = 0;
+			}
+		}
+		break;
+	case '-':
+		while (value != 0) {
+			if (value >= tm->tm_mday) {
+				value -= tm->tm_mday;
+				tm->tm_mday = 1;
+				if (!adjmon(tm, '-', 1, false, false))
+					return (0);
+				tm->tm_mday = daysinmonth(tm);
+			} else {
+				tm->tm_mday -= value;
+				value = 0;
+			}
+		}
+		break;
+	default:
+		if (value > 0 && value <= daysinmonth(tm))
+			tm->tm_mday = (int)value;
+		else
+			return (0);
+		break;
+	}
+
+	return (!normalize || normalize_tm(tm, type));
+}
+
+static int
+adjwday(struct tm *tm, char type, int64_t value, bool is_text, bool normalize)
+{
+	if (value < 0)
+		return (0);
+
+	switch (type) {
+	case '+':
+		if (is_text) {
+			if (value < tm->tm_wday)
+				value = 7 - tm->tm_wday + value;
+			else
+				value -= tm->tm_wday;
+		} else {
+			value *= 7;
+		}
+		return (!value || adjday(tm, '+', value, normalize));
+	case '-':
+		if (is_text) {
+			if (value > tm->tm_wday)
+				value = 7 - value + tm->tm_wday;
+			else
+				value = tm->tm_wday - value;
+		} else {
+			value *= 7;
+		}
+		return (!value || adjday(tm, '-', value, normalize));
+	default:
+		if (value < tm->tm_wday)
+			return (adjday(tm, '-', tm->tm_wday - value, normalize));
+		if (value > 6)
+			return (0);
+		if (value > tm->tm_wday)
+			return (adjday(tm, '+', value - tm->tm_wday, normalize));
+		break;
+	}
+
+	return (1);
+}
+
+static int
+adjhour(struct tm *tm, char type, int64_t value, bool normalize)
+{
+	if (value < 0)
+		return (0);
+
+	switch (type) {
+	case '+':
+		if (value != 0) {
+			int days;
+
+			days = (int)((tm->tm_hour + value) / 24);
+			value %= 24;
+			tm->tm_hour += value;
+			tm->tm_hour %= 24;
+			if (!adjday(tm, '+', days, false))
+				return (0);
+		}
+		break;
+	case '-':
+		if (value != 0) {
+			int days;
+
+			days = (int)(value / 24);
+			value %= 24;
+			if (value > tm->tm_hour) {
+				days++;
+				value -= 24;
+			}
+			tm->tm_hour -= value;
+			if (!adjday(tm, '-', days, false))
+				return (0);
+		}
+		break;
+	default:
+		if (value > 23)
+			return (0);
+		tm->tm_hour = (int)value;
+		break;
+	}
+
+	return (!normalize || normalize_tm(tm, type));
+}
+
+static int
+adjmin(struct tm *tm, char type, int64_t value, bool normalize)
+{
+	if (value < 0)
+		return (0);
+
+	switch (type) {
+	case '+':
+		if (value != 0) {
+			if (!adjhour(tm, '+', (tm->tm_min + value) / 60, false))
+				return (0);
+			value %= 60;
+			tm->tm_min += value;
+			if (tm->tm_min > 59)
+				tm->tm_min -= 60;
+		}
+		break;
+	case '-':
+		if (value != 0) {
+			if (!adjhour(tm, '-', value / 60, false))
+				return (0);
+			value %= 60;
+			if (value > tm->tm_min) {
+				if (!adjhour(tm, '-', 1, false))
+					return (0);
+				value -= 60;
+			}
+			tm->tm_min -= value;
+		}
+		break;
+	default:
+		if (value > 59)
+			return (0);
+		tm->tm_min = (int)value;
+		break;
+	}
+
+	return (!normalize || normalize_tm(tm, type));
+}
+
+static int
+adjsec(struct tm *tm, char type, int64_t value, bool normalize)
+{
+	if (value < 0)
+		return (0);
+
+	switch (type) {
+	case '+':
+		if (value != 0) {
+			if (!adjmin(tm, '+', (tm->tm_sec + value) / 60, false))
+				return (0);
+			value %= 60;
+			tm->tm_sec += value;
+			if (tm->tm_sec > 59)
+				tm->tm_sec -= 60;
+		}
+		break;
+	case '-':
+		if (value != 0) {
+			if (!adjmin(tm, '-', value / 60, false))
+				return (0);
+			value %= 60;
+			if (value > tm->tm_sec) {
+				if (!adjmin(tm, '-', 1, false))
+					return (0);
+				value -= 60;
+			}
+			tm->tm_sec -= value;
+		}
+		break;
+	default:
+		if (value > 59)
+			return (0);
+		tm->tm_sec = (int)value;
+		break;
+	}
+
+	return (!normalize || normalize_tm(tm, type));
+}
+
+const struct vary *
+vary_apply(const struct vary *chain, struct tm *tm)
+{
+	const struct vary *node;
+
+	for (node = chain; node != NULL; node = node->next) {
+		const char *arg;
+		char type;
+		char unit;
+		int64_t value;
+		size_t len;
+		int translated;
+
+		type = node->arg[0];
+		arg = node->arg;
+		if (type == '+' || type == '-')
+			arg++;
+		else
+			type = '\0';
+
+		len = strlen(arg);
+		if (len < 2)
+			return (node);
+
+		if (type == '\0')
+			tm->tm_isdst = -1;
+
+		if (!parse_decimal_component(arg, len - 1, &value)) {
+			translated = translate_token(trans_wday, arg);
+			if (translated != -1) {
+				if (!adjwday(tm, type, translated, true, true))
+					return (node);
+				continue;
+			}
+
+			translated = translate_token(trans_mon, arg);
+			if (translated != -1) {
+				if (!adjmon(tm, type, translated, true, true))
+					return (node);
+				continue;
+			}
+
+			return (node);
+		}
+
+		unit = arg[len - 1];
+		switch (unit) {
+		case 'S':
+			if (!adjsec(tm, type, value, true))
+				return (node);
+			break;
+		case 'M':
+			if (!adjmin(tm, type, value, true))
+				return (node);
+			break;
+		case 'H':
+			if (!adjhour(tm, type, value, true))
+				return (node);
+			break;
+		case 'd':
+			tm->tm_isdst = -1;
+			if (!adjday(tm, type, value, true))
+				return (node);
+			break;
+		case 'w':
+			tm->tm_isdst = -1;
+			if (!adjwday(tm, type, value, false, true))
+				return (node);
+			break;
+		case 'm':
+			tm->tm_isdst = -1;
+			if (!adjmon(tm, type, value, false, true))
+				return (node);
+			break;
+		case 'y':
+			tm->tm_isdst = -1;
+			if (!adjyear(tm, type, value, true))
+				return (node);
+			break;
+		default:
+			return (node);
+		}
+	}
+
+	return (NULL);
+}
+
+void
+vary_destroy(struct vary *chain)
+{
+	struct vary *next;
+
+	while (chain != NULL) {
+		next = chain->next;
+		free(chain);
+		chain = next;
+	}
+}