hare

commit 0783e33c2fb5f74d1787a23aae227249a91d7e58
parent e8ac6ea44ea58db723977d9603a894aa7baf03aa
Author: Nihal Jere <nihal@nihaljere.xyz>
Date:   Sat,  7 May 2022 11:26:32 -0500

datetime: implement %U format specifier and add a test

This is stolen from musl, adjusted to deal with the way datetime
stores yeardays and weekdays.

Signed-off-by: Nihal Jere <nihal@nihaljere.xyz>

Diffstat:
M
datetime/chronology.ha
 | 
22
++++++++++++++++++++++
M
datetime/date.ha
 | 
34
++++++++++++++++++++++++++++++++++
M
datetime/datetime.ha
 | 
2
++
M
datetime/format.ha
 | 
3
+--

4 files changed, 59 insertions(+), 2 deletions(-)
diff --git a/datetime/chronology.ha b/datetime/chronology.ha
@@ -34,6 +34,9 @@ export fn isoweekyear(dt: *datetime) int = _isoweekyear(dt);
 // Returns a [[datetime]]'s Gregorian week
 export fn week(dt: *datetime) int = _week(dt);
 
+// Returns a [[datetime]]'s Gregorian week starting Sunday
+export fn week_starting_sunday(dt: *datetime) int = _week_starting_sunday(dt);
+
 // Returns a [[datetime]]'s ISO week
 export fn isoweek(dt: *datetime) int = _isoweek(dt);
 
@@ -190,6 +193,25 @@ fn _week(dt: *datetime) int = {
 	};
 };
 
+fn _week_starting_sunday(dt: *datetime) int = {
+	match (dt.week) {
+	case void =>
+		if (dt.yearday is void) {
+			_yearday(dt);
+		};
+		if (dt.weekday is void) {
+			_weekday(dt);
+		};
+		dt.weeksunday = calc_week_starting_sunday(
+			dt.yearday: int,
+			dt.weekday: int,
+		);
+		return dt.weeksunday: int;
+	case let w: int =>
+		return w;
+	};
+};
+
 fn _isoweek(dt: *datetime) int = {
 	match (dt.isoweek) {
 	case void =>
diff --git a/datetime/date.ha b/datetime/date.ha
@@ -183,6 +183,13 @@ fn calc_week(yd: int, wd: int) int = {
 	return (yd + 7 - wd) / 7;
 };
 
+// Calculates the week within a Gregorian year [0..53],
+// given a yearday and Gregorian weekday.
+// All days in a new year before the year's first Sunday belong to week 0.
+fn calc_week_starting_sunday(yd: int, wd: int) int = {
+	return (yd + 6 - (wd % 7)) / 7;
+};
+
 // Calculates the weekday, given a epochal day,
 // from Monday=1 to Sunday=7
 fn calc_weekday(e: chrono::epochal) int = {
@@ -529,6 +536,33 @@ fn calc_epochal_from_yd(y: int, yd: int) (chrono::epochal | invalid) = {
 	};
 };
 
+@test fn calc_week_starting_sunday() void = {
+	const cases = [
+		((1, 1), 0),
+		((1, 2), 0),
+		((1, 3), 0),
+		((1, 4), 0),
+		((1, 5), 0),
+		((1, 6), 0),
+		((1, 7), 1),
+		((21, 2), 3),
+		((61, 3), 9),
+		((193, 5), 27),
+		((229, 1), 33),
+		((286, 4), 41),
+		((341, 7), 49),
+		((365, 6), 52),
+		((366, 1), 53),
+	];
+
+	for (let i = 0z; i < len(cases); i += 1) {
+		const params = cases[i].0;
+		const expect = cases[i].1;
+		const actual = calc_week_starting_sunday(params.0, params.1);
+		assert(expect == actual, "week miscalculation");
+	};
+};
+
 @test fn calc_weekday() void = {
 	const cases = [
 		(-999999,  4), // -0768-02-05
diff --git a/datetime/datetime.ha b/datetime/datetime.ha
@@ -19,6 +19,7 @@ export type datetime = struct {
 	isoweekyear: (void | int),
 	isoweek:     (void | int),
 	week:        (void | int),
+	weeksunday:  (void | int),
 	weekday:     (void | int),
 
 	hour:        (void | int),
@@ -41,6 +42,7 @@ fn init() datetime = datetime {
 	isoweekyear = void,
 	isoweek     = void,
 	week        = void,
+	weeksunday  = void,
 	weekday     = void,
 
 	hour        = void,
diff --git a/datetime/format.ha b/datetime/format.ha
@@ -131,8 +131,7 @@ fn fmtout(out: io::handle, r: rune, dt: *datetime) (size | io::error) = {
 	case 'u' =>
 		return fmt::fprint(out, strconv::itos(weekday(dt)));
 	case 'U' =>
-		// return fmt::fprintf(out, "{:02}", week_starting_sunday(dt));
-		abort("datetime::format: %U: TODO"); // TODO
+		return fmt::fprintf(out, "{:02}", week_starting_sunday(dt));
 	case 'w' =>
 		return fmt::fprint(out, strconv::itos(weekday(dt) % 7));
 	case 'W' =>