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Optimise the Japanese calendar #7323

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d1ad434
optimize era storage
robertbastian Dec 16, 2025
2d248bb
era indices
robertbastian Dec 16, 2025
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10 changes: 5 additions & 5 deletions components/calendar/src/any_calendar.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1612,14 +1612,14 @@ mod tests {
fn japanese() {
let japanese = AnyCalendar::new(AnyCalendarKind::Japanese);
let japanese = Ref(&japanese);
single_test_roundtrip(japanese, Some(("reiwa", None)), 3, Month::new(3), 1);
single_test_roundtrip(japanese, Some(("heisei", None)), 6, Month::new(12), 1);
single_test_roundtrip(japanese, Some(("meiji", None)), 10, Month::new(3), 1);
single_test_roundtrip(japanese, Some(("ce", None)), 1000, Month::new(3), 1);
single_test_roundtrip(japanese, Some(("reiwa", Some(6))), 3, Month::new(3), 1);
single_test_roundtrip(japanese, Some(("heisei", Some(5))), 6, Month::new(12), 1);
single_test_roundtrip(japanese, Some(("meiji", Some(2))), 10, Month::new(3), 1);
single_test_roundtrip(japanese, Some(("ce", Some(1))), 1000, Month::new(3), 1);
single_test_roundtrip(japanese, None, 1000, Month::new(3), 1);
single_test_roundtrip(japanese, None, -100, Month::new(3), 1);
single_test_roundtrip(japanese, None, 2024, Month::new(3), 1);
single_test_roundtrip(japanese, Some(("bce", None)), 10, Month::new(3), 1);
single_test_roundtrip(japanese, Some(("bce", Some(0))), 10, Month::new(3), 1);
// Since #6910, the era range is not enforced in try_from_codes
/*
single_test_error(
Expand Down
223 changes: 106 additions & 117 deletions components/calendar/src/cal/japanese.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,10 +8,12 @@ use crate::cal::abstract_gregorian::{
use crate::cal::gregorian::CeBce;
use crate::calendar_arithmetic::ArithmeticDate;
use crate::error::{DateError, UnknownEraError};
use crate::provider::{CalendarJapaneseExtendedV1, CalendarJapaneseModernV1, EraStartDate};
use crate::provider::{
CalendarJapaneseExtendedV1, CalendarJapaneseModernV1, EraStartDate, PackedEra,
};
use crate::{types, AsCalendar, Date};
use icu_provider::prelude::*;
use tinystr::tinystr;
use tinystr::{tinystr, TinyAsciiStr};

/// The [Japanese Calendar] (with modern eras only)
///
Expand Down Expand Up @@ -39,9 +41,17 @@ use tinystr::tinystr;
///
/// These eras are loaded from data, requiring a data provider capable of providing [`CalendarJapaneseModernV1`]
/// data.
#[derive(Clone, Debug, Default)]
#[derive(Clone, Debug, Copy)]
pub struct Japanese {
eras: DataPayload<CalendarJapaneseModernV1>,
last_era: PackedEra,
}

impl Default for Japanese {
fn default() -> Self {
Self {
last_era: PackedEra::pack(REIWA),
}
}
}

/// The [Japanese Calendar] (with historical eras)
Expand Down Expand Up @@ -86,9 +96,7 @@ impl Japanese {
#[cfg(feature = "compiled_data")]
pub const fn new() -> Self {
Self {
eras: DataPayload::from_static_ref(
crate::provider::Baked::SINGLETON_CALENDAR_JAPANESE_MODERN_V1,
),
last_era: *crate::provider::Baked::SINGLETON_CALENDAR_JAPANESE_MODERN_V1,
}
}

Expand All @@ -105,7 +113,7 @@ impl Japanese {
provider: &D,
) -> Result<Self, DataError> {
Ok(Self {
eras: provider.load(Default::default())?.payload,
last_era: *provider.load(Default::default())?.payload.get(),
})
}
}
Expand Down Expand Up @@ -143,31 +151,46 @@ impl JapaneseExtended {
}
}

const MEIJI_START: EraStartDate = EraStartDate {
year: 1868,
month: 10,
day: 23,
};
const TAISHO_START: EraStartDate = EraStartDate {
year: 1912,
month: 7,
day: 30,
};
const SHOWA_START: EraStartDate = EraStartDate {
year: 1926,
month: 12,
day: 25,
};
const HEISEI_START: EraStartDate = EraStartDate {
year: 1989,
month: 1,
day: 8,
};
const REIWA_START: EraStartDate = EraStartDate {
year: 2019,
month: 5,
day: 1,
};
const MEIJI: (EraStartDate, TinyAsciiStr<16>) = (
EraStartDate {
year: 1868,
month: 10,
day: 23,
},
tinystr!(16, "meiji"),
);
const TAISHO: (EraStartDate, TinyAsciiStr<16>) = (
EraStartDate {
year: 1912,
month: 7,
day: 30,
},
tinystr!(16, "taisho"),
);
const SHOWA: (EraStartDate, TinyAsciiStr<16>) = (
EraStartDate {
year: 1926,
month: 12,
day: 25,
},
tinystr!(16, "showa"),
);
const HEISEI: (EraStartDate, TinyAsciiStr<16>) = (
EraStartDate {
year: 1989,
month: 1,
day: 8,
},
tinystr!(16, "heisei"),
);
pub(crate) const REIWA: (EraStartDate, TinyAsciiStr<16>) = (
EraStartDate {
year: 2019,
month: 5,
day: 1,
},
tinystr!(16, "reiwa"),
);

impl GregorianYears for &'_ Japanese {
fn extended_from_era_year(
Expand All @@ -178,80 +201,39 @@ impl GregorianYears for &'_ Japanese {
if let Ok(g) = CeBce.extended_from_era_year(era, year) {
return Ok(g);
}
let Some(era) = era else {
// unreachable, handled by CeBce
return Err(UnknownEraError);
};

// Avoid linear search by trying well known eras
if era == b"reiwa" {
return Ok(year - 1 + REIWA_START.year);
} else if era == b"heisei" {
return Ok(year - 1 + HEISEI_START.year);
} else if era == b"showa" {
return Ok(year - 1 + SHOWA_START.year);
} else if era == b"taisho" {
return Ok(year - 1 + TAISHO_START.year);
} else if era == b"meiji" {
return Ok(year - 1 + MEIJI_START.year);
}

let era_start = self
.eras
.get()
.dates_to_eras
.iter()
.rev()
.find_map(|(s, e)| (e.as_bytes() == era).then_some(s))
let (start, _) = [self.last_era.unpack(), REIWA, HEISEI, SHOWA, TAISHO, MEIJI]
.into_iter()
.find(|(_, name)| era == Some(name.as_bytes()))
.ok_or(UnknownEraError)?;
Ok(era_start.year + year - 1)

Ok(year - 1 + start.year)
}

fn era_year_from_extended(&self, year: i32, month: u8, day: u8) -> types::EraYear {
let date: EraStartDate = EraStartDate { year, month, day };

let (start, era) = if date >= MEIJI_START
&& self
.eras
.get()
.dates_to_eras
.last()
.is_some_and(|(_, e)| e == tinystr!(16, "reiwa"))
if let Some((idx, (start, era))) = [
(7, self.last_era.unpack()),
(6, REIWA),
(5, HEISEI),
(4, SHOWA),
(3, TAISHO),
(2, MEIJI),
]
.into_iter()
.skip((self.last_era == const { PackedEra::pack(REIWA) }) as usize)
.find(|&(_, (start, _))| date >= start)
{
// We optimize for the five "modern" post-Meiji eras, which are stored in a smaller
// array and also hardcoded. The hardcoded version is not used if data indicates the
// presence of newer eras.
if date >= REIWA_START {
(REIWA_START, tinystr!(16, "reiwa"))
} else if date >= HEISEI_START {
(HEISEI_START, tinystr!(16, "heisei"))
} else if date >= SHOWA_START {
(SHOWA_START, tinystr!(16, "showa"))
} else if date >= TAISHO_START {
(TAISHO_START, tinystr!(16, "taisho"))
} else {
(MEIJI_START, tinystr!(16, "meiji"))
types::EraYear {
era,
era_index: Some(idx),
year: year - start.year + 1,
extended_year: year,
ambiguity: types::YearAmbiguity::CenturyRequired,
}
} else {
let data = &self.eras.get().dates_to_eras;
match data.iter().rfind(|&(s, _)| date >= s) {
None => {
return types::EraYear {
// TODO: return era indices?
era_index: None,
..CeBce.era_year_from_extended(year, month, day)
};
}
Some((s, e)) => (s, e),
}
};

types::EraYear {
era,
era_index: None,
year: year - start.year + 1,
extended_year: year,
ambiguity: types::YearAmbiguity::CenturyRequired,
CeBce.era_year_from_extended(year, month, day)
}
}

Expand Down Expand Up @@ -281,16 +263,16 @@ impl GregorianYears for &'_ JapaneseExtended {
};

// Avoid linear search by trying well known eras
if era == b"reiwa" {
return Ok(year - 1 + REIWA_START.year);
} else if era == b"heisei" {
return Ok(year - 1 + HEISEI_START.year);
} else if era == b"showa" {
return Ok(year - 1 + SHOWA_START.year);
} else if era == b"taisho" {
return Ok(year - 1 + TAISHO_START.year);
} else if era == b"meiji" {
return Ok(year - 1 + MEIJI_START.year);
if era == REIWA.1.as_bytes() {
return Ok(year - 1 + REIWA.0.year);
} else if era == HEISEI.1.as_bytes() {
return Ok(year - 1 + HEISEI.0.year);
} else if era == SHOWA.1.as_bytes() {
return Ok(year - 1 + SHOWA.0.year);
} else if era == TAISHO.1.as_bytes() {
return Ok(year - 1 + TAISHO.0.year);
} else if era == MEIJI.1.as_bytes() {
return Ok(year - 1 + MEIJI.0.year);
}

let data = &self.eras.get().dates_to_eras;
Expand Down Expand Up @@ -324,7 +306,7 @@ impl GregorianYears for &'_ JapaneseExtended {
fn era_year_from_extended(&self, year: i32, month: u8, day: u8) -> types::EraYear {
let date: EraStartDate = EraStartDate { year, month, day };

let (start, era) = if date >= MEIJI_START
let (start, era) = if date >= MEIJI.0
&& self
.eras
.get()
Expand All @@ -335,16 +317,16 @@ impl GregorianYears for &'_ JapaneseExtended {
// We optimize for the five "modern" post-Meiji eras, which are stored in a smaller
// array and also hardcoded. The hardcoded version is not used if data indicates the
// presence of newer eras.
if date >= REIWA_START {
(REIWA_START, tinystr!(16, "reiwa"))
} else if date >= HEISEI_START {
(HEISEI_START, tinystr!(16, "heisei"))
} else if date >= SHOWA_START {
(SHOWA_START, tinystr!(16, "showa"))
} else if date >= TAISHO_START {
(TAISHO_START, tinystr!(16, "taisho"))
if date >= REIWA.0 {
REIWA
} else if date >= HEISEI.0 {
HEISEI
} else if date >= SHOWA.0 {
SHOWA
} else if date >= TAISHO.0 {
TAISHO
} else {
(MEIJI_START, tinystr!(16, "meiji"))
MEIJI
}
} else {
let data = &self.eras.get().dates_to_eras;
Expand Down Expand Up @@ -616,6 +598,13 @@ mod tests {
)
}

#[test]
#[ignore]
fn sizes() {
assert_eq!(core::mem::size_of::<Japanese>(), 11);
assert_eq!(core::mem::size_of::<JapaneseExtended>(), 32);
}

#[test]
fn test_japanese() {
let calendar = Japanese::new();
Expand Down
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