diff options
Diffstat (limited to 'vendor/time/src/format_description/well_known/iso8601/adt_hack.rs')
-rw-r--r-- | vendor/time/src/format_description/well_known/iso8601/adt_hack.rs | 249 |
1 files changed, 249 insertions, 0 deletions
diff --git a/vendor/time/src/format_description/well_known/iso8601/adt_hack.rs b/vendor/time/src/format_description/well_known/iso8601/adt_hack.rs new file mode 100644 index 000000000..757a68b18 --- /dev/null +++ b/vendor/time/src/format_description/well_known/iso8601/adt_hack.rs @@ -0,0 +1,249 @@ +//! Hackery to work around not being able to use ADTs in const generics on stable. + +use core::num::NonZeroU8; + +#[cfg(feature = "formatting")] +use super::Iso8601; +use super::{Config, DateKind, FormattedComponents as FC, OffsetPrecision, TimePrecision}; + +// This provides a way to include `EncodedConfig` in documentation without displaying the type it is +// aliased to. +#[doc(hidden)] +pub type DoNotRelyOnWhatThisIs = u128; + +/// An encoded [`Config`] that can be used as a const parameter to [`Iso8601`]. +/// +/// The type this is aliased to must not be relied upon. It can change in any release without +/// notice. +pub type EncodedConfig = DoNotRelyOnWhatThisIs; + +#[cfg(feature = "formatting")] +impl<const CONFIG: EncodedConfig> Iso8601<CONFIG> { + /// The user-provided configuration for the ISO 8601 format. + const CONFIG: Config = Config::decode(CONFIG); + /// Whether the date should be formatted. + pub(crate) const FORMAT_DATE: bool = matches!( + Self::CONFIG.formatted_components, + FC::Date | FC::DateTime | FC::DateTimeOffset + ); + /// Whether the time should be formatted. + pub(crate) const FORMAT_TIME: bool = matches!( + Self::CONFIG.formatted_components, + FC::Time | FC::DateTime | FC::DateTimeOffset | FC::TimeOffset + ); + /// Whether the UTC offset should be formatted. + pub(crate) const FORMAT_OFFSET: bool = matches!( + Self::CONFIG.formatted_components, + FC::Offset | FC::DateTimeOffset | FC::TimeOffset + ); + /// Whether the year is six digits. + pub(crate) const YEAR_IS_SIX_DIGITS: bool = Self::CONFIG.year_is_six_digits; + /// Whether the format contains separators (such as `-` or `:`). + pub(crate) const USE_SEPARATORS: bool = Self::CONFIG.use_separators; + /// Which format to use for the date. + pub(crate) const DATE_KIND: DateKind = Self::CONFIG.date_kind; + /// The precision and number of decimal digits to use for the time. + pub(crate) const TIME_PRECISION: TimePrecision = Self::CONFIG.time_precision; + /// The precision for the UTC offset. + pub(crate) const OFFSET_PRECISION: OffsetPrecision = Self::CONFIG.offset_precision; +} + +impl Config { + /// Encode the configuration, permitting it to be used as a const parameter of [`Iso8601`]. + /// + /// The value returned by this method must only be used as a const parameter to [`Iso8601`]. Any + /// other usage is unspecified behavior. + pub const fn encode(&self) -> EncodedConfig { + let mut bytes = [0; EncodedConfig::BITS as usize / 8]; + + bytes[0] = match self.formatted_components { + FC::None => 0, + FC::Date => 1, + FC::Time => 2, + FC::Offset => 3, + FC::DateTime => 4, + FC::DateTimeOffset => 5, + FC::TimeOffset => 6, + }; + bytes[1] = self.use_separators as _; + bytes[2] = self.year_is_six_digits as _; + bytes[3] = match self.date_kind { + DateKind::Calendar => 0, + DateKind::Week => 1, + DateKind::Ordinal => 2, + }; + bytes[4] = match self.time_precision { + TimePrecision::Hour { .. } => 0, + TimePrecision::Minute { .. } => 1, + TimePrecision::Second { .. } => 2, + }; + bytes[5] = match self.time_precision { + TimePrecision::Hour { decimal_digits } + | TimePrecision::Minute { decimal_digits } + | TimePrecision::Second { decimal_digits } => match decimal_digits { + None => 0, + Some(decimal_digits) => decimal_digits.get(), + }, + }; + bytes[6] = match self.offset_precision { + OffsetPrecision::Hour => 0, + OffsetPrecision::Minute => 1, + }; + + EncodedConfig::from_be_bytes(bytes) + } + + /// Decode the configuration. The configuration must have been generated from + /// [`Config::encode`]. + pub(super) const fn decode(encoded: EncodedConfig) -> Self { + let bytes = encoded.to_be_bytes(); + + let formatted_components = match bytes[0] { + 0 => FC::None, + 1 => FC::Date, + 2 => FC::Time, + 3 => FC::Offset, + 4 => FC::DateTime, + 5 => FC::DateTimeOffset, + 6 => FC::TimeOffset, + _ => panic!("invalid configuration"), + }; + let use_separators = match bytes[1] { + 0 => false, + 1 => true, + _ => panic!("invalid configuration"), + }; + let year_is_six_digits = match bytes[2] { + 0 => false, + 1 => true, + _ => panic!("invalid configuration"), + }; + let date_kind = match bytes[3] { + 0 => DateKind::Calendar, + 1 => DateKind::Week, + 2 => DateKind::Ordinal, + _ => panic!("invalid configuration"), + }; + let time_precision = match bytes[4] { + 0 => TimePrecision::Hour { + decimal_digits: NonZeroU8::new(bytes[5]), + }, + 1 => TimePrecision::Minute { + decimal_digits: NonZeroU8::new(bytes[5]), + }, + 2 => TimePrecision::Second { + decimal_digits: NonZeroU8::new(bytes[5]), + }, + _ => panic!("invalid configuration"), + }; + let offset_precision = match bytes[6] { + 0 => OffsetPrecision::Hour, + 1 => OffsetPrecision::Minute, + _ => panic!("invalid configuration"), + }; + + // No `for` loops in `const fn`. + let mut idx = 7; // first unused byte + while idx < EncodedConfig::BITS as usize / 8 { + assert!(bytes[idx] == 0, "invalid configuration"); + idx += 1; + } + + Self { + formatted_components, + use_separators, + year_is_six_digits, + date_kind, + time_precision, + offset_precision, + } + } +} + +#[cfg(test)] +mod tests { + use super::*; + + macro_rules! eq { + ($a:expr, $b:expr) => {{ + let a = $a; + let b = $b; + a.formatted_components == b.formatted_components + && a.use_separators == b.use_separators + && a.year_is_six_digits == b.year_is_six_digits + && a.date_kind == b.date_kind + && a.time_precision == b.time_precision + && a.offset_precision == b.offset_precision + }}; + } + + #[test] + fn encoding_roundtrip() { + macro_rules! assert_roundtrip { + ($config:expr) => { + let config = $config; + let encoded = config.encode(); + let decoded = Config::decode(encoded); + assert!(eq!(config, decoded)); + }; + } + + assert_roundtrip!(Config::DEFAULT); + assert_roundtrip!(Config::DEFAULT.set_formatted_components(FC::None)); + assert_roundtrip!(Config::DEFAULT.set_formatted_components(FC::Date)); + assert_roundtrip!(Config::DEFAULT.set_formatted_components(FC::Time)); + assert_roundtrip!(Config::DEFAULT.set_formatted_components(FC::Offset)); + assert_roundtrip!(Config::DEFAULT.set_formatted_components(FC::DateTime)); + assert_roundtrip!(Config::DEFAULT.set_formatted_components(FC::DateTimeOffset)); + assert_roundtrip!(Config::DEFAULT.set_formatted_components(FC::TimeOffset)); + assert_roundtrip!(Config::DEFAULT.set_use_separators(false)); + assert_roundtrip!(Config::DEFAULT.set_use_separators(true)); + assert_roundtrip!(Config::DEFAULT.set_year_is_six_digits(false)); + assert_roundtrip!(Config::DEFAULT.set_year_is_six_digits(true)); + assert_roundtrip!(Config::DEFAULT.set_date_kind(DateKind::Calendar)); + assert_roundtrip!(Config::DEFAULT.set_date_kind(DateKind::Week)); + assert_roundtrip!(Config::DEFAULT.set_date_kind(DateKind::Ordinal)); + assert_roundtrip!(Config::DEFAULT.set_time_precision(TimePrecision::Hour { + decimal_digits: None, + })); + assert_roundtrip!(Config::DEFAULT.set_time_precision(TimePrecision::Minute { + decimal_digits: None, + })); + assert_roundtrip!(Config::DEFAULT.set_time_precision(TimePrecision::Second { + decimal_digits: None, + })); + assert_roundtrip!(Config::DEFAULT.set_time_precision(TimePrecision::Hour { + decimal_digits: NonZeroU8::new(1), + })); + assert_roundtrip!(Config::DEFAULT.set_time_precision(TimePrecision::Minute { + decimal_digits: NonZeroU8::new(1), + })); + assert_roundtrip!(Config::DEFAULT.set_time_precision(TimePrecision::Second { + decimal_digits: NonZeroU8::new(1), + })); + assert_roundtrip!(Config::DEFAULT.set_offset_precision(OffsetPrecision::Hour)); + assert_roundtrip!(Config::DEFAULT.set_offset_precision(OffsetPrecision::Minute)); + } + + macro_rules! assert_decode_fail { + ($encoding:expr) => { + assert!( + std::panic::catch_unwind(|| { + Config::decode($encoding); + }) + .is_err() + ); + }; + } + + #[test] + fn decode_fail() { + assert_decode_fail!(0x07_00_00_00_00_00_00_00_00_00_00_00_00_00_00_00); + assert_decode_fail!(0x00_02_00_00_00_00_00_00_00_00_00_00_00_00_00_00); + assert_decode_fail!(0x00_00_02_00_00_00_00_00_00_00_00_00_00_00_00_00); + assert_decode_fail!(0x00_00_00_03_00_00_00_00_00_00_00_00_00_00_00_00); + assert_decode_fail!(0x00_00_00_00_03_00_00_00_00_00_00_00_00_00_00_00); + assert_decode_fail!(0x00_00_00_00_00_00_02_00_00_00_00_00_00_00_00_00); + assert_decode_fail!(0x00_00_00_00_00_00_00_01_00_00_00_00_00_00_00_00); + } +} |