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// This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
use core::cmp::Ordering;
use core::fmt;
/// A 24-bit numeric data type that is expected to be a Unicode scalar value, but is not
/// validated as such.
///
/// Use this type instead of `char` when you want to deal with data that is expected to be valid
/// Unicode scalar values, but you want control over when or if you validate that assumption.
///
/// # Examples
///
/// ```
/// use potential_utf::PotentialCodePoint;
///
/// assert_eq!(PotentialCodePoint::from_u24(0x68).try_to_char(), Ok('h'));
/// assert_eq!(PotentialCodePoint::from_char('i').try_to_char(), Ok('i'));
/// assert_eq!(
/// PotentialCodePoint::from_u24(0x1F44B).try_to_char(),
/// Ok('👋')
/// );
///
/// assert!(PotentialCodePoint::from_u24(0xDE01).try_to_char().is_err());
/// assert_eq!(
/// PotentialCodePoint::from_u24(0xDE01).to_char_lossy(),
/// char::REPLACEMENT_CHARACTER
/// );
/// ```
#[repr(transparent)]
#[allow(clippy::exhaustive_structs)] // transparent newtype
#[derive(PartialEq, Eq, Clone, Copy, Hash)]
pub struct PotentialCodePoint([u8; 3]);
impl PotentialCodePoint {
/// Create a [`PotentialCodePoint`] from a `char`.
///
/// # Examples
///
/// ```
/// use potential_utf::PotentialCodePoint;
///
/// let a = PotentialCodePoint::from_char('a');
/// assert_eq!(a.try_to_char().unwrap(), 'a');
/// ```
#[inline]
pub const fn from_char(c: char) -> Self {
let [u0, u1, u2, _u3] = (c as u32).to_le_bytes();
Self([u0, u1, u2])
}
/// Create [`PotentialCodePoint`] from a u32 value, ignoring the most significant 8 bits.
#[inline]
pub const fn from_u24(c: u32) -> Self {
let [u0, u1, u2, _u3] = c.to_le_bytes();
Self([u0, u1, u2])
}
/// Attempt to convert a [`PotentialCodePoint`] to a `char`.
///
/// # Examples
///
/// ```
/// use potential_utf::PotentialCodePoint;
/// use zerovec::ule::AsULE;
///
/// let a = PotentialCodePoint::from_char('a');
/// assert_eq!(a.try_to_char(), Ok('a'));
///
/// let b = PotentialCodePoint::from_unaligned([0xFF, 0xFF, 0xFF].into());
/// assert!(matches!(b.try_to_char(), Err(_)));
/// ```
#[inline]
pub fn try_to_char(self) -> Result<char, core::char::CharTryFromError> {
char::try_from(u32::from(self))
}
/// Convert a [`PotentialCodePoint`] to a `char', returning [`char::REPLACEMENT_CHARACTER`]
/// if the `PotentialCodePoint` does not represent a valid Unicode scalar value.
///
/// # Examples
///
/// ```
/// use potential_utf::PotentialCodePoint;
/// use zerovec::ule::AsULE;
///
/// let a = PotentialCodePoint::from_unaligned([0xFF, 0xFF, 0xFF].into());
/// assert_eq!(a.to_char_lossy(), char::REPLACEMENT_CHARACTER);
/// ```
#[inline]
pub fn to_char_lossy(self) -> char {
self.try_to_char().unwrap_or(char::REPLACEMENT_CHARACTER)
}
/// Convert a [`PotentialCodePoint`] to a `char` without checking that it is
/// a valid Unicode scalar value.
///
/// # Safety
///
/// The `PotentialCodePoint` must be a valid Unicode scalar value in little-endian order.
///
/// # Examples
///
/// ```
/// use potential_utf::PotentialCodePoint;
///
/// let a = PotentialCodePoint::from_char('a');
/// assert_eq!(unsafe { a.to_char_unchecked() }, 'a');
/// ```
#[inline]
pub unsafe fn to_char_unchecked(self) -> char {
char::from_u32_unchecked(u32::from(self))
}
/// For converting to the ULE type in a const context
///
/// Can be removed once const traits are a thing
#[inline]
#[cfg(feature = "zerovec")]
pub const fn to_unaligned(self) -> zerovec::ule::RawBytesULE<3> {
zerovec::ule::RawBytesULE(self.0)
}
}
/// This impl requires enabling the optional `zerovec` Cargo feature
#[cfg(feature = "zerovec")]
impl zerovec::ule::AsULE for PotentialCodePoint {
type ULE = zerovec::ule::RawBytesULE<3>;
#[inline]
fn to_unaligned(self) -> Self::ULE {
zerovec::ule::RawBytesULE(self.0)
}
#[inline]
fn from_unaligned(unaligned: Self::ULE) -> Self {
Self(unaligned.0)
}
}
// Safety: PotentialCodePoint is always the little-endian representation of a char,
// which corresponds to its AsULE::ULE type
/// This impl requires enabling the optional `zerovec` Cargo feature
#[cfg(feature = "zerovec")]
unsafe impl zerovec::ule::EqULE for PotentialCodePoint {}
impl fmt::Debug for PotentialCodePoint {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
// Debug as a char if possible
match self.try_to_char() {
Ok(c) => fmt::Debug::fmt(&c, f),
Err(_) => fmt::Debug::fmt(&self.0, f),
}
}
}
impl PartialOrd for PotentialCodePoint {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl Ord for PotentialCodePoint {
// custom implementation, as derived Ord would compare lexicographically
fn cmp(&self, other: &Self) -> Ordering {
let a = u32::from(*self);
let b = u32::from(*other);
a.cmp(&b)
}
}
impl From<PotentialCodePoint> for u32 {
fn from(x: PotentialCodePoint) -> Self {
let [a0, a1, a2] = x.0;
u32::from_le_bytes([a0, a1, a2, 0])
}
}
impl TryFrom<u32> for PotentialCodePoint {
type Error = ();
fn try_from(x: u32) -> Result<Self, ()> {
let [u0, u1, u2, u3] = x.to_le_bytes();
if u3 != 0 {
return Err(());
}
Ok(Self([u0, u1, u2]))
}
}
impl From<char> for PotentialCodePoint {
#[inline]
fn from(value: char) -> Self {
Self::from_char(value)
}
}
impl TryFrom<PotentialCodePoint> for char {
type Error = core::char::CharTryFromError;
#[inline]
fn try_from(value: PotentialCodePoint) -> Result<char, Self::Error> {
value.try_to_char()
}
}
/// This impl requires enabling the optional `serde` Cargo feature
#[cfg(feature = "serde")]
impl serde::Serialize for PotentialCodePoint {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: serde::Serializer,
{
use serde::ser::Error;
let c = self
.try_to_char()
.map_err(|_| S::Error::custom("invalid Unicode scalar value in PotentialCodePoint"))?;
if serializer.is_human_readable() {
serializer.serialize_char(c)
} else {
self.0.serialize(serializer)
}
}
}
/// This impl requires enabling the optional `serde` Cargo feature
#[cfg(feature = "serde")]
impl<'de> serde::Deserialize<'de> for PotentialCodePoint {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: serde::Deserializer<'de>,
{
if deserializer.is_human_readable() {
let c = <char>::deserialize(deserializer)?;
Ok(PotentialCodePoint::from_char(c))
} else {
let bytes = <[u8; 3]>::deserialize(deserializer)?;
Ok(PotentialCodePoint(bytes))
}
}
}
/// This impl requires enabling the optional `databake` Cargo feature
#[cfg(feature = "databake")]
impl databake::Bake for PotentialCodePoint {
fn bake(&self, env: &databake::CrateEnv) -> databake::TokenStream {
match self.try_to_char() {
Ok(ch) => {
env.insert("potential_utf");
let ch = ch.bake(env);
databake::quote! {
potential_utf::PotentialCodePoint::from_char(#ch)
}
}
Err(_) => {
env.insert("potential_utf");
let u24 = u32::from_le_bytes([self.0[0], self.0[1], self.0[2], 0]);
databake::quote! {
potential_utf::PotentialCodePoint::from_u24(#u24)
}
}
}
}
}
#[cfg(test)]
mod test {
use super::*;
use zerovec::ZeroVec;
#[test]
fn test_serde_fail() {
let uc = PotentialCodePoint([0xFF, 0xFF, 0xFF]);
serde_json::to_string(&uc).expect_err("serialize invalid char bytes");
bincode::serialize(&uc).expect_err("serialize invalid char bytes");
}
#[test]
fn test_serde_json() {
let c = '🙃';
let uc = PotentialCodePoint::from_char(c);
let json_ser = serde_json::to_string(&uc).unwrap();
assert_eq!(json_ser, r#""🙃""#);
let json_de: PotentialCodePoint = serde_json::from_str(&json_ser).unwrap();
assert_eq!(uc, json_de);
}
#[test]
fn test_serde_bincode() {
let c = '🙃';
let uc = PotentialCodePoint::from_char(c);
let bytes_ser = bincode::serialize(&uc).unwrap();
assert_eq!(bytes_ser, [0x43, 0xF6, 0x01]);
let bytes_de: PotentialCodePoint = bincode::deserialize(&bytes_ser).unwrap();
assert_eq!(uc, bytes_de);
}
#[test]
fn test_representation() {
let chars = ['w', 'ω', '文', '𑄃', '🙃'];
// backed by [PotentialCodePoint]
let uvchars: Vec<_> = chars
.iter()
.copied()
.map(PotentialCodePoint::from_char)
.collect();
// backed by [RawBytesULE<3>]
let zvec: ZeroVec<_> = uvchars.clone().into_iter().collect();
let ule_bytes = zvec.as_bytes();
let uvbytes;
unsafe {
let ptr = &uvchars[..] as *const _ as *const u8;
uvbytes = core::slice::from_raw_parts(ptr, ule_bytes.len());
}
// PotentialCodePoint is defined as little-endian, so this must be true on all platforms
// also asserts that to_unaligned/from_unaligned are no-ops
assert_eq!(uvbytes, ule_bytes);
assert_eq!(
&[119, 0, 0, 201, 3, 0, 135, 101, 0, 3, 17, 1, 67, 246, 1],
ule_bytes
);
}
#[test]
fn test_char_bake() {
databake::test_bake!(
PotentialCodePoint,
const,
crate::PotentialCodePoint::from_char('b'),
potential_utf
);
// surrogate code point
databake::test_bake!(
PotentialCodePoint,
const,
crate::PotentialCodePoint::from_u24(55296u32),
potential_utf
);
}
}