| //! UTF-8 and UTF-16 decoding iterators |
| |
| use crate::fmt; |
| |
| use super::from_u32_unchecked; |
| |
| /// An iterator that decodes UTF-16 encoded code points from an iterator of `u16`s. |
| #[stable(feature = "decode_utf16", since = "1.9.0")] |
| #[derive(Clone, Debug)] |
| pub struct DecodeUtf16<I> |
| where I: Iterator<Item = u16> |
| { |
| iter: I, |
| buf: Option<u16>, |
| } |
| |
| /// An error that can be returned when decoding UTF-16 code points. |
| #[stable(feature = "decode_utf16", since = "1.9.0")] |
| #[derive(Debug, Clone, Eq, PartialEq)] |
| pub struct DecodeUtf16Error { |
| code: u16, |
| } |
| |
| /// Creates an iterator over the UTF-16 encoded code points in `iter`, |
| /// returning unpaired surrogates as `Err`s. |
| /// |
| /// # Examples |
| /// |
| /// Basic usage: |
| /// |
| /// ``` |
| /// use std::char::decode_utf16; |
| /// |
| /// fn main() { |
| /// // 𝄞mus<invalid>ic<invalid> |
| /// let v = [0xD834, 0xDD1E, 0x006d, 0x0075, |
| /// 0x0073, 0xDD1E, 0x0069, 0x0063, |
| /// 0xD834]; |
| /// |
| /// assert_eq!(decode_utf16(v.iter().cloned()) |
| /// .map(|r| r.map_err(|e| e.unpaired_surrogate())) |
| /// .collect::<Vec<_>>(), |
| /// vec![Ok('𝄞'), |
| /// Ok('m'), Ok('u'), Ok('s'), |
| /// Err(0xDD1E), |
| /// Ok('i'), Ok('c'), |
| /// Err(0xD834)]); |
| /// } |
| /// ``` |
| /// |
| /// A lossy decoder can be obtained by replacing `Err` results with the replacement character: |
| /// |
| /// ``` |
| /// use std::char::{decode_utf16, REPLACEMENT_CHARACTER}; |
| /// |
| /// fn main() { |
| /// // 𝄞mus<invalid>ic<invalid> |
| /// let v = [0xD834, 0xDD1E, 0x006d, 0x0075, |
| /// 0x0073, 0xDD1E, 0x0069, 0x0063, |
| /// 0xD834]; |
| /// |
| /// assert_eq!(decode_utf16(v.iter().cloned()) |
| /// .map(|r| r.unwrap_or(REPLACEMENT_CHARACTER)) |
| /// .collect::<String>(), |
| /// "𝄞mus�ic�"); |
| /// } |
| /// ``` |
| #[stable(feature = "decode_utf16", since = "1.9.0")] |
| #[inline] |
| pub fn decode_utf16<I: IntoIterator<Item = u16>>(iter: I) -> DecodeUtf16<I::IntoIter> { |
| DecodeUtf16 { |
| iter: iter.into_iter(), |
| buf: None, |
| } |
| } |
| |
| #[stable(feature = "decode_utf16", since = "1.9.0")] |
| impl<I: Iterator<Item = u16>> Iterator for DecodeUtf16<I> { |
| type Item = Result<char, DecodeUtf16Error>; |
| |
| fn next(&mut self) -> Option<Result<char, DecodeUtf16Error>> { |
| let u = match self.buf.take() { |
| Some(buf) => buf, |
| None => self.iter.next()? |
| }; |
| |
| if u < 0xD800 || 0xDFFF < u { |
| // not a surrogate |
| Some(Ok(unsafe { from_u32_unchecked(u as u32) })) |
| } else if u >= 0xDC00 { |
| // a trailing surrogate |
| Some(Err(DecodeUtf16Error { code: u })) |
| } else { |
| let u2 = match self.iter.next() { |
| Some(u2) => u2, |
| // eof |
| None => return Some(Err(DecodeUtf16Error { code: u })), |
| }; |
| if u2 < 0xDC00 || u2 > 0xDFFF { |
| // not a trailing surrogate so we're not a valid |
| // surrogate pair, so rewind to redecode u2 next time. |
| self.buf = Some(u2); |
| return Some(Err(DecodeUtf16Error { code: u })); |
| } |
| |
| // all ok, so lets decode it. |
| let c = (((u - 0xD800) as u32) << 10 | (u2 - 0xDC00) as u32) + 0x1_0000; |
| Some(Ok(unsafe { from_u32_unchecked(c) })) |
| } |
| } |
| |
| #[inline] |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| let (low, high) = self.iter.size_hint(); |
| // we could be entirely valid surrogates (2 elements per |
| // char), or entirely non-surrogates (1 element per char) |
| (low / 2, high) |
| } |
| } |
| |
| impl DecodeUtf16Error { |
| /// Returns the unpaired surrogate which caused this error. |
| #[stable(feature = "decode_utf16", since = "1.9.0")] |
| pub fn unpaired_surrogate(&self) -> u16 { |
| self.code |
| } |
| } |
| |
| #[stable(feature = "decode_utf16", since = "1.9.0")] |
| impl fmt::Display for DecodeUtf16Error { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| write!(f, "unpaired surrogate found: {:x}", self.code) |
| } |
| } |