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| -rw-r--r-- | library/std/src/sys_common/wtf8.rs | 926 |
1 files changed, 926 insertions, 0 deletions
diff --git a/library/std/src/sys_common/wtf8.rs b/library/std/src/sys_common/wtf8.rs new file mode 100644 index 000000000..57fa49893 --- /dev/null +++ b/library/std/src/sys_common/wtf8.rs @@ -0,0 +1,926 @@ +//! Implementation of [the WTF-8 encoding](https://simonsapin.github.io/wtf-8/). +//! +//! This library uses Rust’s type system to maintain +//! [well-formedness](https://simonsapin.github.io/wtf-8/#well-formed), +//! like the `String` and `&str` types do for UTF-8. +//! +//! Since [WTF-8 must not be used +//! for interchange](https://simonsapin.github.io/wtf-8/#intended-audience), +//! this library deliberately does not provide access to the underlying bytes +//! of WTF-8 strings, +//! nor can it decode WTF-8 from arbitrary bytes. +//! WTF-8 strings can be obtained from UTF-8, UTF-16, or code points. + +// this module is imported from @SimonSapin's repo and has tons of dead code on +// unix (it's mostly used on windows), so don't worry about dead code here. +#![allow(dead_code)] + +#[cfg(test)] +mod tests; + +use core::str::next_code_point; + +use crate::borrow::Cow; +use crate::char; +use crate::collections::TryReserveError; +use crate::fmt; +use crate::hash::{Hash, Hasher}; +use crate::iter::FusedIterator; +use crate::mem; +use crate::ops; +use crate::rc::Rc; +use crate::slice; +use crate::str; +use crate::sync::Arc; +use crate::sys_common::AsInner; + +const UTF8_REPLACEMENT_CHARACTER: &str = "\u{FFFD}"; + +/// A Unicode code point: from U+0000 to U+10FFFF. +/// +/// Compares with the `char` type, +/// which represents a Unicode scalar value: +/// a code point that is not a surrogate (U+D800 to U+DFFF). +#[derive(Eq, PartialEq, Ord, PartialOrd, Clone, Copy)] +pub struct CodePoint { + value: u32, +} + +/// Format the code point as `U+` followed by four to six hexadecimal digits. +/// Example: `U+1F4A9` +impl fmt::Debug for CodePoint { + #[inline] + fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(formatter, "U+{:04X}", self.value) + } +} + +impl CodePoint { + /// Unsafely creates a new `CodePoint` without checking the value. + /// + /// Only use when `value` is known to be less than or equal to 0x10FFFF. + #[inline] + pub unsafe fn from_u32_unchecked(value: u32) -> CodePoint { + CodePoint { value } + } + + /// Creates a new `CodePoint` if the value is a valid code point. + /// + /// Returns `None` if `value` is above 0x10FFFF. + #[inline] + pub fn from_u32(value: u32) -> Option<CodePoint> { + match value { + 0..=0x10FFFF => Some(CodePoint { value }), + _ => None, + } + } + + /// Creates a new `CodePoint` from a `char`. + /// + /// Since all Unicode scalar values are code points, this always succeeds. + #[inline] + pub fn from_char(value: char) -> CodePoint { + CodePoint { value: value as u32 } + } + + /// Returns the numeric value of the code point. + #[inline] + pub fn to_u32(&self) -> u32 { + self.value + } + + /// Optionally returns a Unicode scalar value for the code point. + /// + /// Returns `None` if the code point is a surrogate (from U+D800 to U+DFFF). + #[inline] + pub fn to_char(&self) -> Option<char> { + match self.value { + 0xD800..=0xDFFF => None, + _ => Some(unsafe { char::from_u32_unchecked(self.value) }), + } + } + + /// Returns a Unicode scalar value for the code point. + /// + /// Returns `'\u{FFFD}'` (the replacement character “�”) + /// if the code point is a surrogate (from U+D800 to U+DFFF). + #[inline] + pub fn to_char_lossy(&self) -> char { + self.to_char().unwrap_or('\u{FFFD}') + } +} + +/// An owned, growable string of well-formed WTF-8 data. +/// +/// Similar to `String`, but can additionally contain surrogate code points +/// if they’re not in a surrogate pair. +#[derive(Eq, PartialEq, Ord, PartialOrd, Clone)] +pub struct Wtf8Buf { + bytes: Vec<u8>, +} + +impl ops::Deref for Wtf8Buf { + type Target = Wtf8; + + fn deref(&self) -> &Wtf8 { + self.as_slice() + } +} + +impl ops::DerefMut for Wtf8Buf { + fn deref_mut(&mut self) -> &mut Wtf8 { + self.as_mut_slice() + } +} + +/// Format the string with double quotes, +/// and surrogates as `\u` followed by four hexadecimal digits. +/// Example: `"a\u{D800}"` for a string with code points [U+0061, U+D800] +impl fmt::Debug for Wtf8Buf { + #[inline] + fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt::Debug::fmt(&**self, formatter) + } +} + +impl Wtf8Buf { + /// Creates a new, empty WTF-8 string. + #[inline] + pub fn new() -> Wtf8Buf { + Wtf8Buf { bytes: Vec::new() } + } + + /// Creates a new, empty WTF-8 string with pre-allocated capacity for `capacity` bytes. + #[inline] + pub fn with_capacity(capacity: usize) -> Wtf8Buf { + Wtf8Buf { bytes: Vec::with_capacity(capacity) } + } + + /// Creates a WTF-8 string from a UTF-8 `String`. + /// + /// This takes ownership of the `String` and does not copy. + /// + /// Since WTF-8 is a superset of UTF-8, this always succeeds. + #[inline] + pub fn from_string(string: String) -> Wtf8Buf { + Wtf8Buf { bytes: string.into_bytes() } + } + + /// Creates a WTF-8 string from a UTF-8 `&str` slice. + /// + /// This copies the content of the slice. + /// + /// Since WTF-8 is a superset of UTF-8, this always succeeds. + #[inline] + pub fn from_str(str: &str) -> Wtf8Buf { + Wtf8Buf { bytes: <[_]>::to_vec(str.as_bytes()) } + } + + pub fn clear(&mut self) { + self.bytes.clear() + } + + /// Creates a WTF-8 string from a potentially ill-formed UTF-16 slice of 16-bit code units. + /// + /// This is lossless: calling `.encode_wide()` on the resulting string + /// will always return the original code units. + pub fn from_wide(v: &[u16]) -> Wtf8Buf { + let mut string = Wtf8Buf::with_capacity(v.len()); + for item in char::decode_utf16(v.iter().cloned()) { + match item { + Ok(ch) => string.push_char(ch), + Err(surrogate) => { + let surrogate = surrogate.unpaired_surrogate(); + // Surrogates are known to be in the code point range. + let code_point = unsafe { CodePoint::from_u32_unchecked(surrogate as u32) }; + // Skip the WTF-8 concatenation check, + // surrogate pairs are already decoded by decode_utf16 + string.push_code_point_unchecked(code_point) + } + } + } + string + } + + /// Copied from String::push + /// This does **not** include the WTF-8 concatenation check. + fn push_code_point_unchecked(&mut self, code_point: CodePoint) { + let mut bytes = [0; 4]; + let bytes = char::encode_utf8_raw(code_point.value, &mut bytes); + self.bytes.extend_from_slice(bytes) + } + + #[inline] + pub fn as_slice(&self) -> &Wtf8 { + unsafe { Wtf8::from_bytes_unchecked(&self.bytes) } + } + + #[inline] + pub fn as_mut_slice(&mut self) -> &mut Wtf8 { + unsafe { Wtf8::from_mut_bytes_unchecked(&mut self.bytes) } + } + + /// Reserves capacity for at least `additional` more bytes to be inserted + /// in the given `Wtf8Buf`. + /// The collection may reserve more space to avoid frequent reallocations. + /// + /// # Panics + /// + /// Panics if the new capacity overflows `usize`. + #[inline] + pub fn reserve(&mut self, additional: usize) { + self.bytes.reserve(additional) + } + + /// Tries to reserve capacity for at least `additional` more length units + /// in the given `Wtf8Buf`. The `Wtf8Buf` may reserve more space to avoid + /// frequent reallocations. After calling `try_reserve`, capacity will be + /// greater than or equal to `self.len() + additional`. Does nothing if + /// capacity is already sufficient. + /// + /// # Errors + /// + /// If the capacity overflows, or the allocator reports a failure, then an error + /// is returned. + #[inline] + pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> { + self.bytes.try_reserve(additional) + } + + #[inline] + pub fn reserve_exact(&mut self, additional: usize) { + self.bytes.reserve_exact(additional) + } + + /// Tries to reserve the minimum capacity for exactly `additional` + /// length units in the given `Wtf8Buf`. After calling + /// `try_reserve_exact`, capacity will be greater than or equal to + /// `self.len() + additional` if it returns `Ok(())`. + /// Does nothing if the capacity is already sufficient. + /// + /// Note that the allocator may give the `Wtf8Buf` more space than it + /// requests. Therefore, capacity can not be relied upon to be precisely + /// minimal. Prefer [`try_reserve`] if future insertions are expected. + /// + /// [`try_reserve`]: Wtf8Buf::try_reserve + /// + /// # Errors + /// + /// If the capacity overflows, or the allocator reports a failure, then an error + /// is returned. + #[inline] + pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> { + self.bytes.try_reserve_exact(additional) + } + + #[inline] + pub fn shrink_to_fit(&mut self) { + self.bytes.shrink_to_fit() + } + + #[inline] + pub fn shrink_to(&mut self, min_capacity: usize) { + self.bytes.shrink_to(min_capacity) + } + + /// Returns the number of bytes that this string buffer can hold without reallocating. + #[inline] + pub fn capacity(&self) -> usize { + self.bytes.capacity() + } + + /// Append a UTF-8 slice at the end of the string. + #[inline] + pub fn push_str(&mut self, other: &str) { + self.bytes.extend_from_slice(other.as_bytes()) + } + + /// Append a WTF-8 slice at the end of the string. + /// + /// This replaces newly paired surrogates at the boundary + /// with a supplementary code point, + /// like concatenating ill-formed UTF-16 strings effectively would. + #[inline] + pub fn push_wtf8(&mut self, other: &Wtf8) { + match ((&*self).final_lead_surrogate(), other.initial_trail_surrogate()) { + // Replace newly paired surrogates by a supplementary code point. + (Some(lead), Some(trail)) => { + let len_without_lead_surrogate = self.len() - 3; + self.bytes.truncate(len_without_lead_surrogate); + let other_without_trail_surrogate = &other.bytes[3..]; + // 4 bytes for the supplementary code point + self.bytes.reserve(4 + other_without_trail_surrogate.len()); + self.push_char(decode_surrogate_pair(lead, trail)); + self.bytes.extend_from_slice(other_without_trail_surrogate); + } + _ => self.bytes.extend_from_slice(&other.bytes), + } + } + + /// Append a Unicode scalar value at the end of the string. + #[inline] + pub fn push_char(&mut self, c: char) { + self.push_code_point_unchecked(CodePoint::from_char(c)) + } + + /// Append a code point at the end of the string. + /// + /// This replaces newly paired surrogates at the boundary + /// with a supplementary code point, + /// like concatenating ill-formed UTF-16 strings effectively would. + #[inline] + pub fn push(&mut self, code_point: CodePoint) { + if let trail @ 0xDC00..=0xDFFF = code_point.to_u32() { + if let Some(lead) = (&*self).final_lead_surrogate() { + let len_without_lead_surrogate = self.len() - 3; + self.bytes.truncate(len_without_lead_surrogate); + self.push_char(decode_surrogate_pair(lead, trail as u16)); + return; + } + } + + // No newly paired surrogates at the boundary. + self.push_code_point_unchecked(code_point) + } + + /// Shortens a string to the specified length. + /// + /// # Panics + /// + /// Panics if `new_len` > current length, + /// or if `new_len` is not a code point boundary. + #[inline] + pub fn truncate(&mut self, new_len: usize) { + assert!(is_code_point_boundary(self, new_len)); + self.bytes.truncate(new_len) + } + + /// Consumes the WTF-8 string and tries to convert it to UTF-8. + /// + /// This does not copy the data. + /// + /// If the contents are not well-formed UTF-8 + /// (that is, if the string contains surrogates), + /// the original WTF-8 string is returned instead. + pub fn into_string(self) -> Result<String, Wtf8Buf> { + match self.next_surrogate(0) { + None => Ok(unsafe { String::from_utf8_unchecked(self.bytes) }), + Some(_) => Err(self), + } + } + + /// Consumes the WTF-8 string and converts it lossily to UTF-8. + /// + /// This does not copy the data (but may overwrite parts of it in place). + /// + /// Surrogates are replaced with `"\u{FFFD}"` (the replacement character “�”) + pub fn into_string_lossy(mut self) -> String { + let mut pos = 0; + loop { + match self.next_surrogate(pos) { + Some((surrogate_pos, _)) => { + pos = surrogate_pos + 3; + self.bytes[surrogate_pos..pos] + .copy_from_slice(UTF8_REPLACEMENT_CHARACTER.as_bytes()); + } + None => return unsafe { String::from_utf8_unchecked(self.bytes) }, + } + } + } + + /// Converts this `Wtf8Buf` into a boxed `Wtf8`. + #[inline] + pub fn into_box(self) -> Box<Wtf8> { + unsafe { mem::transmute(self.bytes.into_boxed_slice()) } + } + + /// Converts a `Box<Wtf8>` into a `Wtf8Buf`. + pub fn from_box(boxed: Box<Wtf8>) -> Wtf8Buf { + let bytes: Box<[u8]> = unsafe { mem::transmute(boxed) }; + Wtf8Buf { bytes: bytes.into_vec() } + } +} + +/// Creates a new WTF-8 string from an iterator of code points. +/// +/// This replaces surrogate code point pairs with supplementary code points, +/// like concatenating ill-formed UTF-16 strings effectively would. +impl FromIterator<CodePoint> for Wtf8Buf { + fn from_iter<T: IntoIterator<Item = CodePoint>>(iter: T) -> Wtf8Buf { + let mut string = Wtf8Buf::new(); + string.extend(iter); + string + } +} + +/// Append code points from an iterator to the string. +/// +/// This replaces surrogate code point pairs with supplementary code points, +/// like concatenating ill-formed UTF-16 strings effectively would. +impl Extend<CodePoint> for Wtf8Buf { + fn extend<T: IntoIterator<Item = CodePoint>>(&mut self, iter: T) { + let iterator = iter.into_iter(); + let (low, _high) = iterator.size_hint(); + // Lower bound of one byte per code point (ASCII only) + self.bytes.reserve(low); + iterator.for_each(move |code_point| self.push(code_point)); + } + + #[inline] + fn extend_one(&mut self, code_point: CodePoint) { + self.push(code_point); + } + + #[inline] + fn extend_reserve(&mut self, additional: usize) { + // Lower bound of one byte per code point (ASCII only) + self.bytes.reserve(additional); + } +} + +/// A borrowed slice of well-formed WTF-8 data. +/// +/// Similar to `&str`, but can additionally contain surrogate code points +/// if they’re not in a surrogate pair. +#[derive(Eq, Ord, PartialEq, PartialOrd)] +pub struct Wtf8 { + bytes: [u8], +} + +impl AsInner<[u8]> for Wtf8 { + fn as_inner(&self) -> &[u8] { + &self.bytes + } +} + +/// Format the slice with double quotes, +/// and surrogates as `\u` followed by four hexadecimal digits. +/// Example: `"a\u{D800}"` for a slice with code points [U+0061, U+D800] +impl fmt::Debug for Wtf8 { + fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result { + fn write_str_escaped(f: &mut fmt::Formatter<'_>, s: &str) -> fmt::Result { + use crate::fmt::Write; + for c in s.chars().flat_map(|c| c.escape_debug()) { + f.write_char(c)? + } + Ok(()) + } + + formatter.write_str("\"")?; + let mut pos = 0; + while let Some((surrogate_pos, surrogate)) = self.next_surrogate(pos) { + write_str_escaped(formatter, unsafe { + str::from_utf8_unchecked(&self.bytes[pos..surrogate_pos]) + })?; + write!(formatter, "\\u{{{:x}}}", surrogate)?; + pos = surrogate_pos + 3; + } + write_str_escaped(formatter, unsafe { str::from_utf8_unchecked(&self.bytes[pos..]) })?; + formatter.write_str("\"") + } +} + +impl fmt::Display for Wtf8 { + fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result { + let wtf8_bytes = &self.bytes; + let mut pos = 0; + loop { + match self.next_surrogate(pos) { + Some((surrogate_pos, _)) => { + formatter.write_str(unsafe { + str::from_utf8_unchecked(&wtf8_bytes[pos..surrogate_pos]) + })?; + formatter.write_str(UTF8_REPLACEMENT_CHARACTER)?; + pos = surrogate_pos + 3; + } + None => { + let s = unsafe { str::from_utf8_unchecked(&wtf8_bytes[pos..]) }; + if pos == 0 { return s.fmt(formatter) } else { return formatter.write_str(s) } + } + } + } + } +} + +impl Wtf8 { + /// Creates a WTF-8 slice from a UTF-8 `&str` slice. + /// + /// Since WTF-8 is a superset of UTF-8, this always succeeds. + #[inline] + pub fn from_str(value: &str) -> &Wtf8 { + unsafe { Wtf8::from_bytes_unchecked(value.as_bytes()) } + } + + /// Creates a WTF-8 slice from a WTF-8 byte slice. + /// + /// Since the byte slice is not checked for valid WTF-8, this functions is + /// marked unsafe. + #[inline] + unsafe fn from_bytes_unchecked(value: &[u8]) -> &Wtf8 { + mem::transmute(value) + } + + /// Creates a mutable WTF-8 slice from a mutable WTF-8 byte slice. + /// + /// Since the byte slice is not checked for valid WTF-8, this functions is + /// marked unsafe. + #[inline] + unsafe fn from_mut_bytes_unchecked(value: &mut [u8]) -> &mut Wtf8 { + mem::transmute(value) + } + + /// Returns the length, in WTF-8 bytes. + #[inline] + pub fn len(&self) -> usize { + self.bytes.len() + } + + #[inline] + pub fn is_empty(&self) -> bool { + self.bytes.is_empty() + } + + /// Returns the code point at `position` if it is in the ASCII range, + /// or `b'\xFF' otherwise. + /// + /// # Panics + /// + /// Panics if `position` is beyond the end of the string. + #[inline] + pub fn ascii_byte_at(&self, position: usize) -> u8 { + match self.bytes[position] { + ascii_byte @ 0x00..=0x7F => ascii_byte, + _ => 0xFF, + } + } + + /// Returns an iterator for the string’s code points. + #[inline] + pub fn code_points(&self) -> Wtf8CodePoints<'_> { + Wtf8CodePoints { bytes: self.bytes.iter() } + } + + /// Tries to convert the string to UTF-8 and return a `&str` slice. + /// + /// Returns `None` if the string contains surrogates. + /// + /// This does not copy the data. + #[inline] + pub fn as_str(&self) -> Option<&str> { + // Well-formed WTF-8 is also well-formed UTF-8 + // if and only if it contains no surrogate. + match self.next_surrogate(0) { + None => Some(unsafe { str::from_utf8_unchecked(&self.bytes) }), + Some(_) => None, + } + } + + /// Lossily converts the string to UTF-8. + /// Returns a UTF-8 `&str` slice if the contents are well-formed in UTF-8. + /// + /// Surrogates are replaced with `"\u{FFFD}"` (the replacement character “�”). + /// + /// This only copies the data if necessary (if it contains any surrogate). + pub fn to_string_lossy(&self) -> Cow<'_, str> { + let surrogate_pos = match self.next_surrogate(0) { + None => return Cow::Borrowed(unsafe { str::from_utf8_unchecked(&self.bytes) }), + Some((pos, _)) => pos, + }; + let wtf8_bytes = &self.bytes; + let mut utf8_bytes = Vec::with_capacity(self.len()); + utf8_bytes.extend_from_slice(&wtf8_bytes[..surrogate_pos]); + utf8_bytes.extend_from_slice(UTF8_REPLACEMENT_CHARACTER.as_bytes()); + let mut pos = surrogate_pos + 3; + loop { + match self.next_surrogate(pos) { + Some((surrogate_pos, _)) => { + utf8_bytes.extend_from_slice(&wtf8_bytes[pos..surrogate_pos]); + utf8_bytes.extend_from_slice(UTF8_REPLACEMENT_CHARACTER.as_bytes()); + pos = surrogate_pos + 3; + } + None => { + utf8_bytes.extend_from_slice(&wtf8_bytes[pos..]); + return Cow::Owned(unsafe { String::from_utf8_unchecked(utf8_bytes) }); + } + } + } + } + + /// Converts the WTF-8 string to potentially ill-formed UTF-16 + /// and return an iterator of 16-bit code units. + /// + /// This is lossless: + /// calling `Wtf8Buf::from_ill_formed_utf16` on the resulting code units + /// would always return the original WTF-8 string. + #[inline] + pub fn encode_wide(&self) -> EncodeWide<'_> { + EncodeWide { code_points: self.code_points(), extra: 0 } + } + + #[inline] + fn next_surrogate(&self, mut pos: usize) -> Option<(usize, u16)> { + let mut iter = self.bytes[pos..].iter(); + loop { + let b = *iter.next()?; + if b < 0x80 { + pos += 1; + } else if b < 0xE0 { + iter.next(); + pos += 2; + } else if b == 0xED { + match (iter.next(), iter.next()) { + (Some(&b2), Some(&b3)) if b2 >= 0xA0 => { + return Some((pos, decode_surrogate(b2, b3))); + } + _ => pos += 3, + } + } else if b < 0xF0 { + iter.next(); + iter.next(); + pos += 3; + } else { + iter.next(); + iter.next(); + iter.next(); + pos += 4; + } + } + } + + #[inline] + fn final_lead_surrogate(&self) -> Option<u16> { + match self.bytes { + [.., 0xED, b2 @ 0xA0..=0xAF, b3] => Some(decode_surrogate(b2, b3)), + _ => None, + } + } + + #[inline] + fn initial_trail_surrogate(&self) -> Option<u16> { + match self.bytes { + [0xED, b2 @ 0xB0..=0xBF, b3, ..] => Some(decode_surrogate(b2, b3)), + _ => None, + } + } + + pub fn clone_into(&self, buf: &mut Wtf8Buf) { + self.bytes.clone_into(&mut buf.bytes) + } + + /// Boxes this `Wtf8`. + #[inline] + pub fn into_box(&self) -> Box<Wtf8> { + let boxed: Box<[u8]> = self.bytes.into(); + unsafe { mem::transmute(boxed) } + } + + /// Creates a boxed, empty `Wtf8`. + pub fn empty_box() -> Box<Wtf8> { + let boxed: Box<[u8]> = Default::default(); + unsafe { mem::transmute(boxed) } + } + + #[inline] + pub fn into_arc(&self) -> Arc<Wtf8> { + let arc: Arc<[u8]> = Arc::from(&self.bytes); + unsafe { Arc::from_raw(Arc::into_raw(arc) as *const Wtf8) } + } + + #[inline] + pub fn into_rc(&self) -> Rc<Wtf8> { + let rc: Rc<[u8]> = Rc::from(&self.bytes); + unsafe { Rc::from_raw(Rc::into_raw(rc) as *const Wtf8) } + } + + #[inline] + pub fn make_ascii_lowercase(&mut self) { + self.bytes.make_ascii_lowercase() + } + + #[inline] + pub fn make_ascii_uppercase(&mut self) { + self.bytes.make_ascii_uppercase() + } + + #[inline] + pub fn to_ascii_lowercase(&self) -> Wtf8Buf { + Wtf8Buf { bytes: self.bytes.to_ascii_lowercase() } + } + + #[inline] + pub fn to_ascii_uppercase(&self) -> Wtf8Buf { + Wtf8Buf { bytes: self.bytes.to_ascii_uppercase() } + } + + #[inline] + pub fn is_ascii(&self) -> bool { + self.bytes.is_ascii() + } + + #[inline] + pub fn eq_ignore_ascii_case(&self, other: &Self) -> bool { + self.bytes.eq_ignore_ascii_case(&other.bytes) + } +} + +/// Returns a slice of the given string for the byte range \[`begin`..`end`). +/// +/// # Panics +/// +/// Panics when `begin` and `end` do not point to code point boundaries, +/// or point beyond the end of the string. +impl ops::Index<ops::Range<usize>> for Wtf8 { + type Output = Wtf8; + + #[inline] + fn index(&self, range: ops::Range<usize>) -> &Wtf8 { + // is_code_point_boundary checks that the index is in [0, .len()] + if range.start <= range.end + && is_code_point_boundary(self, range.start) + && is_code_point_boundary(self, range.end) + { + unsafe { slice_unchecked(self, range.start, range.end) } + } else { + slice_error_fail(self, range.start, range.end) + } + } +} + +/// Returns a slice of the given string from byte `begin` to its end. +/// +/// # Panics +/// +/// Panics when `begin` is not at a code point boundary, +/// or is beyond the end of the string. +impl ops::Index<ops::RangeFrom<usize>> for Wtf8 { + type Output = Wtf8; + + #[inline] + fn index(&self, range: ops::RangeFrom<usize>) -> &Wtf8 { + // is_code_point_boundary checks that the index is in [0, .len()] + if is_code_point_boundary(self, range.start) { + unsafe { slice_unchecked(self, range.start, self.len()) } + } else { + slice_error_fail(self, range.start, self.len()) + } + } +} + +/// Returns a slice of the given string from its beginning to byte `end`. +/// +/// # Panics +/// +/// Panics when `end` is not at a code point boundary, +/// or is beyond the end of the string. +impl ops::Index<ops::RangeTo<usize>> for Wtf8 { + type Output = Wtf8; + + #[inline] + fn index(&self, range: ops::RangeTo<usize>) -> &Wtf8 { + // is_code_point_boundary checks that the index is in [0, .len()] + if is_code_point_boundary(self, range.end) { + unsafe { slice_unchecked(self, 0, range.end) } + } else { + slice_error_fail(self, 0, range.end) + } + } +} + +impl ops::Index<ops::RangeFull> for Wtf8 { + type Output = Wtf8; + + #[inline] + fn index(&self, _range: ops::RangeFull) -> &Wtf8 { + self + } +} + +#[inline] +fn decode_surrogate(second_byte: u8, third_byte: u8) -> u16 { + // The first byte is assumed to be 0xED + 0xD800 | (second_byte as u16 & 0x3F) << 6 | third_byte as u16 & 0x3F +} + +#[inline] +fn decode_surrogate_pair(lead: u16, trail: u16) -> char { + let code_point = 0x10000 + ((((lead - 0xD800) as u32) << 10) | (trail - 0xDC00) as u32); + unsafe { char::from_u32_unchecked(code_point) } +} + +/// Copied from core::str::StrPrelude::is_char_boundary +#[inline] +pub fn is_code_point_boundary(slice: &Wtf8, index: usize) -> bool { + if index == slice.len() { + return true; + } + match slice.bytes.get(index) { + None => false, + Some(&b) => b < 128 || b >= 192, + } +} + +/// Copied from core::str::raw::slice_unchecked +#[inline] +pub unsafe fn slice_unchecked(s: &Wtf8, begin: usize, end: usize) -> &Wtf8 { + // memory layout of a &[u8] and &Wtf8 are the same + Wtf8::from_bytes_unchecked(slice::from_raw_parts(s.bytes.as_ptr().add(begin), end - begin)) +} + +/// Copied from core::str::raw::slice_error_fail +#[inline(never)] +pub fn slice_error_fail(s: &Wtf8, begin: usize, end: usize) -> ! { + assert!(begin <= end); + panic!("index {begin} and/or {end} in `{s:?}` do not lie on character boundary"); +} + +/// Iterator for the code points of a WTF-8 string. +/// +/// Created with the method `.code_points()`. +#[derive(Clone)] +pub struct Wtf8CodePoints<'a> { + bytes: slice::Iter<'a, u8>, +} + +impl<'a> Iterator for Wtf8CodePoints<'a> { + type Item = CodePoint; + + #[inline] + fn next(&mut self) -> Option<CodePoint> { + // SAFETY: `self.bytes` has been created from a WTF-8 string + unsafe { next_code_point(&mut self.bytes).map(|c| CodePoint { value: c }) } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + let len = self.bytes.len(); + (len.saturating_add(3) / 4, Some(len)) + } +} + +/// Generates a wide character sequence for potentially ill-formed UTF-16. +#[stable(feature = "rust1", since = "1.0.0")] +#[derive(Clone)] +pub struct EncodeWide<'a> { + code_points: Wtf8CodePoints<'a>, + extra: u16, +} + +// Copied from libunicode/u_str.rs +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a> Iterator for EncodeWide<'a> { + type Item = u16; + + #[inline] + fn next(&mut self) -> Option<u16> { + if self.extra != 0 { + let tmp = self.extra; + self.extra = 0; + return Some(tmp); + } + + let mut buf = [0; 2]; + self.code_points.next().map(|code_point| { + let n = char::encode_utf16_raw(code_point.value, &mut buf).len(); + if n == 2 { + self.extra = buf[1]; + } + buf[0] + }) + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + let (low, high) = self.code_points.size_hint(); + let ext = (self.extra != 0) as usize; + // every code point gets either one u16 or two u16, + // so this iterator is between 1 or 2 times as + // long as the underlying iterator. + (low + ext, high.and_then(|n| n.checked_mul(2)).and_then(|n| n.checked_add(ext))) + } +} + +#[stable(feature = "encode_wide_fused_iterator", since = "1.62.0")] +impl FusedIterator for EncodeWide<'_> {} + +impl Hash for CodePoint { + #[inline] + fn hash<H: Hasher>(&self, state: &mut H) { + self.value.hash(state) + } +} + +impl Hash for Wtf8Buf { + #[inline] + fn hash<H: Hasher>(&self, state: &mut H) { + state.write(&self.bytes); + 0xfeu8.hash(state) + } +} + +impl Hash for Wtf8 { + #[inline] + fn hash<H: Hasher>(&self, state: &mut H) { + state.write(&self.bytes); + 0xfeu8.hash(state) + } +} |