mod.rs - source
Description: Source of the Rust file `library/alloc/src/wtf8/mod.rs`.

#
alloc/wtf8/
mod.rs

    1//! Heap-allocated counterpart to core `wtf8` module.
    2#![unstable(
    3    feature = "wtf8_internals",
    4    issue = "none",
    5    reason = "this is internal code for representing OsStr on some platforms and not a public API"
    6)]
    7// rustdoc bug: doc(hidden) on the module won't stop types in the module from showing up in trait
    8// implementations, so, we'll have to add more doc(hidden)s anyway
    9#![doc(hidden)]
    10
    11// Note: This module is also included in the alloctests crate using #[path] to
    12// run the tests. See the comment there for an explanation why this is the case.
    13
    14#[cfg(test)]
    15mod tests;
    16
    17use core::char::encode_utf8_raw;
    18use core::hash::{Hash, Hasher};
    19pub use core::wtf8::{CodePoint, Wtf8};
    20#[cfg(not(test))]
    21pub use core::wtf8::{EncodeWide, Wtf8CodePoints};
    22use core::{fmt, mem, ops, str};
    23
    24use crate::borrow::{Cow, ToOwned};
    25use crate::boxed::Box;
    26use crate::collections::TryReserveError;
    27#[cfg(not(test))]
    28use crate::rc::Rc;
    29use crate::string::String;
    30#[cfg(all(not(test), target_has_atomic = "ptr"))]
    31use crate::sync::Arc;
    32use crate::vec::Vec;
    33
    34/// An owned, growable string of well-formed WTF-8 data.
    35///
    36/// Similar to `String`, but can additionally contain surrogate code points
    37/// if they’re not in a surrogate pair.
    38#[derive(Eq, PartialEq, Ord, PartialOrd, Clone)]
    39#[doc(hidden)]
    40pub struct Wtf8Buf {
    41    bytes: Vec<u8>,
    42
    43    /// Do we know that `bytes` holds a valid UTF-8 encoding? We can easily
    44    /// know this if we're constructed from a `String` or `&str`.
    45    ///
    46    /// It is possible for `bytes` to have valid UTF-8 without this being
    47    /// set, such as when we're concatenating `&Wtf8`'s and surrogates become
    48    /// paired, as we don't bother to rescan the entire string.
    49    is_known_utf8: bool,
    50}
    51
    52impl ops::Deref for Wtf8Buf {
    53    type Target = Wtf8;
    54
    55    fn deref(&self) -> &Wtf8 {
    56        self.as_slice()
    57    }
    58}
    59
    60impl ops::DerefMut for Wtf8Buf {
    61    fn deref_mut(&mut self) -> &mut Wtf8 {
    62        self.as_mut_slice()
    63    }
    64}
    65
    66/// Formats the string in double quotes, with characters escaped according to
    67/// [`char::escape_debug`] and unpaired surrogates represented as `\u{xxxx}`,
    68/// where each `x` is a hexadecimal digit.
    69///
    70/// For example, the code units [U+0061, U+D800, U+000A] are formatted as
    71/// `"a\u{D800}\n"`.
    72impl fmt::Debug for Wtf8Buf {
    73    #[inline]
    74    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
    75        fmt::Debug::fmt(&**self, formatter)
    76    }
    77}
    78
    79/// Formats the string with unpaired surrogates substituted with the replacement
    80/// character, U+FFFD.
    81impl fmt::Display for Wtf8Buf {
    82    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
    83        if let Some(s) = self.as_known_utf8() {
    84            fmt::Display::fmt(s, formatter)
    85        } else {
    86            fmt::Display::fmt(&**self, formatter)
    87        }
    88    }
    89}
    90
    91#[cfg_attr(test, allow(dead_code))]
    92impl Wtf8Buf {
    93    /// Creates a new, empty WTF-8 string.
    94    #[inline]
    95    pub fn new() -> Wtf8Buf {
    96        Wtf8Buf { bytes: Vec::new(), is_known_utf8: true }
    97    }
    98
    99    /// Creates a new, empty WTF-8 string with pre-allocated capacity for `capacity` bytes.
    100    #[inline]
    101    pub fn with_capacity(capacity: usize) -> Wtf8Buf {
    102        Wtf8Buf { bytes: Vec::with_capacity(capacity), is_known_utf8: true }
    103    }
    104
    105    /// Creates a WTF-8 string from a WTF-8 byte vec.
    106    ///
    107    /// Since the byte vec is not checked for valid WTF-8, this function is
    108    /// marked unsafe.
    109    #[inline]
    110    pub unsafe fn from_bytes_unchecked(value: Vec<u8>) -> Wtf8Buf {
    111        Wtf8Buf { bytes: value, is_known_utf8: false }
    112    }
    113
    114    /// Creates a WTF-8 string from a UTF-8 `String`.
    115    ///
    116    /// This takes ownership of the `String` and does not copy.
    117    ///
    118    /// Since WTF-8 is a superset of UTF-8, this always succeeds.
    119    #[inline]
    120    pub const fn from_string(string: String) -> Wtf8Buf {
    121        Wtf8Buf { bytes: string.into_bytes(), is_known_utf8: true }
    122    }
    123
    124    /// Creates a WTF-8 string from a UTF-8 `&str` slice.
    125    ///
    126    /// This copies the content of the slice.
    127    ///
    128    /// Since WTF-8 is a superset of UTF-8, this always succeeds.
    129    #[inline]
    130    pub fn from_str(s: &str) -> Wtf8Buf {
    131        Wtf8Buf { bytes: s.as_bytes().to_vec(), is_known_utf8: true }
    132    }
    133
    134    pub fn clear(&mut self) {
    135        self.bytes.clear();
    136        self.is_known_utf8 = true;
    137    }
    138
    139    /// Creates a WTF-8 string from a potentially ill-formed UTF-16 slice of 16-bit code units.
    140    ///
    141    /// This is lossless: calling `.encode_wide()` on the resulting string
    142    /// will always return the original code units.
    143    pub fn from_wide(v: &[u16]) -> Wtf8Buf {
    144        let mut string = Wtf8Buf::with_capacity(v.len());
    145        for item in char::decode_utf16(v.iter().cloned()) {
    146            match item {
    147                Ok(ch) => string.push_char(ch),
    148                Err(surrogate) => {
    149                    let surrogate = surrogate.unpaired_surrogate();
    150                    // Surrogates are known to be in the code point range.
    151                    let code_point = unsafe { CodePoint::from_u32_unchecked(surrogate as u32) };
    152                    // The string will now contain an unpaired surrogate.
    153                    string.is_known_utf8 = false;
    154                    // Skip the WTF-8 concatenation check,
    155                    // surrogate pairs are already decoded by decode_utf16
    156                    unsafe {
    157                        string.push_code_point_unchecked(code_point);
    158                    }
    159                }
    160            }
    161        }
    162        string
    163    }
    164
    165    /// Appends the given `char` to the end of this string.
    166    /// This does **not** include the WTF-8 concatenation check or `is_known_utf8` check.
    167    /// Copied from String::push.
    168    unsafe fn push_code_point_unchecked(&mut self, code_point: CodePoint) {
    169        let mut bytes = [0; char::MAX_LEN_UTF8];
    170        let bytes = encode_utf8_raw(code_point.to_u32(), &mut bytes);
    171        self.bytes.extend_from_slice(bytes)
    172    }
    173
    174    #[inline]
    175    pub fn as_slice(&self) -> &Wtf8 {
    176        unsafe { Wtf8::from_bytes_unchecked(&self.bytes) }
    177    }
    178
    179    #[inline]
    180    pub fn as_mut_slice(&mut self) -> &mut Wtf8 {
    181        // Safety: `Wtf8` doesn't expose any way to mutate the bytes that would
    182        // cause them to change from well-formed UTF-8 to ill-formed UTF-8,
    183        // which would break the assumptions of the `is_known_utf8` field.
    184        unsafe { Wtf8::from_mut_bytes_unchecked(&mut self.bytes) }
    185    }
    186
    187    /// Converts the string to UTF-8 without validation, if it was created from
    188    /// valid UTF-8.
    189    #[inline]
    190    fn as_known_utf8(&self) -> Option<&str> {
    191        if self.is_known_utf8 {
    192            // SAFETY: The buffer is known to be valid UTF-8.
    193            Some(unsafe { str::from_utf8_unchecked(self.as_bytes()) })
    194        } else {
    195            None
    196        }
    197    }
    198
    199    /// Reserves capacity for at least `additional` more bytes to be inserted
    200    /// in the given `Wtf8Buf`.
    201    /// The collection may reserve more space to avoid frequent reallocations.
    202    ///
    203    /// # Panics
    204    ///
    205    /// Panics if the new capacity exceeds `isize::MAX` bytes.
    206    #[inline]
    207    pub fn reserve(&mut self, additional: usize) {
    208        self.bytes.reserve(additional)
    209    }
    210
    211    /// Tries to reserve capacity for at least `additional` more bytes to be
    212    /// inserted in the given `Wtf8Buf`. The `Wtf8Buf` may reserve more space to
    213    /// avoid frequent reallocations. After calling `try_reserve`, capacity will
    214    /// be greater than or equal to `self.len() + additional`. Does nothing if
    215    /// capacity is already sufficient. This method preserves the contents even
    216    /// if an error occurs.
    217    ///
    218    /// # Errors
    219    ///
    220    /// If the capacity overflows, or the allocator reports a failure, then an error
    221    /// is returned.
    222    #[inline]
    223    pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
    224        self.bytes.try_reserve(additional)
    225    }
    226
    227    #[inline]
    228    pub fn reserve_exact(&mut self, additional: usize) {
    229        self.bytes.reserve_exact(additional)
    230    }
    231
    232    /// Tries to reserve the minimum capacity for exactly `additional` more
    233    /// bytes to be inserted in the given `Wtf8Buf`. After calling
    234    /// `try_reserve_exact`, capacity will be greater than or equal to
    235    /// `self.len() + additional` if it returns `Ok(())`.
    236    /// Does nothing if the capacity is already sufficient.
    237    ///
    238    /// Note that the allocator may give the `Wtf8Buf` more space than it
    239    /// requests. Therefore, capacity can not be relied upon to be precisely
    240    /// minimal. Prefer [`try_reserve`] if future insertions are expected.
    241    ///
    242    /// [`try_reserve`]: Wtf8Buf::try_reserve
    243    ///
    244    /// # Errors
    245    ///
    246    /// If the capacity overflows, or the allocator reports a failure, then an error
    247    /// is returned.
    248    #[inline]
    249    pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), TryReserveError> {
    250        self.bytes.try_reserve_exact(additional)
    251    }
    252
    253    #[inline]
    254    pub fn shrink_to_fit(&mut self) {
    255        self.bytes.shrink_to_fit()
    256    }
    257
    258    #[inline]
    259    pub fn shrink_to(&mut self, min_capacity: usize) {
    260        self.bytes.shrink_to(min_capacity)
    261    }
    262
    263    #[inline]
    264    pub fn leak<'a>(self) -> &'a mut Wtf8 {
    265        unsafe { Wtf8::from_mut_bytes_unchecked(self.bytes.leak()) }
    266    }
    267
    268    /// Returns the number of bytes that this string buffer can hold without reallocating.
    269    #[inline]
    270    pub fn capacity(&self) -> usize {
    271        self.bytes.capacity()
    272    }
    273
    274    /// Append a UTF-8 slice at the end of the string.
    275    #[inline]
    276    pub fn push_str(&mut self, other: &str) {
    277        self.bytes.extend_from_slice(other.as_bytes())
    278    }
    279
    280    /// Append a WTF-8 slice at the end of the string.
    281    ///
    282    /// This replaces newly paired surrogates at the boundary
    283    /// with a supplementary code point,
    284    /// like concatenating ill-formed UTF-16 strings effectively would.
    285    #[inline]
    286    pub fn push_wtf8(&mut self, other: &Wtf8) {
    287        match ((&*self).final_lead_surrogate(), other.initial_trail_surrogate()) {
    288            // Replace newly paired surrogates by a supplementary code point.
    289            (Some(lead), Some(trail)) => {
    290                let len_without_lead_surrogate = self.len() - 3;
    291                self.bytes.truncate(len_without_lead_surrogate);
    292                let other_without_trail_surrogate = &other.as_bytes()[3..];
    293                // 4 bytes for the supplementary code point
    294                self.bytes.reserve(4 + other_without_trail_surrogate.len());
    295                self.push_char(decode_surrogate_pair(lead, trail));
    296                self.bytes.extend_from_slice(other_without_trail_surrogate);
    297            }
    298            _ => {
    299                // If we'll be pushing a string containing a surrogate, we may
    300                // no longer have UTF-8.
    301                if self.is_known_utf8 && other.next_surrogate(0).is_some() {
    302                    self.is_known_utf8 = false;
    303                }
    304
    305                self.bytes.extend_from_slice(other.as_bytes());
    306            }
    307        }
    308    }
    309
    310    /// Append a Unicode scalar value at the end of the string.
    311    #[inline]
    312    pub fn push_char(&mut self, c: char) {
    313        // SAFETY: It's always safe to push a char.
    314        unsafe { self.push_code_point_unchecked(CodePoint::from_char(c)) }
    315    }
    316
    317    /// Append a code point at the end of the string.
    318    ///
    319    /// This replaces newly paired surrogates at the boundary
    320    /// with a supplementary code point,
    321    /// like concatenating ill-formed UTF-16 strings effectively would.
    322    #[inline]
    323    pub fn push(&mut self, code_point: CodePoint) {
    324        if let Some(trail) = code_point.to_trail_surrogate() {
    325            if let Some(lead) = (&*self).final_lead_surrogate() {
    326                let len_without_lead_surrogate = self.len() - 3;
    327                self.bytes.truncate(len_without_lead_surrogate);
    328                self.push_char(decode_surrogate_pair(lead, trail));
    329                return;
    330            }
    331
    332            // We're pushing a trailing surrogate.
    333            self.is_known_utf8 = false;
    334        } else if code_point.to_lead_surrogate().is_some() {
    335            // We're pushing a leading surrogate.
    336            self.is_known_utf8 = false;
    337        }
    338
    339        // No newly paired surrogates at the boundary.
    340        unsafe { self.push_code_point_unchecked(code_point) }
    341    }
    342
    343    /// Shortens a string to the specified length.
    344    ///
    345    /// # Panics
    346    ///
    347    /// Panics if `new_len` > current length,
    348    /// or if `new_len` is not a code point boundary.
    349    #[inline]
    350    pub fn truncate(&mut self, new_len: usize) {
    351        assert!(self.is_code_point_boundary(new_len));
    352        self.bytes.truncate(new_len)
    353    }
    354
    355    /// Consumes the WTF-8 string and tries to convert it to a vec of bytes.
    356    #[inline]
    357    pub fn into_bytes(self) -> Vec<u8> {
    358        self.bytes
    359    }
    360
    361    /// Consumes the WTF-8 string and tries to convert it to UTF-8.
    362    ///
    363    /// This does not copy the data.
    364    ///
    365    /// If the contents are not well-formed UTF-8
    366    /// (that is, if the string contains surrogates),
    367    /// the original WTF-8 string is returned instead.
    368    pub fn into_string(self) -> Result<String, Wtf8Buf> {
    369        if self.is_known_utf8 || self.next_surrogate(0).is_none() {
    370            Ok(unsafe { String::from_utf8_unchecked(self.bytes) })
    371        } else {
    372            Err(self)
    373        }
    374    }
    375
    376    /// Consumes the WTF-8 string and converts it lossily to UTF-8.
    377    ///
    378    /// This does not copy the data (but may overwrite parts of it in place).
    379    ///
    380    /// Surrogates are replaced with `"\u{FFFD}"` (the replacement character “�”)
    381    pub fn into_string_lossy(mut self) -> String {
    382        if !self.is_known_utf8 {
    383            let mut pos = 0;
    384            while let Some((surrogate_pos, _)) = self.next_surrogate(pos) {
    385                pos = surrogate_pos + 3;
    386                // Surrogates and the replacement character are all 3 bytes, so
    387                // they can substituted in-place.
    388                self.bytes[surrogate_pos..pos].copy_from_slice("\u{FFFD}".as_bytes());
    389            }
    390        }
    391        unsafe { String::from_utf8_unchecked(self.bytes) }
    392    }
    393
    394    /// Converts this `Wtf8Buf` into a boxed `Wtf8`.
    395    #[inline]
    396    pub fn into_box(self) -> Box<Wtf8> {
    397        // SAFETY: relies on `Wtf8` being `repr(transparent)`.
    398        unsafe { mem::transmute(self.bytes.into_boxed_slice()) }
    399    }
    400
    401    /// Converts a `Box<Wtf8>` into a `Wtf8Buf`.
    402    pub fn from_box(boxed: Box<Wtf8>) -> Wtf8Buf {
    403        let bytes: Box<[u8]> = unsafe { mem::transmute(boxed) };
    404        Wtf8Buf { bytes: bytes.into_vec(), is_known_utf8: false }
    405    }
    406
    407    /// Provides plumbing to core `Vec::extend_from_slice`.
    408    /// More well behaving alternative to allowing outer types
    409    /// full mutable access to the core `Vec`.
    410    #[inline]
    411    pub unsafe fn extend_from_slice_unchecked(&mut self, other: &[u8]) {
    412        self.bytes.extend_from_slice(other);
    413        self.is_known_utf8 = false;
    414    }
    415}
    416
    417/// Creates a new WTF-8 string from an iterator of code points.
    418///
    419/// This replaces surrogate code point pairs with supplementary code points,
    420/// like concatenating ill-formed UTF-16 strings effectively would.
    421impl FromIterator<CodePoint> for Wtf8Buf {
    422    fn from_iter<T: IntoIterator<Item = CodePoint>>(iter: T) -> Wtf8Buf {
    423        let mut string = Wtf8Buf::new();
    424        string.extend(iter);
    425        string
    426    }
    427}
    428
    429/// Append code points from an iterator to the string.
    430///
    431/// This replaces surrogate code point pairs with supplementary code points,
    432/// like concatenating ill-formed UTF-16 strings effectively would.
    433impl Extend<CodePoint> for Wtf8Buf {
    434    fn extend<T: IntoIterator<Item = CodePoint>>(&mut self, iter: T) {
    435        let iterator = iter.into_iter();
    436        let (low, _high) = iterator.size_hint();
    437        // Lower bound of one byte per code point (ASCII only)
    438        self.bytes.reserve(low);
    439        iterator.for_each(move |code_point| self.push(code_point));
    440    }
    441
    442    #[inline]
    443    fn extend_one(&mut self, code_point: CodePoint) {
    444        self.push(code_point);
    445    }
    446
    447    #[inline]
    448    fn extend_reserve(&mut self, additional: usize) {
    449        // Lower bound of one byte per code point (ASCII only)
    450        self.bytes.reserve(additional);
    451    }
    452}
    453
    454/// Creates an owned `Wtf8Buf` from a borrowed `Wtf8`.
    455pub(super) fn to_owned(slice: &Wtf8) -> Wtf8Buf {
    456    Wtf8Buf { bytes: slice.as_bytes().to_vec(), is_known_utf8: false }
    457}
    458
    459/// Lossily converts the string to UTF-8.
    460/// Returns a UTF-8 `&str` slice if the contents are well-formed in UTF-8.
    461///
    462/// Surrogates are replaced with `"\u{FFFD}"` (the replacement character “�”).
    463///
    464/// This only copies the data if necessary (if it contains any surrogate).
    465pub(super) fn to_string_lossy(slice: &Wtf8) -> Cow<'_, str> {
    466    let Some((surrogate_pos, _)) = slice.next_surrogate(0) else {
    467        return Cow::Borrowed(unsafe { str::from_utf8_unchecked(slice.as_bytes()) });
    468    };
    469    let wtf8_bytes = slice.as_bytes();
    470    let mut utf8_bytes = Vec::with_capacity(slice.len());
    471    utf8_bytes.extend_from_slice(&wtf8_bytes[..surrogate_pos]);
    472    utf8_bytes.extend_from_slice("\u{FFFD}".as_bytes());
    473    let mut pos = surrogate_pos + 3;
    474    loop {
    475        match slice.next_surrogate(pos) {
    476            Some((surrogate_pos, _)) => {
    477                utf8_bytes.extend_from_slice(&wtf8_bytes[pos..surrogate_pos]);
    478                utf8_bytes.extend_from_slice("\u{FFFD}".as_bytes());
    479                pos = surrogate_pos + 3;
    480            }
    481            None => {
    482                utf8_bytes.extend_from_slice(&wtf8_bytes[pos..]);
    483                return Cow::Owned(unsafe { String::from_utf8_unchecked(utf8_bytes) });
    484            }
    485        }
    486    }
    487}
    488
    489#[inline]
    490pub(super) fn clone_into(slice: &Wtf8, buf: &mut Wtf8Buf) {
    491    buf.is_known_utf8 = false;
    492    slice.as_bytes().clone_into(&mut buf.bytes);
    493}
    494
    495#[cfg(not(test))]
    496impl Wtf8 {
    497    #[rustc_allow_incoherent_impl]
    498    pub fn to_owned(&self) -> Wtf8Buf {
    499        to_owned(self)
    500    }
    501
    502    #[rustc_allow_incoherent_impl]
    503    pub fn clone_into(&self, buf: &mut Wtf8Buf) {
    504        clone_into(self, buf)
    505    }
    506
    507    #[rustc_allow_incoherent_impl]
    508    pub fn to_string_lossy(&self) -> Cow<'_, str> {
    509        to_string_lossy(self)
    510    }
    511
    512    #[rustc_allow_incoherent_impl]
    513    pub fn into_box(&self) -> Box<Wtf8> {
    514        let boxed: Box<[u8]> = self.as_bytes().into();
    515        unsafe { mem::transmute(boxed) }
    516    }
    517
    518    #[rustc_allow_incoherent_impl]
    519    pub fn empty_box() -> Box<Wtf8> {
    520        let boxed: Box<[u8]> = Default::default();
    521        unsafe { mem::transmute(boxed) }
    522    }
    523
    524    #[cfg(target_has_atomic = "ptr")]
    525    #[rustc_allow_incoherent_impl]
    526    pub fn into_arc(&self) -> Arc<Wtf8> {
    527        let arc: Arc<[u8]> = Arc::from(self.as_bytes());
    528        unsafe { Arc::from_raw(Arc::into_raw(arc) as *const Wtf8) }
    529    }
    530
    531    #[rustc_allow_incoherent_impl]
    532    pub fn into_rc(&self) -> Rc<Wtf8> {
    533        let rc: Rc<[u8]> = Rc::from(self.as_bytes());
    534        unsafe { Rc::from_raw(Rc::into_raw(rc) as *const Wtf8) }
    535    }
    536
    537    #[inline]
    538    #[rustc_allow_incoherent_impl]
    539    pub fn to_ascii_lowercase(&self) -> Wtf8Buf {
    540        Wtf8Buf { bytes: self.as_bytes().to_ascii_lowercase(), is_known_utf8: false }
    541    }
    542
    543    #[inline]
    544    #[rustc_allow_incoherent_impl]
    545    pub fn to_ascii_uppercase(&self) -> Wtf8Buf {
    546        Wtf8Buf { bytes: self.as_bytes().to_ascii_uppercase(), is_known_utf8: false }
    547    }
    548}
    549
    550#[inline]
    551fn decode_surrogate_pair(lead: u16, trail: u16) -> char {
    552    let code_point = 0x10000 + ((((lead - 0xD800) as u32) << 10) | (trail - 0xDC00) as u32);
    553    unsafe { char::from_u32_unchecked(code_point) }
    554}
    555
    556impl Hash for Wtf8Buf {
    557    #[inline]
    558    fn hash<H: Hasher>(&self, state: &mut H) {
    559        state.write(&self.bytes);
    560        0xfeu8.hash(state)
    561    }
    562}