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Diffstat (limited to 'library/core/src/str/traits.rs')
| -rw-r--r-- | library/core/src/str/traits.rs | 604 |
1 files changed, 604 insertions, 0 deletions
diff --git a/library/core/src/str/traits.rs b/library/core/src/str/traits.rs new file mode 100644 index 000000000..e9649fc91 --- /dev/null +++ b/library/core/src/str/traits.rs @@ -0,0 +1,604 @@ +//! Trait implementations for `str`. + +use crate::cmp::Ordering; +use crate::ops; +use crate::ptr; +use crate::slice::SliceIndex; + +use super::ParseBoolError; + +/// Implements ordering of strings. +/// +/// Strings are ordered [lexicographically](Ord#lexicographical-comparison) by their byte values. This orders Unicode code +/// points based on their positions in the code charts. This is not necessarily the same as +/// "alphabetical" order, which varies by language and locale. Sorting strings according to +/// culturally-accepted standards requires locale-specific data that is outside the scope of +/// the `str` type. +#[stable(feature = "rust1", since = "1.0.0")] +impl Ord for str { + #[inline] + fn cmp(&self, other: &str) -> Ordering { + self.as_bytes().cmp(other.as_bytes()) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl PartialEq for str { + #[inline] + fn eq(&self, other: &str) -> bool { + self.as_bytes() == other.as_bytes() + } + #[inline] + fn ne(&self, other: &str) -> bool { + !(*self).eq(other) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl Eq for str {} + +/// Implements comparison operations on strings. +/// +/// Strings are compared [lexicographically](Ord#lexicographical-comparison) by their byte values. This compares Unicode code +/// points based on their positions in the code charts. This is not necessarily the same as +/// "alphabetical" order, which varies by language and locale. Comparing strings according to +/// culturally-accepted standards requires locale-specific data that is outside the scope of +/// the `str` type. +#[stable(feature = "rust1", since = "1.0.0")] +impl PartialOrd for str { + #[inline] + fn partial_cmp(&self, other: &str) -> Option<Ordering> { + Some(self.cmp(other)) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +#[rustc_const_unstable(feature = "const_slice_index", issue = "none")] +impl<I> const ops::Index<I> for str +where + I: ~const SliceIndex<str>, +{ + type Output = I::Output; + + #[inline] + fn index(&self, index: I) -> &I::Output { + index.index(self) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +#[rustc_const_unstable(feature = "const_slice_index", issue = "none")] +impl<I> const ops::IndexMut<I> for str +where + I: ~const SliceIndex<str>, +{ + #[inline] + fn index_mut(&mut self, index: I) -> &mut I::Output { + index.index_mut(self) + } +} + +#[inline(never)] +#[cold] +#[track_caller] +const fn str_index_overflow_fail() -> ! { + panic!("attempted to index str up to maximum usize"); +} + +/// Implements substring slicing with syntax `&self[..]` or `&mut self[..]`. +/// +/// Returns a slice of the whole string, i.e., returns `&self` or `&mut +/// self`. Equivalent to `&self[0 .. len]` or `&mut self[0 .. len]`. Unlike +/// other indexing operations, this can never panic. +/// +/// This operation is *O*(1). +/// +/// Prior to 1.20.0, these indexing operations were still supported by +/// direct implementation of `Index` and `IndexMut`. +/// +/// Equivalent to `&self[0 .. len]` or `&mut self[0 .. len]`. +#[stable(feature = "str_checked_slicing", since = "1.20.0")] +#[rustc_const_unstable(feature = "const_slice_index", issue = "none")] +unsafe impl const SliceIndex<str> for ops::RangeFull { + type Output = str; + #[inline] + fn get(self, slice: &str) -> Option<&Self::Output> { + Some(slice) + } + #[inline] + fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> { + Some(slice) + } + #[inline] + unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output { + slice + } + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output { + slice + } + #[inline] + fn index(self, slice: &str) -> &Self::Output { + slice + } + #[inline] + fn index_mut(self, slice: &mut str) -> &mut Self::Output { + slice + } +} + +/// Implements substring slicing with syntax `&self[begin .. end]` or `&mut +/// self[begin .. end]`. +/// +/// Returns a slice of the given string from the byte range +/// [`begin`, `end`). +/// +/// This operation is *O*(1). +/// +/// Prior to 1.20.0, these indexing operations were still supported by +/// direct implementation of `Index` and `IndexMut`. +/// +/// # Panics +/// +/// Panics if `begin` or `end` does not point to the starting byte offset of +/// a character (as defined by `is_char_boundary`), if `begin > end`, or if +/// `end > len`. +/// +/// # Examples +/// +/// ``` +/// let s = "Löwe 老虎 Léopard"; +/// assert_eq!(&s[0 .. 1], "L"); +/// +/// assert_eq!(&s[1 .. 9], "öwe 老"); +/// +/// // these will panic: +/// // byte 2 lies within `ö`: +/// // &s[2 ..3]; +/// +/// // byte 8 lies within `老` +/// // &s[1 .. 8]; +/// +/// // byte 100 is outside the string +/// // &s[3 .. 100]; +/// ``` +#[stable(feature = "str_checked_slicing", since = "1.20.0")] +#[rustc_const_unstable(feature = "const_slice_index", issue = "none")] +unsafe impl const SliceIndex<str> for ops::Range<usize> { + type Output = str; + #[inline] + fn get(self, slice: &str) -> Option<&Self::Output> { + if self.start <= self.end + && slice.is_char_boundary(self.start) + && slice.is_char_boundary(self.end) + { + // SAFETY: just checked that `start` and `end` are on a char boundary, + // and we are passing in a safe reference, so the return value will also be one. + // We also checked char boundaries, so this is valid UTF-8. + Some(unsafe { &*self.get_unchecked(slice) }) + } else { + None + } + } + #[inline] + fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> { + if self.start <= self.end + && slice.is_char_boundary(self.start) + && slice.is_char_boundary(self.end) + { + // SAFETY: just checked that `start` and `end` are on a char boundary. + // We know the pointer is unique because we got it from `slice`. + Some(unsafe { &mut *self.get_unchecked_mut(slice) }) + } else { + None + } + } + #[inline] + unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output { + let slice = slice as *const [u8]; + // SAFETY: the caller guarantees that `self` is in bounds of `slice` + // which satisfies all the conditions for `add`. + let ptr = unsafe { slice.as_ptr().add(self.start) }; + let len = self.end - self.start; + ptr::slice_from_raw_parts(ptr, len) as *const str + } + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output { + let slice = slice as *mut [u8]; + // SAFETY: see comments for `get_unchecked`. + let ptr = unsafe { slice.as_mut_ptr().add(self.start) }; + let len = self.end - self.start; + ptr::slice_from_raw_parts_mut(ptr, len) as *mut str + } + #[inline] + fn index(self, slice: &str) -> &Self::Output { + let (start, end) = (self.start, self.end); + match self.get(slice) { + Some(s) => s, + None => super::slice_error_fail(slice, start, end), + } + } + #[inline] + fn index_mut(self, slice: &mut str) -> &mut Self::Output { + // is_char_boundary checks that the index is in [0, .len()] + // cannot reuse `get` as above, because of NLL trouble + if self.start <= self.end + && slice.is_char_boundary(self.start) + && slice.is_char_boundary(self.end) + { + // SAFETY: just checked that `start` and `end` are on a char boundary, + // and we are passing in a safe reference, so the return value will also be one. + unsafe { &mut *self.get_unchecked_mut(slice) } + } else { + super::slice_error_fail(slice, self.start, self.end) + } + } +} + +/// Implements substring slicing with syntax `&self[.. end]` or `&mut +/// self[.. end]`. +/// +/// Returns a slice of the given string from the byte range \[0, `end`). +/// Equivalent to `&self[0 .. end]` or `&mut self[0 .. end]`. +/// +/// This operation is *O*(1). +/// +/// Prior to 1.20.0, these indexing operations were still supported by +/// direct implementation of `Index` and `IndexMut`. +/// +/// # Panics +/// +/// Panics if `end` does not point to the starting byte offset of a +/// character (as defined by `is_char_boundary`), or if `end > len`. +#[stable(feature = "str_checked_slicing", since = "1.20.0")] +#[rustc_const_unstable(feature = "const_slice_index", issue = "none")] +unsafe impl const SliceIndex<str> for ops::RangeTo<usize> { + type Output = str; + #[inline] + fn get(self, slice: &str) -> Option<&Self::Output> { + if slice.is_char_boundary(self.end) { + // SAFETY: just checked that `end` is on a char boundary, + // and we are passing in a safe reference, so the return value will also be one. + Some(unsafe { &*self.get_unchecked(slice) }) + } else { + None + } + } + #[inline] + fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> { + if slice.is_char_boundary(self.end) { + // SAFETY: just checked that `end` is on a char boundary, + // and we are passing in a safe reference, so the return value will also be one. + Some(unsafe { &mut *self.get_unchecked_mut(slice) }) + } else { + None + } + } + #[inline] + unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output { + let slice = slice as *const [u8]; + let ptr = slice.as_ptr(); + ptr::slice_from_raw_parts(ptr, self.end) as *const str + } + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output { + let slice = slice as *mut [u8]; + let ptr = slice.as_mut_ptr(); + ptr::slice_from_raw_parts_mut(ptr, self.end) as *mut str + } + #[inline] + fn index(self, slice: &str) -> &Self::Output { + let end = self.end; + match self.get(slice) { + Some(s) => s, + None => super::slice_error_fail(slice, 0, end), + } + } + #[inline] + fn index_mut(self, slice: &mut str) -> &mut Self::Output { + if slice.is_char_boundary(self.end) { + // SAFETY: just checked that `end` is on a char boundary, + // and we are passing in a safe reference, so the return value will also be one. + unsafe { &mut *self.get_unchecked_mut(slice) } + } else { + super::slice_error_fail(slice, 0, self.end) + } + } +} + +/// Implements substring slicing with syntax `&self[begin ..]` or `&mut +/// self[begin ..]`. +/// +/// Returns a slice of the given string from the byte range \[`begin`, `len`). +/// Equivalent to `&self[begin .. len]` or `&mut self[begin .. len]`. +/// +/// This operation is *O*(1). +/// +/// Prior to 1.20.0, these indexing operations were still supported by +/// direct implementation of `Index` and `IndexMut`. +/// +/// # Panics +/// +/// Panics if `begin` does not point to the starting byte offset of +/// a character (as defined by `is_char_boundary`), or if `begin > len`. +#[stable(feature = "str_checked_slicing", since = "1.20.0")] +#[rustc_const_unstable(feature = "const_slice_index", issue = "none")] +unsafe impl const SliceIndex<str> for ops::RangeFrom<usize> { + type Output = str; + #[inline] + fn get(self, slice: &str) -> Option<&Self::Output> { + if slice.is_char_boundary(self.start) { + // SAFETY: just checked that `start` is on a char boundary, + // and we are passing in a safe reference, so the return value will also be one. + Some(unsafe { &*self.get_unchecked(slice) }) + } else { + None + } + } + #[inline] + fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> { + if slice.is_char_boundary(self.start) { + // SAFETY: just checked that `start` is on a char boundary, + // and we are passing in a safe reference, so the return value will also be one. + Some(unsafe { &mut *self.get_unchecked_mut(slice) }) + } else { + None + } + } + #[inline] + unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output { + let slice = slice as *const [u8]; + // SAFETY: the caller guarantees that `self` is in bounds of `slice` + // which satisfies all the conditions for `add`. + let ptr = unsafe { slice.as_ptr().add(self.start) }; + let len = slice.len() - self.start; + ptr::slice_from_raw_parts(ptr, len) as *const str + } + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output { + let slice = slice as *mut [u8]; + // SAFETY: identical to `get_unchecked`. + let ptr = unsafe { slice.as_mut_ptr().add(self.start) }; + let len = slice.len() - self.start; + ptr::slice_from_raw_parts_mut(ptr, len) as *mut str + } + #[inline] + fn index(self, slice: &str) -> &Self::Output { + let (start, end) = (self.start, slice.len()); + match self.get(slice) { + Some(s) => s, + None => super::slice_error_fail(slice, start, end), + } + } + #[inline] + fn index_mut(self, slice: &mut str) -> &mut Self::Output { + if slice.is_char_boundary(self.start) { + // SAFETY: just checked that `start` is on a char boundary, + // and we are passing in a safe reference, so the return value will also be one. + unsafe { &mut *self.get_unchecked_mut(slice) } + } else { + super::slice_error_fail(slice, self.start, slice.len()) + } + } +} + +/// Implements substring slicing with syntax `&self[begin ..= end]` or `&mut +/// self[begin ..= end]`. +/// +/// Returns a slice of the given string from the byte range +/// [`begin`, `end`]. Equivalent to `&self [begin .. end + 1]` or `&mut +/// self[begin .. end + 1]`, except if `end` has the maximum value for +/// `usize`. +/// +/// This operation is *O*(1). +/// +/// # Panics +/// +/// Panics if `begin` does not point to the starting byte offset of +/// a character (as defined by `is_char_boundary`), if `end` does not point +/// to the ending byte offset of a character (`end + 1` is either a starting +/// byte offset or equal to `len`), if `begin > end`, or if `end >= len`. +#[stable(feature = "inclusive_range", since = "1.26.0")] +#[rustc_const_unstable(feature = "const_slice_index", issue = "none")] +unsafe impl const SliceIndex<str> for ops::RangeInclusive<usize> { + type Output = str; + #[inline] + fn get(self, slice: &str) -> Option<&Self::Output> { + if *self.end() == usize::MAX { None } else { self.into_slice_range().get(slice) } + } + #[inline] + fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> { + if *self.end() == usize::MAX { None } else { self.into_slice_range().get_mut(slice) } + } + #[inline] + unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output { + // SAFETY: the caller must uphold the safety contract for `get_unchecked`. + unsafe { self.into_slice_range().get_unchecked(slice) } + } + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output { + // SAFETY: the caller must uphold the safety contract for `get_unchecked_mut`. + unsafe { self.into_slice_range().get_unchecked_mut(slice) } + } + #[inline] + fn index(self, slice: &str) -> &Self::Output { + if *self.end() == usize::MAX { + str_index_overflow_fail(); + } + self.into_slice_range().index(slice) + } + #[inline] + fn index_mut(self, slice: &mut str) -> &mut Self::Output { + if *self.end() == usize::MAX { + str_index_overflow_fail(); + } + self.into_slice_range().index_mut(slice) + } +} + +/// Implements substring slicing with syntax `&self[..= end]` or `&mut +/// self[..= end]`. +/// +/// Returns a slice of the given string from the byte range \[0, `end`\]. +/// Equivalent to `&self [0 .. end + 1]`, except if `end` has the maximum +/// value for `usize`. +/// +/// This operation is *O*(1). +/// +/// # Panics +/// +/// Panics if `end` does not point to the ending byte offset of a character +/// (`end + 1` is either a starting byte offset as defined by +/// `is_char_boundary`, or equal to `len`), or if `end >= len`. +#[stable(feature = "inclusive_range", since = "1.26.0")] +#[rustc_const_unstable(feature = "const_slice_index", issue = "none")] +unsafe impl const SliceIndex<str> for ops::RangeToInclusive<usize> { + type Output = str; + #[inline] + fn get(self, slice: &str) -> Option<&Self::Output> { + if self.end == usize::MAX { None } else { (..self.end + 1).get(slice) } + } + #[inline] + fn get_mut(self, slice: &mut str) -> Option<&mut Self::Output> { + if self.end == usize::MAX { None } else { (..self.end + 1).get_mut(slice) } + } + #[inline] + unsafe fn get_unchecked(self, slice: *const str) -> *const Self::Output { + // SAFETY: the caller must uphold the safety contract for `get_unchecked`. + unsafe { (..self.end + 1).get_unchecked(slice) } + } + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut str) -> *mut Self::Output { + // SAFETY: the caller must uphold the safety contract for `get_unchecked_mut`. + unsafe { (..self.end + 1).get_unchecked_mut(slice) } + } + #[inline] + fn index(self, slice: &str) -> &Self::Output { + if self.end == usize::MAX { + str_index_overflow_fail(); + } + (..self.end + 1).index(slice) + } + #[inline] + fn index_mut(self, slice: &mut str) -> &mut Self::Output { + if self.end == usize::MAX { + str_index_overflow_fail(); + } + (..self.end + 1).index_mut(slice) + } +} + +/// Parse a value from a string +/// +/// `FromStr`'s [`from_str`] method is often used implicitly, through +/// [`str`]'s [`parse`] method. See [`parse`]'s documentation for examples. +/// +/// [`from_str`]: FromStr::from_str +/// [`parse`]: str::parse +/// +/// `FromStr` does not have a lifetime parameter, and so you can only parse types +/// that do not contain a lifetime parameter themselves. In other words, you can +/// parse an `i32` with `FromStr`, but not a `&i32`. You can parse a struct that +/// contains an `i32`, but not one that contains an `&i32`. +/// +/// # Examples +/// +/// Basic implementation of `FromStr` on an example `Point` type: +/// +/// ``` +/// use std::str::FromStr; +/// use std::num::ParseIntError; +/// +/// #[derive(Debug, PartialEq)] +/// struct Point { +/// x: i32, +/// y: i32 +/// } +/// +/// impl FromStr for Point { +/// type Err = ParseIntError; +/// +/// fn from_str(s: &str) -> Result<Self, Self::Err> { +/// let (x, y) = s +/// .strip_prefix('(') +/// .and_then(|s| s.strip_suffix(')')) +/// .and_then(|s| s.split_once(',')) +/// .unwrap(); +/// +/// let x_fromstr = x.parse::<i32>()?; +/// let y_fromstr = y.parse::<i32>()?; +/// +/// Ok(Point { x: x_fromstr, y: y_fromstr }) +/// } +/// } +/// +/// let expected = Ok(Point { x: 1, y: 2 }); +/// // Explicit call +/// assert_eq!(Point::from_str("(1,2)"), expected); +/// // Implicit calls, through parse +/// assert_eq!("(1,2)".parse(), expected); +/// assert_eq!("(1,2)".parse::<Point>(), expected); +/// ``` +#[stable(feature = "rust1", since = "1.0.0")] +pub trait FromStr: Sized { + /// The associated error which can be returned from parsing. + #[stable(feature = "rust1", since = "1.0.0")] + type Err; + + /// Parses a string `s` to return a value of this type. + /// + /// If parsing succeeds, return the value inside [`Ok`], otherwise + /// when the string is ill-formatted return an error specific to the + /// inside [`Err`]. The error type is specific to the implementation of the trait. + /// + /// # Examples + /// + /// Basic usage with [`i32`], a type that implements `FromStr`: + /// + /// ``` + /// use std::str::FromStr; + /// + /// let s = "5"; + /// let x = i32::from_str(s).unwrap(); + /// + /// assert_eq!(5, x); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + fn from_str(s: &str) -> Result<Self, Self::Err>; +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl FromStr for bool { + type Err = ParseBoolError; + + /// Parse a `bool` from a string. + /// + /// Yields a `Result<bool, ParseBoolError>`, because `s` may or may not + /// actually be parseable. + /// + /// # Examples + /// + /// ``` + /// use std::str::FromStr; + /// + /// assert_eq!(FromStr::from_str("true"), Ok(true)); + /// assert_eq!(FromStr::from_str("false"), Ok(false)); + /// assert!(<bool as FromStr>::from_str("not even a boolean").is_err()); + /// ``` + /// + /// Note, in many cases, the `.parse()` method on `str` is more proper. + /// + /// ``` + /// assert_eq!("true".parse(), Ok(true)); + /// assert_eq!("false".parse(), Ok(false)); + /// assert!("not even a boolean".parse::<bool>().is_err()); + /// ``` + #[inline] + fn from_str(s: &str) -> Result<bool, ParseBoolError> { + match s { + "true" => Ok(true), + "false" => Ok(false), + _ => Err(ParseBoolError), + } + } +} |