ascii.rs - source
Description: Source of the Rust file `library/std/src/ascii.rs`.
Keywords: rust, rustlang, rust-lang

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    //! Operations on ASCII strings and characters.
    //!
    //! Most string operations in Rust act on UTF-8 strings. However, at times it
    //! makes more sense to only consider the ASCII character set for a specific
    //! operation.
    //!
    //! The [`AsciiExt`] trait provides methods that allow for character
    //! operations that only act on the ASCII subset and leave non-ASCII characters
    //! alone.
    //!
    //! The [`escape_default`] function provides an iterator over the bytes of an
    //! escaped version of the character given.

    #![stable(feature = "rust1", since = "1.0.0")]

    #[stable(feature = "rust1", since = "1.0.0")]
    pub use core::ascii::{escape_default, EscapeDefault};

    /// Extension methods for ASCII-subset only operations.
    ///
    /// Be aware that operations on seemingly non-ASCII characters can sometimes
    /// have unexpected results. Consider this example:
    ///
    /// ```
    /// use std::ascii::AsciiExt;
    ///
    /// assert_eq!(AsciiExt::to_ascii_uppercase("café"), "CAFÉ");
    /// assert_eq!(AsciiExt::to_ascii_uppercase("café"), "CAFé");
    /// ```
    ///
    /// In the first example, the lowercased string is represented `"cafe\u{301}"`
    /// (the last character is an acute accent [combining character]). Unlike the
    /// other characters in the string, the combining character will not get mapped
    /// to an uppercase variant, resulting in `"CAFE\u{301}"`. In the second
    /// example, the lowercased string is represented `"caf\u{e9}"` (the last
    /// character is a single Unicode character representing an 'e' with an acute
    /// accent). Since the last character is defined outside the scope of ASCII,
    /// it will not get mapped to an uppercase variant, resulting in `"CAF\u{e9}"`.
    ///
    /// [combining character]: https://en.wikipedia.org/wiki/Combining_character
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_deprecated(since = "1.26.0", reason = "use inherent methods instead")]
    pub trait AsciiExt {
        /// Container type for copied ASCII characters.
        #[stable(feature = "rust1", since = "1.0.0")]
        type Owned;

        /// Checks if the value is within the ASCII range.
        ///
        /// # Note
        ///
        /// This method is deprecated in favor of the identically-named
        /// inherent methods on `u8`, `char`, `[u8]` and `str`.
        #[stable(feature = "rust1", since = "1.0.0")]
        fn is_ascii(&self) -> bool;

        /// Makes a copy of the value in its ASCII upper case equivalent.
        ///
        /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
        /// but non-ASCII letters are unchanged.
        ///
        /// To uppercase the value in-place, use [`make_ascii_uppercase`].
        ///
        /// To uppercase ASCII characters in addition to non-ASCII characters, use
        /// [`str::to_uppercase`].
        ///
        /// # Note
        ///
        /// This method is deprecated in favor of the identically-named
        /// inherent methods on `u8`, `char`, `[u8]` and `str`.
        ///
        /// [`make_ascii_uppercase`]: AsciiExt::make_ascii_uppercase
        #[stable(feature = "rust1", since = "1.0.0")]
        #[allow(deprecated)]
        fn to_ascii_uppercase(&self) -> Self::Owned;

        /// Makes a copy of the value in its ASCII lower case equivalent.
        ///
        /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
        /// but non-ASCII letters are unchanged.
        ///
        /// To lowercase the value in-place, use [`make_ascii_lowercase`].
        ///
        /// To lowercase ASCII characters in addition to non-ASCII characters, use
        /// [`str::to_lowercase`].
        ///
        /// # Note
        ///
        /// This method is deprecated in favor of the identically-named
        /// inherent methods on `u8`, `char`, `[u8]` and `str`.
        ///
        /// [`make_ascii_lowercase`]: AsciiExt::make_ascii_lowercase
        #[stable(feature = "rust1", since = "1.0.0")]
        #[allow(deprecated)]
        fn to_ascii_lowercase(&self) -> Self::Owned;

        /// Checks that two values are an ASCII case-insensitive match.
        ///
        /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
        /// but without allocating and copying temporaries.
        ///
        /// # Note
        ///
        /// This method is deprecated in favor of the identically-named
        /// inherent methods on `u8`, `char`, `[u8]` and `str`.
        #[stable(feature = "rust1", since = "1.0.0")]
        fn eq_ignore_ascii_case(&self, other: &Self) -> bool;

        /// Converts this type to its ASCII upper case equivalent in-place.
        ///
        /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
        /// but non-ASCII letters are unchanged.
        ///
        /// To return a new uppercased value without modifying the existing one, use
        /// [`to_ascii_uppercase`].
        ///
        /// # Note
        ///
        /// This method is deprecated in favor of the identically-named
        /// inherent methods on `u8`, `char`, `[u8]` and `str`.
        ///
        /// [`to_ascii_uppercase`]: AsciiExt::to_ascii_uppercase
        #[stable(feature = "ascii", since = "1.9.0")]
        fn make_ascii_uppercase(&mut self);

        /// Converts this type to its ASCII lower case equivalent in-place.
        ///
        /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
        /// but non-ASCII letters are unchanged.
        ///
        /// To return a new lowercased value without modifying the existing one, use
        /// [`to_ascii_lowercase`].
        ///
        /// # Note
        ///
        /// This method is deprecated in favor of the identically-named
        /// inherent methods on `u8`, `char`, `[u8]` and `str`.
        ///
        /// [`to_ascii_lowercase`]: AsciiExt::to_ascii_lowercase
        #[stable(feature = "ascii", since = "1.9.0")]
        fn make_ascii_lowercase(&mut self);
    }

    macro_rules! delegating_ascii_methods {
        () => {
            #[inline]
            fn is_ascii(&self) -> bool {
                self.is_ascii()
            }

            #[inline]
            fn to_ascii_uppercase(&self) -> Self::Owned {
                self.to_ascii_uppercase()
            }

            #[inline]
            fn to_ascii_lowercase(&self) -> Self::Owned {
                self.to_ascii_lowercase()
            }

            #[inline]
            fn eq_ignore_ascii_case(&self, o: &Self) -> bool {
                self.eq_ignore_ascii_case(o)
            }

            #[inline]
            fn make_ascii_uppercase(&mut self) {
                self.make_ascii_uppercase();
            }

            #[inline]
            fn make_ascii_lowercase(&mut self) {
                self.make_ascii_lowercase();
            }
        };
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    #[allow(deprecated)]
    impl AsciiExt for u8 {
        type Owned = u8;

        delegating_ascii_methods!();
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    #[allow(deprecated)]
    impl AsciiExt for char {
        type Owned = char;

        delegating_ascii_methods!();
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    #[allow(deprecated)]
    impl AsciiExt for [u8] {
        type Owned = Vec<u8>;

        delegating_ascii_methods!();
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    #[allow(deprecated)]
    impl AsciiExt for str {
        type Owned = String;

        delegating_ascii_methods!();
    }