456 lines
15 KiB
Rust
456 lines
15 KiB
Rust
// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Character manipulation (`char` type, Unicode Scalar Value)
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//!
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//! This module provides the `CharExt` trait, as well as its
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//! implementation for the primitive `char` type, in order to allow
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//! basic character manipulation.
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//!
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//! A `char` actually represents a
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//! *[Unicode Scalar
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//! Value](http://www.unicode.org/glossary/#unicode_scalar_value)*, as it can
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//! contain any Unicode code point except high-surrogate and low-surrogate code
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//! points.
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//!
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//! As such, only values in the ranges \[0x0,0xD7FF\] and \[0xE000,0x10FFFF\]
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//! (inclusive) are allowed. A `char` can always be safely cast to a `u32`;
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//! however the converse is not always true due to the above range limits
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//! and, as such, should be performed via the `from_u32` function.
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#![stable(feature = "rust1", since = "1.0.0")]
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#![doc(primitive = "char")]
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use core::char::CharExt as C;
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use core::option::Option::{self, Some};
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use core::iter::Iterator;
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use tables::{derived_property, property, general_category, conversions, charwidth};
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// stable reexports
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pub use core::char::{MAX, from_u32, from_digit, EscapeUnicode, EscapeDefault};
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// unstable reexports
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#[allow(deprecated)]
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pub use normalize::{decompose_canonical, decompose_compatible, compose};
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#[allow(deprecated)]
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pub use tables::normalization::canonical_combining_class;
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pub use tables::UNICODE_VERSION;
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/// An iterator over the lowercase mapping of a given character, returned from
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/// the [`to_lowercase` method](../primitive.char.html#method.to_lowercase) on
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/// characters.
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct ToLowercase(Option<char>);
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#[stable(feature = "rust1", since = "1.0.0")]
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impl Iterator for ToLowercase {
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type Item = char;
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fn next(&mut self) -> Option<char> { self.0.take() }
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}
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/// An iterator over the uppercase mapping of a given character, returned from
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/// the [`to_uppercase` method](../primitive.char.html#method.to_uppercase) on
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/// characters.
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct ToUppercase(Option<char>);
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#[stable(feature = "rust1", since = "1.0.0")]
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impl Iterator for ToUppercase {
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type Item = char;
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fn next(&mut self) -> Option<char> { self.0.take() }
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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#[lang = "char"]
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impl char {
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/// Checks if a `char` parses as a numeric digit in the given radix.
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///
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/// Compared to `is_numeric()`, this function only recognizes the characters
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/// `0-9`, `a-z` and `A-Z`.
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///
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/// # Return value
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///
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/// Returns `true` if `c` is a valid digit under `radix`, and `false`
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/// otherwise.
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///
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/// # Panics
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///
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/// Panics if given a radix > 36.
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///
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/// # Examples
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///
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/// ```
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/// let c = '1';
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///
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/// assert!(c.is_digit(10));
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///
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/// assert!('f'.is_digit(16));
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn is_digit(self, radix: u32) -> bool { C::is_digit(self, radix) }
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/// Converts a character to the corresponding digit.
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///
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/// # Return value
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///
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/// If `c` is between '0' and '9', the corresponding value between 0 and
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/// 9. If `c` is 'a' or 'A', 10. If `c` is 'b' or 'B', 11, etc. Returns
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/// none if the character does not refer to a digit in the given radix.
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///
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/// # Panics
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///
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/// Panics if given a radix outside the range [0..36].
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///
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/// # Examples
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///
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/// ```
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/// let c = '1';
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///
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/// assert_eq!(c.to_digit(10), Some(1));
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///
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/// assert_eq!('f'.to_digit(16), Some(15));
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn to_digit(self, radix: u32) -> Option<u32> { C::to_digit(self, radix) }
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/// Returns an iterator that yields the hexadecimal Unicode escape of a
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/// character, as `char`s.
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///
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/// All characters are escaped with Rust syntax of the form `\\u{NNNN}`
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/// where `NNNN` is the shortest hexadecimal representation of the code
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/// point.
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///
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/// # Examples
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///
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/// ```
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/// for i in '❤'.escape_unicode() {
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/// println!("{}", i);
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/// }
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/// ```
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///
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/// This prints:
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///
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/// ```text
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/// \
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/// u
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/// {
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/// 2
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/// 7
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/// 6
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/// 4
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/// }
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/// ```
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///
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/// Collecting into a `String`:
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///
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/// ```
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/// let heart: String = '❤'.escape_unicode().collect();
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///
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/// assert_eq!(heart, r"\u{2764}");
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn escape_unicode(self) -> EscapeUnicode { C::escape_unicode(self) }
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/// Returns an iterator that yields the 'default' ASCII and
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/// C++11-like literal escape of a character, as `char`s.
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///
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/// The default is chosen with a bias toward producing literals that are
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/// legal in a variety of languages, including C++11 and similar C-family
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/// languages. The exact rules are:
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///
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/// * Tab, CR and LF are escaped as '\t', '\r' and '\n' respectively.
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/// * Single-quote, double-quote and backslash chars are backslash-
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/// escaped.
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/// * Any other chars in the range [0x20,0x7e] are not escaped.
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/// * Any other chars are given hex Unicode escapes; see `escape_unicode`.
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///
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/// # Examples
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///
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/// ```
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/// for i in '"'.escape_default() {
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/// println!("{}", i);
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/// }
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/// ```
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///
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/// This prints:
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///
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/// ```text
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/// \
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/// "
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/// ```
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///
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/// Collecting into a `String`:
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///
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/// ```
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/// let quote: String = '"'.escape_default().collect();
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///
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/// assert_eq!(quote, "\\\"");
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn escape_default(self) -> EscapeDefault { C::escape_default(self) }
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/// Returns the number of bytes this character would need if encoded in
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/// UTF-8.
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///
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/// # Examples
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///
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/// ```
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/// let n = 'ß'.len_utf8();
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///
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/// assert_eq!(n, 2);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn len_utf8(self) -> usize { C::len_utf8(self) }
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/// Returns the number of 16-bit code units this character would need if
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/// encoded in UTF-16.
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///
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/// # Examples
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///
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/// ```
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/// let n = 'ß'.len_utf16();
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///
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/// assert_eq!(n, 1);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn len_utf16(self) -> usize { C::len_utf16(self) }
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/// Encodes this character as UTF-8 into the provided byte buffer, and then
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/// returns the number of bytes written.
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///
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/// If the buffer is not large enough, nothing will be written into it and a
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/// `None` will be returned. A buffer of length four is large enough to
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/// encode any `char`.
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///
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/// # Examples
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///
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/// In both of these examples, 'ß' takes two bytes to encode.
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///
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/// ```
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/// # #![feature(unicode)]
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/// let mut b = [0; 2];
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///
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/// let result = 'ß'.encode_utf8(&mut b);
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///
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/// assert_eq!(result, Some(2));
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/// ```
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///
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/// A buffer that's too small:
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///
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/// ```
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/// # #![feature(unicode)]
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/// let mut b = [0; 1];
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///
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/// let result = 'ß'.encode_utf8(&mut b);
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///
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/// assert_eq!(result, None);
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/// ```
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#[unstable(feature = "unicode",
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reason = "pending decision about Iterator/Writer/Reader")]
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pub fn encode_utf8(self, dst: &mut [u8]) -> Option<usize> { C::encode_utf8(self, dst) }
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/// Encodes this character as UTF-16 into the provided `u16` buffer, and
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/// then returns the number of `u16`s written.
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///
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/// If the buffer is not large enough, nothing will be written into it and a
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/// `None` will be returned. A buffer of length 2 is large enough to encode
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/// any `char`.
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///
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/// # Examples
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///
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/// In both of these examples, 'ß' takes one `u16` to encode.
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///
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/// ```
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/// # #![feature(unicode)]
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/// let mut b = [0; 1];
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///
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/// let result = 'ß'.encode_utf16(&mut b);
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///
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/// assert_eq!(result, Some(1));
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/// ```
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///
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/// A buffer that's too small:
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///
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/// ```
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/// # #![feature(unicode)]
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/// let mut b = [0; 0];
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///
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/// let result = 'ß'.encode_utf8(&mut b);
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///
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/// assert_eq!(result, None);
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/// ```
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#[unstable(feature = "unicode",
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reason = "pending decision about Iterator/Writer/Reader")]
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pub fn encode_utf16(self, dst: &mut [u16]) -> Option<usize> { C::encode_utf16(self, dst) }
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/// Returns whether the specified character is considered a Unicode
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/// alphabetic code point.
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn is_alphabetic(self) -> bool {
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match self {
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'a' ... 'z' | 'A' ... 'Z' => true,
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c if c > '\x7f' => derived_property::Alphabetic(c),
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_ => false
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}
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}
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/// Returns whether the specified character satisfies the 'XID_Start'
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/// Unicode property.
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///
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/// 'XID_Start' is a Unicode Derived Property specified in
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/// [UAX #31](http://unicode.org/reports/tr31/#NFKC_Modifications),
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/// mostly similar to ID_Start but modified for closure under NFKx.
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#[unstable(feature = "unicode",
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reason = "mainly needed for compiler internals")]
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#[inline]
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pub fn is_xid_start(self) -> bool { derived_property::XID_Start(self) }
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/// Returns whether the specified `char` satisfies the 'XID_Continue'
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/// Unicode property.
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///
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/// 'XID_Continue' is a Unicode Derived Property specified in
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/// [UAX #31](http://unicode.org/reports/tr31/#NFKC_Modifications),
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/// mostly similar to 'ID_Continue' but modified for closure under NFKx.
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#[unstable(feature = "unicode",
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reason = "mainly needed for compiler internals")]
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#[inline]
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pub fn is_xid_continue(self) -> bool { derived_property::XID_Continue(self) }
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/// Indicates whether a character is in lowercase.
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///
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/// This is defined according to the terms of the Unicode Derived Core
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/// Property `Lowercase`.
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn is_lowercase(self) -> bool {
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match self {
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'a' ... 'z' => true,
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c if c > '\x7f' => derived_property::Lowercase(c),
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_ => false
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}
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}
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/// Indicates whether a character is in uppercase.
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///
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/// This is defined according to the terms of the Unicode Derived Core
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/// Property `Uppercase`.
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn is_uppercase(self) -> bool {
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match self {
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'A' ... 'Z' => true,
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c if c > '\x7f' => derived_property::Uppercase(c),
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_ => false
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}
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}
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/// Indicates whether a character is whitespace.
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///
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/// Whitespace is defined in terms of the Unicode Property `White_Space`.
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn is_whitespace(self) -> bool {
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match self {
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' ' | '\x09' ... '\x0d' => true,
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c if c > '\x7f' => property::White_Space(c),
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_ => false
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}
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}
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/// Indicates whether a character is alphanumeric.
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///
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/// Alphanumericness is defined in terms of the Unicode General Categories
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/// 'Nd', 'Nl', 'No' and the Derived Core Property 'Alphabetic'.
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn is_alphanumeric(self) -> bool {
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self.is_alphabetic() || self.is_numeric()
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}
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/// Indicates whether a character is a control code point.
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///
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/// Control code points are defined in terms of the Unicode General
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/// Category `Cc`.
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn is_control(self) -> bool { general_category::Cc(self) }
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/// Indicates whether the character is numeric (Nd, Nl, or No).
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn is_numeric(self) -> bool {
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match self {
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'0' ... '9' => true,
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c if c > '\x7f' => general_category::N(c),
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_ => false
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}
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}
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/// Converts a character to its lowercase equivalent.
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///
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/// The case-folding performed is the common or simple mapping. See
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/// `to_uppercase()` for references and more information.
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///
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/// # Return value
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///
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/// Returns an iterator which yields the characters corresponding to the
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/// lowercase equivalent of the character. If no conversion is possible then
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/// the input character is returned.
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn to_lowercase(self) -> ToLowercase {
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ToLowercase(Some(conversions::to_lower(self)))
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}
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/// Converts a character to its uppercase equivalent.
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///
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/// The case-folding performed is the common or simple mapping: it maps
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/// one Unicode codepoint to its uppercase equivalent according to the
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/// Unicode database [1]. The additional [`SpecialCasing.txt`] is not yet
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/// considered here, but the iterator returned will soon support this form
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/// of case folding.
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///
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/// A full reference can be found here [2].
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///
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/// # Return value
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///
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/// Returns an iterator which yields the characters corresponding to the
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/// uppercase equivalent of the character. If no conversion is possible then
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/// the input character is returned.
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///
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/// [1]: ftp://ftp.unicode.org/Public/UNIDATA/UnicodeData.txt
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///
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/// [`SpecialCasing.txt`]: ftp://ftp.unicode.org/Public/UNIDATA/SpecialCasing.txt
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///
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/// [2]: http://www.unicode.org/versions/Unicode4.0.0/ch03.pdf#G33992
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#[stable(feature = "rust1", since = "1.0.0")]
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#[inline]
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pub fn to_uppercase(self) -> ToUppercase {
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ToUppercase(Some(conversions::to_upper(self)))
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}
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/// Returns this character's displayed width in columns, or `None` if it is a
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/// control character other than `'\x00'`.
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///
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/// `is_cjk` determines behavior for characters in the Ambiguous category:
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/// if `is_cjk` is `true`, these are 2 columns wide; otherwise, they are 1.
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/// In CJK contexts, `is_cjk` should be `true`, else it should be `false`.
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/// [Unicode Standard Annex #11](http://www.unicode.org/reports/tr11/)
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/// recommends that these characters be treated as 1 column (i.e.,
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/// `is_cjk` = `false`) if the context cannot be reliably determined.
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#[deprecated(reason = "use the crates.io `unicode-width` library instead",
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since = "1.0.0")]
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#[unstable(feature = "unicode",
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reason = "needs expert opinion. is_cjk flag stands out as ugly")]
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pub fn width(self, is_cjk: bool) -> Option<usize> { charwidth::width(self, is_cjk) }
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}
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