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// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. //! A character type. //! //! The `char` type represents a single character. More specifically, since //! 'character' isn't a well-defined concept in Unicode, `char` is a '[Unicode //! scalar value]', which is similar to, but not the same as, a '[Unicode code //! point]'. //! //! [Unicode scalar value]: http://www.unicode.org/glossary/#unicode_scalar_value //! [Unicode code point]: http://www.unicode.org/glossary/#code_point //! //! This module exists for technical reasons, the primary documentation for //! `char` is directly on [the `char` primitive type](../../std/primitive.char.html) //! itself. //! //! This module is the home of the iterator implementations for the iterators //! implemented on `char`, as well as some useful constants and conversion //! functions that convert various types to `char`. #![stable(feature = "rust1", since = "1.0.0")] use core::char::CharExt as C; use core::iter::FusedIterator; use core::fmt::{self, Write}; use tables::{conversions, derived_property, general_category, property}; // stable reexports #[stable(feature = "rust1", since = "1.0.0")] pub use core::char::{MAX, from_digit, from_u32, from_u32_unchecked}; #[stable(feature = "rust1", since = "1.0.0")] pub use core::char::{EscapeDebug, EscapeDefault, EscapeUnicode}; #[stable(feature = "char_from_str", since = "1.20.0")] pub use core::char::ParseCharError; // unstable reexports #[unstable(feature = "try_from", issue = "33417")] pub use core::char::CharTryFromError; #[unstable(feature = "decode_utf8", issue = "33906")] pub use core::char::{DecodeUtf8, decode_utf8}; #[unstable(feature = "unicode", issue = "27783")] pub use tables::UNICODE_VERSION; /// Returns an iterator that yields the lowercase equivalent of a `char`. /// /// This `struct` is created by the [`to_lowercase`] method on [`char`]. See /// its documentation for more. /// /// [`to_lowercase`]: ../../std/primitive.char.html#method.to_lowercase /// [`char`]: ../../std/primitive.char.html #[stable(feature = "rust1", since = "1.0.0")] pub struct ToLowercase(CaseMappingIter); #[stable(feature = "rust1", since = "1.0.0")] impl Iterator for ToLowercase { type Item = char; fn next(&mut self) -> Option<char> { self.0.next() } } #[unstable(feature = "fused", issue = "35602")] impl FusedIterator for ToLowercase {} /// Returns an iterator that yields the uppercase equivalent of a `char`. /// /// This `struct` is created by the [`to_uppercase`] method on [`char`]. See /// its documentation for more. /// /// [`to_uppercase`]: ../../std/primitive.char.html#method.to_uppercase /// [`char`]: ../../std/primitive.char.html #[stable(feature = "rust1", since = "1.0.0")] pub struct ToUppercase(CaseMappingIter); #[stable(feature = "rust1", since = "1.0.0")] impl Iterator for ToUppercase { type Item = char; fn next(&mut self) -> Option<char> { self.0.next() } } #[unstable(feature = "fused", issue = "35602")] impl FusedIterator for ToUppercase {} enum CaseMappingIter { Three(char, char, char), Two(char, char), One(char), Zero, } impl CaseMappingIter { fn new(chars: [char; 3]) -> CaseMappingIter { if chars[2] == '\0' { if chars[1] == '\0' { CaseMappingIter::One(chars[0]) // Including if chars[0] == '\0' } else { CaseMappingIter::Two(chars[0], chars[1]) } } else { CaseMappingIter::Three(chars[0], chars[1], chars[2]) } } } impl Iterator for CaseMappingIter { type Item = char; fn next(&mut self) -> Option<char> { match *self { CaseMappingIter::Three(a, b, c) => { *self = CaseMappingIter::Two(b, c); Some(a) } CaseMappingIter::Two(b, c) => { *self = CaseMappingIter::One(c); Some(b) } CaseMappingIter::One(c) => { *self = CaseMappingIter::Zero; Some(c) } CaseMappingIter::Zero => None, } } } impl fmt::Display for CaseMappingIter { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { match *self { CaseMappingIter::Three(a, b, c) => { f.write_char(a)?; f.write_char(b)?; f.write_char(c) } CaseMappingIter::Two(b, c) => { f.write_char(b)?; f.write_char(c) } CaseMappingIter::One(c) => { f.write_char(c) } CaseMappingIter::Zero => Ok(()), } } } #[stable(feature = "char_struct_display", since = "1.16.0")] impl fmt::Display for ToLowercase { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { fmt::Display::fmt(&self.0, f) } } #[stable(feature = "char_struct_display", since = "1.16.0")] impl fmt::Display for ToUppercase { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { fmt::Display::fmt(&self.0, f) } } #[lang = "char"] impl char { /// Checks if a `char` is a digit in the given radix. /// /// A 'radix' here is sometimes also called a 'base'. A radix of two /// indicates a binary number, a radix of ten, decimal, and a radix of /// sixteen, hexadecimal, to give some common values. Arbitrary /// radices are supported. /// /// Compared to `is_numeric()`, this function only recognizes the characters /// `0-9`, `a-z` and `A-Z`. /// /// 'Digit' is defined to be only the following characters: /// /// * `0-9` /// * `a-z` /// * `A-Z` /// /// For a more comprehensive understanding of 'digit', see [`is_numeric`][is_numeric]. /// /// [is_numeric]: #method.is_numeric /// /// # Panics /// /// Panics if given a radix larger than 36. /// /// # Examples /// /// Basic usage: /// /// ``` /// assert!('1'.is_digit(10)); /// assert!('f'.is_digit(16)); /// assert!(!'f'.is_digit(10)); /// ``` /// /// Passing a large radix, causing a panic: /// /// ``` /// use std::thread; /// /// let result = thread::spawn(|| { /// // this panics /// '1'.is_digit(37); /// }).join(); /// /// assert!(result.is_err()); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn is_digit(self, radix: u32) -> bool { C::is_digit(self, radix) } /// Converts a `char` to a digit in the given radix. /// /// A 'radix' here is sometimes also called a 'base'. A radix of two /// indicates a binary number, a radix of ten, decimal, and a radix of /// sixteen, hexadecimal, to give some common values. Arbitrary /// radices are supported. /// /// 'Digit' is defined to be only the following characters: /// /// * `0-9` /// * `a-z` /// * `A-Z` /// /// # Errors /// /// Returns `None` if the `char` does not refer to a digit in the given radix. /// /// # Panics /// /// Panics if given a radix larger than 36. /// /// # Examples /// /// Basic usage: /// /// ``` /// assert_eq!('1'.to_digit(10), Some(1)); /// assert_eq!('f'.to_digit(16), Some(15)); /// ``` /// /// Passing a non-digit results in failure: /// /// ``` /// assert_eq!('f'.to_digit(10), None); /// assert_eq!('z'.to_digit(16), None); /// ``` /// /// Passing a large radix, causing a panic: /// /// ``` /// use std::thread; /// /// let result = thread::spawn(|| { /// '1'.to_digit(37); /// }).join(); /// /// assert!(result.is_err()); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn to_digit(self, radix: u32) -> Option<u32> { C::to_digit(self, radix) } /// Returns an iterator that yields the hexadecimal Unicode escape of a /// character as `char`s. /// /// This will escape characters with the Rust syntax of the form /// `\u{NNNNNN}` where `NNNNNN` is a hexadecimal representation. /// /// # Examples /// /// As an iterator: /// /// ``` /// for c in '❤'.escape_unicode() { /// print!("{}", c); /// } /// println!(); /// ``` /// /// Using `println!` directly: /// /// ``` /// println!("{}", '❤'.escape_unicode()); /// ``` /// /// Both are equivalent to: /// /// ``` /// println!("\\u{{2764}}"); /// ``` /// /// Using `to_string`: /// /// ``` /// assert_eq!('❤'.escape_unicode().to_string(), "\\u{2764}"); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn escape_unicode(self) -> EscapeUnicode { C::escape_unicode(self) } /// Returns an iterator that yields the literal escape code of a character /// as `char`s. /// /// This will escape the characters similar to the `Debug` implementations /// of `str` or `char`. /// /// # Examples /// /// As an iterator: /// /// ``` /// for c in '\n'.escape_debug() { /// print!("{}", c); /// } /// println!(); /// ``` /// /// Using `println!` directly: /// /// ``` /// println!("{}", '\n'.escape_debug()); /// ``` /// /// Both are equivalent to: /// /// ``` /// println!("\\n"); /// ``` /// /// Using `to_string`: /// /// ``` /// assert_eq!('\n'.escape_debug().to_string(), "\\n"); /// ``` #[stable(feature = "char_escape_debug", since = "1.20.0")] #[inline] pub fn escape_debug(self) -> EscapeDebug { C::escape_debug(self) } /// Returns an iterator that yields the literal escape code of a character /// as `char`s. /// /// The default is chosen with a bias toward producing literals that are /// legal in a variety of languages, including C++11 and similar C-family /// languages. The exact rules are: /// /// * Tab is escaped as `\t`. /// * Carriage return is escaped as `\r`. /// * Line feed is escaped as `\n`. /// * Single quote is escaped as `\'`. /// * Double quote is escaped as `\"`. /// * Backslash is escaped as `\\`. /// * Any character in the 'printable ASCII' range `0x20` .. `0x7e` /// inclusive is not escaped. /// * All other characters are given hexadecimal Unicode escapes; see /// [`escape_unicode`][escape_unicode]. /// /// [escape_unicode]: #method.escape_unicode /// /// # Examples /// /// As an iterator: /// /// ``` /// for c in '"'.escape_default() { /// print!("{}", c); /// } /// println!(); /// ``` /// /// Using `println!` directly: /// /// ``` /// println!("{}", '"'.escape_default()); /// ``` /// /// /// Both are equivalent to: /// /// ``` /// println!("\\\""); /// ``` /// /// Using `to_string`: /// /// ``` /// assert_eq!('"'.escape_default().to_string(), "\\\""); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn escape_default(self) -> EscapeDefault { C::escape_default(self) } /// Returns the number of bytes this `char` would need if encoded in UTF-8. /// /// That number of bytes is always between 1 and 4, inclusive. /// /// # Examples /// /// Basic usage: /// /// ``` /// let len = 'A'.len_utf8(); /// assert_eq!(len, 1); /// /// let len = 'ß'.len_utf8(); /// assert_eq!(len, 2); /// /// let len = 'ℝ'.len_utf8(); /// assert_eq!(len, 3); /// /// let len = '💣'.len_utf8(); /// assert_eq!(len, 4); /// ``` /// /// The `&str` type guarantees that its contents are UTF-8, and so we can compare the length it /// would take if each code point was represented as a `char` vs in the `&str` itself: /// /// ``` /// // as chars /// let eastern = '東'; /// let capitol = '京'; /// /// // both can be represented as three bytes /// assert_eq!(3, eastern.len_utf8()); /// assert_eq!(3, capitol.len_utf8()); /// /// // as a &str, these two are encoded in UTF-8 /// let tokyo = "東京"; /// /// let len = eastern.len_utf8() + capitol.len_utf8(); /// /// // we can see that they take six bytes total... /// assert_eq!(6, tokyo.len()); /// /// // ... just like the &str /// assert_eq!(len, tokyo.len()); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn len_utf8(self) -> usize { C::len_utf8(self) } /// Returns the number of 16-bit code units this `char` would need if /// encoded in UTF-16. /// /// See the documentation for [`len_utf8`] for more explanation of this /// concept. This function is a mirror, but for UTF-16 instead of UTF-8. /// /// [`len_utf8`]: #method.len_utf8 /// /// # Examples /// /// Basic usage: /// /// ``` /// let n = 'ß'.len_utf16(); /// assert_eq!(n, 1); /// /// let len = '💣'.len_utf16(); /// assert_eq!(len, 2); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn len_utf16(self) -> usize { C::len_utf16(self) } /// Encodes this character as UTF-8 into the provided byte buffer, /// and then returns the subslice of the buffer that contains the encoded character. /// /// # Panics /// /// Panics if the buffer is not large enough. /// A buffer of length four is large enough to encode any `char`. /// /// # Examples /// /// In both of these examples, 'ß' takes two bytes to encode. /// /// ``` /// let mut b = [0; 2]; /// /// let result = 'ß'.encode_utf8(&mut b); /// /// assert_eq!(result, "ß"); /// /// assert_eq!(result.len(), 2); /// ``` /// /// A buffer that's too small: /// /// ``` /// use std::thread; /// /// let result = thread::spawn(|| { /// let mut b = [0; 1]; /// /// // this panics /// 'ß'.encode_utf8(&mut b); /// }).join(); /// /// assert!(result.is_err()); /// ``` #[stable(feature = "unicode_encode_char", since = "1.15.0")] #[inline] pub fn encode_utf8(self, dst: &mut [u8]) -> &mut str { C::encode_utf8(self, dst) } /// Encodes this character as UTF-16 into the provided `u16` buffer, /// and then returns the subslice of the buffer that contains the encoded character. /// /// # Panics /// /// Panics if the buffer is not large enough. /// A buffer of length 2 is large enough to encode any `char`. /// /// # Examples /// /// In both of these examples, '𝕊' takes two `u16`s to encode. /// /// ``` /// let mut b = [0; 2]; /// /// let result = '𝕊'.encode_utf16(&mut b); /// /// assert_eq!(result.len(), 2); /// ``` /// /// A buffer that's too small: /// /// ``` /// use std::thread; /// /// let result = thread::spawn(|| { /// let mut b = [0; 1]; /// /// // this panics /// '𝕊'.encode_utf16(&mut b); /// }).join(); /// /// assert!(result.is_err()); /// ``` #[stable(feature = "unicode_encode_char", since = "1.15.0")] #[inline] pub fn encode_utf16(self, dst: &mut [u16]) -> &mut [u16] { C::encode_utf16(self, dst) } /// Returns true if this `char` is an alphabetic code point, and false if not. /// /// # Examples /// /// Basic usage: /// /// ``` /// assert!('a'.is_alphabetic()); /// assert!('京'.is_alphabetic()); /// /// let c = '💝'; /// // love is many things, but it is not alphabetic /// assert!(!c.is_alphabetic()); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn is_alphabetic(self) -> bool { match self { 'a'...'z' | 'A'...'Z' => true, c if c > '\x7f' => derived_property::Alphabetic(c), _ => false, } } /// Returns true if this `char` satisfies the 'XID_Start' Unicode property, and false /// otherwise. /// /// 'XID_Start' is a Unicode Derived Property specified in /// [UAX #31](http://unicode.org/reports/tr31/#NFKC_Modifications), /// mostly similar to `ID_Start` but modified for closure under `NFKx`. #[unstable(feature = "rustc_private", reason = "mainly needed for compiler internals", issue = "27812")] #[inline] pub fn is_xid_start(self) -> bool { derived_property::XID_Start(self) } /// Returns true if this `char` satisfies the 'XID_Continue' Unicode property, and false /// otherwise. /// /// 'XID_Continue' is a Unicode Derived Property specified in /// [UAX #31](http://unicode.org/reports/tr31/#NFKC_Modifications), /// mostly similar to 'ID_Continue' but modified for closure under NFKx. #[unstable(feature = "rustc_private", reason = "mainly needed for compiler internals", issue = "27812")] #[inline] pub fn is_xid_continue(self) -> bool { derived_property::XID_Continue(self) } /// Returns true if this `char` is lowercase, and false otherwise. /// /// 'Lowercase' is defined according to the terms of the Unicode Derived Core /// Property `Lowercase`. /// /// # Examples /// /// Basic usage: /// /// ``` /// assert!('a'.is_lowercase()); /// assert!('δ'.is_lowercase()); /// assert!(!'A'.is_lowercase()); /// assert!(!'Δ'.is_lowercase()); /// /// // The various Chinese scripts do not have case, and so: /// assert!(!'中'.is_lowercase()); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn is_lowercase(self) -> bool { match self { 'a'...'z' => true, c if c > '\x7f' => derived_property::Lowercase(c), _ => false, } } /// Returns true if this `char` is uppercase, and false otherwise. /// /// 'Uppercase' is defined according to the terms of the Unicode Derived Core /// Property `Uppercase`. /// /// # Examples /// /// Basic usage: /// /// ``` /// assert!(!'a'.is_uppercase()); /// assert!(!'δ'.is_uppercase()); /// assert!('A'.is_uppercase()); /// assert!('Δ'.is_uppercase()); /// /// // The various Chinese scripts do not have case, and so: /// assert!(!'中'.is_uppercase()); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn is_uppercase(self) -> bool { match self { 'A'...'Z' => true, c if c > '\x7f' => derived_property::Uppercase(c), _ => false, } } /// Returns true if this `char` is whitespace, and false otherwise. /// /// 'Whitespace' is defined according to the terms of the Unicode Derived Core /// Property `White_Space`. /// /// # Examples /// /// Basic usage: /// /// ``` /// assert!(' '.is_whitespace()); /// /// // a non-breaking space /// assert!('\u{A0}'.is_whitespace()); /// /// assert!(!'越'.is_whitespace()); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn is_whitespace(self) -> bool { match self { ' ' | '\x09'...'\x0d' => true, c if c > '\x7f' => property::White_Space(c), _ => false, } } /// Returns true if this `char` is alphanumeric, and false otherwise. /// /// 'Alphanumeric'-ness is defined in terms of the Unicode General Categories /// 'Nd', 'Nl', 'No' and the Derived Core Property 'Alphabetic'. /// /// # Examples /// /// Basic usage: /// /// ``` /// assert!('٣'.is_alphanumeric()); /// assert!('7'.is_alphanumeric()); /// assert!('৬'.is_alphanumeric()); /// assert!('K'.is_alphanumeric()); /// assert!('و'.is_alphanumeric()); /// assert!('藏'.is_alphanumeric()); /// assert!(!'¾'.is_alphanumeric()); /// assert!(!'①'.is_alphanumeric()); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn is_alphanumeric(self) -> bool { self.is_alphabetic() || self.is_numeric() } /// Returns true if this `char` is a control code point, and false otherwise. /// /// 'Control code point' is defined in terms of the Unicode General /// Category `Cc`. /// /// # Examples /// /// Basic usage: /// /// ``` /// // U+009C, STRING TERMINATOR /// assert!(''.is_control()); /// assert!(!'q'.is_control()); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn is_control(self) -> bool { general_category::Cc(self) } /// Returns true if this `char` is numeric, and false otherwise. /// /// 'Numeric'-ness is defined in terms of the Unicode General Categories /// 'Nd', 'Nl', 'No'. /// /// # Examples /// /// Basic usage: /// /// ``` /// assert!('٣'.is_numeric()); /// assert!('7'.is_numeric()); /// assert!('৬'.is_numeric()); /// assert!(!'K'.is_numeric()); /// assert!(!'و'.is_numeric()); /// assert!(!'藏'.is_numeric()); /// assert!(!'¾'.is_numeric()); /// assert!(!'①'.is_numeric()); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn is_numeric(self) -> bool { match self { '0'...'9' => true, c if c > '\x7f' => general_category::N(c), _ => false, } } /// Returns an iterator that yields the lowercase equivalent of a `char` /// as one or more `char`s. /// /// If a character does not have a lowercase equivalent, the same character /// will be returned back by the iterator. /// /// This performs complex unconditional mappings with no tailoring: it maps /// one Unicode character to its lowercase equivalent according to the /// [Unicode database] and the additional complex mappings /// [`SpecialCasing.txt`]. Conditional mappings (based on context or /// language) are not considered here. /// /// For a full reference, see [here][reference]. /// /// [Unicode database]: ftp://ftp.unicode.org/Public/UNIDATA/UnicodeData.txt /// /// [`SpecialCasing.txt`]: ftp://ftp.unicode.org/Public/UNIDATA/SpecialCasing.txt /// /// [reference]: http://www.unicode.org/versions/Unicode7.0.0/ch03.pdf#G33992 /// /// # Examples /// /// As an iterator: /// /// ``` /// for c in 'İ'.to_lowercase() { /// print!("{}", c); /// } /// println!(); /// ``` /// /// Using `println!` directly: /// /// ``` /// println!("{}", 'İ'.to_lowercase()); /// ``` /// /// Both are equivalent to: /// /// ``` /// println!("i\u{307}"); /// ``` /// /// Using `to_string`: /// /// ``` /// assert_eq!('C'.to_lowercase().to_string(), "c"); /// /// // Sometimes the result is more than one character: /// assert_eq!('İ'.to_lowercase().to_string(), "i\u{307}"); /// /// // Characters that do not have both uppercase and lowercase /// // convert into themselves. /// assert_eq!('山'.to_lowercase().to_string(), "山"); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn to_lowercase(self) -> ToLowercase { ToLowercase(CaseMappingIter::new(conversions::to_lower(self))) } /// Returns an iterator that yields the uppercase equivalent of a `char` /// as one or more `char`s. /// /// If a character does not have an uppercase equivalent, the same character /// will be returned back by the iterator. /// /// This performs complex unconditional mappings with no tailoring: it maps /// one Unicode character to its uppercase equivalent according to the /// [Unicode database] and the additional complex mappings /// [`SpecialCasing.txt`]. Conditional mappings (based on context or /// language) are not considered here. /// /// For a full reference, see [here][reference]. /// /// [Unicode database]: ftp://ftp.unicode.org/Public/UNIDATA/UnicodeData.txt /// /// [`SpecialCasing.txt`]: ftp://ftp.unicode.org/Public/UNIDATA/SpecialCasing.txt /// /// [reference]: http://www.unicode.org/versions/Unicode7.0.0/ch03.pdf#G33992 /// /// # Examples /// /// As an iterator: /// /// ``` /// for c in 'ß'.to_uppercase() { /// print!("{}", c); /// } /// println!(); /// ``` /// /// Using `println!` directly: /// /// ``` /// println!("{}", 'ß'.to_uppercase()); /// ``` /// /// Both are equivalent to: /// /// ``` /// println!("SS"); /// ``` /// /// Using `to_string`: /// /// ``` /// assert_eq!('c'.to_uppercase().to_string(), "C"); /// /// // Sometimes the result is more than one character: /// assert_eq!('ß'.to_uppercase().to_string(), "SS"); /// /// // Characters that do not have both uppercase and lowercase /// // convert into themselves. /// assert_eq!('山'.to_uppercase().to_string(), "山"); /// ``` /// /// # Note on locale /// /// In Turkish, the equivalent of 'i' in Latin has five forms instead of two: /// /// * 'Dotless': I / ı, sometimes written ï /// * 'Dotted': İ / i /// /// Note that the lowercase dotted 'i' is the same as the Latin. Therefore: /// /// ``` /// let upper_i = 'i'.to_uppercase().to_string(); /// ``` /// /// The value of `upper_i` here relies on the language of the text: if we're /// in `en-US`, it should be `"I"`, but if we're in `tr_TR`, it should /// be `"İ"`. `to_uppercase()` does not take this into account, and so: /// /// ``` /// let upper_i = 'i'.to_uppercase().to_string(); /// /// assert_eq!(upper_i, "I"); /// ``` /// /// holds across languages. #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn to_uppercase(self) -> ToUppercase { ToUppercase(CaseMappingIter::new(conversions::to_upper(self))) } } /// An iterator that decodes UTF-16 encoded code points from an iterator of `u16`s. #[stable(feature = "decode_utf16", since = "1.9.0")] #[derive(Clone)] pub struct DecodeUtf16<I> where I: Iterator<Item = u16> { iter: I, buf: Option<u16>, } /// An iterator that decodes UTF-16 encoded code points from an iterator of `u16`s. #[stable(feature = "decode_utf16", since = "1.9.0")] #[derive(Debug, Clone, Eq, PartialEq)] pub struct DecodeUtf16Error { code: u16, } /// Create an iterator over the UTF-16 encoded code points in `iter`, /// returning unpaired surrogates as `Err`s. /// /// # Examples /// /// Basic usage: /// /// ``` /// use std::char::decode_utf16; /// /// fn main() { /// // 𝄞mus<invalid>ic<invalid> /// let v = [0xD834, 0xDD1E, 0x006d, 0x0075, /// 0x0073, 0xDD1E, 0x0069, 0x0063, /// 0xD834]; /// /// assert_eq!(decode_utf16(v.iter().cloned()) /// .map(|r| r.map_err(|e| e.unpaired_surrogate())) /// .collect::<Vec<_>>(), /// vec![Ok('𝄞'), /// Ok('m'), Ok('u'), Ok('s'), /// Err(0xDD1E), /// Ok('i'), Ok('c'), /// Err(0xD834)]); /// } /// ``` /// /// A lossy decoder can be obtained by replacing `Err` results with the replacement character: /// /// ``` /// use std::char::{decode_utf16, REPLACEMENT_CHARACTER}; /// /// fn main() { /// // 𝄞mus<invalid>ic<invalid> /// let v = [0xD834, 0xDD1E, 0x006d, 0x0075, /// 0x0073, 0xDD1E, 0x0069, 0x0063, /// 0xD834]; /// /// assert_eq!(decode_utf16(v.iter().cloned()) /// .map(|r| r.unwrap_or(REPLACEMENT_CHARACTER)) /// .collect::<String>(), /// "𝄞mus�ic�"); /// } /// ``` #[stable(feature = "decode_utf16", since = "1.9.0")] #[inline] pub fn decode_utf16<I: IntoIterator<Item = u16>>(iter: I) -> DecodeUtf16<I::IntoIter> { DecodeUtf16 { iter: iter.into_iter(), buf: None, } } #[stable(feature = "decode_utf16", since = "1.9.0")] impl<I: Iterator<Item = u16>> Iterator for DecodeUtf16<I> { type Item = Result<char, DecodeUtf16Error>; fn next(&mut self) -> Option<Result<char, DecodeUtf16Error>> { let u = match self.buf.take() { Some(buf) => buf, None => { match self.iter.next() { Some(u) => u, None => return None, } } }; if u < 0xD800 || 0xDFFF < u { // not a surrogate Some(Ok(unsafe { from_u32_unchecked(u as u32) })) } else if u >= 0xDC00 { // a trailing surrogate Some(Err(DecodeUtf16Error { code: u })) } else { let u2 = match self.iter.next() { Some(u2) => u2, // eof None => return Some(Err(DecodeUtf16Error { code: u })), }; if u2 < 0xDC00 || u2 > 0xDFFF { // not a trailing surrogate so we're not a valid // surrogate pair, so rewind to redecode u2 next time. self.buf = Some(u2); return Some(Err(DecodeUtf16Error { code: u })); } // all ok, so lets decode it. let c = (((u - 0xD800) as u32) << 10 | (u2 - 0xDC00) as u32) + 0x1_0000; Some(Ok(unsafe { from_u32_unchecked(c) })) } } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { let (low, high) = self.iter.size_hint(); // we could be entirely valid surrogates (2 elements per // char), or entirely non-surrogates (1 element per char) (low / 2, high) } } impl DecodeUtf16Error { /// Returns the unpaired surrogate which caused this error. #[stable(feature = "decode_utf16", since = "1.9.0")] pub fn unpaired_surrogate(&self) -> u16 { self.code } } #[stable(feature = "decode_utf16", since = "1.9.0")] impl fmt::Display for DecodeUtf16Error { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "unpaired surrogate found: {:x}", self.code) } } /// `U+FFFD REPLACEMENT CHARACTER` (�) is used in Unicode to represent a /// decoding error. /// /// It can occur, for example, when giving ill-formed UTF-8 bytes to /// [`String::from_utf8_lossy`](../../std/string/struct.String.html#method.from_utf8_lossy). #[stable(feature = "decode_utf16", since = "1.9.0")] pub const REPLACEMENT_CHARACTER: char = '\u{FFFD}';