1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 // ignore-lexer-test FIXME #15679
13 //! String manipulation
15 //! For more details, see std::str
17 #![doc(primitive = "str")]
19 use self::Searcher::{Naive, TwoWay, TwoWayLong};
26 use iter::ExactSizeIterator;
27 use iter::{Map, Iterator, IteratorExt, DoubleEndedIterator};
32 use option::Option::{self, None, Some};
34 use raw::{Repr, Slice};
35 use result::Result::{self, Ok, Err};
36 use slice::{self, SliceExt};
39 macro_rules! delegate_iter {
40 (exact $te:ty : $ti:ty) => {
41 delegate_iter!{$te : $ti}
42 impl<'a> ExactSizeIterator for $ti {
44 fn len(&self) -> usize {
49 ($te:ty : $ti:ty) => {
50 #[stable(feature = "rust1", since = "1.0.0")]
51 impl<'a> Iterator for $ti {
55 fn next(&mut self) -> Option<$te> {
59 fn size_hint(&self) -> (usize, Option<usize>) {
63 #[stable(feature = "rust1", since = "1.0.0")]
64 impl<'a> DoubleEndedIterator for $ti {
66 fn next_back(&mut self) -> Option<$te> {
71 (pattern $te:ty : $ti:ty) => {
72 #[stable(feature = "rust1", since = "1.0.0")]
73 impl<'a, P: CharEq> Iterator for $ti {
77 fn next(&mut self) -> Option<$te> {
81 fn size_hint(&self) -> (usize, Option<usize>) {
85 #[stable(feature = "rust1", since = "1.0.0")]
86 impl<'a, P: CharEq> DoubleEndedIterator for $ti {
88 fn next_back(&mut self) -> Option<$te> {
93 (pattern forward $te:ty : $ti:ty) => {
94 #[stable(feature = "rust1", since = "1.0.0")]
95 impl<'a, P: CharEq> Iterator for $ti {
99 fn next(&mut self) -> Option<$te> {
103 fn size_hint(&self) -> (usize, Option<usize>) {
110 /// A trait to abstract the idea of creating a new instance of a type from a
112 #[stable(feature = "rust1", since = "1.0.0")]
114 /// The associated error which can be returned from parsing.
115 #[stable(feature = "rust1", since = "1.0.0")]
118 /// Parses a string `s` to return an optional value of this type. If the
119 /// string is ill-formatted, the None is returned.
120 #[stable(feature = "rust1", since = "1.0.0")]
121 fn from_str(s: &str) -> Result<Self, Self::Err>;
124 #[stable(feature = "rust1", since = "1.0.0")]
125 impl FromStr for bool {
126 type Err = ParseBoolError;
128 /// Parse a `bool` from a string.
130 /// Yields an `Option<bool>`, because `s` may or may not actually be
136 /// assert_eq!("true".parse(), Ok(true));
137 /// assert_eq!("false".parse(), Ok(false));
138 /// assert!("not even a boolean".parse::<bool>().is_err());
141 fn from_str(s: &str) -> Result<bool, ParseBoolError> {
144 "false" => Ok(false),
145 _ => Err(ParseBoolError { _priv: () }),
150 /// An error returned when parsing a `bool` from a string fails.
151 #[derive(Debug, Clone, PartialEq)]
152 #[stable(feature = "rust1", since = "1.0.0")]
153 pub struct ParseBoolError { _priv: () }
155 #[stable(feature = "rust1", since = "1.0.0")]
156 impl fmt::Display for ParseBoolError {
157 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
158 "provided string was not `true` or `false`".fmt(f)
162 #[stable(feature = "rust1", since = "1.0.0")]
163 impl Error for ParseBoolError {
164 fn description(&self) -> &str { "failed to parse bool" }
168 Section: Creating a string
171 /// Errors which can occur when attempting to interpret a byte slice as a `str`.
172 #[derive(Copy, Eq, PartialEq, Clone, Debug)]
173 #[unstable(feature = "core",
174 reason = "error enumeration recently added and definitions may be refined")]
176 /// An invalid byte was detected at the byte offset given.
178 /// The offset is guaranteed to be in bounds of the slice in question, and
179 /// the byte at the specified offset was the first invalid byte in the
180 /// sequence detected.
183 /// The byte slice was invalid because more bytes were needed but no more
184 /// bytes were available.
188 /// Converts a slice of bytes to a string slice without performing any
191 /// Once the slice has been validated as utf-8, it is transmuted in-place and
192 /// returned as a '&str' instead of a '&[u8]'
196 /// Returns `Err` if the slice is not utf-8 with a description as to why the
197 /// provided slice is not utf-8.
198 #[stable(feature = "rust1", since = "1.0.0")]
199 pub fn from_utf8(v: &[u8]) -> Result<&str, Utf8Error> {
200 try!(run_utf8_validation_iterator(&mut v.iter()));
201 Ok(unsafe { from_utf8_unchecked(v) })
204 /// Converts a slice of bytes to a string slice without checking
205 /// that the string contains valid UTF-8.
206 #[stable(feature = "rust1", since = "1.0.0")]
207 pub unsafe fn from_utf8_unchecked<'a>(v: &'a [u8]) -> &'a str {
211 /// Constructs a static string slice from a given raw pointer.
213 /// This function will read memory starting at `s` until it finds a 0, and then
214 /// transmute the memory up to that point as a string slice, returning the
215 /// corresponding `&'static str` value.
217 /// This function is unsafe because the caller must ensure the C string itself
218 /// has the static lifetime and that the memory `s` is valid up to and including
219 /// the first null byte.
223 /// This function will panic if the string pointed to by `s` is not valid UTF-8.
224 #[unstable(feature = "core")]
225 #[deprecated(since = "1.0.0",
226 reason = "use std::ffi::c_str_to_bytes + str::from_utf8")]
227 pub unsafe fn from_c_str(s: *const i8) -> &'static str {
228 let s = s as *const u8;
230 while *s.offset(len as isize) != 0 {
233 let v: &'static [u8] = ::mem::transmute(Slice { data: s, len: len });
234 from_utf8(v).ok().expect("from_c_str passed invalid utf-8 data")
237 /// Something that can be used to compare against a character
238 #[unstable(feature = "core",
239 reason = "definition may change as pattern-related methods are stabilized")]
241 /// Determine if the splitter should split at the given character
242 fn matches(&mut self, char) -> bool;
243 /// Indicate if this is only concerned about ASCII characters,
244 /// which can allow for a faster implementation.
245 fn only_ascii(&self) -> bool;
248 impl CharEq for char {
250 fn matches(&mut self, c: char) -> bool { *self == c }
253 fn only_ascii(&self) -> bool { (*self as u32) < 128 }
256 impl<F> CharEq for F where F: FnMut(char) -> bool {
258 fn matches(&mut self, c: char) -> bool { (*self)(c) }
261 fn only_ascii(&self) -> bool { false }
264 impl<'a> CharEq for &'a [char] {
266 fn matches(&mut self, c: char) -> bool {
267 self.iter().any(|&m| { let mut m = m; m.matches(c) })
271 fn only_ascii(&self) -> bool {
272 self.iter().all(|m| m.only_ascii())
276 #[stable(feature = "rust1", since = "1.0.0")]
277 impl Error for Utf8Error {
278 fn description(&self) -> &str {
280 Utf8Error::TooShort => "invalid utf-8: not enough bytes",
281 Utf8Error::InvalidByte(..) => "invalid utf-8: corrupt contents",
286 #[stable(feature = "rust1", since = "1.0.0")]
287 impl fmt::Display for Utf8Error {
288 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
290 Utf8Error::InvalidByte(n) => {
291 write!(f, "invalid utf-8: invalid byte at index {}", n)
293 Utf8Error::TooShort => {
294 write!(f, "invalid utf-8: byte slice too short")
304 /// Iterator for the char (representing *Unicode Scalar Values*) of a string
306 /// Created with the method `.chars()`.
308 #[stable(feature = "rust1", since = "1.0.0")]
309 pub struct Chars<'a> {
310 iter: slice::Iter<'a, u8>
313 // Return the initial codepoint accumulator for the first byte.
314 // The first byte is special, only want bottom 5 bits for width 2, 4 bits
315 // for width 3, and 3 bits for width 4
316 macro_rules! utf8_first_byte {
317 ($byte:expr, $width:expr) => (($byte & (0x7F >> $width)) as u32)
320 // return the value of $ch updated with continuation byte $byte
321 macro_rules! utf8_acc_cont_byte {
322 ($ch:expr, $byte:expr) => (($ch << 6) | ($byte & CONT_MASK) as u32)
325 macro_rules! utf8_is_cont_byte {
326 ($byte:expr) => (($byte & !CONT_MASK) == TAG_CONT_U8)
330 fn unwrap_or_0(opt: Option<&u8>) -> u8 {
337 /// Reads the next code point out of a byte iterator (assuming a
338 /// UTF-8-like encoding).
339 #[unstable(feature = "core")]
340 pub fn next_code_point(bytes: &mut slice::Iter<u8>) -> Option<u32> {
342 let x = match bytes.next() {
344 Some(&next_byte) if next_byte < 128 => return Some(next_byte as u32),
345 Some(&next_byte) => next_byte,
348 // Multibyte case follows
349 // Decode from a byte combination out of: [[[x y] z] w]
350 // NOTE: Performance is sensitive to the exact formulation here
351 let init = utf8_first_byte!(x, 2);
352 let y = unwrap_or_0(bytes.next());
353 let mut ch = utf8_acc_cont_byte!(init, y);
356 // 5th bit in 0xE0 .. 0xEF is always clear, so `init` is still valid
357 let z = unwrap_or_0(bytes.next());
358 let y_z = utf8_acc_cont_byte!((y & CONT_MASK) as u32, z);
359 ch = init << 12 | y_z;
362 // use only the lower 3 bits of `init`
363 let w = unwrap_or_0(bytes.next());
364 ch = (init & 7) << 18 | utf8_acc_cont_byte!(y_z, w);
371 #[stable(feature = "rust1", since = "1.0.0")]
372 impl<'a> Iterator for Chars<'a> {
376 fn next(&mut self) -> Option<char> {
377 next_code_point(&mut self.iter).map(|ch| {
378 // str invariant says `ch` is a valid Unicode Scalar Value
386 fn size_hint(&self) -> (usize, Option<usize>) {
387 let (len, _) = self.iter.size_hint();
388 (len.saturating_add(3) / 4, Some(len))
392 #[stable(feature = "rust1", since = "1.0.0")]
393 impl<'a> DoubleEndedIterator for Chars<'a> {
395 fn next_back(&mut self) -> Option<char> {
396 let w = match self.iter.next_back() {
398 Some(&back_byte) if back_byte < 128 => return Some(back_byte as char),
399 Some(&back_byte) => back_byte,
402 // Multibyte case follows
403 // Decode from a byte combination out of: [x [y [z w]]]
405 let z = unwrap_or_0(self.iter.next_back());
406 ch = utf8_first_byte!(z, 2);
407 if utf8_is_cont_byte!(z) {
408 let y = unwrap_or_0(self.iter.next_back());
409 ch = utf8_first_byte!(y, 3);
410 if utf8_is_cont_byte!(y) {
411 let x = unwrap_or_0(self.iter.next_back());
412 ch = utf8_first_byte!(x, 4);
413 ch = utf8_acc_cont_byte!(ch, y);
415 ch = utf8_acc_cont_byte!(ch, z);
417 ch = utf8_acc_cont_byte!(ch, w);
419 // str invariant says `ch` is a valid Unicode Scalar Value
421 Some(mem::transmute(ch))
426 /// External iterator for a string's characters and their byte offsets.
427 /// Use with the `std::iter` module.
429 #[stable(feature = "rust1", since = "1.0.0")]
430 pub struct CharIndices<'a> {
435 #[stable(feature = "rust1", since = "1.0.0")]
436 impl<'a> Iterator for CharIndices<'a> {
437 type Item = (usize, char);
440 fn next(&mut self) -> Option<(usize, char)> {
441 let (pre_len, _) = self.iter.iter.size_hint();
442 match self.iter.next() {
445 let index = self.front_offset;
446 let (len, _) = self.iter.iter.size_hint();
447 self.front_offset += pre_len - len;
454 fn size_hint(&self) -> (usize, Option<usize>) {
455 self.iter.size_hint()
459 #[stable(feature = "rust1", since = "1.0.0")]
460 impl<'a> DoubleEndedIterator for CharIndices<'a> {
462 fn next_back(&mut self) -> Option<(usize, char)> {
463 match self.iter.next_back() {
466 let (len, _) = self.iter.iter.size_hint();
467 let index = self.front_offset + len;
474 /// External iterator for a string's bytes.
475 /// Use with the `std::iter` module.
477 /// Created with `StrExt::bytes`
478 #[stable(feature = "rust1", since = "1.0.0")]
480 pub struct Bytes<'a>(Map<slice::Iter<'a, u8>, BytesDeref>);
481 delegate_iter!{exact u8 : Bytes<'a>}
483 /// A temporary fn new type that ensures that the `Bytes` iterator
485 #[derive(Copy, Clone)]
488 impl<'a> Fn<(&'a u8,)> for BytesDeref {
492 extern "rust-call" fn call(&self, (ptr,): (&'a u8,)) -> u8 {
497 /// An iterator over the substrings of a string, separated by `sep`.
499 struct CharSplits<'a, Sep> {
500 /// The slice remaining to be iterated
503 /// Whether an empty string at the end is allowed
504 allow_trailing_empty: bool,
509 /// An iterator over the substrings of a string, separated by `sep`,
510 /// splitting at most `count` times.
512 struct CharSplitsN<'a, Sep> {
513 iter: CharSplits<'a, Sep>,
514 /// The number of splits remaining
519 /// An iterator over the lines of a string, separated by `\n`.
520 #[stable(feature = "rust1", since = "1.0.0")]
521 pub struct Lines<'a> {
522 inner: CharSplits<'a, char>,
525 /// An iterator over the lines of a string, separated by either `\n` or (`\r\n`).
526 #[stable(feature = "rust1", since = "1.0.0")]
527 pub struct LinesAny<'a> {
528 inner: Map<Lines<'a>, fn(&str) -> &str>,
531 impl<'a, Sep> CharSplits<'a, Sep> {
533 fn get_end(&mut self) -> Option<&'a str> {
534 if !self.finished && (self.allow_trailing_empty || self.string.len() > 0) {
535 self.finished = true;
543 #[stable(feature = "rust1", since = "1.0.0")]
544 impl<'a, Sep: CharEq> Iterator for CharSplits<'a, Sep> {
548 fn next(&mut self) -> Option<&'a str> {
549 if self.finished { return None }
551 let mut next_split = None;
553 for (idx, byte) in self.string.bytes().enumerate() {
554 if self.sep.matches(byte as char) && byte < 128u8 {
555 next_split = Some((idx, idx + 1));
560 for (idx, ch) in self.string.char_indices() {
561 if self.sep.matches(ch) {
562 next_split = Some((idx, self.string.char_range_at(idx).next));
568 Some((a, b)) => unsafe {
569 let elt = self.string.slice_unchecked(0, a);
570 self.string = self.string.slice_unchecked(b, self.string.len());
573 None => self.get_end(),
578 #[stable(feature = "rust1", since = "1.0.0")]
579 impl<'a, Sep: CharEq> DoubleEndedIterator for CharSplits<'a, Sep> {
581 fn next_back(&mut self) -> Option<&'a str> {
582 if self.finished { return None }
584 if !self.allow_trailing_empty {
585 self.allow_trailing_empty = true;
586 match self.next_back() {
587 Some(elt) if !elt.is_empty() => return Some(elt),
588 _ => if self.finished { return None }
591 let len = self.string.len();
592 let mut next_split = None;
595 for (idx, byte) in self.string.bytes().enumerate().rev() {
596 if self.sep.matches(byte as char) && byte < 128u8 {
597 next_split = Some((idx, idx + 1));
602 for (idx, ch) in self.string.char_indices().rev() {
603 if self.sep.matches(ch) {
604 next_split = Some((idx, self.string.char_range_at(idx).next));
610 Some((a, b)) => unsafe {
611 let elt = self.string.slice_unchecked(b, len);
612 self.string = self.string.slice_unchecked(0, a);
615 None => { self.finished = true; Some(self.string) }
620 #[stable(feature = "rust1", since = "1.0.0")]
621 impl<'a, Sep: CharEq> Iterator for CharSplitsN<'a, Sep> {
625 fn next(&mut self) -> Option<&'a str> {
628 if self.invert { self.iter.next_back() } else { self.iter.next() }
635 /// The internal state of an iterator that searches for matches of a substring
636 /// within a larger string using naive search
638 struct NaiveSearcher {
643 fn new() -> NaiveSearcher {
644 NaiveSearcher { position: 0 }
647 fn next(&mut self, haystack: &[u8], needle: &[u8]) -> Option<(usize, usize)> {
648 while self.position + needle.len() <= haystack.len() {
649 if &haystack[self.position .. self.position + needle.len()] == needle {
650 let match_pos = self.position;
651 self.position += needle.len(); // add 1 for all matches
652 return Some((match_pos, match_pos + needle.len()));
661 /// The internal state of an iterator that searches for matches of a substring
662 /// within a larger string using two-way search
664 struct TwoWaySearcher {
676 This is the Two-Way search algorithm, which was introduced in the paper:
677 Crochemore, M., Perrin, D., 1991, Two-way string-matching, Journal of the ACM 38(3):651-675.
679 Here's some background information.
681 A *word* is a string of symbols. The *length* of a word should be a familiar
682 notion, and here we denote it for any word x by |x|.
683 (We also allow for the possibility of the *empty word*, a word of length zero).
685 If x is any non-empty word, then an integer p with 0 < p <= |x| is said to be a
686 *period* for x iff for all i with 0 <= i <= |x| - p - 1, we have x[i] == x[i+p].
687 For example, both 1 and 2 are periods for the string "aa". As another example,
688 the only period of the string "abcd" is 4.
690 We denote by period(x) the *smallest* period of x (provided that x is non-empty).
691 This is always well-defined since every non-empty word x has at least one period,
692 |x|. We sometimes call this *the period* of x.
694 If u, v and x are words such that x = uv, where uv is the concatenation of u and
695 v, then we say that (u, v) is a *factorization* of x.
697 Let (u, v) be a factorization for a word x. Then if w is a non-empty word such
698 that both of the following hold
700 - either w is a suffix of u or u is a suffix of w
701 - either w is a prefix of v or v is a prefix of w
703 then w is said to be a *repetition* for the factorization (u, v).
705 Just to unpack this, there are four possibilities here. Let w = "abc". Then we
708 - w is a suffix of u and w is a prefix of v. ex: ("lolabc", "abcde")
709 - w is a suffix of u and v is a prefix of w. ex: ("lolabc", "ab")
710 - u is a suffix of w and w is a prefix of v. ex: ("bc", "abchi")
711 - u is a suffix of w and v is a prefix of w. ex: ("bc", "a")
713 Note that the word vu is a repetition for any factorization (u,v) of x = uv,
714 so every factorization has at least one repetition.
716 If x is a string and (u, v) is a factorization for x, then a *local period* for
717 (u, v) is an integer r such that there is some word w such that |w| = r and w is
718 a repetition for (u, v).
720 We denote by local_period(u, v) the smallest local period of (u, v). We sometimes
721 call this *the local period* of (u, v). Provided that x = uv is non-empty, this
722 is well-defined (because each non-empty word has at least one factorization, as
725 It can be proven that the following is an equivalent definition of a local period
726 for a factorization (u, v): any positive integer r such that x[i] == x[i+r] for
727 all i such that |u| - r <= i <= |u| - 1 and such that both x[i] and x[i+r] are
728 defined. (i.e. i > 0 and i + r < |x|).
730 Using the above reformulation, it is easy to prove that
732 1 <= local_period(u, v) <= period(uv)
734 A factorization (u, v) of x such that local_period(u,v) = period(x) is called a
735 *critical factorization*.
737 The algorithm hinges on the following theorem, which is stated without proof:
739 **Critical Factorization Theorem** Any word x has at least one critical
740 factorization (u, v) such that |u| < period(x).
742 The purpose of maximal_suffix is to find such a critical factorization.
745 impl TwoWaySearcher {
746 fn new(needle: &[u8]) -> TwoWaySearcher {
747 let (crit_pos_false, period_false) = TwoWaySearcher::maximal_suffix(needle, false);
748 let (crit_pos_true, period_true) = TwoWaySearcher::maximal_suffix(needle, true);
750 let (crit_pos, period) =
751 if crit_pos_false > crit_pos_true {
752 (crit_pos_false, period_false)
754 (crit_pos_true, period_true)
757 // This isn't in the original algorithm, as far as I'm aware.
758 let byteset = needle.iter()
759 .fold(0, |a, &b| (1 << ((b & 0x3f) as usize)) | a);
761 // A particularly readable explanation of what's going on here can be found
762 // in Crochemore and Rytter's book "Text Algorithms", ch 13. Specifically
763 // see the code for "Algorithm CP" on p. 323.
765 // What's going on is we have some critical factorization (u, v) of the
766 // needle, and we want to determine whether u is a suffix of
767 // &v[..period]. If it is, we use "Algorithm CP1". Otherwise we use
768 // "Algorithm CP2", which is optimized for when the period of the needle
770 if &needle[..crit_pos] == &needle[period.. period + crit_pos] {
782 period: cmp::max(crit_pos, needle.len() - crit_pos) + 1,
786 memory: usize::MAX // Dummy value to signify that the period is long
791 // One of the main ideas of Two-Way is that we factorize the needle into
792 // two halves, (u, v), and begin trying to find v in the haystack by scanning
793 // left to right. If v matches, we try to match u by scanning right to left.
794 // How far we can jump when we encounter a mismatch is all based on the fact
795 // that (u, v) is a critical factorization for the needle.
797 fn next(&mut self, haystack: &[u8], needle: &[u8], long_period: bool)
798 -> Option<(usize, usize)> {
800 // Check that we have room to search in
801 if self.position + needle.len() > haystack.len() {
805 // Quickly skip by large portions unrelated to our substring
807 ((haystack[self.position + needle.len() - 1] & 0x3f)
808 as usize)) & 1 == 0 {
809 self.position += needle.len();
816 // See if the right part of the needle matches
817 let start = if long_period { self.crit_pos }
818 else { cmp::max(self.crit_pos, self.memory) };
819 for i in start..needle.len() {
820 if needle[i] != haystack[self.position + i] {
821 self.position += i - self.crit_pos + 1;
829 // See if the left part of the needle matches
830 let start = if long_period { 0 } else { self.memory };
831 for i in (start..self.crit_pos).rev() {
832 if needle[i] != haystack[self.position + i] {
833 self.position += self.period;
835 self.memory = needle.len() - self.period;
841 // We have found a match!
842 let match_pos = self.position;
843 self.position += needle.len(); // add self.period for all matches
845 self.memory = 0; // set to needle.len() - self.period for all matches
847 return Some((match_pos, match_pos + needle.len()));
851 // Computes a critical factorization (u, v) of `arr`.
852 // Specifically, returns (i, p), where i is the starting index of v in some
853 // critical factorization (u, v) and p = period(v)
855 fn maximal_suffix(arr: &[u8], reversed: bool) -> (usize, usize) {
856 let mut left = -1; // Corresponds to i in the paper
857 let mut right = 0; // Corresponds to j in the paper
858 let mut offset = 1; // Corresponds to k in the paper
859 let mut period = 1; // Corresponds to p in the paper
861 while right + offset < arr.len() {
865 a = arr[left + offset];
866 b = arr[right + offset];
868 a = arr[right + offset];
869 b = arr[left + offset];
872 // Suffix is smaller, period is entire prefix so far.
875 period = right - left;
877 // Advance through repetition of the current period.
878 if offset == period {
885 // Suffix is larger, start over from current location.
896 /// The internal state of an iterator that searches for matches of a substring
897 /// within a larger string using a dynamically chosen search algorithm
900 Naive(NaiveSearcher),
901 TwoWay(TwoWaySearcher),
902 TwoWayLong(TwoWaySearcher)
906 fn new(haystack: &[u8], needle: &[u8]) -> Searcher {
908 // FIXME(#16715): This unsigned integer addition will probably not
909 // overflow because that would mean that the memory almost solely
910 // consists of the needle. Needs #16715 to be formally fixed.
911 if needle.len() + 20 > haystack.len() {
912 Naive(NaiveSearcher::new())
914 let searcher = TwoWaySearcher::new(needle);
915 if searcher.memory == usize::MAX { // If the period is long
924 /// An iterator over the start and end indices of the matches of a
925 /// substring within a larger string
927 #[unstable(feature = "core", reason = "type may be removed")]
928 pub struct MatchIndices<'a> {
935 /// An iterator over the substrings of a string separated by a given
938 #[unstable(feature = "core", reason = "type may be removed")]
939 pub struct SplitStr<'a> {
940 it: MatchIndices<'a>,
945 #[stable(feature = "rust1", since = "1.0.0")]
946 impl<'a> Iterator for MatchIndices<'a> {
947 type Item = (usize, usize);
950 fn next(&mut self) -> Option<(usize, usize)> {
951 match self.searcher {
952 Naive(ref mut searcher)
953 => searcher.next(self.haystack.as_bytes(), self.needle.as_bytes()),
954 TwoWay(ref mut searcher)
955 => searcher.next(self.haystack.as_bytes(), self.needle.as_bytes(), false),
956 TwoWayLong(ref mut searcher)
957 => searcher.next(self.haystack.as_bytes(), self.needle.as_bytes(), true)
962 #[stable(feature = "rust1", since = "1.0.0")]
963 impl<'a> Iterator for SplitStr<'a> {
967 fn next(&mut self) -> Option<&'a str> {
968 if self.finished { return None; }
970 match self.it.next() {
971 Some((from, to)) => {
972 let ret = Some(&self.it.haystack[self.last_end .. from]);
977 self.finished = true;
978 Some(&self.it.haystack[self.last_end .. self.it.haystack.len()])
986 Section: Comparing strings
989 // share the implementation of the lang-item vs. non-lang-item
991 /// NOTE: This function is (ab)used in rustc::middle::trans::_match
992 /// to compare &[u8] byte slices that are not necessarily valid UTF-8.
994 fn eq_slice_(a: &str, b: &str) -> bool {
995 // NOTE: In theory n should be libc::size_t and not usize, but libc is not available here
996 #[allow(improper_ctypes)]
997 extern { fn memcmp(s1: *const i8, s2: *const i8, n: usize) -> i32; }
998 a.len() == b.len() && unsafe {
999 memcmp(a.as_ptr() as *const i8,
1000 b.as_ptr() as *const i8,
1005 /// Bytewise slice equality
1006 /// NOTE: This function is (ab)used in rustc::middle::trans::_match
1007 /// to compare &[u8] byte slices that are not necessarily valid UTF-8.
1010 fn eq_slice(a: &str, b: &str) -> bool {
1018 /// Walk through `iter` checking that it's a valid UTF-8 sequence,
1019 /// returning `true` in that case, or, if it is invalid, `false` with
1020 /// `iter` reset such that it is pointing at the first byte in the
1021 /// invalid sequence.
1023 fn run_utf8_validation_iterator(iter: &mut slice::Iter<u8>)
1024 -> Result<(), Utf8Error> {
1025 let whole = iter.as_slice();
1027 // save the current thing we're pointing at.
1028 let old = iter.clone();
1030 // restore the iterator we had at the start of this codepoint.
1031 macro_rules! err { () => {{
1032 *iter = old.clone();
1033 return Err(Utf8Error::InvalidByte(whole.len() - iter.as_slice().len()))
1036 macro_rules! next { () => {
1039 // we needed data, but there was none: error!
1040 None => return Err(Utf8Error::TooShort),
1044 let first = match iter.next() {
1046 // we're at the end of the iterator and a codepoint
1047 // boundary at the same time, so this string is valid.
1048 None => return Ok(())
1051 // ASCII characters are always valid, so only large
1052 // bytes need more examination.
1054 let w = UTF8_CHAR_WIDTH[first as usize] as usize;
1055 let second = next!();
1056 // 2-byte encoding is for codepoints \u{0080} to \u{07ff}
1057 // first C2 80 last DF BF
1058 // 3-byte encoding is for codepoints \u{0800} to \u{ffff}
1059 // first E0 A0 80 last EF BF BF
1060 // excluding surrogates codepoints \u{d800} to \u{dfff}
1061 // ED A0 80 to ED BF BF
1062 // 4-byte encoding is for codepoints \u{1000}0 to \u{10ff}ff
1063 // first F0 90 80 80 last F4 8F BF BF
1065 // Use the UTF-8 syntax from the RFC
1067 // https://tools.ietf.org/html/rfc3629
1069 // UTF8-2 = %xC2-DF UTF8-tail
1070 // UTF8-3 = %xE0 %xA0-BF UTF8-tail / %xE1-EC 2( UTF8-tail ) /
1071 // %xED %x80-9F UTF8-tail / %xEE-EF 2( UTF8-tail )
1072 // UTF8-4 = %xF0 %x90-BF 2( UTF8-tail ) / %xF1-F3 3( UTF8-tail ) /
1073 // %xF4 %x80-8F 2( UTF8-tail )
1075 2 => if second & !CONT_MASK != TAG_CONT_U8 {err!()},
1077 match (first, second, next!() & !CONT_MASK) {
1078 (0xE0 , 0xA0 ... 0xBF, TAG_CONT_U8) |
1079 (0xE1 ... 0xEC, 0x80 ... 0xBF, TAG_CONT_U8) |
1080 (0xED , 0x80 ... 0x9F, TAG_CONT_U8) |
1081 (0xEE ... 0xEF, 0x80 ... 0xBF, TAG_CONT_U8) => {}
1086 match (first, second, next!() & !CONT_MASK, next!() & !CONT_MASK) {
1087 (0xF0 , 0x90 ... 0xBF, TAG_CONT_U8, TAG_CONT_U8) |
1088 (0xF1 ... 0xF3, 0x80 ... 0xBF, TAG_CONT_U8, TAG_CONT_U8) |
1089 (0xF4 , 0x80 ... 0x8F, TAG_CONT_U8, TAG_CONT_U8) => {}
1099 // https://tools.ietf.org/html/rfc3629
1100 static UTF8_CHAR_WIDTH: [u8; 256] = [
1101 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1102 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // 0x1F
1103 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1104 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // 0x3F
1105 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1106 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // 0x5F
1107 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1108 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // 0x7F
1109 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
1110 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 0x9F
1111 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
1112 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 0xBF
1113 0,0,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
1114 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, // 0xDF
1115 3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3, // 0xEF
1116 4,4,4,4,4,0,0,0,0,0,0,0,0,0,0,0, // 0xFF
1119 /// Struct that contains a `char` and the index of the first byte of
1120 /// the next `char` in a string. This can be used as a data structure
1121 /// for iterating over the UTF-8 bytes of a string.
1123 #[unstable(feature = "core",
1124 reason = "naming is uncertain with container conventions")]
1125 pub struct CharRange {
1128 /// Index of the first byte of the next `char`
1132 /// Mask of the value bits of a continuation byte
1133 const CONT_MASK: u8 = 0b0011_1111u8;
1134 /// Value of the tag bits (tag mask is !CONT_MASK) of a continuation byte
1135 const TAG_CONT_U8: u8 = 0b1000_0000u8;
1138 Section: Trait implementations
1142 use cmp::{Ordering, Ord, PartialEq, PartialOrd, Eq};
1143 use cmp::Ordering::{Less, Equal, Greater};
1144 use iter::IteratorExt;
1146 use option::Option::Some;
1148 use str::{StrExt, eq_slice};
1150 #[stable(feature = "rust1", since = "1.0.0")]
1153 fn cmp(&self, other: &str) -> Ordering {
1154 for (s_b, o_b) in self.bytes().zip(other.bytes()) {
1155 match s_b.cmp(&o_b) {
1156 Greater => return Greater,
1157 Less => return Less,
1162 self.len().cmp(&other.len())
1166 #[stable(feature = "rust1", since = "1.0.0")]
1167 impl PartialEq for str {
1169 fn eq(&self, other: &str) -> bool {
1170 eq_slice(self, other)
1173 fn ne(&self, other: &str) -> bool { !(*self).eq(other) }
1176 #[stable(feature = "rust1", since = "1.0.0")]
1179 #[stable(feature = "rust1", since = "1.0.0")]
1180 impl PartialOrd for str {
1182 fn partial_cmp(&self, other: &str) -> Option<Ordering> {
1183 Some(self.cmp(other))
1187 /// Returns a slice of the given string from the byte range
1188 /// [`begin`..`end`).
1190 /// This operation is `O(1)`.
1192 /// Panics when `begin` and `end` do not point to valid characters
1193 /// or point beyond the last character of the string.
1198 /// let s = "Löwe 老虎 Léopard";
1199 /// assert_eq!(&s[0 .. 1], "L");
1201 /// assert_eq!(&s[1 .. 9], "öwe 老");
1203 /// // these will panic:
1204 /// // byte 2 lies within `ö`:
1207 /// // byte 8 lies within `老`
1210 /// // byte 100 is outside the string
1211 /// // &s[3 .. 100];
1213 #[stable(feature = "rust1", since = "1.0.0")]
1214 impl ops::Index<ops::Range<usize>> for str {
1217 fn index(&self, index: &ops::Range<usize>) -> &str {
1218 // is_char_boundary checks that the index is in [0, .len()]
1219 if index.start <= index.end &&
1220 self.is_char_boundary(index.start) &&
1221 self.is_char_boundary(index.end) {
1222 unsafe { self.slice_unchecked(index.start, index.end) }
1224 super::slice_error_fail(self, index.start, index.end)
1229 /// Returns a slice of the string from the beginning to byte
1232 /// Equivalent to `self[0 .. end]`.
1234 /// Panics when `end` does not point to a valid character, or is
1236 #[stable(feature = "rust1", since = "1.0.0")]
1237 impl ops::Index<ops::RangeTo<usize>> for str {
1240 fn index(&self, index: &ops::RangeTo<usize>) -> &str {
1241 // is_char_boundary checks that the index is in [0, .len()]
1242 if self.is_char_boundary(index.end) {
1243 unsafe { self.slice_unchecked(0, index.end) }
1245 super::slice_error_fail(self, 0, index.end)
1250 /// Returns a slice of the string from `begin` to its end.
1252 /// Equivalent to `self[begin .. self.len()]`.
1254 /// Panics when `begin` does not point to a valid character, or is
1256 #[stable(feature = "rust1", since = "1.0.0")]
1257 impl ops::Index<ops::RangeFrom<usize>> for str {
1260 fn index(&self, index: &ops::RangeFrom<usize>) -> &str {
1261 // is_char_boundary checks that the index is in [0, .len()]
1262 if self.is_char_boundary(index.start) {
1263 unsafe { self.slice_unchecked(index.start, self.len()) }
1265 super::slice_error_fail(self, index.start, self.len())
1270 #[stable(feature = "rust1", since = "1.0.0")]
1271 impl ops::Index<ops::RangeFull> for str {
1274 fn index(&self, _index: &ops::RangeFull) -> &str {
1280 /// Any string that can be represented as a slice
1281 #[unstable(feature = "core",
1282 reason = "Instead of taking this bound generically, this trait will be \
1283 replaced with one of slicing syntax (&foo[..]), deref coercions, or \
1284 a more generic conversion trait")]
1286 /// Work with `self` as a slice.
1287 fn as_slice<'a>(&'a self) -> &'a str;
1292 fn as_slice<'a>(&'a self) -> &'a str { self }
1295 impl<'a, S: ?Sized> Str for &'a S where S: Str {
1297 fn as_slice(&self) -> &str { Str::as_slice(*self) }
1300 /// Return type of `StrExt::split`
1302 #[stable(feature = "rust1", since = "1.0.0")]
1303 pub struct Split<'a, P>(CharSplits<'a, P>);
1304 delegate_iter!{pattern &'a str : Split<'a, P>}
1306 /// Return type of `StrExt::split_terminator`
1308 #[unstable(feature = "core",
1309 reason = "might get removed in favour of a constructor method on Split")]
1310 pub struct SplitTerminator<'a, P>(CharSplits<'a, P>);
1311 delegate_iter!{pattern &'a str : SplitTerminator<'a, P>}
1313 /// Return type of `StrExt::splitn`
1315 #[stable(feature = "rust1", since = "1.0.0")]
1316 pub struct SplitN<'a, P>(CharSplitsN<'a, P>);
1317 delegate_iter!{pattern forward &'a str : SplitN<'a, P>}
1319 /// Return type of `StrExt::rsplitn`
1321 #[stable(feature = "rust1", since = "1.0.0")]
1322 pub struct RSplitN<'a, P>(CharSplitsN<'a, P>);
1323 delegate_iter!{pattern forward &'a str : RSplitN<'a, P>}
1325 /// Methods for string slices
1326 #[allow(missing_docs)]
1328 // NB there are no docs here are they're all located on the StrExt trait in
1329 // libcollections, not here.
1331 fn contains(&self, pat: &str) -> bool;
1332 fn contains_char<P: CharEq>(&self, pat: P) -> bool;
1333 fn chars<'a>(&'a self) -> Chars<'a>;
1334 fn bytes<'a>(&'a self) -> Bytes<'a>;
1335 fn char_indices<'a>(&'a self) -> CharIndices<'a>;
1336 fn split<'a, P: CharEq>(&'a self, pat: P) -> Split<'a, P>;
1337 fn splitn<'a, P: CharEq>(&'a self, count: usize, pat: P) -> SplitN<'a, P>;
1338 fn split_terminator<'a, P: CharEq>(&'a self, pat: P) -> SplitTerminator<'a, P>;
1339 fn rsplitn<'a, P: CharEq>(&'a self, count: usize, pat: P) -> RSplitN<'a, P>;
1340 fn match_indices<'a>(&'a self, sep: &'a str) -> MatchIndices<'a>;
1341 fn split_str<'a>(&'a self, pat: &'a str) -> SplitStr<'a>;
1342 fn lines<'a>(&'a self) -> Lines<'a>;
1343 fn lines_any<'a>(&'a self) -> LinesAny<'a>;
1344 fn char_len(&self) -> usize;
1345 fn slice_chars<'a>(&'a self, begin: usize, end: usize) -> &'a str;
1346 unsafe fn slice_unchecked<'a>(&'a self, begin: usize, end: usize) -> &'a str;
1347 fn starts_with(&self, pat: &str) -> bool;
1348 fn ends_with(&self, pat: &str) -> bool;
1349 fn trim_matches<'a, P: CharEq>(&'a self, pat: P) -> &'a str;
1350 fn trim_left_matches<'a, P: CharEq>(&'a self, pat: P) -> &'a str;
1351 fn trim_right_matches<'a, P: CharEq>(&'a self, pat: P) -> &'a str;
1352 fn is_char_boundary(&self, index: usize) -> bool;
1353 fn char_range_at(&self, start: usize) -> CharRange;
1354 fn char_range_at_reverse(&self, start: usize) -> CharRange;
1355 fn char_at(&self, i: usize) -> char;
1356 fn char_at_reverse(&self, i: usize) -> char;
1357 fn as_bytes<'a>(&'a self) -> &'a [u8];
1358 fn find<P: CharEq>(&self, pat: P) -> Option<usize>;
1359 fn rfind<P: CharEq>(&self, pat: P) -> Option<usize>;
1360 fn find_str(&self, pat: &str) -> Option<usize>;
1361 fn slice_shift_char<'a>(&'a self) -> Option<(char, &'a str)>;
1362 fn subslice_offset(&self, inner: &str) -> usize;
1363 fn as_ptr(&self) -> *const u8;
1364 fn len(&self) -> usize;
1365 fn is_empty(&self) -> bool;
1366 fn parse<T: FromStr>(&self) -> Result<T, T::Err>;
1370 fn slice_error_fail(s: &str, begin: usize, end: usize) -> ! {
1371 assert!(begin <= end);
1372 panic!("index {} and/or {} in `{}` do not lie on character boundary",
1376 impl StrExt for str {
1378 fn contains(&self, needle: &str) -> bool {
1379 self.find_str(needle).is_some()
1383 fn contains_char<P: CharEq>(&self, pat: P) -> bool {
1384 self.find(pat).is_some()
1388 fn chars(&self) -> Chars {
1389 Chars{iter: self.as_bytes().iter()}
1393 fn bytes(&self) -> Bytes {
1394 Bytes(self.as_bytes().iter().map(BytesDeref))
1398 fn char_indices(&self) -> CharIndices {
1399 CharIndices { front_offset: 0, iter: self.chars() }
1403 fn split<P: CharEq>(&self, pat: P) -> Split<P> {
1406 only_ascii: pat.only_ascii(),
1408 allow_trailing_empty: true,
1414 fn splitn<P: CharEq>(&self, count: usize, pat: P) -> SplitN<P> {
1415 SplitN(CharSplitsN {
1416 iter: self.split(pat).0,
1423 fn split_terminator<P: CharEq>(&self, pat: P) -> SplitTerminator<P> {
1424 SplitTerminator(CharSplits {
1425 allow_trailing_empty: false,
1431 fn rsplitn<P: CharEq>(&self, count: usize, pat: P) -> RSplitN<P> {
1432 RSplitN(CharSplitsN {
1433 iter: self.split(pat).0,
1440 fn match_indices<'a>(&'a self, sep: &'a str) -> MatchIndices<'a> {
1441 assert!(!sep.is_empty());
1445 searcher: Searcher::new(self.as_bytes(), sep.as_bytes())
1450 fn split_str<'a>(&'a self, sep: &'a str) -> SplitStr<'a> {
1452 it: self.match_indices(sep),
1459 fn lines(&self) -> Lines {
1460 Lines { inner: self.split_terminator('\n').0 }
1463 fn lines_any(&self) -> LinesAny {
1464 fn f(line: &str) -> &str {
1466 if l > 0 && line.as_bytes()[l - 1] == b'\r' { &line[0 .. l - 1] }
1470 let f: fn(&str) -> &str = f; // coerce to fn pointer
1471 LinesAny { inner: self.lines().map(f) }
1475 fn char_len(&self) -> usize { self.chars().count() }
1477 fn slice_chars(&self, begin: usize, end: usize) -> &str {
1478 assert!(begin <= end);
1480 let mut begin_byte = None;
1481 let mut end_byte = None;
1483 // This could be even more efficient by not decoding,
1484 // only finding the char boundaries
1485 for (idx, _) in self.char_indices() {
1486 if count == begin { begin_byte = Some(idx); }
1487 if count == end { end_byte = Some(idx); break; }
1490 if begin_byte.is_none() && count == begin { begin_byte = Some(self.len()) }
1491 if end_byte.is_none() && count == end { end_byte = Some(self.len()) }
1493 match (begin_byte, end_byte) {
1494 (None, _) => panic!("slice_chars: `begin` is beyond end of string"),
1495 (_, None) => panic!("slice_chars: `end` is beyond end of string"),
1496 (Some(a), Some(b)) => unsafe { self.slice_unchecked(a, b) }
1501 unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str {
1502 mem::transmute(Slice {
1503 data: self.as_ptr().offset(begin as isize),
1509 fn starts_with(&self, needle: &str) -> bool {
1510 let n = needle.len();
1511 self.len() >= n && needle.as_bytes() == &self.as_bytes()[..n]
1515 fn ends_with(&self, needle: &str) -> bool {
1516 let (m, n) = (self.len(), needle.len());
1517 m >= n && needle.as_bytes() == &self.as_bytes()[m-n..]
1521 fn trim_matches<P: CharEq>(&self, mut pat: P) -> &str {
1522 let cur = match self.find(|c: char| !pat.matches(c)) {
1524 Some(i) => unsafe { self.slice_unchecked(i, self.len()) }
1526 match cur.rfind(|c: char| !pat.matches(c)) {
1529 let right = cur.char_range_at(i).next;
1530 unsafe { cur.slice_unchecked(0, right) }
1536 fn trim_left_matches<P: CharEq>(&self, mut pat: P) -> &str {
1537 match self.find(|c: char| !pat.matches(c)) {
1539 Some(first) => unsafe { self.slice_unchecked(first, self.len()) }
1544 fn trim_right_matches<P: CharEq>(&self, mut pat: P) -> &str {
1545 match self.rfind(|c: char| !pat.matches(c)) {
1548 let next = self.char_range_at(last).next;
1549 unsafe { self.slice_unchecked(0, next) }
1555 fn is_char_boundary(&self, index: usize) -> bool {
1556 if index == self.len() { return true; }
1557 match self.as_bytes().get(index) {
1559 Some(&b) => b < 128u8 || b >= 192u8,
1564 fn char_range_at(&self, i: usize) -> CharRange {
1565 let (c, n) = char_range_at_raw(self.as_bytes(), i);
1566 CharRange { ch: unsafe { mem::transmute(c) }, next: n }
1570 fn char_range_at_reverse(&self, start: usize) -> CharRange {
1571 let mut prev = start;
1573 prev = prev.saturating_sub(1);
1574 if self.as_bytes()[prev] < 128 {
1575 return CharRange{ch: self.as_bytes()[prev] as char, next: prev}
1578 // Multibyte case is a fn to allow char_range_at_reverse to inline cleanly
1579 fn multibyte_char_range_at_reverse(s: &str, mut i: usize) -> CharRange {
1580 // while there is a previous byte == 10......
1581 while i > 0 && s.as_bytes()[i] & !CONT_MASK == TAG_CONT_U8 {
1585 let mut val = s.as_bytes()[i] as u32;
1586 let w = UTF8_CHAR_WIDTH[val as usize] as usize;
1589 val = utf8_first_byte!(val, w);
1590 val = utf8_acc_cont_byte!(val, s.as_bytes()[i + 1]);
1591 if w > 2 { val = utf8_acc_cont_byte!(val, s.as_bytes()[i + 2]); }
1592 if w > 3 { val = utf8_acc_cont_byte!(val, s.as_bytes()[i + 3]); }
1594 return CharRange {ch: unsafe { mem::transmute(val) }, next: i};
1597 return multibyte_char_range_at_reverse(self, prev);
1601 fn char_at(&self, i: usize) -> char {
1602 self.char_range_at(i).ch
1606 fn char_at_reverse(&self, i: usize) -> char {
1607 self.char_range_at_reverse(i).ch
1611 fn as_bytes(&self) -> &[u8] {
1612 unsafe { mem::transmute(self) }
1615 fn find<P: CharEq>(&self, mut pat: P) -> Option<usize> {
1616 if pat.only_ascii() {
1617 self.bytes().position(|b| pat.matches(b as char))
1619 for (index, c) in self.char_indices() {
1620 if pat.matches(c) { return Some(index); }
1626 fn rfind<P: CharEq>(&self, mut pat: P) -> Option<usize> {
1627 if pat.only_ascii() {
1628 self.bytes().rposition(|b| pat.matches(b as char))
1630 for (index, c) in self.char_indices().rev() {
1631 if pat.matches(c) { return Some(index); }
1637 fn find_str(&self, needle: &str) -> Option<usize> {
1638 if needle.is_empty() {
1641 self.match_indices(needle)
1643 .map(|(start, _end)| start)
1648 fn slice_shift_char(&self) -> Option<(char, &str)> {
1649 if self.is_empty() {
1652 let CharRange {ch, next} = self.char_range_at(0);
1653 let next_s = unsafe { self.slice_unchecked(next, self.len()) };
1658 fn subslice_offset(&self, inner: &str) -> usize {
1659 let a_start = self.as_ptr() as usize;
1660 let a_end = a_start + self.len();
1661 let b_start = inner.as_ptr() as usize;
1662 let b_end = b_start + inner.len();
1664 assert!(a_start <= b_start);
1665 assert!(b_end <= a_end);
1670 fn as_ptr(&self) -> *const u8 {
1675 fn len(&self) -> usize { self.repr().len }
1678 fn is_empty(&self) -> bool { self.len() == 0 }
1681 fn parse<T: FromStr>(&self) -> Result<T, T::Err> { FromStr::from_str(self) }
1684 /// Pluck a code point out of a UTF-8-like byte slice and return the
1685 /// index of the next code point.
1687 #[unstable(feature = "core")]
1688 pub fn char_range_at_raw(bytes: &[u8], i: usize) -> (u32, usize) {
1689 if bytes[i] < 128u8 {
1690 return (bytes[i] as u32, i + 1);
1693 // Multibyte case is a fn to allow char_range_at to inline cleanly
1694 fn multibyte_char_range_at(bytes: &[u8], i: usize) -> (u32, usize) {
1695 let mut val = bytes[i] as u32;
1696 let w = UTF8_CHAR_WIDTH[val as usize] as usize;
1699 val = utf8_first_byte!(val, w);
1700 val = utf8_acc_cont_byte!(val, bytes[i + 1]);
1701 if w > 2 { val = utf8_acc_cont_byte!(val, bytes[i + 2]); }
1702 if w > 3 { val = utf8_acc_cont_byte!(val, bytes[i + 3]); }
1704 return (val, i + w);
1707 multibyte_char_range_at(bytes, i)
1710 #[stable(feature = "rust1", since = "1.0.0")]
1711 impl<'a> Default for &'a str {
1712 #[stable(feature = "rust1", since = "1.0.0")]
1713 fn default() -> &'a str { "" }
1716 #[stable(feature = "rust1", since = "1.0.0")]
1717 impl<'a> Iterator for Lines<'a> {
1718 type Item = &'a str;
1721 fn next(&mut self) -> Option<&'a str> { self.inner.next() }
1723 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1726 #[stable(feature = "rust1", since = "1.0.0")]
1727 impl<'a> DoubleEndedIterator for Lines<'a> {
1729 fn next_back(&mut self) -> Option<&'a str> { self.inner.next_back() }
1732 #[stable(feature = "rust1", since = "1.0.0")]
1733 impl<'a> Iterator for LinesAny<'a> {
1734 type Item = &'a str;
1737 fn next(&mut self) -> Option<&'a str> { self.inner.next() }
1739 fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
1742 #[stable(feature = "rust1", since = "1.0.0")]
1743 impl<'a> DoubleEndedIterator for LinesAny<'a> {
1745 fn next_back(&mut self) -> Option<&'a str> { self.inner.next_back() }