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//! Parallel iterator types for [strings][std::str]
//!
//! You will rarely need to interact with this module directly unless you need
//! to name one of the iterator types.
//!
//! Note: [`ParallelString::par_split()`] and [`par_split_terminator()`]
//! reference a `Pattern` trait which is not visible outside this crate.
//! This trait is intentionally kept private, for use only by Rayon itself.
//! It is implemented for `char` and any `F: Fn(char) -> bool + Sync + Send`.
//!
//! [`ParallelString::par_split()`]: trait.ParallelString.html#method.par_split
//! [`par_split_terminator()`]: trait.ParallelString.html#method.par_split_terminator
//!
use crate::iter::plumbing::*;
use crate::iter::*;
use crate::split_producer::*;
/// Test if a byte is the start of a UTF-8 character.
/// (extracted from `str::is_char_boundary`)
#[inline]
fn is_char_boundary(b: u8) -> bool {
// This is bit magic equivalent to: b < 128 || b >= 192
(b as i8) >= -0x40
}
/// Find the index of a character boundary near the midpoint.
#[inline]
fn find_char_midpoint(chars: &str) -> usize {
let mid = chars.len() / 2;
// We want to split near the midpoint, but we need to find an actual
// character boundary. So we look at the raw bytes, first scanning
// forward from the midpoint for a boundary, then trying backward.
let (left, right) = chars.as_bytes().split_at(mid);
match right.iter().cloned().position(is_char_boundary) {
Some(i) => mid + i,
None => left
.iter()
.cloned()
.rposition(is_char_boundary)
.unwrap_or(0),
}
}
/// Try to split a string near the midpoint.
#[inline]
fn split(chars: &str) -> Option<(&str, &str)> {
let index = find_char_midpoint(chars);
if index > 0 {
Some(chars.split_at(index))
} else {
None
}
}
/// Parallel extensions for strings.
pub trait ParallelString {
/// Returns a plain string slice, which is used to implement the rest of
/// the parallel methods.
fn as_parallel_string(&self) -> &str;
/// Returns a parallel iterator over the characters of a string.
///
/// # Examples
///
/// ```
/// use rayon::prelude::*;
/// let max = "hello".par_chars().max_by_key(|c| *c as i32);
/// assert_eq!(Some('o'), max);
/// ```
fn par_chars(&self) -> Chars<'_> {
Chars {
chars: self.as_parallel_string(),
}
}
/// Returns a parallel iterator over the characters of a string, with their positions.
///
/// # Examples
///
/// ```
/// use rayon::prelude::*;
/// let min = "hello".par_char_indices().min_by_key(|&(_i, c)| c as i32);
/// assert_eq!(Some((1, 'e')), min);
/// ```
fn par_char_indices(&self) -> CharIndices<'_> {
CharIndices {
chars: self.as_parallel_string(),
}
}
/// Returns a parallel iterator over the bytes of a string.
///
/// Note that multi-byte sequences (for code points greater than `U+007F`)
/// are produced as separate items, but will not be split across threads.
/// If you would prefer an indexed iterator without that guarantee, consider
/// `string.as_bytes().par_iter().cloned()` instead.
///
/// # Examples
///
/// ```
/// use rayon::prelude::*;
/// let max = "hello".par_bytes().max();
/// assert_eq!(Some(b'o'), max);
/// ```
fn par_bytes(&self) -> Bytes<'_> {
Bytes {
chars: self.as_parallel_string(),
}
}
/// Returns a parallel iterator over a string encoded as UTF-16.
///
/// Note that surrogate pairs (for code points greater than `U+FFFF`) are
/// produced as separate items, but will not be split across threads.
///
/// # Examples
///
/// ```
/// use rayon::prelude::*;
///
/// let max = "hello".par_encode_utf16().max();
/// assert_eq!(Some(b'o' as u16), max);
///
/// let text = "Zażółć gęślą jaźń";
/// let utf8_len = text.len();
/// let utf16_len = text.par_encode_utf16().count();
/// assert!(utf16_len <= utf8_len);
/// ```
fn par_encode_utf16(&self) -> EncodeUtf16<'_> {
EncodeUtf16 {
chars: self.as_parallel_string(),
}
}
/// Returns a parallel iterator over substrings separated by a
/// given character or predicate, similar to `str::split`.
///
/// Note: the `Pattern` trait is private, for use only by Rayon itself.
/// It is implemented for `char` and any `F: Fn(char) -> bool + Sync + Send`.
///
/// # Examples
///
/// ```
/// use rayon::prelude::*;
/// let total = "1, 2, buckle, 3, 4, door"
/// .par_split(',')
/// .filter_map(|s| s.trim().parse::<i32>().ok())
/// .sum();
/// assert_eq!(10, total);
/// ```
fn par_split<P: Pattern>(&self, separator: P) -> Split<'_, P> {
Split::new(self.as_parallel_string(), separator)
}
/// Returns a parallel iterator over substrings terminated by a
/// given character or predicate, similar to `str::split_terminator`.
/// It's equivalent to `par_split`, except it doesn't produce an empty
/// substring after a trailing terminator.
///
/// Note: the `Pattern` trait is private, for use only by Rayon itself.
/// It is implemented for `char` and any `F: Fn(char) -> bool + Sync + Send`.
///
/// # Examples
///
/// ```
/// use rayon::prelude::*;
/// let parts: Vec<_> = "((1 + 3) * 2)"
/// .par_split_terminator(|c| c == '(' || c == ')')
/// .collect();
/// assert_eq!(vec!["", "", "1 + 3", " * 2"], parts);
/// ```
fn par_split_terminator<P: Pattern>(&self, terminator: P) -> SplitTerminator<'_, P> {
SplitTerminator::new(self.as_parallel_string(), terminator)
}
/// Returns a parallel iterator over the lines of a string, ending with an
/// optional carriage return and with a newline (`\r\n` or just `\n`).
/// The final line ending is optional, and line endings are not included in
/// the output strings.
///
/// # Examples
///
/// ```
/// use rayon::prelude::*;
/// let lengths: Vec<_> = "hello world\nfizbuzz"
/// .par_lines()
/// .map(|l| l.len())
/// .collect();
/// assert_eq!(vec![11, 7], lengths);
/// ```
fn par_lines(&self) -> Lines<'_> {
Lines(self.as_parallel_string())
}
/// Returns a parallel iterator over the sub-slices of a string that are
/// separated by any amount of whitespace.
///
/// As with `str::split_whitespace`, 'whitespace' is defined according to
/// the terms of the Unicode Derived Core Property `White_Space`.
///
/// # Examples
///
/// ```
/// use rayon::prelude::*;
/// let longest = "which is the longest word?"
/// .par_split_whitespace()
/// .max_by_key(|word| word.len());
/// assert_eq!(Some("longest"), longest);
/// ```
fn par_split_whitespace(&self) -> SplitWhitespace<'_> {
SplitWhitespace(self.as_parallel_string())
}
/// Returns a parallel iterator over substrings that match a
/// given character or predicate, similar to `str::matches`.
///
/// Note: the `Pattern` trait is private, for use only by Rayon itself.
/// It is implemented for `char` and any `F: Fn(char) -> bool + Sync + Send`.
///
/// # Examples
///
/// ```
/// use rayon::prelude::*;
/// let total = "1, 2, buckle, 3, 4, door"
/// .par_matches(char::is_numeric)
/// .map(|s| s.parse::<i32>().expect("digit"))
/// .sum();
/// assert_eq!(10, total);
/// ```
fn par_matches<P: Pattern>(&self, pattern: P) -> Matches<'_, P> {
Matches {
chars: self.as_parallel_string(),
pattern,
}
}
/// Returns a parallel iterator over substrings that match a given character
/// or predicate, with their positions, similar to `str::match_indices`.
///
/// Note: the `Pattern` trait is private, for use only by Rayon itself.
/// It is implemented for `char` and any `F: Fn(char) -> bool + Sync + Send`.
///
/// # Examples
///
/// ```
/// use rayon::prelude::*;
/// let digits: Vec<_> = "1, 2, buckle, 3, 4, door"
/// .par_match_indices(char::is_numeric)
/// .collect();
/// assert_eq!(digits, vec![(0, "1"), (3, "2"), (14, "3"), (17, "4")]);
/// ```
fn par_match_indices<P: Pattern>(&self, pattern: P) -> MatchIndices<'_, P> {
MatchIndices {
chars: self.as_parallel_string(),
pattern,
}
}
}
impl ParallelString for str {
#[inline]
fn as_parallel_string(&self) -> &str {
self
}
}
// /////////////////////////////////////////////////////////////////////////
/// We hide the `Pattern` trait in a private module, as its API is not meant
/// for general consumption. If we could have privacy on trait items, then it
/// would be nicer to have its basic existence and implementors public while
/// keeping all of the methods private.
mod private {
use crate::iter::plumbing::Folder;
/// Pattern-matching trait for `ParallelString`, somewhat like a mix of
/// `std::str::pattern::{Pattern, Searcher}`.
///
/// Implementing this trait is not permitted outside of `rayon`.
pub trait Pattern: Sized + Sync + Send {
private_decl! {}
fn find_in(&self, haystack: &str) -> Option<usize>;
fn rfind_in(&self, haystack: &str) -> Option<usize>;
fn is_suffix_of(&self, haystack: &str) -> bool;
fn fold_splits<'ch, F>(&self, haystack: &'ch str, folder: F, skip_last: bool) -> F
where
F: Folder<&'ch str>;
fn fold_matches<'ch, F>(&self, haystack: &'ch str, folder: F) -> F
where
F: Folder<&'ch str>;
fn fold_match_indices<'ch, F>(&self, haystack: &'ch str, folder: F, base: usize) -> F
where
F: Folder<(usize, &'ch str)>;
}
}
use self::private::Pattern;
#[inline]
fn offset<T>(base: usize) -> impl Fn((usize, T)) -> (usize, T) {
move |(i, x)| (base + i, x)
}
impl Pattern for char {
private_impl! {}
#[inline]
fn find_in(&self, chars: &str) -> Option<usize> {
chars.find(*self)
}
#[inline]
fn rfind_in(&self, chars: &str) -> Option<usize> {
chars.rfind(*self)
}
#[inline]
fn is_suffix_of(&self, chars: &str) -> bool {
chars.ends_with(*self)
}
fn fold_splits<'ch, F>(&self, chars: &'ch str, folder: F, skip_last: bool) -> F
where
F: Folder<&'ch str>,
{
let mut split = chars.split(*self);
if skip_last {
split.next_back();
}
folder.consume_iter(split)
}
fn fold_matches<'ch, F>(&self, chars: &'ch str, folder: F) -> F
where
F: Folder<&'ch str>,
{
folder.consume_iter(chars.matches(*self))
}
fn fold_match_indices<'ch, F>(&self, chars: &'ch str, folder: F, base: usize) -> F
where
F: Folder<(usize, &'ch str)>,
{
folder.consume_iter(chars.match_indices(*self).map(offset(base)))
}
}
impl<FN: Sync + Send + Fn(char) -> bool> Pattern for FN {
private_impl! {}
fn find_in(&self, chars: &str) -> Option<usize> {
chars.find(self)
}
fn rfind_in(&self, chars: &str) -> Option<usize> {
chars.rfind(self)
}
fn is_suffix_of(&self, chars: &str) -> bool {
chars.ends_with(self)
}
fn fold_splits<'ch, F>(&self, chars: &'ch str, folder: F, skip_last: bool) -> F
where
F: Folder<&'ch str>,
{
let mut split = chars.split(self);
if skip_last {
split.next_back();
}
folder.consume_iter(split)
}
fn fold_matches<'ch, F>(&self, chars: &'ch str, folder: F) -> F
where
F: Folder<&'ch str>,
{
folder.consume_iter(chars.matches(self))
}
fn fold_match_indices<'ch, F>(&self, chars: &'ch str, folder: F, base: usize) -> F
where
F: Folder<(usize, &'ch str)>,
{
folder.consume_iter(chars.match_indices(self).map(offset(base)))
}
}
// /////////////////////////////////////////////////////////////////////////
/// Parallel iterator over the characters of a string
#[derive(Debug, Clone)]
pub struct Chars<'ch> {
chars: &'ch str,
}
struct CharsProducer<'ch> {
chars: &'ch str,
}
impl<'ch> ParallelIterator for Chars<'ch> {
type Item = char;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
bridge_unindexed(CharsProducer { chars: self.chars }, consumer)
}
}
impl<'ch> UnindexedProducer for CharsProducer<'ch> {
type Item = char;
fn split(self) -> (Self, Option<Self>) {
match split(self.chars) {
Some((left, right)) => (
CharsProducer { chars: left },
Some(CharsProducer { chars: right }),
),
None => (self, None),
}
}
fn fold_with<F>(self, folder: F) -> F
where
F: Folder<Self::Item>,
{
folder.consume_iter(self.chars.chars())
}
}
// /////////////////////////////////////////////////////////////////////////
/// Parallel iterator over the characters of a string, with their positions
#[derive(Debug, Clone)]
pub struct CharIndices<'ch> {
chars: &'ch str,
}
struct CharIndicesProducer<'ch> {
index: usize,
chars: &'ch str,
}
impl<'ch> ParallelIterator for CharIndices<'ch> {
type Item = (usize, char);
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
let producer = CharIndicesProducer {
index: 0,
chars: self.chars,
};
bridge_unindexed(producer, consumer)
}
}
impl<'ch> UnindexedProducer for CharIndicesProducer<'ch> {
type Item = (usize, char);
fn split(self) -> (Self, Option<Self>) {
match split(self.chars) {
Some((left, right)) => (
CharIndicesProducer {
chars: left,
..self
},
Some(CharIndicesProducer {
chars: right,
index: self.index + left.len(),
}),
),
None => (self, None),
}
}
fn fold_with<F>(self, folder: F) -> F
where
F: Folder<Self::Item>,
{
let base = self.index;
folder.consume_iter(self.chars.char_indices().map(offset(base)))
}
}
// /////////////////////////////////////////////////////////////////////////
/// Parallel iterator over the bytes of a string
#[derive(Debug, Clone)]
pub struct Bytes<'ch> {
chars: &'ch str,
}
struct BytesProducer<'ch> {
chars: &'ch str,
}
impl<'ch> ParallelIterator for Bytes<'ch> {
type Item = u8;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
bridge_unindexed(BytesProducer { chars: self.chars }, consumer)
}
}
impl<'ch> UnindexedProducer for BytesProducer<'ch> {
type Item = u8;
fn split(self) -> (Self, Option<Self>) {
match split(self.chars) {
Some((left, right)) => (
BytesProducer { chars: left },
Some(BytesProducer { chars: right }),
),
None => (self, None),
}
}
fn fold_with<F>(self, folder: F) -> F
where
F: Folder<Self::Item>,
{
folder.consume_iter(self.chars.bytes())
}
}
// /////////////////////////////////////////////////////////////////////////
/// Parallel iterator over a string encoded as UTF-16
#[derive(Debug, Clone)]
pub struct EncodeUtf16<'ch> {
chars: &'ch str,
}
struct EncodeUtf16Producer<'ch> {
chars: &'ch str,
}
impl<'ch> ParallelIterator for EncodeUtf16<'ch> {
type Item = u16;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
bridge_unindexed(EncodeUtf16Producer { chars: self.chars }, consumer)
}
}
impl<'ch> UnindexedProducer for EncodeUtf16Producer<'ch> {
type Item = u16;
fn split(self) -> (Self, Option<Self>) {
match split(self.chars) {
Some((left, right)) => (
EncodeUtf16Producer { chars: left },
Some(EncodeUtf16Producer { chars: right }),
),
None => (self, None),
}
}
fn fold_with<F>(self, folder: F) -> F
where
F: Folder<Self::Item>,
{
folder.consume_iter(self.chars.encode_utf16())
}
}
// /////////////////////////////////////////////////////////////////////////
/// Parallel iterator over substrings separated by a pattern
#[derive(Debug, Clone)]
pub struct Split<'ch, P: Pattern> {
chars: &'ch str,
separator: P,
}
impl<'ch, P: Pattern> Split<'ch, P> {
fn new(chars: &'ch str, separator: P) -> Self {
Split { chars, separator }
}
}
impl<'ch, P: Pattern> ParallelIterator for Split<'ch, P> {
type Item = &'ch str;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
let producer = SplitProducer::new(self.chars, &self.separator);
bridge_unindexed(producer, consumer)
}
}
/// Implement support for `SplitProducer`.
impl<'ch, P: Pattern> Fissile<P> for &'ch str {
fn length(&self) -> usize {
self.len()
}
fn midpoint(&self, end: usize) -> usize {
// First find a suitable UTF-8 boundary.
find_char_midpoint(&self[..end])
}
fn find(&self, separator: &P, start: usize, end: usize) -> Option<usize> {
separator.find_in(&self[start..end])
}
fn rfind(&self, separator: &P, end: usize) -> Option<usize> {
separator.rfind_in(&self[..end])
}
fn split_once(self, index: usize) -> (Self, Self) {
let (left, right) = self.split_at(index);
let mut right_iter = right.chars();
right_iter.next(); // skip the separator
(left, right_iter.as_str())
}
fn fold_splits<F>(self, separator: &P, folder: F, skip_last: bool) -> F
where
F: Folder<Self>,
{
separator.fold_splits(self, folder, skip_last)
}
}
// /////////////////////////////////////////////////////////////////////////
/// Parallel iterator over substrings separated by a terminator pattern
#[derive(Debug, Clone)]
pub struct SplitTerminator<'ch, P: Pattern> {
chars: &'ch str,
terminator: P,
}
struct SplitTerminatorProducer<'ch, 'sep, P: Pattern> {
splitter: SplitProducer<'sep, P, &'ch str>,
skip_last: bool,
}
impl<'ch, P: Pattern> SplitTerminator<'ch, P> {
fn new(chars: &'ch str, terminator: P) -> Self {
SplitTerminator { chars, terminator }
}
}
impl<'ch, 'sep, P: Pattern + 'sep> SplitTerminatorProducer<'ch, 'sep, P> {
fn new(chars: &'ch str, terminator: &'sep P) -> Self {
SplitTerminatorProducer {
splitter: SplitProducer::new(chars, terminator),
skip_last: chars.is_empty() || terminator.is_suffix_of(chars),
}
}
}
impl<'ch, P: Pattern> ParallelIterator for SplitTerminator<'ch, P> {
type Item = &'ch str;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
let producer = SplitTerminatorProducer::new(self.chars, &self.terminator);
bridge_unindexed(producer, consumer)
}
}
impl<'ch, 'sep, P: Pattern + 'sep> UnindexedProducer for SplitTerminatorProducer<'ch, 'sep, P> {
type Item = &'ch str;
fn split(mut self) -> (Self, Option<Self>) {
let (left, right) = self.splitter.split();
self.splitter = left;
let right = right.map(|right| {
let skip_last = self.skip_last;
self.skip_last = false;
SplitTerminatorProducer {
splitter: right,
skip_last,
}
});
(self, right)
}
fn fold_with<F>(self, folder: F) -> F
where
F: Folder<Self::Item>,
{
self.splitter.fold_with(folder, self.skip_last)
}
}
// /////////////////////////////////////////////////////////////////////////
/// Parallel iterator over lines in a string
#[derive(Debug, Clone)]
pub struct Lines<'ch>(&'ch str);
#[inline]
fn no_carriage_return(line: &str) -> &str {
if line.ends_with('\r') {
&line[..line.len() - 1]
} else {
line
}
}
impl<'ch> ParallelIterator for Lines<'ch> {
type Item = &'ch str;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
self.0
.par_split_terminator('\n')
.map(no_carriage_return)
.drive_unindexed(consumer)
}
}
// /////////////////////////////////////////////////////////////////////////
/// Parallel iterator over substrings separated by whitespace
#[derive(Debug, Clone)]
pub struct SplitWhitespace<'ch>(&'ch str);
#[inline]
fn not_empty(s: &&str) -> bool {
!s.is_empty()
}
impl<'ch> ParallelIterator for SplitWhitespace<'ch> {
type Item = &'ch str;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
self.0
.par_split(char::is_whitespace)
.filter(not_empty)
.drive_unindexed(consumer)
}
}
// /////////////////////////////////////////////////////////////////////////
/// Parallel iterator over substrings that match a pattern
#[derive(Debug, Clone)]
pub struct Matches<'ch, P: Pattern> {
chars: &'ch str,
pattern: P,
}
struct MatchesProducer<'ch, 'pat, P: Pattern> {
chars: &'ch str,
pattern: &'pat P,
}
impl<'ch, P: Pattern> ParallelIterator for Matches<'ch, P> {
type Item = &'ch str;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
let producer = MatchesProducer {
chars: self.chars,
pattern: &self.pattern,
};
bridge_unindexed(producer, consumer)
}
}
impl<'ch, 'pat, P: Pattern> UnindexedProducer for MatchesProducer<'ch, 'pat, P> {
type Item = &'ch str;
fn split(self) -> (Self, Option<Self>) {
match split(self.chars) {
Some((left, right)) => (
MatchesProducer {
chars: left,
..self
},
Some(MatchesProducer {
chars: right,
..self
}),
),
None => (self, None),
}
}
fn fold_with<F>(self, folder: F) -> F
where
F: Folder<Self::Item>,
{
self.pattern.fold_matches(self.chars, folder)
}
}
// /////////////////////////////////////////////////////////////////////////
/// Parallel iterator over substrings that match a pattern, with their positions
#[derive(Debug, Clone)]
pub struct MatchIndices<'ch, P: Pattern> {
chars: &'ch str,
pattern: P,
}
struct MatchIndicesProducer<'ch, 'pat, P: Pattern> {
index: usize,
chars: &'ch str,
pattern: &'pat P,
}
impl<'ch, P: Pattern> ParallelIterator for MatchIndices<'ch, P> {
type Item = (usize, &'ch str);
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
let producer = MatchIndicesProducer {
index: 0,
chars: self.chars,
pattern: &self.pattern,
};
bridge_unindexed(producer, consumer)
}
}
impl<'ch, 'pat, P: Pattern> UnindexedProducer for MatchIndicesProducer<'ch, 'pat, P> {
type Item = (usize, &'ch str);
fn split(self) -> (Self, Option<Self>) {
match split(self.chars) {
Some((left, right)) => (
MatchIndicesProducer {
chars: left,
..self
},
Some(MatchIndicesProducer {
chars: right,
index: self.index + left.len(),
..self
}),
),
None => (self, None),
}
}
fn fold_with<F>(self, folder: F) -> F
where
F: Folder<Self::Item>,
{
self.pattern
.fold_match_indices(self.chars, folder, self.index)
}
}