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Move Zip and ZipImpl to own module
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@clarfonthey
clarfonthey committed Jan 22, 2019
1 parent 9228f3c commit 3c44e1f
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Showing 2 changed files with 266 additions and 258 deletions.
263 changes: 5 additions & 258 deletions src/libcore/iter/adapters/mod.rs
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Expand Up @@ -7,6 +7,11 @@ use intrinsics;
use super::{Iterator, DoubleEndedIterator, ExactSizeIterator, FusedIterator, TrustedLen};
use super::LoopState;

mod zip;

pub use self::zip::Zip;
pub(super) use self::zip::ZipImpl;

/// A double-ended iterator with the direction inverted.
///
/// This `struct` is created by the [`rev`] method on [`Iterator`]. See its
Expand Down Expand Up @@ -703,264 +708,6 @@ unsafe impl<A, B> TrustedLen for Chain<A, B>
where A: TrustedLen, B: TrustedLen<Item=A::Item>,
{}

/// An iterator that iterates two other iterators simultaneously.
///
/// This `struct` is created by the [`zip`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`zip`]: trait.Iterator.html#method.zip
/// [`Iterator`]: trait.Iterator.html
#[derive(Clone, Debug)]
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Zip<A, B> {
a: A,
b: B,
// index and len are only used by the specialized version of zip
index: usize,
len: usize,
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<A, B> Iterator for Zip<A, B> where A: Iterator, B: Iterator
{
type Item = (A::Item, B::Item);

#[inline]
fn next(&mut self) -> Option<Self::Item> {
ZipImpl::next(self)
}

#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
ZipImpl::size_hint(self)
}

#[inline]
fn nth(&mut self, n: usize) -> Option<Self::Item> {
ZipImpl::nth(self, n)
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<A, B> DoubleEndedIterator for Zip<A, B> where
A: DoubleEndedIterator + ExactSizeIterator,
B: DoubleEndedIterator + ExactSizeIterator,
{
#[inline]
fn next_back(&mut self) -> Option<(A::Item, B::Item)> {
ZipImpl::next_back(self)
}
}

// Zip specialization trait
#[doc(hidden)]
pub(super) trait ZipImpl<A, B> {
type Item;
fn new(a: A, b: B) -> Self;
fn next(&mut self) -> Option<Self::Item>;
fn size_hint(&self) -> (usize, Option<usize>);
fn nth(&mut self, n: usize) -> Option<Self::Item>;
fn super_nth(&mut self, mut n: usize) -> Option<Self::Item> {
while let Some(x) = self.next() {
if n == 0 { return Some(x) }
n -= 1;
}
None
}
fn next_back(&mut self) -> Option<Self::Item>
where A: DoubleEndedIterator + ExactSizeIterator,
B: DoubleEndedIterator + ExactSizeIterator;
}

// General Zip impl
#[doc(hidden)]
impl<A, B> ZipImpl<A, B> for Zip<A, B>
where A: Iterator, B: Iterator
{
type Item = (A::Item, B::Item);
default fn new(a: A, b: B) -> Self {
Zip {
a,
b,
index: 0, // unused
len: 0, // unused
}
}

#[inline]
default fn next(&mut self) -> Option<(A::Item, B::Item)> {
self.a.next().and_then(|x| {
self.b.next().and_then(|y| {
Some((x, y))
})
})
}

#[inline]
default fn nth(&mut self, n: usize) -> Option<Self::Item> {
self.super_nth(n)
}

#[inline]
default fn next_back(&mut self) -> Option<(A::Item, B::Item)>
where A: DoubleEndedIterator + ExactSizeIterator,
B: DoubleEndedIterator + ExactSizeIterator
{
let a_sz = self.a.len();
let b_sz = self.b.len();
if a_sz != b_sz {
// Adjust a, b to equal length
if a_sz > b_sz {
for _ in 0..a_sz - b_sz { self.a.next_back(); }
} else {
for _ in 0..b_sz - a_sz { self.b.next_back(); }
}
}
match (self.a.next_back(), self.b.next_back()) {
(Some(x), Some(y)) => Some((x, y)),
(None, None) => None,
_ => unreachable!(),
}
}

#[inline]
default fn size_hint(&self) -> (usize, Option<usize>) {
let (a_lower, a_upper) = self.a.size_hint();
let (b_lower, b_upper) = self.b.size_hint();

let lower = cmp::min(a_lower, b_lower);

let upper = match (a_upper, b_upper) {
(Some(x), Some(y)) => Some(cmp::min(x,y)),
(Some(x), None) => Some(x),
(None, Some(y)) => Some(y),
(None, None) => None
};

(lower, upper)
}
}

#[doc(hidden)]
impl<A, B> ZipImpl<A, B> for Zip<A, B>
where A: TrustedRandomAccess, B: TrustedRandomAccess
{
fn new(a: A, b: B) -> Self {
let len = cmp::min(a.len(), b.len());
Zip {
a,
b,
index: 0,
len,
}
}

#[inline]
fn next(&mut self) -> Option<(A::Item, B::Item)> {
if self.index < self.len {
let i = self.index;
self.index += 1;
unsafe {
Some((self.a.get_unchecked(i), self.b.get_unchecked(i)))
}
} else if A::may_have_side_effect() && self.index < self.a.len() {
// match the base implementation's potential side effects
unsafe {
self.a.get_unchecked(self.index);
}
self.index += 1;
None
} else {
None
}
}

#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let len = self.len - self.index;
(len, Some(len))
}

#[inline]
fn nth(&mut self, n: usize) -> Option<Self::Item> {
let delta = cmp::min(n, self.len - self.index);
let end = self.index + delta;
while self.index < end {
let i = self.index;
self.index += 1;
if A::may_have_side_effect() {
unsafe { self.a.get_unchecked(i); }
}
if B::may_have_side_effect() {
unsafe { self.b.get_unchecked(i); }
}
}

self.super_nth(n - delta)
}

#[inline]
fn next_back(&mut self) -> Option<(A::Item, B::Item)>
where A: DoubleEndedIterator + ExactSizeIterator,
B: DoubleEndedIterator + ExactSizeIterator
{
// Adjust a, b to equal length
if A::may_have_side_effect() {
let sz = self.a.len();
if sz > self.len {
for _ in 0..sz - cmp::max(self.len, self.index) {
self.a.next_back();
}
}
}
if B::may_have_side_effect() {
let sz = self.b.len();
if sz > self.len {
for _ in 0..sz - self.len {
self.b.next_back();
}
}
}
if self.index < self.len {
self.len -= 1;
let i = self.len;
unsafe {
Some((self.a.get_unchecked(i), self.b.get_unchecked(i)))
}
} else {
None
}
}
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<A, B> ExactSizeIterator for Zip<A, B>
where A: ExactSizeIterator, B: ExactSizeIterator {}

#[doc(hidden)]
unsafe impl<A, B> TrustedRandomAccess for Zip<A, B>
where A: TrustedRandomAccess,
B: TrustedRandomAccess,
{
unsafe fn get_unchecked(&mut self, i: usize) -> (A::Item, B::Item) {
(self.a.get_unchecked(i), self.b.get_unchecked(i))
}

fn may_have_side_effect() -> bool {
A::may_have_side_effect() || B::may_have_side_effect()
}
}

#[stable(feature = "fused", since = "1.26.0")]
impl<A, B> FusedIterator for Zip<A, B>
where A: FusedIterator, B: FusedIterator, {}

#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<A, B> TrustedLen for Zip<A, B>
where A: TrustedLen, B: TrustedLen,
{}

/// An iterator that maps the values of `iter` with `f`.
///
/// This `struct` is created by the [`map`] method on [`Iterator`]. See its
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