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Optimized string FromIterator + Extend impls #56548

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merged 3 commits into from
Dec 6, 2018
Merged

Optimized string FromIterator + Extend impls #56548

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180dcc3
Optimized string FromIterator impls
Lucretiel Dec 5, 2018
823dd8c
Fixed mutability
Lucretiel Dec 5, 2018
811a2bf
Added explainatory comments
Lucretiel Dec 6, 2018
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41 changes: 23 additions & 18 deletions src/liballoc/string.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1732,18 +1732,31 @@ impl<'a> FromIterator<&'a str> for String {
#[stable(feature = "extend_string", since = "1.4.0")]
impl FromIterator<String> for String {
fn from_iter<I: IntoIterator<Item = String>>(iter: I) -> String {
let mut buf = String::new();
buf.extend(iter);
buf
let mut iterator = iter.into_iter();
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match iterator.next() {
None => String::new(),
Some(mut buf) => {
buf.extend(iterator);
buf
}
}
}
}

#[stable(feature = "herd_cows", since = "1.19.0")]
impl<'a> FromIterator<Cow<'a, str>> for String {
fn from_iter<I: IntoIterator<Item = Cow<'a, str>>>(iter: I) -> String {
let mut buf = String::new();
buf.extend(iter);
buf
let mut iterator = iter.into_iter();

match iterator.next() {
None => String::new(),
Some(cow) => {
let mut buf = cow.into_owned();
buf.extend(iterator);
buf
}
}
}
}

Expand All @@ -1753,9 +1766,7 @@ impl Extend<char> for String {
let iterator = iter.into_iter();
let (lower_bound, _) = iterator.size_hint();
self.reserve(lower_bound);
for ch in iterator {
self.push(ch)
}
iterator.for_each(move |c| self.push(c));
}
}

Expand All @@ -1769,27 +1780,21 @@ impl<'a> Extend<&'a char> for String {
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a> Extend<&'a str> for String {
fn extend<I: IntoIterator<Item = &'a str>>(&mut self, iter: I) {
for s in iter {
self.push_str(s)
}
iter.into_iter().for_each(move |s| self.push_str(s));
}
}

#[stable(feature = "extend_string", since = "1.4.0")]
impl Extend<String> for String {
fn extend<I: IntoIterator<Item = String>>(&mut self, iter: I) {
for s in iter {
self.push_str(&s)
}
iter.into_iter().for_each(move |s| self.push_str(&s));
}
}

#[stable(feature = "herd_cows", since = "1.19.0")]
impl<'a> Extend<Cow<'a, str>> for String {
fn extend<I: IntoIterator<Item = Cow<'a, str>>>(&mut self, iter: I) {
for s in iter {
self.push_str(&s)
}
iter.into_iter().for_each(move |s| self.push_str(&s));
}
}

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