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Modify String::push to reallocate more conservatively in case of the character's UTF-8 representation is bigger than 1 byte

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This commit is contained in:
marcell 2015-06-10 02:03:56 +02:00
parent c5d0e2a073
commit e87c62fb12
1 changed files with 17 additions and 17 deletions
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34
src/libcollections/string.rs
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@ -468,24 +468,24 @@ impl String {
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn push(&mut self, ch: char) {
if (ch as u32) < 0x80 {
self.vec.push(ch as u8);
return;
}
match ch.len_utf8() {
1 => self.vec.push(ch as u8),
ch_len => {
let cur_len = self.len();
// This may use up to 4 bytes.
self.vec.reserve(ch_len);
let cur_len = self.len();
// This may use up to 4 bytes.
self.vec.reserve(4);
unsafe {
// Attempt to not use an intermediate buffer by just pushing bytes
// directly onto this string.
let slice = slice::from_raw_parts_mut (
self.vec.as_mut_ptr().offset(cur_len as isize),
4
);
let used = ch.encode_utf8(slice).unwrap_or(0);
self.vec.set_len(cur_len + used);
unsafe {
// Attempt to not use an intermediate buffer by just pushing bytes
// directly onto this string.
let slice = slice::from_raw_parts_mut (
self.vec.as_mut_ptr().offset(cur_len as isize),
ch_len
);
let used = ch.encode_utf8(slice).unwrap_or(0);
self.vec.set_len(cur_len + used);
}
}
}
}