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make memrchr use align_offset #52744

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merged 2 commits into from
Jul 28, 2018
Merged

make memrchr use align_offset #52744

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70cb75c
make memrchr use align_offset
RalfJung Jul 26, 2018
3bc59b5
use slice::align_to
RalfJung Jul 27, 2018
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17 changes: 7 additions & 10 deletions src/libcore/slice/memchr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -102,16 +102,13 @@ pub fn memrchr(x: u8, text: &[u8]) -> Option<usize> {
let ptr = text.as_ptr();
let usize_bytes = mem::size_of::<usize>();

// search to an aligned boundary
let end_align = (ptr as usize + len) & (usize_bytes - 1);
let mut offset;
if end_align > 0 {
offset = if end_align >= len { 0 } else { len - end_align };
if let Some(index) = text[offset..].iter().rposition(|elt| *elt == x) {
return Some(offset + index);
}
} else {
offset = len;
let mut offset = {
// We call this just to obtain the length of the suffix
let (_, _, suffix) = unsafe { text.align_to::<usize>() };
len - suffix.len()
};
if let Some(index) = text[offset..].iter().rposition(|elt| *elt == x) {
return Some(offset + index);
}

// search the body of the text
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