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use slice::align_to

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This commit is contained in:
Ralf Jung 2018-07-27 11:54:38 +02:00
parent 70cb75c31e
commit 3bc59b5205
1 changed files with 7 additions and 26 deletions
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33
src/libcore/slice/memchr.rs
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@ -102,32 +102,13 @@ pub fn memrchr(x: u8, text: &[u8]) -> Option<usize> {
let ptr = text.as_ptr();
let usize_bytes = mem::size_of::<usize>();
// a version of align_offset that says how much must be *subtracted*
// from a pointer to be aligned.
#[inline(always)]
fn align_offset_down(ptr: *const u8, align: usize) -> usize {
let align_offset = ptr.align_offset(align);
if align_offset > align {
// Not possible to align
usize::max_value()
} else if align_offset == 0 {
0
} else {
// E.g. if align=8 and we have to add 1, then we can also subtract 7.
align - align_offset
}
}
// search to an aligned boundary
let end_align = align_offset_down(unsafe { ptr.offset(len as isize) }, usize_bytes);
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