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Use raw pointers for .swap(i, j) #903

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Jan 30, 2021
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Use raw pointers for .swap(i, j) #903

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18 changes: 12 additions & 6 deletions src/impl_methods.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,6 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use std::ptr as std_ptr;
use alloc::slice;
use alloc::vec;
use alloc::vec::Vec;
Expand Down Expand Up @@ -630,11 +629,18 @@ where
S: DataMut,
I: NdIndex<D>,
{
let ptr1: *mut _ = &mut self[index1];
let ptr2: *mut _ = &mut self[index2];
unsafe {
std_ptr::swap(ptr1, ptr2);
let ptr = self.as_mut_ptr();
let offset1 = index1.index_checked(&self.dim, &self.strides);
let offset2 = index2.index_checked(&self.dim, &self.strides);
if let Some(offset1) = offset1 {
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Fwiw, as of Rust 1.46, things like this can be written a little more nicely using Option::zip:

if let Some((offset1, offset2)) = offset1.zip(offset2) {
    unsafe { ... }
} else {
    panic!(...);
}

(or if let Some((offset1, offset2)) = Option::zip(offset1, offset2) if that looks better)

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@bluss bluss Jan 30, 2021 •
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if let (Some(_), Some(_)) = (offset1, offset2) also works IMO. Now which option gives better code :) I wouldn't bother to investigate though.

if let Some(offset2) = offset2 {
unsafe {
std::ptr::swap(ptr.offset(offset1), ptr.offset(offset2));
}
return;
}
}
panic!("swap: index out of bounds for indices {:?} {:?}", index1, index2);
}

/// Swap elements *unchecked* at indices `index1` and `index2`.
Expand All @@ -661,7 +667,7 @@ where
arraytraits::debug_bounds_check(self, &index2);
let off1 = index1.index_unchecked(&self.strides);
let off2 = index2.index_unchecked(&self.strides);
std_ptr::swap(
std::ptr::swap(
self.ptr.as_ptr().offset(off1),
self.ptr.as_ptr().offset(off2),
);
Expand Down