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Avoid using derive on non-Copy packed type #2834

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Nov 18, 2022
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Avoid using derive on non-Copy packed type #2834

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8 changes: 7 additions & 1 deletion utils/zerovec/src/flexzerovec/slice.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,6 @@ const USIZE_WIDTH: usize = mem::size_of::<usize>();

/// A zero-copy "slice" that efficiently represents `[usize]`.
#[repr(packed)]
#[derive(Eq, PartialEq)]
pub struct FlexZeroSlice {
// Hard Invariant: 1 <= width <= USIZE_WIDTH (which is target_pointer_width)
// Soft Invariant: width == the width of the largest element
Expand All @@ -23,6 +22,13 @@ pub struct FlexZeroSlice {
data: [u8],
}

impl PartialEq for FlexZeroSlice {
fn eq(&self, other: &Self) -> bool {
self.width == other.width && self.data == other.data
}
}
impl Eq for FlexZeroSlice {}
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Nit (optional): I usually like a comment explaining why Eq is safe to implement... but I guess it's fairly obvious here


/// Helper function to decode a little-endian "chunk" (byte slice of a specific length)
/// into a `usize`. We cannot call `usize::from_le_bytes` directly because that function
/// requires the high bits to be set to 0.
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