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docs: std::hash::Hash should ensure prefix-free data #89438

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Oct 10, 2021
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docs: std::hash::Hash should ensure prefix-free data #89438

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docs: `std::hash::Hash` should ensure prefix-free data
pierwill Oct 1, 2021
2a5dcd5
fix: edit description of "prefix-free"
pierwill Oct 1, 2021
749194d
Update library/core/src/hash/mod.rs
pierwill Oct 9, 2021
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12 changes: 12 additions & 0 deletions library/core/src/hash/mod.rs
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Expand Up @@ -153,9 +153,21 @@ mod sip;
/// Thankfully, you won't need to worry about upholding this property when
/// deriving both [`Eq`] and `Hash` with `#[derive(PartialEq, Eq, Hash)]`.
///
/// ## Prefix collisions
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Thinking more about this... "Collision" isn't the right term, here, is it?

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It's not but I can't think of a better word to use.

///
/// Implementations of `hash` should ensure that the data they
/// pass to the `Hasher` are prefix-free. That is,
/// unequal values should cause two different byte sequences to be written,
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/// and neither of the two sequences should be a prefix of the other.
///
/// For example, the standard implementation of [`Hash` for `&str`][impl] passes an extra
/// `0xFF` byte to the `Hasher` so that the values `("ab", "c")` and `("a",
/// "bc")` hash differently.
///
/// [`HashMap`]: ../../std/collections/struct.HashMap.html
/// [`HashSet`]: ../../std/collections/struct.HashSet.html
/// [`hash`]: Hash::hash
/// [impl]: ../../std/primitive.str.html#impl-Hash
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_diagnostic_item = "Hash"]
pub trait Hash {
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