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invert_b128

binius_field::arch::portable::arithmetic::itoh_tsujii

Function invert_b128 

Source 
pub fn invert_b128<P>(x: P) -> P
where
    P: Copy + Square + Mul<Output = P> + Divisible<BinaryField128bGhash>,
Expand description

Invert each GHASH element (scalar or packed) via the Itoh-Tsujii algorithm.

Zero elements map to zero, matching InvertOrZero semantics.

The bound is phrased in terms of the field operations (Square, Mul) plus Divisible<GhashB128> rather than P: PackedField. PackedField’s blanket impl lists InvertOrZero in its where-clause, so requiring it here would form a trait-resolution cycle when this function backs the InvertOrZero impls. Divisible<GhashB128> carries no such obligation, keeps the function statically GHASH-typed, and is satisfied both by the GHASH packed fields and (reflexively) by the scalar BinaryField128bGhash, so the scalar inverts directly without routing through a packed type.