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Make Scalar::from_bits a const fn.

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const_fn is stable since Rust 1.31
(https://github.com/rust-lang/rust/pull/54835) and enables calling
`Scalar::from_bits(..)` from other const fn contexts, potentially
saving some overhead here and there.

Especially useful in contexts where constants are being built from a bit
pattern.
This commit is contained in:
Ruben De Smet 2020-05-28 10:28:28 +02:00
parent 805cdbfd3c
commit 3a61a0b70c
1 changed files with 1 additions and 1 deletions
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2
src/scalar.rs
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@ -243,7 +243,7 @@ impl Scalar {
/// This function is intended for applications like X25519 which /// This function is intended for applications like X25519 which
/// require specific bit-patterns when performing scalar /// require specific bit-patterns when performing scalar
/// multiplication. /// multiplication.
pub fn from_bits(bytes: [u8; 32]) -> Scalar { pub const fn from_bits(bytes: [u8; 32]) -> Scalar {
let mut s = Scalar{bytes}; let mut s = Scalar{bytes};
// Ensure that s < 2^255 by masking the high bit // Ensure that s < 2^255 by masking the high bit
s.bytes[31] &= 0b0111_1111; s.bytes[31] &= 0b0111_1111;