p256 0.12.0

Pure Rust implementation of the NIST P-256 (a.k.a. secp256r1, prime256v1) elliptic curve with support for ECDH, ECDSA signing/verification, and general purpose curve arithmetic
Documentation 
//! Helper functions.
// TODO(tarcieri): replace these with `crypto-bigint`

/// Computes `a + b + carry`, returning the result along with the new carry. 64-bit version.
#[inline(always)]
pub const fn adc(a: u64, b: u64, carry: u64) -> (u64, u64) {
    let ret = (a as u128) + (b as u128) + (carry as u128);
    (ret as u64, (ret >> 64) as u64)
}

/// Computes `a - (b + borrow)`, returning the result along with the new borrow. 64-bit version.
#[inline(always)]
pub const fn sbb(a: u64, b: u64, borrow: u64) -> (u64, u64) {
    let ret = (a as u128).wrapping_sub((b as u128) + ((borrow >> 63) as u128));
    (ret as u64, (ret >> 64) as u64)
}

/// Computes `a + (b * c) + carry`, returning the result along with the new carry.
#[inline(always)]
pub const fn mac(a: u64, b: u64, c: u64, carry: u64) -> (u64, u64) {
    let ret = (a as u128) + ((b as u128) * (c as u128)) + (carry as u128);
    (ret as u64, (ret >> 64) as u64)
}