Function add [src]

Return x+y (mod L)
Prototype

pub fn add(x: Scalar, y: Scalar) Scalar
Parameters

x: Scalary: Scalar
Source

  pub fn add(x: Scalar, y: Scalar) Scalar {
    const carry0 = (x.limbs[0] + y.limbs[0]) >> 56;
    const t0 = (x.limbs[0] + y.limbs[0]) & 0xffffffffffffff;
    const t00 = t0;
    const c0 = carry0;
    const carry1 = (x.limbs[1] + y.limbs[1] + c0) >> 56;
    const t1 = (x.limbs[1] + y.limbs[1] + c0) & 0xffffffffffffff;
    const t10 = t1;
    const c1 = carry1;
    const carry2 = (x.limbs[2] + y.limbs[2] + c1) >> 56;
    const t2 = (x.limbs[2] + y.limbs[2] + c1) & 0xffffffffffffff;
    const t20 = t2;
    const c2 = carry2;
    const carry = (x.limbs[3] + y.limbs[3] + c2) >> 56;
    const t3 = (x.limbs[3] + y.limbs[3] + c2) & 0xffffffffffffff;
    const t30 = t3;
    const c3 = carry;
    const t4 = x.limbs[4] + y.limbs[4] + c3;

    const y01: u64 = 5175514460705773;
    const y11: u64 = 70332060721272408;
    const y21: u64 = 5342;
    const y31: u64 = 0;
    const y41: u64 = 268435456;

    const b5 = (t00 -% y01) >> 63;
    const t5 = ((b5 << 56) + t00) -% y01;
    const b0 = b5;
    const t01 = t5;
    const b6 = (t10 -% (y11 + b0)) >> 63;
    const t6 = ((b6 << 56) + t10) -% (y11 + b0);
    const b1 = b6;
    const t11 = t6;
    const b7 = (t20 -% (y21 + b1)) >> 63;
    const t7 = ((b7 << 56) + t20) -% (y21 + b1);
    const b2 = b7;
    const t21 = t7;
    const b8 = (t30 -% (y31 + b2)) >> 63;
    const t8 = ((b8 << 56) + t30) -% (y31 + b2);
    const b3 = b8;
    const t31 = t8;
    const b = (t4 -% (y41 + b3)) >> 63;
    const t = ((b << 56) + t4) -% (y41 + b3);
    const b4 = b;
    const t41 = t;

    const mask = (b4 -% 1);
    const z00 = t00 ^ (mask & (t00 ^ t01));
    const z10 = t10 ^ (mask & (t10 ^ t11));
    const z20 = t20 ^ (mask & (t20 ^ t21));
    const z30 = t30 ^ (mask & (t30 ^ t31));
    const z40 = t4 ^ (mask & (t4 ^ t41));

    return Scalar{ .limbs = .{ z00, z10, z20, z30, z40 } };
}  