Zig 0.17.0-dev (Split by item)

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neg

Return -s (mod L)

scalar.neg

pub fn neg(s: CompressedScalar) CompressedScalar

File

lib/std/crypto/25519/scalar.zig:83

Code

pub fn neg(s: CompressedScalar) CompressedScalar {
    const fs: [64]u8 = field_order_s ++ @as([32]u8, @splat(0));
    var sx: [64]u8 = undefined;
    sx[0..32].* = s;
    @memset(sx[32..], 0);
    var carry: u32 = 0;
    var i: usize = 0;
    while (i < 64) : (i += 1) {
        carry = @as(u32, fs[i]) -% sx[i] -% @as(u32, carry);
        sx[i] = @as(u8, @truncate(carry));
        carry = (carry >> 8) & 1;
    }
    return reduce64(sx);
}