Function addScalar [src]

r = a + scalar r and a may be aliases. scalar is a primitive integer type. Asserts the result fits in r. An upper bound on the number of limbs needed by r is @max(a.limbs.len, calcLimbLen(scalar)) + 1.

Prototype

pub fn addScalar(r: *Mutable, a: Const, scalar: anytype) void

Parameters

r: *Mutablea: Const

Source

  pub fn addScalar(r: *Mutable, a: Const, scalar: anytype) void {
    // Normally we could just determine the number of limbs needed with calcLimbLen,
    // but that is not comptime-known when scalar is not a comptime_int.  Instead, we
    // use calcTwosCompLimbCount for a non-comptime_int scalar, which can be pessimistic
    // in the case that scalar happens to be small in magnitude within its type, but it
    // is well worth being able to use the stack and not needing an allocator passed in.
    // Note that Mutable.init still sets len to calcLimbLen(scalar) in any case.
    const limb_len = comptime switch (@typeInfo(@TypeOf(scalar))) {
        .comptime_int => calcLimbLen(scalar),
        .int => |info| calcTwosCompLimbCount(info.bits),
        else => @compileError("expected scalar to be an int"),
    };
    var limbs: [limb_len]Limb = undefined;
    const operand = init(&limbs, scalar).toConst();
    return add(r, a, operand);
}  