libcxx/test/std/time/time.cal/euclidian.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9
  10 //  Assumption: minValue < maxValue
  11 //  Assumption: minValue <= rhs <= maxValue
  12 //  Assumption: minValue <= lhs <= maxValue
  13 //  Assumption: minValue >= 0
  14 template <typename T, T minValue, T maxValue>
  15 constexpr T euclidian_addition(T rhs, T lhs) {
  16   const T modulus = maxValue - minValue + 1;
  17   T ret           = rhs + lhs;
  18   if (ret > maxValue)
  19     ret -= modulus;
  20   return ret;
  21 }
  22
  23 //  Assumption: minValue < maxValue
  24 //  Assumption: minValue <= rhs <= maxValue
  25 //  Assumption: minValue <= lhs <= maxValue
  26 //  Assumption: minValue >= 0
  27 template <typename T, T minValue, T maxValue>
  28 constexpr T euclidian_subtraction(T lhs, T rhs) {
  29   const T modulus = maxValue - minValue + 1;
  30   T ret           = lhs - rhs;
  31   if (ret < minValue)
  32     ret += modulus;
  33   if (ret > maxValue) // this can happen if T is unsigned
  34     ret += modulus;
  35   return ret;
  36 }