| /* |
| * Copyright (C) 2019 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| namespace android::audio_utils { |
| |
| // safe_sub_overflow is used ensure that subtraction occurs in the same native |
| // type with proper 2's complement overflow. Without calling this function, it |
| // is possible, for example, that optimizing compilers may elect to treat 32 bit |
| // subtraction as 64 bit subtraction when storing into a 64 bit destination as |
| // integer overflow is technically undefined. |
| template <typename T, typename U, |
| typename = std::enable_if_t< |
| std::is_same<std::decay_t<T>, std::decay_t<U>>{}>> |
| // ensure arguments are same type (ignoring volatile, which is used in cblk |
| // variables). |
| auto safe_sub_overflow(const T& a, const U& b) { |
| std::decay_t<T> result; |
| (void)__builtin_sub_overflow(a, b, &result); |
| // note if __builtin_sub_overflow returns true, an overflow occurred. |
| return result; |
| } |
| |
| // similar to safe_sub_overflow but for add operator. |
| template <typename T, typename U, |
| typename = std::enable_if_t< |
| std::is_same<std::decay_t<T>, std::decay_t<U>>{}>> |
| // ensure arguments are same type (ignoring volatile, which is used in cblk |
| // variables). |
| auto safe_add_overflow(const T& a, const U& b) { |
| std::decay_t<T> result; |
| (void)__builtin_add_overflow(a, b, &result); |
| // note if __builtin_add_overflow returns true, an overflow occurred. |
| return result; |
| } |
| |
| } // namespace android::audio_utils |