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