1 /* 2 * Copyright (C) 2020 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include <stddef.h> 18 #include <sys/uio.h> 19 #include <cstdint> 20 #include <optional> 21 22 #include <log/log.h> 23 #include <utils/Errors.h> 24 25 #define TEST_AND_RETURN(value, expr) \ 26 do { \ 27 if (!(expr)) { \ 28 ALOGE("Failed to call: %s", #expr); \ 29 return value; \ 30 } \ 31 } while (0) 32 33 namespace android { 34 35 // avoid optimizations 36 void zeroMemory(uint8_t* data, size_t size); 37 38 // View of contiguous sequence. Similar to std::span. 39 template <typename T> 40 struct Span { 41 T* data = nullptr; 42 size_t size = 0; 43 byteSizeSpan44 size_t byteSize() { return size * sizeof(T); } 45 toIovecSpan46 iovec toIovec() { return {const_cast<std::remove_const_t<T>*>(data), byteSize()}; } 47 48 // Truncates `this` to a length of `offset` and returns a span with the 49 // remainder. 50 // 51 // `std::nullopt` iff offset > size. splitOffSpan52 std::optional<Span<T>> splitOff(size_t offset) { 53 if (offset > size) { 54 return std::nullopt; 55 } 56 Span<T> rest = {data + offset, size - offset}; 57 size = offset; 58 return rest; 59 } 60 61 // Returns nullopt if the byte size of `this` isn't evenly divisible by sizeof(U). 62 template <typename U> reinterpretSpan63 std::optional<Span<U>> reinterpret() const { 64 // Only allow casting from bytes for simplicity. 65 static_assert(std::is_same_v<std::remove_const_t<T>, uint8_t>); 66 if (size % sizeof(U) != 0) { 67 return std::nullopt; 68 } 69 return Span<U>{reinterpret_cast<U*>(data), size / sizeof(U)}; 70 } 71 }; 72 73 } // namespace android 74