1 // Copyright 2021 The Dawn Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef DAWNWIRE_BUFFERCONSUMER_H_ 16 #define DAWNWIRE_BUFFERCONSUMER_H_ 17 18 #include "dawn_wire/WireResult.h" 19 20 #include <cstddef> 21 22 namespace dawn_wire { 23 24 // BufferConsumer is a utility class that allows reading bytes from a buffer 25 // while simultaneously decrementing the amount of remaining space by exactly 26 // the amount read. It helps prevent bugs where incrementing a pointer and 27 // decrementing a size value are not kept in sync. 28 // BufferConsumer also contains bounds checks to prevent reading out-of-bounds. 29 template <typename BufferT> 30 class BufferConsumer { 31 static_assert(sizeof(BufferT) == 1, 32 "BufferT must be 1-byte, but may have const/volatile qualifiers."); 33 34 public: BufferConsumer(BufferT * buffer,size_t size)35 BufferConsumer(BufferT* buffer, size_t size) : mBuffer(buffer), mSize(size) { 36 } 37 Buffer()38 BufferT* Buffer() const { 39 return mBuffer; 40 } AvailableSize()41 size_t AvailableSize() const { 42 return mSize; 43 } 44 45 protected: 46 template <typename T, typename N> 47 WireResult NextN(N count, T** data); 48 49 template <typename T> 50 WireResult Next(T** data); 51 52 template <typename T> 53 WireResult Peek(T** data); 54 55 private: 56 BufferT* mBuffer; 57 size_t mSize; 58 }; 59 60 class SerializeBuffer : public BufferConsumer<char> { 61 public: 62 using BufferConsumer::BufferConsumer; 63 using BufferConsumer::Next; 64 using BufferConsumer::NextN; 65 }; 66 67 class DeserializeBuffer : public BufferConsumer<const volatile char> { 68 public: 69 using BufferConsumer::BufferConsumer; 70 using BufferConsumer::Peek; 71 72 template <typename T, typename N> ReadN(N count,const volatile T ** data)73 WireResult ReadN(N count, const volatile T** data) { 74 return NextN(count, data); 75 } 76 77 template <typename T> Read(const volatile T ** data)78 WireResult Read(const volatile T** data) { 79 return Next(data); 80 } 81 }; 82 83 } // namespace dawn_wire 84 85 #endif // DAWNWIRE_BUFFERCONSUMER_H_