1 /* 2 * Copyright (C) 2016 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 #ifndef BYTE_BUFFER_H_ 18 #define BYTE_BUFFER_H_ 19 20 #include <array> 21 #include <cstring> 22 23 #include "android-base/logging.h" 24 25 #include "wifilogd/local_utils.h" 26 27 namespace android { 28 namespace wifilogd { 29 30 // A fixed-size buffer, which provides the ability to accumulate bytes. 31 // The buffer tracks its (populated) size, and does not require dynamic 32 // memory allocation. 33 // 34 // Usage could be as follows: 35 // const auto buffer = ByteBuffer<1024>() 36 // .AppendOrDie(header.data(), header.size()) 37 // .AppendOrDie(body.data(), body.size()); 38 // write(fd, buffer.data(), buffer.size()); 39 template <size_t SizeBytes> 40 class ByteBuffer { 41 public: ByteBuffer()42 ByteBuffer() : write_pos_(0) {} 43 44 // Appends data to the end of this buffer. Aborts if the available 45 // space in the buffer is less than |data_len|. Returns a reference to 46 // the ByteBuffer, to support chaining. AppendOrDie(NONNULL const void * data,size_t data_len)47 ByteBuffer<SizeBytes>& AppendOrDie(NONNULL const void* data, 48 size_t data_len) { 49 CHECK(data_len <= raw_buffer_.size() - write_pos_); 50 std::memcpy(raw_buffer_.data() + write_pos_, data, data_len); 51 write_pos_ += data_len; 52 return *this; 53 } 54 55 // Returns a pointer to the head of this buffer. data()56 RETURNS_NONNULL const uint8_t* data() const { return raw_buffer_.data(); } 57 58 // Returns the number of bytes written to this buffer. size()59 size_t size() const { return write_pos_; } 60 61 private: 62 std::array<uint8_t, SizeBytes> raw_buffer_; 63 size_t write_pos_; 64 }; 65 66 } // namespace wifilogd 67 } // namespace android 68 #endif // BYTE_BUFFER_H_ 69