mukesh agrawal | 5a4f6db | 2016-10-13 16:06:50 -0700 | [diff] [blame] | 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 MEMORY_READER_H_ |
| 18 | #define MEMORY_READER_H_ |
| 19 | |
| 20 | #include <cstdint> |
| 21 | #include <tuple> |
| 22 | |
| 23 | #include "wifilogd/local_utils.h" |
| 24 | |
| 25 | namespace android { |
| 26 | namespace wifilogd { |
| 27 | |
| 28 | // A non-owning adapter, which helps with reading protocol messages out |
| 29 | // of a buffer. This is, essentially, the inverse of ByteBuffer. |
| 30 | // |
| 31 | // The user is responsible for ensuring that a MemoryReader does not |
| 32 | // outlive the underlying buffer. |
| 33 | class MemoryReader { |
| 34 | public: |
| 35 | MemoryReader(const void* buf, size_t buflen) |
| 36 | : head_(static_cast<const uint8_t*>(buf)), n_bytes_avail_(buflen) {} |
| 37 | |
| 38 | explicit MemoryReader(std::tuple<const uint8_t*, size_t> buf) |
| 39 | : head_(std::get<0>(buf)), n_bytes_avail_(std::get<1>(buf)) {} |
| 40 | |
| 41 | // Copies a |T| out of our referenced memory, aborting if sizeof(T) exceeds |
| 42 | // the number of bytes available. On success, updates the read position, and |
| 43 | // the number of bytes available. |
| 44 | template <typename T> |
| 45 | T CopyOutOrDie() { |
| 46 | CHECK(head_); |
| 47 | const T out{local_utils::CopyFromBufferOrDie<T>(head_, n_bytes_avail_)}; |
| 48 | head_ += sizeof(T); |
| 49 | n_bytes_avail_ -= sizeof(T); |
| 50 | return out; |
| 51 | } |
| 52 | |
| 53 | // Returns a pointer to the next bytes available for reading. Aborts if |
| 54 | // the number of available bytes is less than |n_bytes|. On success, updates |
| 55 | // the read position, and the number of bytes available. |
| 56 | RETURNS_NONNULL const uint8_t* GetBytesOrDie(size_t n_bytes); |
| 57 | |
| 58 | // Returns true if the referenced memory is non-NULL, and has at least |
| 59 | // one byte available for reading. |
| 60 | explicit operator bool() const { return head_ && n_bytes_avail_; } |
| 61 | |
| 62 | // Returns the number of bytes available for reading. |
| 63 | size_t size() const { return (head_ ? n_bytes_avail_ : 0); } |
| 64 | |
| 65 | private: |
| 66 | const uint8_t* head_; // non-owned |
| 67 | size_t n_bytes_avail_; |
| 68 | }; |
| 69 | |
| 70 | } // namespace wifilogd |
| 71 | } // namespace android |
| 72 | |
| 73 | #endif // MEMORY_READER_H_ |