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 NANOPACKET_H_ 18 #define NANOPACKET_H_ 19 20 #include <cstddef> 21 #include <cstdint> 22 #include <vector> 23 24 #include "noncopyable.h" 25 26 namespace android { 27 28 /* 29 * The various reasons for a NanoPacket to be sent. 30 */ 31 enum class PacketReason : uint32_t { 32 Acknowledge = 0x00000000, 33 NAcknowledge = 0x00000001, 34 NAcknowledgeBusy = 0x00000002, 35 GetHardwareVersion = 0x00001000, 36 ReadEventRequest = 0x00001090, 37 WriteEventRequest = 0x00001091, 38 }; 39 40 /* 41 * A NanoPacket parsing engine. Used to take a stream of bytes and convert them 42 * into an object that can more easily be worked with. 43 */ 44 class NanoPacket : public NonCopyable { 45 public: 46 /* 47 * The result of parsing a buffer into the packet. 48 */ 49 enum class ParseResult { 50 Success, 51 Incomplete, 52 CrcMismatch, 53 }; 54 55 // Formats data into NanoPacket format in the provided buffer. 56 NanoPacket(uint32_t sequence_number, PacketReason reason, 57 const std::vector<uint8_t> *data = nullptr); 58 59 // Creates an empty NanoPacket for data to be parsed into. 60 NanoPacket(); 61 62 // Resets the parsing engine to the idle state and clears parsed content. 63 void Reset(); 64 65 // Parses content from a buffer. Returns true if a packet has been entirely 66 // parsed. 67 ParseResult Parse(uint8_t *buffer, size_t length, size_t *bytes_parsed); 68 69 // Indicated that parsing of the packet has completed. 70 bool ParsingIsComplete() const; 71 72 // The entire content of the message. 73 const std::vector<uint8_t>& packet_buffer() const; 74 75 // Obtains the reason for the packet. 76 uint32_t reason() const; 77 78 // Obtains the reason as a PacketReason. 79 PacketReason TypedReason() const; 80 81 // Obtains the data content of the packet. 82 const std::vector<uint8_t>& packet_content() const; 83 84 private: 85 /* 86 * The current state of the parser. 87 */ 88 enum class ParsingState { 89 Idle, 90 ParsingSequenceNumber, 91 ParsingReason, 92 ParsingLength, 93 ParsingContent, 94 ParsingCrc, 95 Complete, 96 }; 97 98 // Parsing engine state. 99 std::vector<uint8_t> packet_buffer_; 100 ParsingState parsing_state_; 101 uint32_t parsing_progress_; 102 103 // Parsed protocol fields. 104 uint32_t sequence_number_; 105 uint32_t reason_; 106 std::vector<uint8_t> packet_content_; 107 uint32_t crc_; 108 109 // Validates that the received packet has a CRC that matches a generated 110 // CRC. 111 bool ValidateCrc(); 112 113 // Deserializes a little-endian word using the parsing_progress_ member to 114 // maintain state. 115 template<typename T> 116 bool DeserializeWord(T *destination, uint8_t byte); 117 }; 118 119 } // namespace android 120 121 #include "nanopacket_impl.h" 122 123 #endif // NANOPACKET_H_ 124