123 lines
3.0 KiB
Dart
123 lines
3.0 KiB
Dart
import 'dart:typed_data';
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class BlePacket {
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final int command;
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final Uint8List payload;
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const BlePacket({required this.command, required this.payload});
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}
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/// 有状态的 BLE 协议解析器
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/// 支持分片接收：多次调用 [append] 累积数据，[parse] 提取完整帧
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class ProtocolParser {
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static const int _header1 = 0xAB;
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static const int _header2 = 0xAA;
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static const int _tail1 = 0xAA;
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static const int _tail2 = 0xAB;
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final List<int> _buffer = [];
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/// 清空缓冲区
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void clear() {
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_buffer.clear();
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}
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/// 获取缓冲区长度
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int get bufferLength => _buffer.length;
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/// 打包命令为字节帧（用于发送）
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/// CRC16 覆盖 command + payload 确保整帧完整性
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static Uint8List pack(int command, List<int> payload) {
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final dataToCheck = [command, ...payload];
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final crc = _crc16(dataToCheck);
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final builder = BytesBuilder()
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..addByte(_header1)
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..addByte(_header2)
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..addByte(command)
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..add(payload)
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..addByte(crc & 0xFF)
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..addByte((crc >> 8) & 0xFF)
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..addByte(_tail1)
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..addByte(_tail2);
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return builder.takeBytes();
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}
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/// 追加新接收的数据到缓冲区
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void append(List<int> data) {
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_buffer.addAll(data);
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}
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/// 从缓冲区解析所有完整的数据包
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/// 未完成的帧保留在缓冲区等待后续数据
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List<BlePacket> parse() {
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final List<BlePacket> packets = [];
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while (_buffer.length >= 6) {
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// 1. 查找帧头
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int headIdx = -1;
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for (int i = 0; i < _buffer.length - 1; i++) {
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if (_buffer[i] == _header1 && _buffer[i + 1] == _header2) {
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headIdx = i;
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break;
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}
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}
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if (headIdx == -1) {
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// 无有效帧头，清空缓冲区
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_buffer.clear();
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break;
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}
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// 移除帧头前的垃圾数据
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if (headIdx > 0) _buffer.removeRange(0, headIdx);
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// 2. 查找帧尾
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int tailIdx = -1;
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for (int i = 2; i < _buffer.length - 1; i++) {
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if (_buffer[i] == _tail1 && _buffer[i + 1] == _tail2) {
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tailIdx = i;
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break;
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}
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}
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if (tailIdx == -1) {
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// 帧尾未找到，可能是分片数据，等待更多数据
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break;
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}
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// 3. 提取数据包
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if (_buffer.length >= 5) {
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final cmd = _buffer[2];
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final payload = Uint8List.fromList(_buffer.sublist(3, tailIdx));
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packets.add(BlePacket(command: cmd, payload: payload));
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}
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// 4. 移除已处理的帧
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_buffer.removeRange(0, tailIdx + 2);
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}
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return packets;
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}
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/// 便捷方法：追加数据并立即解析
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List<BlePacket> appendAndParse(List<int> data) {
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append(data);
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return parse();
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}
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/// CRC16-Modbus: polynomial=0x8005, init=0xFFFF, refIn/refOut=true
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static int _crc16(List<int> data) {
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int crc = 0xFFFF;
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for (final b in data) {
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crc ^= b;
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for (int j = 0; j < 8; j++) {
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if ((crc & 0x0001) != 0) {
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crc = (crc >> 1) ^ 0xA001;
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} else {
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crc >>= 1;
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}
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}
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}
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return crc;
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}
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}
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