abawo-bt-app/lib/service/dfu_protocol.dart

import 'dart:typed_data';

import 'package:abawo_bt_app/model/shifter_types.dart';

const int _startPayloadLength = 19;

class BootloaderDfuStartPayload {
  const BootloaderDfuStartPayload({
    required this.totalLength,
    required this.imageCrc32,
    this.appStart = universalShifterDfuAppStart,
    this.imageVersion = 0,
    required this.sessionId,
    required this.flags,
  });

  final int totalLength;
  final int imageCrc32;
  final int appStart;
  final int imageVersion;
  final int sessionId;
  final int flags;
}

class BootloaderDfuDataFrame {
  const BootloaderDfuDataFrame({
    required this.sessionId,
    required this.offset,
    required this.payloadLength,
    required this.bytes,
  });

  final int sessionId;
  final int offset;
  final int payloadLength;
  final Uint8List bytes;
}

class BootloaderDfuProtocol {
  const BootloaderDfuProtocol._();

  static const int crc32Initial = 0xFFFFFFFF;
  static const int _crc32PolynomialReflected = 0xEDB88320;

  static Uint8List encodeStartPayload(BootloaderDfuStartPayload payload) {
    final data = ByteData(_startPayloadLength);
    data.setUint8(0, universalShifterDfuOpcodeStart);
    data.setUint32(1, payload.totalLength, Endian.little);
    data.setUint32(5, payload.imageCrc32, Endian.little);
    data.setUint32(9, payload.appStart, Endian.little);
    data.setUint32(13, payload.imageVersion, Endian.little);
    data.setUint8(17, payload.sessionId & 0xFF);
    data.setUint8(18, payload.flags & 0xFF);
    return data.buffer.asUint8List();
  }

  static Uint8List encodeFinishPayload(int sessionId) {
    return Uint8List.fromList([
      universalShifterDfuOpcodeFinish,
      sessionId & 0xFF,
    ]);
  }

  static Uint8List encodeAbortPayload(int sessionId) {
    return Uint8List.fromList([
      universalShifterDfuOpcodeAbort,
      sessionId & 0xFF,
    ]);
  }

  static Uint8List encodeGetStatusPayload() {
    return Uint8List.fromList([universalShifterDfuOpcodeGetStatus]);
  }

  static BootloaderDfuDataFrame buildDataFrame({
    required List<int> imageBytes,
    required int sessionId,
    required int offset,
    int payloadSize = universalShifterBootloaderDfuMaxPayloadSizeBytes,
  }) {
    if (offset < 0 || offset >= imageBytes.length) {
      throw RangeError.range(offset, 0, imageBytes.length - 1, 'offset');
    }
    if (payloadSize <= 0 ||
        payloadSize > universalShifterBootloaderDfuMaxPayloadSizeBytes) {
      throw RangeError.range(
        payloadSize,
        1,
        universalShifterBootloaderDfuMaxPayloadSizeBytes,
        'payloadSize',
      );
    }

    final remaining = imageBytes.length - offset;
    final payloadLength = remaining < payloadSize ? remaining : payloadSize;
    final payloadEnd = offset + payloadLength;
    final payload = imageBytes.sublist(offset, payloadEnd);
    final frame = Uint8List(
      universalShifterBootloaderDfuDataHeaderSizeBytes + payloadLength,
    );

    frame[0] = sessionId & 0xFF;
    final data = ByteData.view(frame.buffer);
    data.setUint32(1, offset, Endian.little);
    data.setUint32(5, crc32(payload), Endian.little);
    frame.setRange(
      universalShifterBootloaderDfuDataHeaderSizeBytes,
      universalShifterBootloaderDfuDataHeaderSizeBytes + payloadLength,
      payload,
    );

    return BootloaderDfuDataFrame(
      sessionId: sessionId & 0xFF,
      offset: offset,
      payloadLength: payloadLength,
      bytes: frame,
    );
  }

  static List<BootloaderDfuDataFrame> buildDataFrames({
    required List<int> imageBytes,
    required int sessionId,
    int payloadSize = universalShifterBootloaderDfuMaxPayloadSizeBytes,
  }) {
    final frames = <BootloaderDfuDataFrame>[];
    var offset = 0;
    while (offset < imageBytes.length) {
      final frame = buildDataFrame(
        imageBytes: imageBytes,
        sessionId: sessionId,
        offset: offset,
        payloadSize: payloadSize,
      );
      frames.add(frame);
      offset += frame.payloadLength;
    }
    return frames;
  }

  static int maxPayloadSizeForMtu(int negotiatedMtu) {
    final writePayloadBytes =
        negotiatedMtu - universalShifterAttWriteOverheadBytes;
    final availablePayload =
        writePayloadBytes - universalShifterBootloaderDfuDataHeaderSizeBytes;
    if (availablePayload <= 0) {
      return 0;
    }
    if (availablePayload > universalShifterBootloaderDfuMaxPayloadSizeBytes) {
      return universalShifterBootloaderDfuMaxPayloadSizeBytes;
    }
    return availablePayload;
  }

  static DfuBootloaderStatus parseStatusPayload(List<int> payload) {
    if (payload.length != universalShifterBootloaderDfuStatusSizeBytes) {
      throw const FormatException(
          'DFU status payload must be exactly 6 bytes.');
    }
    final data = ByteData.sublistView(Uint8List.fromList(payload));
    final rawCode = data.getUint8(0);
    return DfuBootloaderStatus(
      code: DfuBootloaderStatusCode.fromRaw(rawCode),
      rawCode: rawCode,
      sessionId: data.getUint8(1),
      expectedOffset: data.getUint32(2, Endian.little),
    );
  }

  static int crc32Update(int crc, List<int> bytes) {
    var next = crc & 0xFFFFFFFF;
    for (final byte in bytes) {
      next ^= byte;
      for (var bit = 0; bit < 8; bit++) {
        if ((next & 0x1) != 0) {
          next = (next >> 1) ^ _crc32PolynomialReflected;
        } else {
          next >>= 1;
        }
      }
    }
    return next & 0xFFFFFFFF;
  }

  static int crc32Finalize(int crc) {
    return (crc ^ 0xFFFFFFFF) & 0xFFFFFFFF;
  }

  static int crc32(List<int> bytes) {
    return crc32Finalize(crc32Update(crc32Initial, bytes));
  }
}