问目标C到Swift代码转换，似乎无法正确处理Swift中的字节

EN

// Instance method to get the heart rate BPM information
- (void) getHeartBPMData:(CBCharacteristic *)characteristic error:(NSError *)error
{
    // Get the Heart Rate Monitor BPM
    NSData *data = [characteristic value];      // 1
    const uint8_t *reportData = [data bytes];
    uint16_t bpm = 0;

    if ((reportData[0] & 0x01) == 0) {          // 2
        // Retrieve the BPM value for the Heart Rate Monitor
        bpm = reportData[1];
    }
    else {
        bpm = CFSwapInt16LittleToHost(*(uint16_t *)(&reportData[1]));  // 3
    }
    // Display the heart rate value to the UI if no error occurred
    if( (characteristic.value)  || !error ) {   // 4
        self.heartRate = bpm;
        self.heartRateBPM.text = [NSString stringWithFormat:@"%i bpm", bpm];
        self.heartRateBPM.font = [UIFont fontWithName:@"Futura-CondensedMedium" size:28];
        [self doHeartBeat];
        self.pulseTimer = [NSTimer scheduledTimerWithTimeInterval:(60. / self.heartRate) target:self selector:@selector(doHeartBeat) userInfo:nil repeats:NO];
    }
    return;
}

func peripheral(peripheral: CBPeripheral!,
    didUpdateValueForCharacteristic characteristic: CBCharacteristic!,
    error: NSError!) -> String
{

    // Get the Heart Rate Monitor BPM
    var data = characteristic.value
    var reportData = data.bytes
    var bpm : UInt16
    var rawByte : UInt8
    var outputString = ""
    rawByte = UInt8(reportData[0])
    bpm = 0

    if ((rawByte & 0x01) == 0) {          // 2
        // Retrieve the BPM value for the Heart Rate Monitor
        bpm = UInt16( reportData[4] )
    }
    else {
        bpm = CFSwapInt16LittleToHost(UInt16(reportData[1]))
    }

    outputString = String(bpm)
    return outputString
}