如何使用HAL库实现不定长UART数据包的DMA接收？

uint8_t txbuf[1000]="helloworldrn";
uint8_t rxbuf[1000]="";
ART_HandleTypeDef huart1;


HAL_UART_Receive_DMA( huart1,rxbuf,sizeof(rxbuf))；

函数原型如下：
/**
  * @brief  Receives an amount of data in non blocking mode.
  * @param  huart: pointer to a UART_HandleTypeDef structure that contains
  *                the configuration information for the specified UART module.
  * @param  pData: Pointer to data buffer
  * @param  Size: Amount of data to be received
  * @note   When the UART parity is enabled (PCE = 1) the data received contain the parity bit.
  * @retval HAL status
  */
HAL_StatusTypeDef HAL_UART_Receive_DMA(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size)
{
  uint32_t *tmp;
  uint32_t tmp1 = 0;

  tmp1 = huart->State;   
  if((tmp1 == HAL_UART_STATE_READY) || (tmp1 == HAL_UART_STATE_BUSY_TX))
  {
    if((pData == NULL ) || (Size == 0))
    {
      return HAL_ERROR;
    }

    /* Process Locked */
    __HAL_LOCK(huart);

    huart->pRxBuffPtr = pData;
    huart->RxXferSize = Size;

    huart->ErrorCode = HAL_UART_ERROR_NONE;
    /* Check if a transmit process is ongoing or not */
    if(huart->State == HAL_UART_STATE_BUSY_TX)
    {
      huart->State = HAL_UART_STATE_BUSY_TX_RX;
    }
    else
    {
      huart->State = HAL_UART_STATE_BUSY_RX;
    }

    /* Set the UART DMA transfer complete callback */
    huart->hdmarx->XferCpltCallback = UART_DMAReceiveCplt;

    /* Set the UART DMA Half transfer complete callback */
    huart->hdmarx->XferHalfCpltCallback = UART_DMARxHalfCplt;

    /* Set the DMA error callback */
    huart->hdmarx->XferErrorCallback = UART_DMAError;

    /* Enable the DMA Stream */
    tmp = (uint32_t*) pData;
    HAL_DMA_Start_IT(huart->hdmarx, (uint32_t) huart->Instance->DR, *(uint32_t*)tmp, Size);

    /* Enable the DMA transfer for the receiver request by setting the DMAR bit
    in the UART CR3 register */
    huart->Instance->CR3 |= USART_CR3_DMAR;

    /* Process Unlocked */
    __HAL_UNLOCK(huart);

    return HAL_OK;
  }
  else
  {
    return HAL_BUSY;
  }
}