CC2652R: External flash related functions not defined in cc2652 sdk v2.30 in Z-STACK zed_switch_ota project

What is the use of below code in "ota_client_app.c", because if I enable   "FACTORY_IMAGE" and  "EXTERNAL_IMAGE_CHECK", it has some functions related to external flash which are not defined.

#ifdef FACTORY_IMAGE
/******************************************************************************
 * @fn          SampleApp_hasFactoryImage
 *
 * @brief       Is the factory image available?
 *
 * @param       none
 *
 * @return      none
 */
static bool OTA_hasFactoryImage(void)
{
#if defined(EXTERNAL_IMAGE_CHECK)
  bool  valid;
  valid = extFlashOpen();

  if(valid)
  {
    uint16_t  buffer[2];

    // 1. Check reset vector
    valid = extFlashRead(EFL_ADDR_RECOVERY, sizeof(buffer),
                         (uint8_t *) buffer);
    if(valid)
    {
      valid = (buffer[0] != 0xFFFF && buffer[1] != 0xFFFF) &&
              (buffer[0] != 0x0000 && buffer[1] != 0x0000);
    }

    extFlashClose();
  }

  return valid;
#else
  return (true);
#endif
}


/*******************************************************************************
 * @fn      SampleAppSaveFactoryImage
 *
 * @brief   Save the current image to external flash as a factory image
 *
 * @return  none
 */
static bool OTA_saveFactoryImage(void)
{
  bool success;
  
  success = extFlashOpen();
  
  if (success)
  {
    uint32_t address;

    // Erase external flash
    for (address= 0; address<EFL_FLASH_SIZE; address+=EFL_PAGE_SIZE)
    {
      extFlashErase(address,EFL_PAGE_SIZE);
    }

    // Install factory image
    for (address=0; address<EFL_SIZE_RECOVERY && success; address+=EFL_PAGE_SIZE)
    {
      success = extFlashErase(EFL_ADDR_RECOVERY+address, EFL_PAGE_SIZE);
      if (success)
      {
        size_t offset;
        static uint8_t buf[256];  // RAM storage needed due to SPI/DMA limitation
        
        for (offset=0; offset<EFL_PAGE_SIZE; offset+=sizeof(buf))
        {
          const uint8_t *pIntFlash;
          
          // Copy from internal to external flash
          pIntFlash = (const uint8_t*)address + offset;
          memcpy(buf,pIntFlash,sizeof(buf));
          success = extFlashWrite(EFL_ADDR_RECOVERY+address+offset, sizeof(buf), buf);
          
          // Verify first few bytes
          if (success)
          {
            extFlashRead(EFL_ADDR_RECOVERY+address+offset, sizeof(buf), buf);
            success = buf[2] == pIntFlash[2] && buf[3] == pIntFlash[3];
          }
        }
      }
      
      
    }
    
    extFlashClose();
  }

  return success;
}
#endif