总结：python使用ctypes模块调用C++动态库，未设置参数的接收类型而引发的BUG

一、宇视SDK抓图流程

NETDEV_Init 初始化
NETDEV_Login_V30 ipc设备登录
NETDEV_QueryVideoChlDetailList 查询视频通道信息列表
NETDEV_CaptureNoPreview 设备抓图

image.png

二、python code

使用restype 设置接收参数的类型
HIKSDK.NETDEV_Login_V30.restype = ctypes.c_void_p
假如不设置接收参数的类型，会抛出异常：内存地址不一致

def _uni_login(address, username, password, port, channel):
    HIKSDK.NETDEV_Init()
    pst_dev_login_info = NETDEVDeviceLoginInfo()
    pst_dev_login_info.szIPAddr = bytes(address, "ascii")
    pst_dev_login_info.szUserName = bytes(username, "ascii")
    pst_dev_login_info.szPassword = bytes(password, "ascii")
    pst_dev_login_info.dwPort = port
    pst_dev_login_info.dwLoginProto = 0
    pst_dev_login_info.dwDeviceType = 1
    pst_security_login_info = NETDEVSELogInfo()
    login_info_1 = byref(pst_dev_login_info)
    login_info_2 = byref(pst_security_login_info)
    HIKSDK.NETDEV_Login_V30.restype = ctypes.c_void_p  # 设定接收登录的参数类型为c_void_p
    lUserID = HIKSDK.NETDEV_Login_V30(login_info_1, login_info_2)
    if lUserID == 0:
        logging.error("unisdk failed to login (%s): %s", address, _errmsg())
    logging.debug('unisdk._uni_login: login success：loginID = {}'.format(lUserID))
    channel_info = NETDEVVideoChlDetailInfo()
    # 查询视频通道信息列表
    channel_num = HIKSDK.NETDEV_QueryVideoChlDetailList(ctypes.c_void_p(lUserID), pointer(ctypes.c_int(channel)),
                                                        byref(channel_info))
    if channel_num != True:
        raise RuntimeError("unisdk failed to get channel info ({}): {}".format(address, _errmsg()))
    logging.debug('unisdk._uni_login: address = {} channel_num  = {}'.format(address, channel_num))
    return lUserID

2.1 异常原因：

指针类型作为返回值传递给python时，在未设置类型的时候，会发生默认截断的问题

sdk日志：

image.png

python日志：101200（用户不在线）

image.png

三、参考连接

https://docs.python.org/3.6/library/ctypes.html#fundamental-data-types
http://icejoywoo.github.io/2018/12/10/intro-python-ctyps.html