我如何从 C 函数的递归结构中获取数据？

Question

我正在为 usb hid 设备编写一个包装器，并想为此使用 hidapi。在 writing/learning 的过程中得到了递归结构的指针。我怎样才能从中获取数据？

我试图从contents获取数据，但里面只有_field_。

来自 hidapi 的 C 结构和 C 函数：

struct hid_device_info {
            /** Platform-specific device path */
            char *path;
            /** Device Vendor ID */
            unsigned short vendor_id;
            /** Device Product ID */
            unsigned short product_id;
            /** Serial Number */
            wchar_t *serial_number;
            /** Device Release Number in binary-coded decimal,
                also known as Device Version Number */
            unsigned short release_number;
            /** Manufacturer String */
            wchar_t *manufacturer_string;
            /** Product string */
            wchar_t *product_string;
            /** Usage Page for this Device/Interface
                (Windows/Mac only). */
            unsigned short usage_page;
            /** Usage for this Device/Interface
                (Windows/Mac only).*/
            unsigned short usage;
            /** The USB interface which this logical device
                represents. Valid on both Linux implementations
                in all cases, and valid on the Windows implementation
                only if the device contains more than one interface. */
            int interface_number;

            /** Pointer to the next device */
            struct hid_device_info *next;
        };

struct hid_device_info HID_API_EXPORT * HID_API_CALL hid_enumerate(unsigned short vendor_id, unsigned short product_id);

Python代码：

import ctypes


class HidDeviceInfo(ctypes.Structure):
    pass

HidDeviceInfo._field_ = [
    ('path', ctypes.c_char_p),
    ('vendor_id', ctypes.c_ushort),
    ('product_id', ctypes.c_ushort),
    ('serial_number', ctypes.c_wchar_p),
    ('release_number', ctypes.c_ushort),
    ('manufacturer_string', ctypes.c_wchar_p),
    ('product_string', ctypes.c_wchar_p),
    ('usage_page', ctypes.c_ushort),
    ('usage', ctypes.c_ushort),
    ('interface_number', ctypes.c_int),
    ('next', ctypes.POINTER(HidDeviceInfo))
]


hid_api_dll = ctypes.CDLL("hidapi.dll")

def get_devs(vid, pid):
    hid_enumerate = hid_api_dll.hid_enumerate

    hid_api_dll.hid_enumerate.argtypes = [
        ctypes.c_ushort,
        ctypes.c_ushort
    ]
    hid_api_dll.hid_enumerate.restype = ctypes.POINTER(HidDeviceInfo)

    vid_t = ctypes.c_ushort(vid)
    pid_t = ctypes.c_ushort(pid)

    res = ctypes.POINTER(HidDeviceInfo)()

    res = hid_enumerate(vid_t, pid_t)
    return res


devs = get_devs(0x0, 0x0)
print(devs.contents)
frameInfo = devs.contents
print(frameInfo.path)

我尝试从中获取 path 属性并得到 AttributeError: 'HidDeviceInfo' object has no attribute 'path'。

必须有所有隐藏设备的递归列表。我怎样才能检索数据？或者我做错了什么？

Answer 1

根据[Python 3]: Structures and unions（重点是我的）：

Structures and unions must derive from the Structure and Union base classes which are defined in the ctypes module. Each subclass must define a _fields_ attribute. _fields_ must be a list of 2-tuples, containing a field name and a field type.

将HidDeviceInfo._field_替换为HidDeviceInfo._field<strong>s</strong>_（复数），应该没问题。

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c

ctypes

python-3.x

hidapi