Python Ctypes转换CM_POWER_DATA 解决DEVICE_POWER_STATE报错

你遇到的报错和结构体定义错误来自三点：

1. 未提前定义DEVICE_POWER_STATE、SYSTEM_POWER_STATE两个类型，这两个是WDM定义的枚举类型，C语言中枚举默认占4字节内存，对应ctypes的32位整型类型。
2. 你写的_fields_序列存在语法错误：PD_D1Latency、PD_D3Latency字段行末尾缺失逗号，会导致Python错误合并相邻元组，字段解析失败。
3. 数组成员定义方式错误：ctypes中数组类型需要用基础类型 * 长度的语法声明，不能把数组长度写在字段名的字符串里；另外最后一个成员PD_DeepestSystemWake原生类型是SYSTEM_POWER_STATE，你误写为DEVICE_POWER_STATE。

import ctypes as ct
from ctypes import wintypes as w
from enum import IntEnum

# 映射WDM中DEVICE_POWER_STATE枚举
class DEVICE_POWER_STATE(IntEnum):
    PowerDeviceUnspecified = 0
    PowerDeviceD0 = 1
    PowerDeviceD1 = 2
    PowerDeviceD2 = 3
    PowerDeviceD3 = 4
    PowerDeviceMaximum = 5

# 映射WDM中SYSTEM_POWER_STATE枚举
class SYSTEM_POWER_STATE(IntEnum):
    PowerSystemUnspecified = 0
    PowerSystemWorking = 1
    PowerSystemSleeping1 = 2
    PowerSystemSleeping2 = 3
    PowerSystemSleeping3 = 4
    PowerSystemHibernate = 5
    PowerSystemShutdown = 6
    PowerSystemMaximum = 7

POWER_SYSTEM_MAXIMUM = SYSTEM_POWER_STATE.PowerSystemMaximum

class CM_POWER_DATA(ct.Structure):
    _fields_ = [
        ("PD_Size", w.ULONG),
        ("PD_MostRecentPowerState", ct.c_long),
        ("PD_Capabilities", w.ULONG),
        ("PD_D1Latency", w.ULONG),
        ("PD_D2Latency", w.ULONG),
        ("PD_D3Latency", w.ULONG),
        ("PD_PowerStateMapping", DEVICE_POWER_STATE * POWER_SYSTEM_MAXIMUM),
        ("PD_DeepestSystemWake", ct.c_long)
    ]

• 如果你不需要读取枚举名做调试，可以直接把两个电源状态字段的类型替换为ct.c_ulong或者w.ULONG，内存布局完全匹配，不会出现对齐错误。
• 用继承IntEnum的类作为字段类型时，读取结构体成员会直接返回对应枚举值，不需要手动做数值到状态名的映射。
• 定义完结构体后可以用ct.sizeof(CM_POWER_DATA)验证大小，32位和64位Windows下该结构体大小均为56字节，和原生C结构体大小一致就说明对齐和字段定义正确。

内容的提问来源于stack exchange，提问作者user19212551