Python使用windows API DevicePowerEnumDevices返回总是0 &g

Question

Python Using windows APIDevicePowerEnumDevices返回始终为0我找不到原因https://learn.microsoft.com/zh-TW/windows/win32/api/powrprof/nf-powrprof-devicepowerenumdevices

import ctypes
from ctypes import windll
from ctypes import sizeof
from ctypes import create_string_buffer
from ctypes import POINTER,byref
from ctypes import wintypes

PowrProf = windll.LoadLibrary('PowrProf.dll')
Kernel32 = windll.LoadLibrary('Kernel32.dll')
DevicePowerOpen = PowrProf.DevicePowerOpen()
QueryIndex = 0
QueryInterpretationFlags = 0x08000000
QueryFlags = 0x00000001|0x00000004
pReturnBuffer = create_string_buffer(b'00'*32)
pBufferSize = byref(ctypes.c_uint64(32))
pReturnBuffer = Kernel32.LocalAlloc(0x0040, pBufferSize)

Return = PowrProf.DevicePowerEnumDevices(
QueryIndex,
QueryInterpretationFlags,
QueryFlags,
pReturnBuffer,
pBufferSize,
)
print("Return = ",Return )

DevicePowerClose = PowrProf.DevicePowerClose()
Kernel32.LocalFree(pReturnBuffer)

Answer 1

您的缓冲区太小。从你的链接文档:

[out, optional] pReturnBuffer

指向接收请求信息的缓冲区的指针。

[in, out] pBufferSize

返回缓冲区的大小，以字节为单位。

如果pReturnBuffer为NULL, pBufferSize将被填充返回数据所需的大小

使用null返回缓冲区调用DevicePowerEnumDevices,pBufferSize将包含该返回索引的缓冲区大小:

import ctypes as ct
from ctypes import wintypes as w
PowrProf = ct.WinDLL('PowrProf')
# Recommend always defining .argtypes and .restype for each function.
# It helps ctypes convert parameters from Python to C and detect errors.
PowrProf.DevicePowerOpen.argtypes = w.ULONG,
PowrProf.DevicePowerOpen.restype = w.BOOLEAN
PowrProf.DevicePowerEnumDevices.argtypes = w.ULONG,w.ULONG,w.ULONG,w.PBYTE,w.PULONG
PowrProf.DevicePowerEnumDevices.restype = w.BOOLEAN
PowrProf.DevicePowerClose.argtypes = ()
PowrProf.DevicePowerClose.restype = w.BOOLEAN
DEVICEPOWER_HARDWAREID = 0x80000000
PDCAP_D0_SUPPORTED = 0x00000001
PDCAP_D2_SUPPORTED = 0x00000004
print('open =',PowrProf.DevicePowerOpen(0))
QueryIndex = 0
QueryInterpretationFlags = DEVICEPOWER_HARDWAREID
QueryFlags = PDCAP_D0_SUPPORTED | PDCAP_D2_SUPPORTED
while True:
size = w.ULONG()
# call with None to get required size of returned buffer
PowrProf.DevicePowerEnumDevices(QueryIndex,
QueryInterpretationFlags,
QueryFlags,
None,
ct.byref(size))
#allocate the buffer
buffer = (w.BYTE * size.value)()
if not PowrProf.DevicePowerEnumDevices(QueryIndex,
QueryInterpretationFlags,
QueryFlags,
buffer,
ct.byref(size)):
break
# Returned buffer for DEVICEPOWER_HARDWAREID is a wide multi-string value,
# each null-terminated and the end double null-terminated
result = ct.cast(buffer,ct.POINTER(w.WCHAR))[:size.value // ct.sizeof(w.WCHAR)]
print(result.rstrip('x00').split('x00'))
QueryIndex += 1
print('close =',PowrProf.DevicePowerClose())

输出(截断):

open = 1
['PCI\VEN_11AB&DEV_4364&SUBSYS_81F81043&REV_12', 'PCI\VEN_11AB&DEV_4364&SUBSYS_81F81043', 'PCI\VEN_11AB&DEV_4364&CC_020000', 'PCI\VEN_11AB&DEV_4364&CC_0200']
['ACPI\VEN_PNP&DEV_0C01', 'ACPI\PNP0C01', '*PNP0C01']
...
['PCI\VEN_8086&DEV_3A3E&SUBSYS_82EA1043&REV_00', 'PCI\VEN_8086&DEV_3A3E&SUBSYS_82EA1043', 'PCI\VEN_8086&DEV_3A3E&CC_040300', 'PCI\VEN_8086&DEV_3A3E&CC_0403']
['ms_l2tpminiport']
close = 1