Python ctypes 呼叫 DLL 完整指南：stdcall/cdecl、參數傳遞與緩衝區處理

Python ctypes 模組提供 C 相容資料類型與 DLL 共享庫呼叫功能，支援 stdcall (Windows API) 與 cdecl (C 標準) 兩種呼叫慣例。

載入 DLL

import ctypes

# stdcall (Windows API)
dll = ctypes.windll.LoadLibrary('test.dll')
# 或
dll = ctypes.WinDLL('test.dll')

# cdecl (C 標準庫)
dll = ctypes.cdll.LoadLibrary('test.dll')
# 或
dll = ctypes.CDLL('test.dll')

呼叫無參函數

nRst = dll.test()
print(nRst)

傳遞緩衝區指標與長度

方法一：手動轉型

sBuf = 'aaaaaaaaaabbbbbbbbbbbbbb'
pStr = ctypes.c_char_p()
pStr.value = sBuf
pVoid = ctypes.cast(pStr, ctypes.c_void_p).value
nRst = dll.test(pVoid, len(pStr.value))

方法二：宣告 argtypes/restype（推薦）

test = dll.test
test.argtypes = [ctypes.c_char_p, ctypes.c_int]
test.restype = ctypes.c_int
nRst = test(sBuf, len(sBuf))

呼叫慣例對照表