python - ctypes.cdll.LoadLibrary on a dll in a zipped directory

Question

I call upon the might of StackOverflow, that I might deploy this software!

This software uses ctypes.cdll.LoadLibrary to load a dll. When deployed (mangled by py2exe) the dll is tucked away in a zip that contains a directory structure. The dll is a couple of levels deep in this structure. (I'm not sure if that's a relevant detail.) LoadLibrary fails because it cannot find the dll because the path to it is ...\site.zip\app\dll32\lfx.dll.

I can't find anything for this on SO or Google. I'm considering doing a try-except on the LoadLibrary call and, in the except block, checking whether the given path refers to a zipped location, unzipping, and trying again.

Is there a more graceful way to load a dll from a zip?

标签： pythonpython-2.7zipctypes

Answer 1

清单[Python 3.Docs]：ctypes - Python 的外部函数库。

为了加载.dll，CTypes使用：

• 尼克斯：[man7]：DLOPEN(3)
• Win : [MS.Docs]: LoadLibraryW 函数

两者都需要FS上存在的有效文件名（或NULL，但这在这里无关紧要）。您提供的文件名不符合条件，因为FS在路径中存在时不会自动处理.zip （或其他）文件。
所以.dll需要在加载之前解包。有很多方法可以做到这一点，这里有一种使用上下文管理器（[Python 3.Docs]: Data model - With Statement Context Managers）或CM的方法。

代码00.py：

#!/usr/bin/env python

import sys
import ctypes as ct
import zipfile as zf
import os


if sys.platform[:3].lower() == "win":
    from ctypes import wintypes as wt
    unload_lib = ct.WinDLL("kernel32.dll").FreeLibrary
    unload_lib.argtypes = [wt.HMODULE]
    unload_lib.restype = wt.BOOL
else:
    unload_lib = ct.CDLL(None).dlclose
    unload_lib.argtypes = [ct.c_void_p]
    unload_lib.restype = ct.c_int


class ZippedDll():
    def __init__(self, zip_file_name, member_file_name, loader=ct.CDLL, extract_path=None, suppress_exceptions=False):
        self.zip_file_name = zip_file_name
        self.member_file_name = member_file_name
        self.loader = loader
        self.extract_path = extract_path
        self.suppress_exceptions = suppress_exceptions
        self.dll_path = None
        self.dll = None


    def __enter__(self):
        self.dll_path = os.path.join(self.extract_path, self.member_file_name) if self.extract_path else self.member_file_name
        if os.path.exists(self.dll_path):
            self.dll_path = None
            raise OSError("Target file already exists")
        with zf.ZipFile(self.zip_file_name) as zip_file:
            zip_file.extract(self.member_file_name, path=self.extract_path if self.extract_path else None)
        try:
            self.dll = self.loader(self.dll_path)
        except OSError:
            if not self.__exit__(*sys.exc_info()):
                raise
        return self.dll


    def __exit__(self, exc_type, exc_val, exc_tb):
        if self.dll:
            unload_lib(self.dll._handle)
            self.dll = None
        if self.dll_path and os.path.isfile(self.dll_path):
            os.unlink(self.dll_path)
            self.dll_path = None
        return self.suppress_exceptions


def main(*argv):
    with ZippedDll("arch.zip", "dir00/dll00.dll", loader=ct.WinDLL) as dll:
        print(dll._name, dll.dll00Func00)


if __name__ == "__main__":
    print("Python {0:s} {1:d}bit on {2:s}\n".format(" ".join(item.strip() for item in sys.version.split("\n")), 64 if sys.maxsize > 0x100000000 else 32, sys.platform))
    main(*sys.argv[1:])
    print("\nDone.")

备注：

• 对于此示例，我使用了具有以下结构 的存档arch.zip
  • 目录00/
    • dll00.dll（来自另一个SO答案）导出函数（dll00Func00）
• CM解压.dll并加载它，最后（使用 退出时）清理内容（中间目录除外）
• 可以添加更多错误处理
• 我没有测试Nix部分

输出：

e:\Work\Dev\StackOverflow\q060348430>"e:\Work\Dev\VEnvs\py_pc064_03.07.06_test0\Scripts\python.exe" code00.py
Python 3.7.6 (tags/v3.7.6:43364a7ae0, Dec 19 2019, 00:42:30) [MSC v.1916 64 bit (AMD64)] 64bit on win32

dir00/dll00.dll <_FuncPtr object at 0x000002A045422E18>

Done.