如何从 Python 文件句柄打开 .NET FileStream 对象？

Question

我需要在 Python 中打开一个可写文件句柄，然后将文件描述符传递给 .NET 程序集中的一个函数（通过 pythonnet's clr module.

访问）

从 Python 文件对象到 win32 HANDLE* 相当简单，如 this question:

所示

import clr
from Microsoft.Win32.SafeHandles import SafeFileHandle
from System.IO import FileStream, FileAccess

pyf=open("c:/temp/testing123.txt","w")
fileno=pyf.fileno()
print fileno               # 6
handle = msvcrt.get_osfhandle(fileno)
print handle               # 1832L

According to MSDN，现在应该可以从直接的 IntPtr（句柄）或 SafeFileHandle 包装器构建标准的 FileStream 对象。

FileStream(IntPtr, FileAccess)
FileStream(SafeFileHandle, FileAccess)

问题是...我怎样才能说服 clr 模块将 handle 转换为 IntPtr？

我试过以下各种版本，但它们都给我错误：

FileStream(IntPtr(handle), True)
FileStream(IntPtr(Int64(handle), True)
FileStream(IntPtr(Int32(handle), True)
SafeFileHandle(IntPtr(handle), True)
...

=> TypeError ("value cannot be converted to System.IntPtr")

关于如何将这个该死的文件句柄导入 C# 有什么建议吗？

Answer 1

感谢 pythonnet mailing list 上的好心人，得到了答案。

关键是使用 Overloads 构造函数将 win32 HANDLE 强制转换为 IntPtr 类型。

这是一个完整的工作示例：

import tempfile, msvcrt
import clr, msvcrt
from System.IO import FileStream, FileAccess
from System import IntPtr

with tempfile.NamedTemporaryFile(suffix='.txt', delete=False) as pyf:
    fileno=pyf.fileno()
    print "fileno", fileno
    handle = msvcrt.get_osfhandle(fileno)
    print "HANDLE", handle

    pyf.write("Python\n")
    pyf.flush()

    cs_handle = IntPtr.Overloads[long](handle)
    cs_fs = FileStream(cs_handle, FileAccess.Write)
    cs_fs.Write("CLR\n", 0, 4)
    cs_fs.Flush()

print "file should contain a line from Python and a line from CLR: ", pyf.name

Answer 2

这个答案可能有点太晚了，但是像 this 这样的答案有用吗？

from contextlib import contextmanager
import ctypes
import io
import os, sys
import tempfile

libc = ctypes.CDLL(None)
c_stdout = ctypes.c_void_p.in_dll(libc, 'stdout')

@contextmanager
def stdout_redirector(stream):
    # The original fd stdout points to. Usually 1 on POSIX systems.
    original_stdout_fd = sys.stdout.fileno()

    def _redirect_stdout(to_fd):
        """Redirect stdout to the given file descriptor."""
        # Flush the C-level buffer stdout
        libc.fflush(c_stdout)
        # Flush and close sys.stdout - also closes the file descriptor (fd)
        sys.stdout.close()
        # Make original_stdout_fd point to the same file as to_fd
        os.dup2(to_fd, original_stdout_fd)
        # Create a new sys.stdout that points to the redirected fd
        sys.stdout = io.TextIOWrapper(os.fdopen(original_stdout_fd, 'wb'))

    # Save a copy of the original stdout fd in saved_stdout_fd
    saved_stdout_fd = os.dup(original_stdout_fd)
    try:
        # Create a temporary file and redirect stdout to it
        tfile = tempfile.TemporaryFile(mode='w+b')
        _redirect_stdout(tfile.fileno())
        # Yield to caller, then redirect stdout back to the saved fd
        yield
        _redirect_stdout(saved_stdout_fd)
        # Copy contents of temporary file to the given stream
        tfile.flush()
        tfile.seek(0, io.SEEK_SET)
        stream.write(tfile.read())
    finally:
        tfile.close()
        os.close(saved_stdout_fd)

如何从 Python 文件句柄打开 .NET FileStream 对象？

How can I open a .NET FileStream object from a Python file handle?

c#

python

clr

handle

python.net