使用struct作为python ctypes模块的函数参数

Question

所以我试图将用于处理Windows上的连接/符号链接/等的python C扩展程序移植到使用ctypes模块的纯Python。 不幸的是，由于我之前使用的ctypes非常有限，我想我可能在某处导致我的代码无法正常运行时出错。 这是我到目前为止所拥有的：

from os import path
from ctypes import *
from ctypes.wintypes import *

# Python implementation of:
#
# typedef struct {
#       DWORD   ReparseTag;
#       DWORD   ReparseDataLength;
#       WORD    Reserved;
#       WORD    ReparseTargetLength;
#       WORD    ReparseTargetMaximumLength;
#       WORD    Reserved1;
#       WCHAR   ReparseTarget[1];
# } REPARSE_MOUNTPOINT_DATA_BUFFER, *PREPARSE_MOUNTPOINT_DATA_BUFFER;

class ReparsePoint(Structure):
    _fields_ = [
        ("ReparseTag", DWORD),
        ("ReparseDataLength", DWORD),
        ("Reserved", WORD),

        ("ReparseTargetLength", WORD),
        ("ReparseTargetMaximumLength", WORD),
        ("Reserved1", WORD),
        ("ReparseTarget", c_wchar_p),
    ]

GENERIC_READ = 0x80000000
GENERIC_WRITE = 0x40000000

FILE_SHARE_DELETE = 0x00000004
FILE_SHARE_READ = 0x00000001
FILE_SHARE_WRITE = 0x00000002
FILE_SHARE_READ_WRITE = (FILE_SHARE_READ | FILE_SHARE_WRITE)

OPEN_EXISTING = 3

IO_REPARSE_TAG_MOUNT_POINT = 0xA0000003
REPARSE_MOUNTPOINT_HEADER_SIZE = 8

FSCTL_SET_REPARSE_POINT = 589988
FILE_FLAG_OPEN_REPARSE_POINT = 2097152
FILE_FLAG_BACKUP_SEMANTICS = 33554432
FILE_FLAG_REPARSE_BACKUP = 35651584 # FILE_FLAG_OPEN_REPARSE_POINT | FILE_FLAG_BACKUP_SEMANTICS

INVALID_HANDLE_VALUE = -1
LPOVERLAPPED = c_void_p
LPSECURITY_ATTRIBUTES = c_void_p

NULL = 0
FALSE = BOOL(0)
TRUE = BOOL(1)

def CreateFile(filename, access, sharemode, creation, flags):
    return HANDLE(windll.kernel32.CreateFileW(
        LPWSTR(filename),
        DWORD(access),
        DWORD(sharemode),
        LPSECURITY_ATTRIBUTES(NULL),
        DWORD(creation),
        DWORD(flags),
        HANDLE(NULL)
    ))

def CreateDirectory(fpath):
    return windll.kernel32.CreateDirectoryW(LPWSTR(fpath), LPSECURITY_ATTRIBUTES(NULL)) != FALSE

def RemoveDirectory(fpath):
    return windll.kernel32.RemoveDirectoryW(LPWSTR(fpath)) != FALSE

def translate_path(fpath):
    fpath = path.abspath(fpath)
    if fpath[len(fpath)-1] == '\\' and fpath[len(fpath)-2] == ':':
        fpath = fpath[:len(fpath)-1]
    return '\\??\\%s' % fpath

def junction(source, link_name):
    """ Create a junction at link_name pointing to source directory. """
    if not path.isdir(source):
        raise Exception('Junction source does not exist or is not a directory.')

    link_name = path.abspath(link_name)
    if path.exists(link_name):
        raise Exception('Filepath for new junction already exists.')

    if not CreateDirectory(link_name):
        raise Exception('Failed to create new directory for target junction.')

    source = translate_path(source)
    hFile = CreateFile(link_name, GENERIC_WRITE, 0, OPEN_EXISTING, FILE_FLAG_REPARSE_BACKUP)
    if hFile == HANDLE(INVALID_HANDLE_VALUE):
        raise Exception('Failed to open directory for junction creation.')

    datalen = len(source) * sizeof(c_wchar)
    reparseInfo = ReparsePoint(
        IO_REPARSE_TAG_MOUNT_POINT,
        datalen + 12,
        0,
        datalen,
        datalen + sizeof(c_wchar),
        0,
        source
    )
    pReparseInfo = pointer(reparseInfo)

    print reparseInfo.ReparseTarget
    returnedLength = DWORD(0)
    result = BOOL(
        windll.kernel32.DeviceIoControl(
            hFile,
            DWORD(FSCTL_SET_REPARSE_POINT),
            pReparseInfo,
            DWORD(reparseInfo.ReparseDataLength + REPARSE_MOUNTPOINT_HEADER_SIZE),
            LPVOID(NULL),
            DWORD(0),
            byref(returnedLength),
            LPOVERLAPPED(NULL)
        )
    ) == TRUE

    #if not result:
        #RemoveDirectory(link_name)

    windll.kernel32.CloseHandle(hFile)
    return result

print junction('G:\\cpp.workspace\\tools', 'test')
"""
Just putting this here for the moment so I know how to call the function.   

BOOL WINAPI DeviceIoControl(
  __in         HANDLE hDevice,
  __in         DWORD dwIoControlCode,
  __in_opt     LPVOID lpInBuffer,
  __in         DWORD nInBufferSize,
  __out_opt    LPVOID lpOutBuffer,
  __in         DWORD nOutBufferSize,
  __out_opt    LPDWORD lpBytesReturned,
  __inout_opt  LPOVERLAPPED lpOverlapped
);
"""

目前，在运行时，代码会为目标联结创建一个文件夹。 （在这种情况下，测试）它甚至似乎应用重新分析标记向系统发信号通知该文件夹是一个连接点。 但是，不是指向“G：\\ cpp.workspace \\ tools”（或者更确切地说，指向\\ ?? \\ G：\\ cpp.workspace \\ tools），结点似乎指向：㢨\\獬

现在，显然这是reparseInfo.ReparseTarget的一个问题，但我一直无法弄清楚我做错了什么。

Answer 1

这是一个WCHAR数组，而不是指针：

#       WCHAR   ReparseTarget[1];

[1]是误导性的，API期望在结构的末尾有一个以null结尾的字符串。