124 lines
3.6 KiB
Python
124 lines
3.6 KiB
Python
"""
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This demonstrates the creation of miniversions of a file during a transaction.
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The FSCTL_TXFS_CREATE_MINIVERSION control code saves any changes to a new
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miniversion (effectively a savepoint within a transaction).
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"""
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import os
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import struct
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import win32api
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import win32con
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import win32file
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import win32transaction
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import winerror
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import winioctlcon
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from pywin32_testutil import str2bytes # py3k-friendly helper
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def demo():
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"""
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Definition of buffer used with FSCTL_TXFS_CREATE_MINIVERSION:
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typedef struct _TXFS_CREATE_MINIVERSION_INFO{
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USHORT StructureVersion;
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USHORT StructureLength;
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ULONG BaseVersion;
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USHORT MiniVersion;}
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"""
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buf_fmt = "HHLH0L" ## buffer size must include struct padding
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buf_size = struct.calcsize(buf_fmt)
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tempdir = win32api.GetTempPath()
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tempfile = win32api.GetTempFileName(tempdir, "cft")[0]
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print("Demonstrating transactions on tempfile", tempfile)
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f = open(tempfile, "w")
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f.write("This is original file.\n")
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f.close()
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trans = win32transaction.CreateTransaction(
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Description="Test creating miniversions of a file"
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)
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hfile = win32file.CreateFileW(
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tempfile,
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win32con.GENERIC_READ | win32con.GENERIC_WRITE,
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win32con.FILE_SHARE_READ | win32con.FILE_SHARE_WRITE,
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None,
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win32con.OPEN_EXISTING,
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0,
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None,
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Transaction=trans,
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)
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win32file.WriteFile(hfile, str2bytes("This is first miniversion.\n"))
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buf = win32file.DeviceIoControl(
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hfile, winioctlcon.FSCTL_TXFS_CREATE_MINIVERSION, None, buf_size, None
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)
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struct_ver, struct_len, base_ver, ver_1 = struct.unpack(buf_fmt, buf)
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win32file.SetFilePointer(hfile, 0, win32con.FILE_BEGIN)
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win32file.WriteFile(hfile, str2bytes("This is second miniversion!\n"))
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buf = win32file.DeviceIoControl(
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hfile, winioctlcon.FSCTL_TXFS_CREATE_MINIVERSION, None, buf_size, None
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)
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struct_ver, struct_len, base_ver, ver_2 = struct.unpack(buf_fmt, buf)
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hfile.Close()
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## miniversions can't be opened with write access
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hfile_0 = win32file.CreateFileW(
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tempfile,
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win32con.GENERIC_READ,
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win32con.FILE_SHARE_READ | win32con.FILE_SHARE_WRITE,
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None,
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win32con.OPEN_EXISTING,
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0,
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None,
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Transaction=trans,
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MiniVersion=base_ver,
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)
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print("version:", base_ver, win32file.ReadFile(hfile_0, 100))
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hfile_0.Close()
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hfile_1 = win32file.CreateFileW(
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tempfile,
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win32con.GENERIC_READ,
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win32con.FILE_SHARE_READ | win32con.FILE_SHARE_WRITE,
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None,
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win32con.OPEN_EXISTING,
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0,
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None,
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Transaction=trans,
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MiniVersion=ver_1,
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)
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print("version:", ver_1, win32file.ReadFile(hfile_1, 100))
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hfile_1.Close()
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hfile_2 = win32file.CreateFileW(
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tempfile,
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win32con.GENERIC_READ,
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win32con.FILE_SHARE_READ | win32con.FILE_SHARE_WRITE,
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None,
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win32con.OPEN_EXISTING,
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0,
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None,
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Transaction=trans,
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MiniVersion=ver_2,
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)
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print("version:", ver_2, win32file.ReadFile(hfile_2, 100))
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hfile_2.Close()
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## MiniVersions are destroyed when transaction is committed or rolled back
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win32transaction.CommitTransaction(trans)
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os.unlink(tempfile)
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if __name__ == "__main__":
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# When run on CI, this fails with NOT_SUPPORTED, so don't have that cause "failure"
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try:
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demo()
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except win32file.error as e:
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if e.winerror == winerror.ERROR_NOT_SUPPORTED:
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print("These features are not supported by this filesystem.")
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else:
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raise
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