82 lines
3.2 KiB
Python
82 lines
3.2 KiB
Python
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"""
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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 win32file, win32api, win32transaction, winerror
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import win32con, winioctlcon
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import struct
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import os
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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(Description='Test creating miniversions of a file')
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hfile=win32file.CreateFileW(tempfile, win32con.GENERIC_READ|win32con.GENERIC_WRITE,
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win32con.FILE_SHARE_READ|win32con.FILE_SHARE_WRITE,
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None, win32con.OPEN_EXISTING, 0 , None, Transaction=trans)
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win32file.WriteFile(hfile, str2bytes('This is first miniversion.\n'))
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buf=win32file.DeviceIoControl(hfile, winioctlcon.FSCTL_TXFS_CREATE_MINIVERSION,None,buf_size,None)
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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(hfile, winioctlcon.FSCTL_TXFS_CREATE_MINIVERSION,None,buf_size,None)
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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(tempfile, win32con.GENERIC_READ,
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win32con.FILE_SHARE_READ|win32con.FILE_SHARE_WRITE,
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None, win32con.OPEN_EXISTING, 0 , None, Transaction=trans, MiniVersion=base_ver)
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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(tempfile, win32con.GENERIC_READ,
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win32con.FILE_SHARE_READ|win32con.FILE_SHARE_WRITE,
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None, win32con.OPEN_EXISTING, 0 , None, Transaction=trans, MiniVersion=ver_1)
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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(tempfile, win32con.GENERIC_READ,
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win32con.FILE_SHARE_READ|win32con.FILE_SHARE_WRITE,
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None, win32con.OPEN_EXISTING, 0 , None, Transaction=trans, MiniVersion=ver_2)
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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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