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SetFilePointer (kernel32)

C# Signature:

    public enum EMoveMethod : uint
        Begin = 0,
        Current = 1,
        End = 2

    [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
    static extern unsafe uint SetFilePointer(
        [In] SafeFileHandle hFile,
        [In] int lDistanceToMove,
        [Out] int* lpDistanceToMoveHigh,
        [In] EMoveMethod dwMoveMethod);

    [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
    static extern uint SetFilePointer(
        [In] SafeFileHandle hFile,
        [In] int lDistanceToMove,
        [Out] out int lpDistanceToMoveHigh,
        [In] EMoveMethod dwMoveMethod);

User-Defined Types:


VB Signature:

    Public Enum EMoveMethod As System.UInt32
        FILE_BEGIN = 0
        FILE_CURRENT = 1
        FILE_END = 2
    End Enum

    <DllImport("kernel32.dll", SetLastError:=True)> _
    Shared Function SetFilePointer( _
        ByVal hFile As IntPtr, _
        ByVal lDistanceToMove As Integer, _
        ByRef lpDistanceToMoveHigh As IntPtr, _
        ByVal dwMoveMethod As EMoveMethod) _
        As System.UInt32
    End Function

    Public Const INVALID_SET_FILE_POINTER As Integer = -1


If you are using this function to access hard-disk sectors greater than (2^32 - 2) bytes,

then the third argument will not be null or IntPtr.Zero. So when you pass an IntPtr to

the third argument, pass it as a reference. To do this, just change the third argument signature

to: ref IntPtr lpDistanceToMoveHigh.


Tips & Tricks:

Please add some!

Sample Code:

    [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
    private static extern int SetFilePointer(IntPtr handle, int lDistanceToMove, out int lpDistanceToMoveHigh, uint dwMoveMethod);

    public long Seek(IntPtr handle, long offset, SeekOrigin origin)
    uint moveMethod = 0;

    switch (origin)
        case SeekOrigin.Begin:
        moveMethod = 0;

        case SeekOrigin.Current:
        moveMethod = 1;

        case SeekOrigin.End:
        moveMethod = 2;

    int lo = (int)(offset & 0xffffffff);
    int hi = (int)(offset >> 32);

    lo = SetFilePointer(handle, lo, out hi, moveMethod);

    if (lo == -1)
        if (GetLastError() != 0)
        throw new Exception("INVALID_SET_FILE_POINTER");

    return (((long)hi << 32) | (uint)lo);

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