C# Definition:

[StructLayout(LayoutKind.Sequential)]
struct REPARSE_DATA_BUFFER {
     uint ReparseTag;
     ushort ReparseDataLength;
     ushort Reserved;
     ushort SubstituteNameOffset;
     ushort SubstituteNameLength;
     ushort PrintNameOffset;
     ushort PrintNameLength;
     [MarshalAs(UnmanagedType.ByValArray, SizeConst = 0x3FF0)]
     byte[] PathBuffer;
}

Members

ReparseTag
    Reparse point tag. Must be a Microsoft reparse point tag.
ReparseDataLength
    Size, in bytes, of the data after the Reserved member. This can be calculated by:
       (4 * sizeof(ushort)) + SubstituteNameLength + PrintNameLength +
       (namesAreNullTerminated ? 2 * sizeof(char) : 0);
Reserved
    Reserved; do not use.
SubstituteNameOffset
    Offset, in bytes, of the substitute name string in the PathBuffer array.
SubstituteNameLength
    Length, in bytes, of the substitute name string. If this string is null-terminated,
    SubstituteNameLength does not include space for the null character.
PrintNameOffset
    Offset, in bytes, of the print name string in the PathBuffer array.
PrintNameLength
    Length, in bytes, of the print name string. If this string is null-terminated,
    PrintNameLength does not include space for the null character.
PathBuffer
    A buffer containing the unicode-encoded path string. The path string contains
    the substitute name string and print name string.

Notes:

The maximum size of this structure is 16KiB.

The total size of the structure can be calculated by:

REPARSE_DATA_BUFFER_HEADER_SIZE + ReparseDataLength

where

REPARSE_DATA_BUFFER_HEADER_SIZE = sizeof(uint) + 2 * sizeof(ushort)