Sln Rev2
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16KB info area
16KB Aligned index entries block
16KB ** Data blocks

Info area
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4: Fixed `BDD2' signature
1: LEU16 prefix of base image file path UTF-8
0-255: ...
4: LEU32 Size of block
4: LEU32 Number of block
...: Padding to 64KB

Index entry
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8: LEU32 Offset to file
1: Flags [Allocated,Trimed,...]