Changes

The file structure in a nut-shell nutshell is a header (HEADER), followed by a (SIGNATURES) block, followed by a list of variable length files, and finally ending with an index of the files (INDEX). The index is a list of variable length entries (INDEX_ENTRY). The signatures block is a list of variable length entries (SIGNATURE_ENTRY).

8 bytes : sizeOfEntireMAR FileSize - size in bytes of the entire MAR file

Some old MAR files will not contain the SIGNATURE block nor the sizeOfEntireMAR FileSize field. Old parsers simply skip over it though because of the OffsetToIndex field.