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VIRTUAL FILE SYSTEM BASED ON ONE FILE

Core package contains SimpleSimpleFileSystem - simple interface for file system (example of usages are in tests).
Extended package contains SimpleFileSystemProvider - nio interface for interacting with created file system.
SimpleFileSystemProvider is not fully implemented and tested (example of usages are Demo class).

===Base structure===
SimpleHeader - the one, contains main info about whole file system.
SimpleINode - one for each file or directory, contains main info about file or directory.
SimpleBlock - one or more for each file or directory, contains data of file or directory.

BaseStructureReadWriter - sync operations for base structure.
SpaceAllocator - logic for allocating free blocks and nodes.

===Structure upon base===
SimpleFile - file or directory representation.
SimpleDirectory - directory representation.

DirectoryParser - methods for parsing byte data into directory format.
INodeLocker - logic for sync operations on files.
SimpleFileReadWriter - base operations on files.

===Features===
1. Files data is not read before invoking readData method.
2. If file was changed after it was read and before it is written - exception is raised.
3. Free blocks can be reused.

===Ways to improve===
1. INodeLocker should restrict access to data blocks by file (iNode).
2. SpaceAllocator should cache free blocks.
3. SimpleBlock should be read less (sometimes only fields are required).
4. Use byte array pool
5. We need ability to identify block (if it is header, block or iNode) and check it for freedom.
6. INodes can be cached.
7. Async input/output
8. Throw specific exceptions
9. Write more tests.
10. ...

===Examples===
SimpleSimpleFileSystem - SimpleSimpleFileSystemTest
SimpleFileSystemProvider - Demo