README_HW4

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						Sahil Jain
						110281300
						sahjain@cs.stonybrook.edu
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MAJOR CHANGES MADE:

---	Extensible Files
	Modified the method
	nachos.kernel.filesys.OpenFileReal.writeAt(byte[], int, int, long)
	
	and created a new method:
	nachos.kernel.filesys.FileHeader.allocateAdditionalSectors(int)
	
	that allocates extra memory if we wish to write beyond the file.
	
	Also modified the method:
	nachos.kernel.filesys.Directory.add(String, int)
	
	to implement this feature where if an attempt is made to create more
	than 10 files the directory automatically extends as required.
	
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---	Multiple Directories/Pathnames
	Created a new syscall Mkdir() and Rmdir() that takes name of the directory as an argument.
	
	To run the user program using File System real, we first need to load the user program into
	the nachos memory. The following method has been created for this feature:
	nachos.kernel.userprog.test.ProgTest.copyUserProgramIntoFileSystem(String)
	
	Enter the following in the run arguments:
	-d f -f -x test/Mkdir_test	 
	
	It creates the following directories:
	Directory Name: /
	Directory Name: /1
	Directory Name: /1/1
	Directory Name: /2
	Directory Name: /3
	Directory Name: /4
	
	and then removes the directory /1 using Rmdir(), which automatically also removes /1/1
	since  /1/1 is the child directory of /1.
	
	I've also modified the method to list the name of all the files and directories:
	nachos.kernel.filesys.FileSystemReal.list()
	
	and this method is called from 
	nachos.kernel.userprog.Syscall.makeDirectory(String)
	
	and
	nachos.kernel.userprog.Syscall.removeDirectory(String)
	
	so that every time a directory is created or removed we list the files and directory. 

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---	Long Files
	I've added an array of size 32 for the single indirect block
	nachos.kernel.filesys.FileHeader.singleIndirectBlock
	
	and a 2D array of size 32*32 for double indirect block
	nachos.kernel.filesys.FileHeader.doubleIndirectBlock
	
	I've modified the method 
	nachos.kernel.filesys.FileHeader.allocate(BitMap, int)
	
	that now can increase the maximum size of a NACHOS file
	to (28 + 32 + 32*32)*128 = 138752 bytes.
	
	The method:
	nachos.kernel.filesys.FileHeader.allocateAdditionalSectors(int)
	
	has also been modified accordingly to increase the size of the file, if required.

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---	Test Your Implementation
	I've created the method 
	nachos.kernel.filesys.FileSystemReal.checkFileSystemForConsistency()
	
	in the FileSystemReal class that checks the file system for consistency.
		
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--- Filesystem Exerciser
	The method
	nachos.kernel.Nachos.testFileSystem()
	
	executes several creates, deletes, reads, writes and extends a number of 
	files and directories, then checks the filesystem structure to 
	make sure that it has not been corrupted.	
	
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