**Assignment 2: Buffer Manager**
****************************************************

					**Team:vjonnala,rmuniraj,sallu1,skalava2**
					****************************************

CONTENTS
*********
1)Instructions to run the code
2)Description of functions used
3)Additional Test Cases and Additional error checks

*****************************************************************

1)Instructions to run the code
*******************************

For executing mandatory and additional test cases:

1) In the terminal,navigate to the assignment directory.

2) Type: 
	make -f makefile

****For mandatory test cases ***
3) ./test_assign1

****For additional test cases ***
4) ./test_assign2


*****************************************************************

2)Additional functionalities
**************************
1)We have implemented Clock and LFU Page Replacement Strategy which is included in test_assign2_2.c

2)We have included additional test cases and additional error checks.

*****************************************************************

3)Description of functions used
********************************

	Function :initBufferPool
	-------------------------

1)Initialize all the Buffer Pool contents witht the arguments in the function in initBufferPool.
2)Initialize the linked list frames with page number -1 and all the remaining bits to NULL.
3)Call the intialize_linked_list() method to it.
4)Separate BM_statistics are created to initialise all the Buffer Pool contents with their statistics.
5)Number of pages for LFU are hard-coded to 20, because this involves the change of test case format and Create a temporary array with NULL values.


	Function :shutdownBufferPool
	----------------------------
	
1)If the fix count of a page is not equal to zero,return an appropriate error code.
2)Check if pages are dirty.If true,write the pages back to the disc by calling forceFlushPool function.
3)Free the memory that has been allocated to the buffer pool if the dirty bit is false.

	
	Function : forceFlushPool
	-------------------------

1)Traverse till the end of the buffer pool and check if dirty bit is set and fix count is zero.
2)In that case , call the  writeBlock function to write the contents to the disk.
3)On success,return RC_OK to the calling function. 


	Function : markDirty
	---------------------
1)Traverse the contents of the page frame from the 1st node till last and if the pagenumber requested is found,set dirty bit to true
2)On success,return RC_OK to the calling function.


	Function : unpinPage
	---------------------
	
1)Check if the buffer pool has been initialized.If not,throw an appropriate error code.	
2)Traverse the contents of the page frame from the 1st node till last and set the fix count to zero for the apprpriate page number.
3)If the dirty flag is set and fixed count is zero ,write the page to disk.
4)If the fix count of the frame array is less than zero ,return an appropriate error code.


	Function : forcePage
	--------------------
1)Check if the buffer pool has been initialized.If not,throw an appropriate error code.	
2)Write the current content of the page back to the page file on disk .
3)Increase the count of pages_wrote.
4)On success,return RC_OK to the calling function.


	Function : pinPage 
	------------------
This involves two cases:-
1)Check if the page is already present in the buffer pool.If yes,	
	
	a)Traverse the contents of the page frame from the 1st node till last and increase the fix count of the page
	c)Check if the replacement strategy is either FIFO / LRU / CLOCK / LFU .If not,throw an appropriate error code.

2)If the page is not present in the buffer pool,
	
	a)Check for minimum possible frame and get the page from file using required Page Replacement Strategy .
	b)Assign the values of the page frame. 

3)On success,return RC_OK to the calling function.


**Statistics Functions**
-------------------------

	Function : getFrameContents
	----------------------------
	
1)Check if the buffer pool is null.If not,throw an appropriate error code.
2)Traverse till the end of page frame and read the page numbers to the array.
3)Return the array pointer of Frame Contents.
 
	Function : getDirtyFlags
	------------------------
	
	
1)Check if the buffer pool is null.If not,throw an appropriate error code.
2)Traverse till the end of page frame and check if the page is dirty and set if TRUE.
3)Read the values to the array and return the dirty flags.

	Function : getFixCounts
	------------------------
	
1)Check if the buffer pool is null.If not,throw an appropriate error code.
2)Traverse till the end of page frame and check the fix count of the pages in the page frame.
3)Read the values to the array and return the fix counts.


	Function : getNumReadIO
	------------------------

1)Refer to the pool manager structure,which contains the information of the pages read.
2)Return the pages read. 


	Function: getNumWriteIO
	-----------------------
	
1)Refer to the pool manager structure,which contains the information of the pages wrote.
2) Return the pages written. 

****************************************************************

4) Additional Test Cases and Additional Error Checks
----------------------------------------------------

	Test cases
	-----------------
test_assign2_1.c = Given Test Case = Implements LRU,FIFO.
test_assign2_2.c = Additional Test Case = Implements LFU,CLOCK.

	Error Checks
	-----------------
	
We have included the following additional error checks


1) RC_BM_POOL_INIT_ERROR 100;			// Pool initialization error
2) RC_BM_CANNOT_UNPIN_A_PAGE 101;		// Un-Pinned Failed
3) RC_BM_CANNOT_WRITE_A_UNPIN_PAGE 102;		//failed to write an unpin page
4) RC_BM_INVALID_STRATEGY 103;			//Strategy passed is invalid ** Valid are RS_FIFO , RS_LRU , RS_LFU , RS_CLOCK
5) RC_REQUESTED_PAGE_NOT_FOUND 104;		//Page requsted wasnt found in the pool
6) RC_BM_NODE_CREATION_FAILED 105;		//Node creation failed.

*****************************************************************