Storage Manager

How to run the code

make && make run_test && make clean

Solution Approach

Interfaces for manipulating page in files

• initStorageManager():

  • Initialize the globally defined fileHandle attributes to default values

• createPageFile():

  • Create a file pointer and open the file in write in binary mode
  • If the file is non existent, return RC_FILE_NOT_FOUND
  • Create a new page of size PAGE_SIZE
  • If the page is not created, return RC_WRITE_FAILED
  • Fill the page with 0's as it is a new page
  • If the write is not successful, return RC_WRITE_FAILED
  • Close the file and free the page to avoid memory leaks
  • Return RC_OK if the file is created successfully

• openPageFile():

  • Open the file in read and write(+) in binary mode
  • If the file is non existent, return RC_FILE_NOT_FOUND
  • Assign the fileHandle attributes to the values of the file, totalNumPages = FILE_SIZE / PAGE_SIZE
  • Close the file to avoid memory leaks
  • Return RC_OK if the file is opened successfully

• closePageFile():

  • If the fileHandle or its fileName is not initialized, return RC_FILE_HANDLE_NOT_INIT
  • Clear the file handle's members
  • If the fileHandle is initialized, free the fileName to avoid memory leaks
  • Return RC_OK if the file is closed successfully

• destroyPageFile():

  • Remove the file from the disk
  • If the file is non existent, return RC_FILE_NOT_FOUND
  • Return RC_OK if the file is destroyed successfully

Interfaces for reading blocks from disc

• readBlock():

  • Open the file in r+ mode
  • Seek till the starting of the page
  • If seek failed return RC_FILE_SEEK_FAILED
  • Read the page contents to memPage with byte size as 1 till PAGE_SIZE bytes
  • Update current page position using ftell
  • Close the file
  • Return RC_OK

• getBlockPos():

  • Return current page position

• readFirstBlock():

  • Call readBlock on the first page

• readPreviousBlock():

  • Call readBlock on the previous page

• readCurrentBlock():

  • Call readBlock on current page

• readNextBlock():

  • Call readBlock on next page

• readLastBlock():

  • Call readBlock on last page - totalNumPages - 1

Interfaces for writing blocks to disc

• writeBlock():

  • OPEN FILE IN MODE THAT CAN BE BOTH WRITTEN AND READ
  • CHECK IF FILE IS NULL
  • RETURN RC_FILE_NOT_FOUND IF FILE IS NULL
  • CHECK IF FHANDLE IS NOT INITIALIZED OR NOT
  • RETURN RC_FILE_HANDLE_NOT_INIT IF IT IS NOT INITIALIZED
  • CHECK FOR ERRORS THAT MAY CAUSE FAILURE
  • RETURN RC_WRITE_FAILED IF THESE ERRORS EXIST
  • MOVE TO GIVEN POSITION WHERE WRITE SHOULD BE PERFORMED
  • WRITE THE PAGE TO THE DISK
  • RETURN RC_OK AFTER SUCCESSFUL METHOD CALL
  • IF FSEEK HAS FAILED RETURN RC_WRITE_FAILED
  • CLOSE THE FILE

• writeCurrentBlock():

  • CREATE VARIABLES TO STORE THE RETURN CODE AND CURRENT POSITION
  • CHECK IF FILE HANDLE IS INITIALISED
  • IF NOT,RETURN RC_FILE_HANDLE_NOT_INIT
  • IF YES,GET THE CURRENT POSITION USING GETBLOCKPOS()
  • PERFORM WRITEBLOCK() USING CURRENT POSITION AND STORE THE RETURN CODE
  • RETURN THE RETURNCODE WHICH IS EITHER RC_OK IF SUCCESSFULL OR RC_WRITE_FAILED IF UNSUCCESSFUL

• appendEmptyBlock():

  • CHECK IF FILE HANDLE IS INITIALISED
  • IF NOT,RETURN RC_FILE_HANDLE_NOT_INIT
  • OTHERWISE,OPEN FILE IN READ AND WRITE MODE
  • MOVE TO END OF THE FILE
  • CREATE A WHILE LOOP THAT ITERATES "PAGE_SIZE" TIMES
  • PRINT '\0' IN EACH ITERATION OF THE LOOP
  • CLOSE THE FILE
  • RETURN RC_OK IF THE BLOCK IS APPENDED SUCCESSFULLY

• ensureCapacity():

  • CHECK IF FILE HANDLE IS INITIALISED
  • IF NOT,RETURN RC_FILE_HANDLE_NOT_INIT
  • IF YES,CHECK IF THERE IS A DIFFERENCE IN NUMBER OF PAGES AND TOTAL NUMBER OF PAGES
  • IF A DIFFERENCE EXISTS,USE A WHILE LOOP TO APPEND PAGES UNTIL THE DIFFERENCE IS NULLIFIED
  • RETURN RC_OK AFTER SUCCESSFUL OPERATION