$2\mathrm{.}1.$ Data structures. The page size is hard$-$coded in the header file dberror. $h($PAGE$\_$SIZE$).$ Each of the methods

defined in the storage manager interface returns an integer return code also defined in dberror.h $($RC$).$ For details

see return codes below.

The methods in the interface use the following two data structures to store information about files and pages:

File Handle SM$\_$FileHandle

A file handle SM$\_$FileHandle represents an open page file. Besides the file name, the handle stores the

total number of pages in the file and the current page position.

The current page position is used by some of the read and write methods of the storage manager.

For example, readCurrentBlock reads the curPagePos$=$th page counted from the beginning of the

file. When opening a file, the current page should be the first page in the file $($curPagePos$=0)$ and the

totalNumPages has to be initialized based on the file size.

Use the mgmtInfo to store additional information about the file needed by your implementation, e$.$g$.,$ a

POSIX file descriptor.

Hint: You should reserve some space in the beginning of a file to store information such as the total

number of pages.

Hint: Use mgmtInfo to store any bookkeeping info about a file your storage manager needs.

typedef struct SM$\_$FileHandle $\{$

char $*$fileName;

int totalNumPages;

int curPagePos;

void $*$mgmtinfo;

$\}.$ SM$\_$FileHandle;

Page Handle SM$\_$PageHandle

A page handle is a pointer to an area in memory storing the data of a page.

Methods that write the data pointed to by a page handle to disk or read a page from disk into the area

of memory pointed to by the page handle require that the handle is pointing to an previously allocated

block of memory that is at least PAGE$\_$SIZE number of bytes long.

typedef char$*$ SM$\_$PageHandle;

$2\mathrm{.}2.$ File Related Methods.

createPageFile

Create a new page file fileName. The initial file size should be one page. This method should fill this

single page with $\text{'}\frac{\frac{?}{?}}{0^{\text{'}}}$ bytes.

openPageFile

Opens an existing page file. Should return RC$\_$FILE$\_$NOT$\_$FOUND if the file does not exist.

The second parameter is an existing file handle.

If opening the file is successful, then the fields of this file handle should be initialized with the information

about the opened file. For instance, you would have to read the total number of pages that are stored

in the file from disk.

closePageFile, destroyPageFile

Close an open page file or destroy $($delete$)$ a page file.