ShareableSpreadSheet

In this project, we asked to make shareable spreadsheet (shareable: can be accessed by multiplying users).
For make it possible,
we had to set locks on resources,
in a way that will prevent a deadlock or another reader-writer common problems (dirty write, dirty read, phantom, and so).

The approach we have adopted is to separate the Spread Sheet object methods into sections,
and each section will get a unique locking mechanism using the Spread Sheet object data members.
The methods were separated into 4 groups: Reading, Writing, Structure changing, Searching.
Each group have a unique locking mechanism responsibility.
The lockers groups are: ReadLock, WriteLock, StructureChangeLock, SearchLock.
(Every lock option has the mirroring operation.

For example:
ReadLock method that locking the related resources in Reading operations,
have the opposite ReadLockRelease methos which releasing the locks).
Each method has the same method structure inside of it.
Every critical section of every function is wrapped by locking and releasing,
the lock type depending on method purposes (methods groups).

For example,
the method “Search string” which searching for a cell contains a given string value:

As can be seen, the method’s critical section is wrapped by Read Lock and Search Lock.

The Spread Sheet object data members that used in order to be able to manage the locking system: (following comments explains each data members purpose).

A diagram represents the locking flow of an example method “Add row”:
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