Exercise 3 POSIX Shared Memory APIs

Computer Systems I
Assignment Exercise 3
Objectives
Gain familiarity with POSIX Shared Memory APIs.
Submitting Your Work
Submit your C program files along with your analysis of task 5 as the Assignment Exercise 3 Submission
item on the course web site. You will submit 3 files – “shm.h”, “server.c” and “client.c”. Skeleton version
of these files are available to you. You must submit your program by the deadline in 2 weeks.
Background
In Assignments 1 and 2, you gained familiarity with communicating between threads within the same
process. Inter-thread communication within the same process is relatively straight forward, because the
Data segment for the process is shared between all threads within that process. The only challenge is to
ensure you provide a means for mutual exclusion when the same data is accessed from multiple threads.
Inter-process communication (IPC) refers to communication between different process spaces. In this
situation, you don’t have the luxury of sharing a common data segment. Of the many inter-process
communication methods employed in software, the easiest and most efficient method when both
processes belong to a common host machine is referred to as “Shared memory”.
Your task in this assignment is to explore the POSIX shared memory APIs available in the Linux OS.
Assignment Tasks
Task 1: Populate shm.h
In the file “shm.h”, define an “enum” called “StatusEnum” which has the following enumerations: INVALID, VALID
and CONSUMED.
Also in the file “shm.h” typedef a structure called “ShmData” that includes the enum above and an additional “int”
variable type called “data”.
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Task 2: Populate Server.c
This file contains the server code to create and populate the shared memory. Research the APIs “shm_open”,
“ftruntcate”, “mmap”, “munmap”, “close”, and “shm_unlink” to fully populate this file.
Task 3: Populate Client.c
This file contains the client code to map and read the contents of shared memory. It uses some of the same APIs
used in the server code above. Populate this file with all the APIs listed in the comments in this file.
Task 4: Test your inter-process communication
Compile and run the Server and pass an argument in the command line. Compile and run the Client and confirm
you are receiving the argument passed to the server in your client.
Task 5: Postulate how you could use this IPC
Based on your knowledge of timers from the previous assignment, postulate (by providing a small analytical
paragraph) how you would use this method of IPC where a server is a producer of data and a client is a consumer
of data, to periodically get the data from the producer at regular intervals.
Grading guidelines
 Working code (4 points)
 Conforming to good coding practice (4 points)
 Analysis (2 points)