Due April 19th, 2002, at 9 PM
forkcommand and mutual exclusion techniques (use your partner for design and code review). This barbershop is on a military base, so there are 3 categories of people needing haircuts - officers, NonComs, and grunts. You are to use a producer/consumer paradigm with a shared circular buffer.
Mutual exclusion is to be provided
by Solaris semaphores (see
The shared buffer is to be provided by
Solaris shared memory (see
a fat old Sergeant, is a process that periodically attempts
to add a new person with long hair
to the buffer of chairs in the barbershop.
"Periodically" means that the producer uses
function with a sleep time determined by a
command line input parameter.
The sleep time must be between 1 and 5 seconds, with a default of 3 seconds.
If there are no open seats, then
the Sergeant waits until there is an empty chair (note that in this
case more than 5 seconds might elapse before the next person is seated).
The producer and consumer share a buffer of 20 chairs, but there are 3 FIFO lists within the 20 chairs. At any time there may be only 20 people in the barbershop chairs with a random distribution of Officers, NonComs, and Grunts, and 1 person getting a haircut. Note: if there is only one type of person in the barbershop, then the shop queue acts like a circular buffer.
The FIFO lists must be implemented as linked lists using integer indices as pointers.
Your consumer process is the Barber, a wiry old private. Haircuts have an individual time between 1 and 5 seconds, controlled by the input file (see below). The Barber gives priority for service: if there are any officers waiting, they get their haircuts first, even if a NonCom or grunt has been waiting longer; similarly, NonComs get priority over grunts.
The pattern of people arriving for haircuts is controlled by an input file, read from the standard input. The input is a series of 2-digit numbers that encode both the type of soldier and the time needed for a haircut:
You may assume that the input file consists exclusively of numbers, but you must make sure that the numbers are valid, rejecting illegal soldier types and invalid haircut times. The easiest way to process the input is to read a number and then separate the digits using integer division and the modulus operator.
Here is a sample input file that will not stress your program very much.
As in the Dining Philosophers project, the participants in the game are so busy doing things that they don't have a chance to figure out what is going on. Thus you MUST have another process, the Lieutenant, who monitors the overall barbershop. Because he is young and stupid, every 2 seconds the Lieutenant pokes his head into the barbershop to determine:
The Lieutenant numbers each output line sequentially (easier to watch the time fly).
Optionally (controlled by the second parameter to the program) the Lieutenant can also dump the contents of the three queues (everyone in the queue, their chair number, etc.).
A short example of the output should clarify some of these points. Your output must match the sample format exactly to make grading easier.
In the sample output, lines 1-6 of each group are what is normally printed out, while lines 7-10 are the additional lines produced if parameter 2 is nonzero. Note that the person in the chair with the lowest number is the next person of that category to have their hair cut. Also note how position numbers change as someone's hair is cut, i.e., in the first group (watch #20), the next NC is 18, in the second group (watch #21), the next NC is 17 (because the guy in 18 moved to the barber chair. Finally, note how there is only one entry in each column (since each array slot can only hold one type of person) and the grunt queue is not in any particular order.
The barbershop program must be invoked with three arguments:
When the input file is empty, the Sergeant terminates, but the barber continues until the last longhair has had his haircut. The Lieutenant continues until both the Sergeant and the Barber have terminated. Look at some of the semaphore operations for ways to do this. Thus, the final output from the Lieutenant should show an equal number of long hairs entering the system and short hairs produced, with an empty waiting room at the end.
Submit your code in the usual way, using
script.txt, containing a listing of a run against the trivial sample input file.
We will either test your program against other input cases, or ask you to demonstrate your program to the graders (procedure to be determined later).
removeipcto clean up when your code breaks. You will lose points for holding old semaphores and/or shared memory!!!
We reserve the right to change the problem statement when someone demonstrates the ambiguity of said problem statement.
Last modified April 6, 2002 by email@example.com