In the middle of a major battle, General Harley Davidson needs to
send an urgent message to Milwaukee headquarters. He finds 2 soldiers
and gives each one of them a part of the message and sends them off.
When they arrive at headquarters, the message is put back together.
Write a program to put this message back together. Each of the 2
soldiers must be implemented as a thread (hence, 2 threads) and each
thread will read its part of the message from a file (thus, there
will be two files - one for each soldier). Each thread will concatentate
on to a single global character array forming the final message.
When the message is put back together the main function will output
the message to the screen. Therefore, your threads will have to watch
for their respective EOFs to know when to quit. Once both threads have
quit the main function will know the message has been put back together.
The trick is to use a critical section control technique (or make one
up) to control which thread gets to append its character onto the
global character array. Note that a strict alternation method will **NOT**
work.
Note that the two files will have 0's (numeric zero) to indicate where the
applicable thread should wait for the other thread.
Example: thisisatest
Person1 Person2
--------- ----------
t 0
0 h
i 0
s 0
0 i
0 s
0 a
t 0
e 0
0 s
t 0
I suggest you test your program with a longer set of data files as we will
use a test set that may be up to 1000 characters (500 in each file).
The main program can only set the global flag and call the threads -
NOTHING ELSE! If you cheat by having the main program do anything that
circumvents the role of the threads you will receive a zero (0).
Your code cannot simply read the data files into an array and seperate
them - that would not be a critical section problem. You must read each
character (1 at a time) and append them on to the global character array
as each character is read.
This is tricky as your code might work once fine, but not the second time.
TEST YOUR CODE MULTIPLE TIMES!
SUGGESTIONS:
------------
1) See the man pages for PTHREAD_CREATE and PTHREAD_EXIT.
2) Don't forget to include the pthread library when you compile the
program (-lpthread).
3) Use a mutex. It will make things easier. See https://docs.oracle.com/
cd/E19683-01/806-6867/sync-12/index.html for a nice and simple example.
REQUIREMENTS:
-------------
1. Your program must run on Linux Mint (Leonard 110/112).
2. Your full name must appear as a comment at the beginning of your
program.
3. Your source code must be named hw3-yourname.c or hw3-yourname.cpp
4. The two data files MUST be named Person1 and Person2.
