In C$/$C$++$ The project will require learning three Unix techniques: forking a child, using POSIX semaphores, using POSIX shared memory. The program should create named semaphores which both parent and child can access. It should then create a block of shared memory that will serve as a shared buffer. The producer should begin placing numbers $1$ to $100$ into the shared buffer while the consumer begins getting the numbers out of the buffer and printing them. The actions should be coordinated using semaphores, as shown in slides $34$ and $35$ of the chapter $6$ slides. The buffer should hold $5$ numbers. Examples of the three needed techniques will be in eLearning.

SLIDES $34$ & $35$

do $\{$

$.../*$ produce an item in next$\_$produced $*/$

$...$

wait$($empty$)$;

wait$($mutex$)$;

$.../*$ add next produced to the buffer $*/$

$...$

signal$($mutex$)$;

signal$($full$)$;

$\}$ while $($true$)$;

Do $\{$

wait$($full$)$;

wait$($mutex$)$;

$.../*$ remove an item from buffer to next$\_$consumed $*/$

$...$

signal$($mutex$)$;

signal$($empty$)$;

$.../*$ consume the item in next consumed $*/$

$...\}$ while $($true$)$;

ADDITIONAL CODE ALSO NEEDED:

int main$()$

$\{$

pid$\_$t pid;

const char $*$semname $="/$delay$"$;

sem$\_$t $*$semaphore $=$ sem$\_$open$($semname$,$ O$\_$CREAT $|$ O$\_$EXCL, $0600,0)$;

if $($semaphore $==$ SEM$\_$FAILED$)$

$\{$

printf$("$Create semaphore

$")$;

exit$(1)$;

$\}$

switch $($pid $=$ fork$())$

$\{$

case $-1$:

cout $<<$ "The fork failed!";

exit$(-1)$;

case $0$:

if $($sem$\_$wait $($semaphore$)==-1)$

$\{$

printf$("$Wait on semaphore

$")$;

exit$(1)$;

$\}$

cout $<<$ "Child: hello!

$"$;

$\_$exit$(0)$;

default:

cout $<<$ "Parent running...

$"$;

if $($sem$\_$post $($semaphore$)==-1)$

$\{$

printf$("$Post semaphore

$")$;

exit$(1)$;

$\}$

waitpid$(-1,$ NULL, $0)$;

if $($sem$\_$close$($semaphore$)==-1)$

$\{$

printf$("$Close semaphore

$")$;

exit$(1)$;

$\}$

if $($sem$\_$unlink$($semname$)==-1)$

$\{$

printf$("$Unlink semaphore

$")$;

exit$(1)$;

$\}$

$\}$

$\}$

int main$()$

$\{$

pid$\_$t pid;

const char $*$shmname $="/$myshare$"$;

int sharefd $=$ shm$\_$open$($shmname$,$ O$\_$CREAT $|$ O$\_$RDWR$,0600)$;

if $($sharefd $==-1)$

$\{$

printf$("$Create shared memory failed

$")$;

exit$(1)$;

$\}$

int trunc $=$ ftruncate$($sharefd$,$ sizeof$($int$))$;

if $($trunc $==-1)$

$\{$

printf$("$Truncate failed

$")$;

exit$(1)$;

$\}$

void $*$ptr $=$ mmap$(0,$ sizeof$($int$),$ PROT$\_$READ $|$ PROT$\_$WRITE, MAP$\_$SHARED, sharefd, $0)$;

if $($ptr $==$ MAP$\_$FAILED$)$

$\{$

printf$("$mmap failed

$")$;

exit$(1)$;

$\}$

int $*$iptr $=($int$*)$ptr;

switch $($pid $=$ fork$())$

$\{$

case $-1$:

cout $<<$ "The fork failed!";

exit$(-1)$;

case $0$:

$\{$

sleep$(2)$; $//$ use semaphore instead

int x $=*$iptr;

cout $<<$ "Child read $"<<$ x $<<$ endl;

$\}$

$\_$exit$(0)$;

default:

$\{$

int y $=5$;

$*$iptr $=$ y;

$\}$

waitpid$(-1,$ NULL, $0)$;

if $($shm$\_$unlink$($shmname$)==-1)$

$\{$

printf$("$Unlink shm

$")$;

exit$(1)$;

$\}$

$\}$

$\}$