System V semaphore——demo
代码
#include sys
/
types.h
>
#include sys
/
ipc.h
>
#include sys
/
sem.h
>
union semun{
int
val;
struct
semid_ds
*
buf;
unsigned
short
*
array;
struct
seminfo
*
__buf;
};
//
create the semaphore set,
//
if key is IPC_PRIVATE, the semaphore is anonymous
int
semaphore_create(key_t key,
int
number)
{
return
semget(key, number, IPC_CREAT
|
IPC_EXCL
|
0666
);
}
//
set all semaphores to val
int
semaphore_setAll(
int
semid,
int
number,
int
val)
{
int
i;
union semun initVal;
unsigned
short
valList[number];
for
(i
=
0
; i
<
number; i
++
)
{
valList[i]
=
val;
}
initVal.array
=
&
valList[
0
];
return
semctl(semid,
0
, SETALL, initVal);
}
//
get all semaphores to val
int
semaphore_getAll(
int
semid, unsigned
short
**
val)
{
union semun ret;
ret.array
=
*
val;
return
semctl(semid,
0
, GETALL, ret);
}
//
set index-th semaphore to val
int
semaphore_set(
int
semid,
int
index,
int
val)
{
union semun un;
un.val
=
val;
return
semctl(semid, index, SETVAL, un);
}
//
get index-th semaphore to val
int
semaphore_get(
int
semid,
int
index,
int
*
val)
{
union semun un;
un.val
=
*
val;
return
semctl(semid, index, GETVAL, un);
}
//
delete the semaphore set
int
semaphore_del(
int
semid)
{
return
semctl(semid,
0
, IPC_RMID);
}
//
v operation, here we just add one for example
int
semaphore_v(
int
semid,
int
index)
{
//
add the semaphore
struct
sembuf operation;
operation.sem_num
=
index;
operation.sem_op
=
1
;
operation.sem_flg
=
SEM_UNDO;
return
semop(semid,
&
operation,
1
);
}
//
p operation, here just del one for example
int
semaphore_p(
int
semid,
int
index)
{
struct
sembuf operation;
operation.sem_num
=
index;
operation.sem_op
=
-
1
;
operation.sem_flg
=
SEM_UNDO;
struct
timespec delay;
delay.tv_sec
=
2
;
delay.tv_nsec
=
0
;
return
semtimedop(semid,
&
operation,
1
,
&
delay);
}