Process, System-V, and POSIX libraries wrapper module. More...

Files
file	process.h
	Process, System-V, and POSIX libraries wrapper module.

Process handling

pid_t	pfork (void)
	`fork` wrapper function. More...

pid_t	pwait (int *status)
	`wait` wrapper function. More...

pid_t	pwaitpid (pid_t pid, int *status, int options)
	`waitpid` wrapper function. More...

System V - shared memory
Example #include <sys/shm.h> ... int shmid; // creation: shmid = pshmget(key, size, 0600 \| IPC_CREAT \| IPC_EXCL); // or, use existing: shmid = pshmget(key, 0, 0); ... // attach shm to pointer address: void* p = pshmat(shmid, NULL, 0); ... // detach shm from pointer address: pshmdt(p); ... // destroy shm: pshmctl(shmid, IPC_RMID, NULL);
int	pshmget (key_t key, size_t size, int shmflg)
	`shmget` wrapper function. More...

int	pshmctl (int shmid, int cmd, struct shmid_ds *buf)
	`shmctl` wrapper function. More...

void *	pshmat (int shmid, const void *shmaddr, int shmflg)
	`shmat` wrapper function. More...

void	pshmdt (const void *shmaddr)
	`shmdt` wrapper function. More...

System V - semaphores
Example #include <sys/sem.h> ... int semid; // creation: semid = psemget(key, 1, 0600 \| IPC_CREAT \| IPC_EXCL); // 1 semaphore! // or, use existing: semid = psemget(key, 0, 0); ... // lock: struct sembuf down = {0, -1, 0}; psemop(semid, &down, 1); // or, simply use provided function: psem_down(semid, 0); ... //unlock: struct sembuf up = {0, 1, 0}; psemop(semid, &up, 1); // or, simply use provided function: psem_up(semid, 0); ... // destroy sem 0: psemctl(semid, 0, IPC_RMID, NULL);
int	psemget (key_t key, int nsems, int semflg)
	`semget` wrapper function. More...

int	psemctl (int semid, int semnum, int cmd)
	`semctl` wrapper function. More...

int	psemctl (int semid, int semnum, int cmd, void *u)

void	psemop (int semid, struct sembuf *sops, size_t nsops)
	`semop` wrapper function. More...

void	psem_up (int semid, short unsigned int index)
	Increment a semaphore (uses psemop()).

void	psem_down (int semid, short unsigned int index)
	Decrements a semaphore (uses psemop()).

System V - message queues
Example #include <sys/msg.h> ... typedef struct Item { ... } Item; typedef struct Message { long type; Item item; } Message; ... int msgid; // creation: msgid = pmsgget(key, 0600 \| IPC_CREAT \| IPC_EXCL); // or, use existing: msgid = pmsgget(key, 0); ... Message msg; // send msg: msg = ...; pmsgsnd(msgid, &msg, sizeof(Item), 0); ... // receive msg: pmsgrcv(msgid, &msg, sizeof(Item), type, 0); ... // destroy msg: pmsgctl(msgid, IPC_RMID, NULL);
int	pmsgget (key_t key, int msgflg)
	`msgget` wrapper function. More...

int	pmsgctl (int msqid, int cmd, struct msqid_ds *buf)
	`msgctl` wrapper function. More...

void	pmsgsnd (int msqid, const void *msgp, size_t msgsz, int msgflg)
	`msgsnd` wrapper function. More...

size_t	pmsgrcv (int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg)
	`msgrcv` wrapper function. More...

POSIX semaphores

sem_t *	psem_open (const char *name, int oflag)
	`sem_open` wrapper function. More...

sem_t *	psem_open (const char *name, int oflag, mode_t mode, unsigned int value)

void	psem_close (sem_t *sem)
	`sem_close` wrapper function. More...

void	psem_unlink (const char *name)
	`sem_unlink` wrapper function. More...

void	psem_init (sem_t *sem, int pshared, unsigned int value)
	`sem_init` wrapper function. More...

void	psem_destroy (sem_t *sem)
	`sem_destroy` wrapper function. More...

void	psem_wait (sem_t *sem)
	`sem_wait` wrapper function. More...

int	psem_trywait (sem_t *sem)
	`sem_trywait` wrapper function. More...

int	psem_timedwait (sem_t sem, const struct timespec abs_timeout)
	`sem_timedwait` wrapper function. More...

void	psem_post (sem_t *sem)
	`sem_post` wrapper function. More...

Detailed Description

Process, System-V, and POSIX libraries wrapper module.

This module removes defensive programming approach of native libraries.

All implemented functions, have exactly the same arguments and/or result of the original function, with the exception of returning an error indication.

Errors are handled by the implementation of two policies:

EXIT_POLICY (default): describes the failed call in stderr (with the identification of the errno error, and the precise location the call), generates a segmentation fault (enabling a stack trace within a debugger like gdb), and exits program execution;
EXCEPTION_POLICY: throws a int exception with the (errno) status error returned by the original function.

System V group of IPC mechanisms

There are three resources for IPC: shared memory, semaphores, and message queues.

Common to all, is resource handling through a non-negative integer identifier. After proper creation and initialization, different processes can establish communication using the same integer identifier.

A key (key_t) is used to establish this common identifier. There are three possibilities to define a key:

IPC_PRIVATE: In this case an alternative channel to communicate the identifier between processes is necessary (parent/child fork, file system, ...).
A fixed predetermined key number (may collide with other existing keys).
ftok function to generate a key from a path and a byte integer.

Usage:

create new identifier: msgget/semget/shmget with a key and IPC_CREAT and IPC_EXCL flags
get existing identifier: msgget/semget/shmget with a key and other arguments as zero

Author: Miguel Oliveira e Silva, 2017-2018

Function Documentation

◆ pfork()

pid_t pfork ( void )

fork wrapper function.

Documentation in

man 2 fork

See also: https://man.cx/fork(2)

◆ pwait()

pid_t pwait ( int * status )

wait wrapper function.

Documentation in

man 2 wait

See also: https://man.cx/wait(2)

◆ pwaitpid()

pid_t pwaitpid	(	pid_t	pid,
		int *	status,
		int	options
	)

waitpid wrapper function.

Documentation in

man 2 waitpid

See also: https://man.cx/waitpid(2)

◆ pshmget()

int pshmget	(	key_t	key,
		size_t	size,
		int	shmflg
	)

shmget wrapper function.

Precondition:: (size > 0) || !(shmflg & IPC_CREAT)

Documentation in

man 2 shmget

See also: https://man.cx/shmget(2)

◆ pshmctl()

int pshmctl	(	int	shmid,
		int	cmd,
		struct shmid_ds *	buf
	)

shmctl wrapper function.

Documentation in

man 2 shmctl

See also: https://man.cx/shmctl(2)

◆ pshmat()

void* pshmat	(	int	shmid,
		const void *	shmaddr,
		int	shmflg
	)

shmat wrapper function.

Documentation in

man 2 shmat

See also: https://man.cx/shmat(2)

◆ pshmdt()

void pshmdt ( const void * shmaddr )

shmdt wrapper function.

Documentation in

man 2 shmdt

See also: https://man.cx/shmdt(2)

◆ psemget()

int psemget	(	key_t	key,
		int	nsems,
		int	semflg
	)

semget wrapper function.

Precondition:: nsems > 0

Documentation in

man 2 semget

See also: https://man.cx/semget(2)

◆ psemctl()

int psemctl	(	int	semid,
		int	semnum,
		int	cmd
	)

semctl wrapper function.

Documentation in

man 2 semctl

See also: https://man.cx/semctl(2)

◆ psemop()

void psemop	(	int	semid,
		struct sembuf *	sops,
		size_t	nsops
	)

semop wrapper function.

Documentation in

man 2 semop

See also: https://man.cx/semop(2)

◆ pmsgget()

int pmsgget	(	key_t	key,
		int	msgflg
	)

msgget wrapper function.

Documentation in

man 2 msgget

See also: https://man.cx/msgget(2)

◆ pmsgctl()

int pmsgctl	(	int	msqid,
		int	cmd,
		struct msqid_ds *	buf
	)

msgctl wrapper function.

Documentation in

man 2 msgctl

See also: https://man.cx/msgctl(2)

◆ pmsgsnd()

void pmsgsnd	(	int	msqid,
		const void *	msgp,
		size_t	msgsz,
		int	msgflg
	)

msgsnd wrapper function.

Documentation in

man 2 msgsnd

See also: https://man.cx/msgsnd(2)

◆ pmsgrcv()

size_t pmsgrcv	(	int	msqid,
		void *	msgp,
		size_t	msgsz,
		long	msgtyp,
		int	msgflg
	)

msgrcv wrapper function.

Documentation in

man 2 msgrcv

See also: https://man.cx/msgrcv(2)

◆ psem_open()

sem_t* psem_open	(	const char *	name,
		int	oflag
	)

sem_open wrapper function.

Documentation in

man 3 sem_open

See also: https://man.cx/sem_open(3)

◆ psem_close()

void psem_close ( sem_t * sem )

sem_close wrapper function.

Precondition:: sem != NULL

Documentation in

man 3 sem_close

See also: https://man.cx/sem_close(3)

◆ psem_unlink()

void psem_unlink ( const char * name )

sem_unlink wrapper function.

Documentation in

man 3 sem_unlink

See also: https://man.cx/sem_unlink(3)

◆ psem_init()

void psem_init	(	sem_t *	sem,
		int	pshared,
		unsigned int	value
	)

sem_init wrapper function.

Precondition:: sem != NULL

Documentation in

man 3 sem_init

See also: https://man.cx/sem_init(3)

◆ psem_destroy()

void psem_destroy ( sem_t * sem )

sem_destroy wrapper function.

Precondition:: sem != NULL

Documentation in

man 3 sem_destroy

See also: https://man.cx/sem_destroy(3)

◆ psem_wait()

void psem_wait ( sem_t * sem )

sem_wait wrapper function.

Precondition:: sem != NULL

Documentation in

man 3 sem_wait

See also: https://man.cx/sem_wait(3)

◆ psem_trywait()

int psem_trywait ( sem_t * sem )

sem_trywait wrapper function.

Precondition:: sem != NULL

Documentation in

man 3 sem_trywait

See also: https://man.cx/sem_trywait(3)

Returns: true (!=0) on success, false (0) if semaphore is zero

◆ psem_timedwait()

int psem_timedwait	(	sem_t *	sem,
		const struct timespec *	abs_timeout
	)

sem_timedwait wrapper function.

Precondition:: sem != NULL

Documentation in

man 3 sem_timedwait

See also: https://man.cx/sem_timedwait(3)

Returns: true (!=0) on success, false (0) if timeout has expired before being able to decrement the semaphore

◆ psem_post()

void psem_post ( sem_t * sem )

sem_post wrapper function.

Precondition:: sem != NULL

Documentation in

man 3 sem_post

See also: https://man.cx/sem_post(3)

Files

Process handling

System V - shared memory

System V - semaphores

System V - message queues

POSIX semaphores

Detailed Description

Function Documentation

◆ pfork()

◆ pwait()

◆ pwaitpid()

◆ pshmget()

◆ pshmctl()

◆ pshmat()

◆ pshmdt()

◆ psemget()

◆ psemctl()

◆ psemop()

◆ pmsgget()

◆ pmsgctl()

◆ pmsgsnd()

◆ pmsgrcv()

◆ psem_open()

◆ psem_close()

◆ psem_unlink()

◆ psem_init()

◆ psem_destroy()

◆ psem_wait()

◆ psem_trywait()

◆ psem_timedwait()

◆ psem_post()