port_associate

, port_dissociate

- associate or dissociate the object with the port

Synopsis

#include <port.h>

int port_associate(int port, int source, uintptr_t object,
     int events, void *user);

int port_dissociate(int port, int source, uintptr_t object);

Description

The port_associate() function associates specific events of a given object with a port. Only objects associated with a particular port are able to generate events that can be retrieved using port_get(3C) or port_getn(3C). The delivery event has its portev_user member set to the value specified in the user parameter. If the specified object is already associated with the specified port, the port_associate() function serves to update the events and user arguments of the association. The port_dissociate() function removes the association of an object with a port.

The objects that can be associated with a port by way of the port_associate() function are objects of type PORT_SOURCE_FD and PORT_SOURCE_FILE. Objects of other types have type-specific association mechanisms. A port_notify_t structure, defined in <port.h>, is used to specify the event port and an application-defined cookie to associate with these event sources. See port_create(3C) and signal.h(3HEAD).

The port_notify_t structure contains the following members:

int       portntfy_port;  /* bind request(s) to port */
void      *portntfy_user; /* user defined cookie */

Objects of type PORT_SOURCE_FD are file descriptors. The event types for PORT_SOURCE_FD objects are described in poll(2). At most one event notification will be generated per associated file descriptor. For example, if a file descriptor is associated with a port for the POLLRDNORM event and data is available on the file descriptor at the time the port_associate() function is called, an event is immediately sent to the port. If data is not yet available, one event is sent to the port when data first becomes available.

When an event for a PORT_SOURCE_FD object is retrieved, the object no longer has an association with the port. The event can be processed without the possibility that another thread can retrieve a subsequent event for the same object. After processing of the file descriptor is completed, the port_associate() function can be called to reassociate the object with the port.

Objects of type PORT_SOURCE_FILE are pointer to the structure file_obj defined in <sys/port.h>. This event source provides event notification when the specified file/directory is accessed or modified or when its status changes. The path name of the file/directory to be watched is passed in the struct file_obj along with the access, modification, and change time stamps acquired from a stat(2) call. If the file name is a symbolic links, it is followed by default. The FILE_NOFOLLOW needs to be passed in along with the specified events if the symbolic link itself needs to be watched and lstat() needs to be used to get the file status of the symbolic link file.

The struct file_obj contains the following elements:

timestruc_t     fo_atime;  /* Access time got from stat() */
timestruc_t     fo_mtime;  /* Modification time from stat() */
timestruc_t     fo_ctime;  /* Change time from stat() */
char            *fo_name;  /* Pointer to a null terminated path name */

At the time the port_associate() function is called, the time stamps passed in the structure file_obj are compared with the file or directory's current time stamps and, if there has been a change, an event is immediately sent to the port. If not, an event will be sent when such a change occurs.

The event types that can be specified at port_associate() time for PORT_SOURCE_FILE are FILE_ACCESS, FILE_MODIFIED, and FILE_ATTRIB, corresponding to the three time stamps. An fo_atime change results in the FILE_ACCESS event, an fo_mtime change results in the FILE_MODIFIED event, and an fo_time change results in the FILE_ATTRIB event.

The following exception events are delivered when they occur. These event types cannot be filtered.

FILE_DELETE       /* Monitored file/directory was deleted */
FILE_RENAME_TO    /* Monitored file/directory was renamed */
FILE_RENAME_FROM  /* Monitored file/directory was renamed */
UNMOUNTED         /* Monitored file system got unmounted */
MOUNTEDOVER       /* Monitored file/directory was mounted over */

At most one event notification will be generated per associated file_obj. When the event for the associated file_obj is retrieved, the object is no longer associated with the port. The event can be processed without the possibility that another thread can retrieve a subsequent event for the same object. The port_associate() can be called to reassociate the file_obj object with the port.

The association is also removed if the port gets closed or when port_dissociate() is called.

The parent and child processes are allowed to retrieve events from file descriptors shared after a call to fork(2). The process performing the first association with a port (parent or child process) is designated as the owner of the association. Only the owner of an association is allowed to dissociate the file descriptor from a port. The association is removed if the owner of the association closes the port .

On NFS file systems, events from only the client side (local) access/modifications to files or directories will be delivered.

Return Values

Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.

Errors

The port_associate() and port_dissociate() functions will fail if:

EBADF

The port identifier is not valid.

EBADFD

The source argument is of type PORT_SOURCE_FD and the object argument is not a valid file descriptor.

EINVAL

The source argument is not valid.

The port_associate() function will fail if:

EACCES

The source argument is PORT_SOURCE_FILE and, Search permission is denied on a component of path prefix or the file exists and the permissions, corresponding to the events argument, are denied.

EAGAIN

The maximum number of objects associated with the port was exceeded. The maximum allowable number of events or association of objects per port is the minimum value of the process.max-port-events resource control at the time port_create(3C) was used to create the port. See setrctl(2) and rctladm(1M) for information on using resource controls.

The number of objects associated with a port is composed of all supported resource types. Some of the source types do not explicitly use the port_associate() function.

ENOENT

The source argument is PORT_SOURCE_FILE and the file does not exist or the path prefix does not exist or the path points to an empty string.

ENOMEM

The physical memory limits of the system have been exceeded.

ENOTSUP

The source argument is PORT_SOURCE_FILE and the file system on which the specified file resides, does not support watching for file events notifications.

The port_dissociate() function will fail if:

EACCES

The process is not the owner of the association.

ENOENT

The specified object is not associated with the port.

Examples

Example 1 Retrieve data from a pipe file descriptor.

The following example retrieves data from a pipe file descriptor.

#include <port.h>

int               port;
int               fd;
int               error;
int               index;
void              *mypointer;
port_event_t      pev;
struct timespec_t timeout;
char              rbuf[STRSIZE];
int               fds[MAXINDEX];

/* create a port */
port = port_create();

for (index = 0; index < MAXINDEX; index++) {
    error = mkfifo(name[index], S_IRWXU | S_IRWXG | S_IRWXO);
    if (error)
            /* handle error code */
    fds[index] = open(name[index], O_RDWR);

    /* associate pipe file descriptor with the port */
    error = port_associate(port, PORT_SOURCE_FD, fds[index],
        POLLIN, mypointer);
}
...
timeout.tv_sec = 1;     /* user defined */
timeout.tv_nsec = 0;

/* loop to retrieve data from the list of pipe file descriptors */
for (...) {
    /* retrieve a single event */
    error = port_get(port, &pev, &timeout);
    if (error) {
            /* handle error code */
    }
    fd = pev.portev_object;
    if (read(fd, rbuf, STRSIZE)) {
            /* handle error code */
    }
    if (fd-still-accepting-data) {
            /*
             * re-associate the file descriptor with the port.
             * The re-association is required for the
             * re-activation of the data detection.
             * Internals events and user arguments are set to the
             * new (or the same) values delivered here.
             */
            error = port_associate(port, PORT_SOURCE_FD, fd, POLLIN,
                pev.portev_user);
    } else {
            /*
             * If file descriptor is no longer required,
             * - it can remain disabled but still associated with
             *   the port, or
             * - it can be dissociated from the port.
             */
        }

Example 2 Bind AIO transaction to a specific port.

The following example binds the AIO transaction to a specific port.

#include <port.h>

int             port;
port_notify_t   pn;
aiocb_t         aiocb;
aiocb_t         *aiocbp;
void            *mypointer;
int             error;
int             my_errno;
int             my_status;
struct timespec_t timeout;
port_event_t    pev;

port = port_create();
...
/* fill AIO specific part */
aiocb.aio_fildes = fd;
aiocb.aio_nbytes = BUFSIZE;
aiocb.aio_buf = bufp;
aiocb.aio_offset = 0;

/* port specific part */
pn.portnfy_port = port;
pn.portnfy_user = mypointer;
aiocb.aio_sigevent.sigev_notify = SIGEV_PORT;
aiocb.aio_sigevent.sigev_value.sival_ptr = &pn

/*
 * The aio_read() function binds internally the asynchronous I/O
 * transaction with the port delivered in port_notify_t.
 */
error = aio_read(&aiocb);

timeout.tv_sec = 1;     /* user defined */
timeout.tv_nsec = 0;

/* retrieve a single event */
error = port_get(port, &pev, &timeout);
if (error) {
        /* handle error code */
}

/*
 * pev.portev_object contains a pointer to the aiocb structure
 * delivered in port_notify_t (see aio_read()).
 */
aiocbp = pev.portev_object;

/* check error code and return value in
my_errno = aio_error(aiocbp);
...
my_status = aio_return(aiocbp);
...

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

rctladm(1M), poll(2), setrctl(2), port_alert(3C), port_create(3C), port_get(3C), port_send(3C), signal.h(3HEAD), attributes(5)