PUTINFO(3PVM)

NAME
pvm_putinfo, pvm_recvinfo, pvm_getmboxinfo, pvm_delinfo - Store and retrieve messages in global mailbox.

SYNOPSIS
C	int index = pvm_putinfo( char *name, int bufid, int flags )
	int bufid = pvm_recvinfo( char *name, int index, int flags )
	int info = pvm_delinfo( char *name, int index, int flags )
	int info = pvm_getmboxinfo( char *pattern, int *nclasses,
	                            struct pvmmboxinfo **classes )

     struct pvmmboxinfo {
        char *mi_name;                /* class name */
        int   mi_nentries;            /* # of entries for this class */
        int  *mi_indices;             /* mbox entry indices */
        int  *mi_owners;              /* mbox entry owner tids */
        int  *mi_flags;               /* mbox entry flags */
     };

Fortran
	call pvmfputinfo( name, bufid, flags, index )
	call pvmfrecvinfo( name, index, flags, bufid )
	call pvmfdelinfo( name, index, flags, info )
	call pvmfgetmboxinfo( pattern, name, nclasses, nentries,
	                      index, owner, flags, info )

PARAMETERS

name
    Database key (class name), any null-terminated string.

index
    Database key (class index), >= 0. Default index = 0.

flags
    User specified options. (see below)

bufid
    Handle of message buffer to put in database, or message returned. A returned bufid < 0 indicates an error.

info
    Resulting status code.

pattern
    GNU regular expression (pattern) to match on names in mailbox database. Additionally, the singular "*" will match on all names.

nclasses
    Number of classes matching pattern.

classes
    Array of pvmmboxinfo mailbox entries matching pattern.

nentries
    Number of entries for a given class.

owner
    Task id that inserted entry into mailbox database.

DESCRIPTION

These functions implement a "message mailbox" database that can be used by PVM tasks to advertise information to other PVM tasks. An example would be to advertise names or locations of services. Another example would be to advertise a common "context" on which two tasks may communicate.

The database entries are PVM messages keyed by a user specified name and an optional index value. The name may be any null-terminated string and the index a non-negative integer. The index value is assigned by PVM and is used to uniquely identify one of multiple named instances within the database.

Entries are "owned" by the task that created them. An entry is automatically removed from the database when the owner task exits unless the database entry was created with flag PvmMboxPersistent.

When a task exits and leaves an entry in the mailbox, the owner tid of that entry is marked as zero (0) to indicate that there is no longer an active owner task.

pvm_putinfo inserts a record in the database, given a key and data (message). It returns mailbox index number if the record is successfully stored, PvmExists if a record with the given key already exists, or PvmDenied if an attempt is made to overwrite a locked record.

The following options are added together as the flags parameter to pvm_putinfo.

PvmMboxDefault
    Inserts entry as the only named instance for a given name. This entry may only be modified and deleted by its owner. It is automatically deleted when its owner exits.

PvmMboxPersistent
    Entry remains in the database when the owner task exits. Entries are removed from the database when PVM is halted or a reset is issued from the console.

PvmMboxMultiInstance
    Permits multiple entry instances of the same name. PVM will assign an index key to each instance.

PvmMboxOverWritable
    Permits other tasks to overwrite and delete this database entry.

PvmMboxDirectIndex( index )
    Performs an atomic delete and re-insert for the mailbox entry at the given index. Valid index values for this macro are limited to the range [ 0 .. PvmMboxMaxDirectIndex ). The given mailbox entry must have been created with the PvmMboxOverWritable flag set. If index is greater than 0, then the mailbox must also have been created with the PvmMboxMultiInstance flag set.

pvm_recvinfo operates just like a pvm_recv() except the message is coming from the database. The message should be unpacked after pvm_recvinfo(). Like pvm_recv, pvm_recvinfo returns a pointer to a message buffer containing the record matching the key <name,index> from the database. Returned value < 0 indicates an error.

The following options are added together as the flags parameter to pvm_recvinfo.

PvmMboxDefault
    Exact match on key <name, index> is returned. Returns PvmNotFound if exact match not found.

PvmMboxFirstAvail
    The first entry in <name> with index greater than or equal to the specified index parameter is retuned. PvmMboxFirstAvail with index = 0 will produce the same results as using PvmMboxDefault.

PvmMboxReadAndDelete
    Return entry and delete from database. Task must be permitted to do both read and delete otherwise an error will occur. bufid returns PvmNotFound if entry does not exist and will return PvmDenied if the record exists but may not be deleted.

pvm_delinfo deletes database entry specified by the key <name, index>. Returns PvmOK if the record was deleted, PvmNotFound if the record does not exist, or PvmDenied if an attempt is made to remove a "locked" record.

There are no flags presently specified for pvm_delinfo.

pvm_getmboxinfo returns an array of pvmmboxinfo for all class names in the database. This is used, for example, by programs that clean up the database or for applications to find out what is available. classes returns a pointer to the array allocated by libpvm and freed on the next call to pvm_getmboxinfo.

The Fortran function returns information on one entry per call. Thus, if called repeatedly until an info value of PvmNotFound is returned, all entries matching the given pattern will have been returned. If a new pattern is desired, calling pvmfgetnames() with info = -1 will reset the entry name list and obtain a new list for the given pattern.

EXAMPLES
C:
	/*
	*  create and insert mailbox entry
	*/
	sprintf( service, "Task_A_service" );
	sprintf( message, "Greetings from task A." );
	pvm_initsend( PvmDataDefault );
	pvm_pkint( &mytid, 1, 1 );
	pvm_pkint( &context, 1, 1 );
	pvm_pkstr( message );
	if (( pvm_putinfo( service, pvm_getsbuf(), PvmMboxDefault )) == PvmExists ){
		printf( "can't register - service already running );
		exit( -1 );
	}

	/*
	*  look for and retrieve specified mailbox
	*/
	sprintf( service, "Task_A_service" );
	if (( msg_buf = pvm_recvinfo(service, 0, PvmMboxFirstAvail )) >= 0 ){
		pvm_setrbuf( msg_buf );
		pvm_upkint( &their_tid, 1, 1 );
		pvm_upkint( &their_context, 1, 1 );
		pvm_upkstr( message );
	}

Fortran:
	we need the fortran examples...

ERRORS
The following error conditions can be returned by one or more of these functions:

PvmBadParam
    An invalid value was specified for bufid argument.

PvmNoSuchBuf
    Message buffer bufid doesn't exist.

PvmNoMem
    Libpvm is unable to allocate memory to pack data.

PvmExists
    The requested key is already in use (pvm_putinfo).

PvmNotFound
    The requested key does not exist (pvm_recvinfo, pvm_delinfo).

PvmDenied
    The key is locked by another task and cannot be replaced or deleted.

SEE ALSO
pvm_initsend(3PVM), pvm_getsbuf(3PVM), pvm_pack(3PVM),