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.TH EVS_MCAST_GROUPS 3 2004-08-31 "corosync Man Page" "Corosync Cluster Engine Programmer's Manual"
.SH NAME
evs_join \- Multicast a message to selected groups
.SH SYNOPSIS
.B #include <sys/uio.h>
.B #include <corosync/evs.h>
.sp
.BI "int evs_mcast_groups(evs_handle_t " handle ", evs_guraantee_t " guarantee ", evs_group_t *" groups ", int group_entries, struct iovec *" iovec ", int " iov_len ");
.SH DESCRIPTION
The
.B evs_mcast_groups(3)
function multicasts a message to all the groups specified in the arguemnt
.I groups.
Messages are delivered to all processors in the system that are described by the current
configuration.
.PP
The argument
.I handle
describes a handle created with
.B evs_initialize(3).
.PP
The argument
.I guarantee
requests a delivery guarantee for the message to be sent.  The evs_guarantee_t type is
defined by:
.IP
.RS
.ne 18
.nf
.ta 4n 30n 33n
typedef enum {
	EVS_TYPE_UNORDERED,	/* not implemented */
	EVS_TYPE_FIFO,          /* same as agreed */
	EVS_TYPE_AGREED,	/* implemented */
	EVS_TYPE_SAFE           /* not implemented */
} evs_guarantee_t;
.ta
.fi
.RE
.IP
.PP
.PP
The meanings of the evs_guarantee_t typedef are:
.TP
.B EVS_GUARANTEE_UNORDERED
Messages are guaranteed to be delivered, but with no particular order.  This
mode is unimplemented in the EVS library.
.TP
.B EVS_GUARANTEE_FIFO
Messages are guaranteed to be delivered in first sent first delivery order
from one one.  In fact, this guarantee is actually the AGREED guarantee.
.TP
.B EVS_GUARANTEE_AGREED
All processors must agree on the order of delivery.  If a message is sent
from two or more processors at about the same time, the delivery will occur
in the same order to all processors.
.TP
.B EVS_GUARANTEE_SAFE
All processors must agree on the order of delivery.  Further all processors
must have a copy of the message before any delivery takes place.  This mode is
unimplemented in the EVS library.
.PP
The
.I groups
argument is of the type evs_group_t which is defined by the structure:

.IP
.RS
.ne 18
.nf
.ta 4n 30n 33n
typedef struct {
	char key[32];
} evs_groups_t;
.ta
.fi
.RE
.IP
.PP
.PP
The
.I group_entries
argument describes the number of entries in the
.I group
argument.
.PP

The
.I iovec
argument describes the scatter/gather list which is used to transmit a message.  This
is a standard socket structure described by:
.IP
.RS
.ne 18
.nf
.ta 4n 30n 33n
struct iovec
{
	void *iov_base;     /* Pointer to data.  */
	unsigned int iov_len;     /* Length of data.  */
};
.ta
.fi
.RE
.IP
.PP
.PP
The
.I iovlen
argument describes the number of entires in the
.I iovec
argument.

.SH RETURN VALUE
This call returns the EVS_OK value if successful, otherwise an error is returned.
.PP
.SH ERRORS
The errors are undocumented.
.SH "SEE ALSO"
.BR evs_overview (8),
.BR evs_initialize (3),
.BR evs_finalize (3),
.BR evs_fd_get (3),
.BR evs_dispatch (3),
.BR evs_leave (3),
.BR evs_join (3),
.BR evs_mcast_joined (3),
.BR evs_membership_get (3)
.BR evs_context_get (3)
.BR evs_context_set (3)
.PP