This is the first check-in of support for groups.

It's very early (it doesn't actually do anything yet!) but you can
define groups and get an idea of how the interface is shaping up.
I also wanted to show that I have actually done something on this! :-)

From here my plan is to add group support to the modules, one by one
(forums first), then go back and clean up some of the central interfaces,
graphics etc.

Finally, test, test, test and get 1.2 out well before the end of February.

lib/datalib.php

@@ -945,6 +945,13 @@ function get_user_info_from_db($field, $value) {
         }
     }
 
+    if ($groups = get_records("group_members", "userid", $user->id)) {
+        foreach ($groups as $group) {
+            $courseid = get_field("group", "courseid", "id", $group->id);
+            $user->groupmember[$courseid] = $group->id;
+        }
+    }
+
     return $user;
 }
 
@@ -1418,6 +1425,69 @@ function get_users_longtimenosee($cutofftime) {
                                AND timeaccess < '$cutofftime' ");
 }
 
+/**
+* Returns an array of group objects that the user is a member of
+* in the given course.  If userid isn't specified, then return a 
+* list of all groups in the course.
+* 
+* @param	type description
+*/
+function get_groups($courseid, $userid=0) {
+    global $CFG;
+
+    if ($userid) {
+        $userselect = "AND m.groupid = g.id AND m.userid = '$userid'";
+    }
+
+    return get_records_sql("SELECT DISTINCT g.*
+                              FROM {$CFG->prefix}group g,
+                                   {$CFG->prefix}group_members m 
+                             WHERE g.courseid = '$courseid' $userselect ");
+}
+
+
+/**
+* Returns an array of user objects
+* 
+* @param	type description
+*/
+function get_users_in_group($groupid) {
+    global $CFG;
+    return get_records_sql("SELECT DISTINCT u.*
+                              FROM {$CFG->prefix}user u,
+                                   {$CFG->prefix}group_members m 
+                             WHERE m.groupid = '$groupid'
+                               AND m.userid = u.id");
+}
+
+/**
+* An efficient way of finding all the users who aren't in groups yet
+* 
+* @param	type description
+*/
+function get_users_not_in_group($courseid) {
+    global $CFG;
+
+    return array();     /// XXX TO BE DONE
+}
+
+/**
+* Returns the user's group in a particular course
+* 
+* @param	type description
+*/
+function user_group($courseid, $userid) {
+    global $CFG;
+
+    return get_record_sql("SELECT g.*
+                             FROM {$CFG->prefix}group g,
+                                  {$CFG->prefix}group_members m
+                             WHERE g.courseid = '$courseid'
+                               AND g.id = m.groupid
+                               AND m.userid = '$userid'");
+}
+
+
 
 
 /// OTHER SITE AND COURSE FUNCTIONS /////////////////////////////////////////////