diff options
Diffstat (limited to '')
| -rw-r--r-- | courses.go | 53 |
1 files changed, 18 insertions, 35 deletions
@@ -94,24 +94,9 @@ func checkCourseGroup(cg courseGroupT) bool { return courseGroups[cg] } -/* - * The courses are simply stored in a map indexed by the course ID, although - * the course struct itself also contains an ID field. A lock is embedded - * inside the struct; we use a lock here instead of a pointer to a lock as - * it would be easy to forget to initialize the lock when creating the - * struct. However, this means that the struct could not be copied (though - * this should only ever happen during creation anyways), therefore we use a - * pointer to the struct as the value of the map, instead of the struct itself. - */ -var courses map[int](*courseT) +var courses sync.Map /* int, *courseT */ -/* - * This RWMutex is only for massive modifications of the course struct, since - * locking it on every write would be inefficient; in normal operation the only - * write that could occur to the courses struct is changing the Selected - * number, which should be handled with courseT.SelectedLock. - */ -var coursesLock sync.RWMutex +var numCourses uint32 /* * Read course information from the database. This should be called during @@ -119,11 +104,6 @@ var coursesLock sync.RWMutex * a null pointer dereference. */ func setupCourses() error { - coursesLock.Lock() - defer coursesLock.Unlock() - - courses = make(map[int](*courseT)) - rows, err := db.Query( context.Background(), "SELECT id, nmax, title, ctype, cgroup, teacher, location FROM courses", @@ -184,7 +164,8 @@ func setupCourses() error { err, ) } - courses[currentCourse.ID] = ¤tCourse + courses.Store(currentCourse.ID, ¤tCourse) + atomic.AddUint32(&numCourses, 1) } return nil @@ -231,11 +212,19 @@ func populateUserCourseGroups( ) } var thisGroupName courseGroupT - func() { - coursesLock.RLock() - defer coursesLock.RUnlock() - thisGroupName = courses[thisCourseID].Group - }() + _course, ok := courses.Load(thisCourseID) + if !ok { + return fmt.Errorf( + "%w: %d", + errNoSuchCourse, + thisCourseID, + ) + } + course, ok := _course.(*courseT) + if !ok { + panic("courses map has non-\"*courseT\" items") + } + thisGroupName = course.Group if _, ok := (*userCourseGroups)[thisGroupName]; ok { return fmt.Errorf( "%w: user %v, group %v", @@ -258,7 +247,7 @@ func (course *courseT) decrementSelectedAndPropagate( defer course.SelectedLock.Unlock() atomic.AddUint32(&course.Selected, ^uint32(0)) }() - go propagateSelectedUpdate(course.ID) + go propagateSelectedUpdate(course) err := sendSelectedUpdate(ctx, conn, course.ID) if err != nil { return fmt.Errorf( @@ -269,9 +258,3 @@ func (course *courseT) decrementSelectedAndPropagate( } return nil } - -func getCourseByID(courseID int) *courseT { - coursesLock.RLock() - defer coursesLock.RUnlock() - return courses[courseID] -} |