// Returns of all the changes made to multiple channels.
func (db *Database) MultiChangesFeed(chans channels.Set, options ChangesOptions) (<-chan *ChangeEntry, error) {
if len(chans) == 0 {
return nil, nil
} else if len(chans) == 1 && !chans.Contains("*") {
for channel, _ := range chans {
base.LogTo("Changes", "ChangesFeed(%s, %+v) ...", channel, options)
return db.ChangesFeed(channel, options)
}
}
base.LogTo("Changes", "MultiChangesFeed(%s, %+v) ...", chans, options)
waitMode := options.Wait
options.Wait = false
output := make(chan *ChangeEntry, kChangesPageSize)
go func() {
defer close(output)
for {
// Restrict to available channels, expand wild-card, and find since when these channels
// have been available to the user:
var channelsSince channels.TimedSet
if db.user != nil {
channelsSince = db.user.FilterToAvailableChannels(chans)
} else {
channelsSince = chans.AtSequence(1)
}
base.LogTo("Changes", "MultiChangesFeed: channels expand to %s ...", channelsSince)
feeds := make([]<-chan *ChangeEntry, 0, len(channelsSince))
for name, _ := range channelsSince {
feedOpts := options
if channelsSince[name] > options.Since {
feedOpts.Since = 0 // channel wasn't available before, so start from beginning
}
feed, err := db.ChangesFeed(name, feedOpts)
if err != nil {
base.Warn("Error reading changes feed %q: %v", name, err)
return
}
feeds = append(feeds, feed)
}
current := make([]*ChangeEntry, len(feeds))
var lastSeqSent uint64
for {
//FIX: This assumes Reverse or Limit aren't set in the options
// Read more entries to fill up the current[] array:
for i, cur := range current {
if cur == nil && feeds[i] != nil {
var ok bool
current[i], ok = <-feeds[i]
if !ok {
feeds[i] = nil
}
}
}
// Find the current entry with the minimum sequence:
var minSeq uint64 = math.MaxUint64
var minEntry *ChangeEntry
for _, cur := range current {
if cur != nil && cur.Seq < minSeq {
minSeq = cur.Seq
minEntry = cur
}
}
if minEntry == nil {
break // Exit the loop when there are no more entries
}
// Clear the current entries for the sequence just sent:
for i, cur := range current {
if cur != nil && cur.Seq == minEntry.Seq {
current[i] = nil
// Also concatenate the matching entries' Removed arrays:
if cur != minEntry && cur.Removed != nil {
if minEntry.Removed == nil {
minEntry.Removed = cur.Removed
} else {
minEntry.Removed = minEntry.Removed.Union(cur.Removed)
}
}
}
}
// Send the entry, and repeat the loop:
output <- minEntry
lastSeqSent = minEntry.Seq
}
// If nothing found, and in wait mode: wait for the db to change, then run again
if lastSeqSent > 0 || !waitMode || !db.WaitForRevision() {
break
}
// Before checking again, update the User object in case its channel access has
// changed while waiting:
if err := db.ReloadUser(); err != nil {
base.Warn("Error reloading user %q: %v", db.user.Name(), err)
return
}
}
base.LogTo("Changes", "MultiChangesFeed done")
}()
return output, nil
}
// If a channel list contains a wildcard ("*"), replace it with all the user's accessible channels.
func (user *userImpl) ExpandWildCardChannel(channels ch.Set) ch.Set {
if channels.Contains("*") {
channels = user.InheritedChannels().AsSet()
}
return channels
}