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optimized_inverted_bitmap.go
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optimized_inverted_bitmap.go
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package matching
import (
"errors"
"strings"
"sync"
"github.com/RoaringBitmap/roaring"
)
var ErrBadTopic = errors.New("Topic does not fit within topic space")
type constituentBitmap struct {
bitmaps map[string]*roaring.Bitmap
}
func newConstituentBitmap() *constituentBitmap {
bitmaps := map[string]*roaring.Bitmap{
empty: roaring.New(),
wildcard: roaring.New(),
}
return &constituentBitmap{bitmaps: bitmaps}
}
func (c *constituentBitmap) index(constituent string, subPos uint32) {
bitmap, ok := c.bitmaps[constituent]
if !ok {
bitmap = roaring.New()
c.bitmaps[constituent] = bitmap
}
bitmap.Add(subPos)
}
func (c *constituentBitmap) lookup(constituent string) *roaring.Bitmap {
if constituent == empty {
return c.bitmaps[empty]
}
bitmap := c.bitmaps[wildcard]
if bm, ok := c.bitmaps[constituent]; ok {
bitmap = roaring.FastOr(bitmap, bm)
}
return bitmap
}
type optimizedInvertedBitmapMatcher struct {
constituentBitmaps []*constituentBitmap
maxConstituents uint
subscribers map[uint32]Subscriber
subPos uint32
deletedPositions []uint32
mu sync.RWMutex
}
func NewOptimizedInvertedBitmapMatcher(topicSpaceSize uint) Matcher {
bitmaps := make([]*constituentBitmap, topicSpaceSize)
for i := uint(0); i < topicSpaceSize; i++ {
bitmaps[i] = newConstituentBitmap()
}
return &optimizedInvertedBitmapMatcher{
constituentBitmaps: bitmaps,
maxConstituents: topicSpaceSize,
subscribers: make(map[uint32]Subscriber),
deletedPositions: []uint32{},
}
}
// Subscribe adds the Subscriber to the topic and returns a Subscription.
func (b *optimizedInvertedBitmapMatcher) Subscribe(topic string, sub Subscriber) (*Subscription, error) {
constituents := strings.Split(topic, delimiter)
if uint(len(constituents)) > b.maxConstituents {
return nil, ErrBadTopic
}
var (
i int
constituent string
pos = b.subPos
)
if len(b.deletedPositions) > 0 {
pos = b.deletedPositions[0]
b.deletedPositions = b.deletedPositions[1:]
} else {
b.subPos++
}
b.mu.Lock()
for i, constituent = range constituents {
b.constituentBitmaps[i].index(constituent, pos)
}
for i := uint(i + 1); i < b.maxConstituents; i++ {
b.constituentBitmaps[i].index(empty, pos)
}
b.subscribers[pos] = sub
b.mu.Unlock()
return &Subscription{id: pos, topic: topic, subscriber: sub}, nil
}
// Unsubscribe removes the Subscription.
func (b *optimizedInvertedBitmapMatcher) Unsubscribe(sub *Subscription) {
constituents := strings.Split(sub.topic, delimiter)
b.mu.Lock()
for i, cb := range b.constituentBitmaps {
if i == len(constituents) {
break
}
if bm, ok := cb.bitmaps[constituents[i]]; ok {
bm.Remove(sub.id)
}
}
b.deletedPositions = append(b.deletedPositions, sub.id)
delete(b.subscribers, sub.id)
b.mu.Unlock()
}
// Lookup returns the Subscribers for the given topic.
func (b *optimizedInvertedBitmapMatcher) Lookup(topic string) []Subscriber {
constituents := strings.Split(topic, delimiter)
if uint(len(constituents)) > b.maxConstituents {
return nil
}
bitmaps := make([]*roaring.Bitmap, b.maxConstituents)
var (
i int
constituent string
)
b.mu.RLock()
for i, constituent = range constituents {
bitmaps[i] = b.constituentBitmaps[i].lookup(constituent)
if bitmaps[i].IsEmpty() {
// If we get an empty bitmap, there are no subscribers.
b.mu.RUnlock()
return nil
}
}
for i := uint(i + 1); i < b.maxConstituents; i++ {
bitmaps[i] = b.constituentBitmaps[i].lookup(empty)
}
result := roaring.FastAnd(bitmaps...)
subscriberSet := make(map[Subscriber]struct{}, result.GetCardinality())
for iter := result.Iterator(); iter.HasNext(); {
subscriberSet[b.subscribers[iter.Next()]] = struct{}{}
}
b.mu.RUnlock()
subscribers := make([]Subscriber, len(subscriberSet))
i = 0
for sub, _ := range subscriberSet {
subscribers[i] = sub
i++
}
return subscribers
}