init

bucket.go

@@ -0,0 +1,64 @@
+package topk
+
+import (
+	"unsafe"
+)
+
+const (
+	sizeOfBucketStruct = int(unsafe.Sizeof(Bucket{}))
+)
+
+type Bucket struct {
+	Fingerprint uint32
+
+	// Counts is a circular buffer (with its first entry at .First)
+	Counts []uint32
+	First  uint32
+	// CountsSum is the current sum of Counts
+	CountsSum uint32
+}
+
+func (me *Bucket) last() uint32 {
+	n := uint32(len(me.Counts))
+	return ((me.First + n) - 1) % n
+}
+
+func (me *Bucket) tick() {
+	if me.CountsSum == 0 {
+		return
+	}
+
+	last := me.First
+	if last == 0 {
+		last = uint32(len(me.Counts) - 1)
+	} else {
+		last = uint32(last - 1)
+	}
+	me.CountsSum -= me.Counts[last]
+	me.Counts[last] = 0
+	me.First = last
+}
+
+func (me *Bucket) findNonzeroMinimumCount() int {
+	countsMinIdx := uint32(0)
+	first := true
+	var countsMin uint32
+	i := me.First
+	for range len(me.Counts) {
+		if i == uint32(len(me.Counts)) {
+			i = 0
+		}
+		c := me.Counts[i]
+		if c == 0 {
+			i++
+			continue
+		}
+		if first || c < countsMin {
+			countsMin = c
+			countsMinIdx = i
+			first = false
+		}
+		i++
+	}
+	return int(countsMinIdx)
+}