Move stats_tracker.go into the extension API and increment MatchedPairs from inside the Emit method (#272)

* Move `stats_tracker.go` into the extension API and increment `MatchedPairs` from inside the `Emit` method

* Replace multiple `sync.Mutex`(es) with low-level atomic memory primitives

tap/api/api.go

@@ -87,6 +87,7 @@ type Dissector interface {
 }
 
 type Emitting struct {
+	AppStats      *AppStats
 	OutputChannel chan *OutputChannelItem
 }
 
@@ -96,6 +97,7 @@ type Emitter interface {
 
 func (e *Emitting) Emit(item *OutputChannelItem) {
 	e.OutputChannel <- item
+	e.AppStats.IncMatchedPairs()
 }
 
 type MizuEntry struct {

tap/api/stats_tracker.go

@@ -0,0 +1,70 @@
+package api
+
+import (
+	"sync/atomic"
+	"time"
+)
+
+type AppStats struct {
+	StartTime                   time.Time `json:"-"`
+	ProcessedBytes              uint64    `json:"processedBytes"`
+	PacketsCount                uint64    `json:"packetsCount"`
+	TcpPacketsCount             uint64    `json:"tcpPacketsCount"`
+	ReassembledTcpPayloadsCount uint64    `json:"reassembledTcpPayloadsCount"`
+	TlsConnectionsCount         uint64    `json:"tlsConnectionsCount"`
+	MatchedPairs                uint64    `json:"matchedPairs"`
+	DroppedTcpStreams           uint64    `json:"droppedTcpStreams"`
+}
+
+func (as *AppStats) IncMatchedPairs() {
+	atomic.AddUint64(&as.MatchedPairs, 1)
+}
+
+func (as *AppStats) IncDroppedTcpStreams() {
+	atomic.AddUint64(&as.DroppedTcpStreams, 1)
+}
+
+func (as *AppStats) IncPacketsCount() uint64 {
+	atomic.AddUint64(&as.PacketsCount, 1)
+	return as.PacketsCount
+}
+
+func (as *AppStats) IncTcpPacketsCount() {
+	atomic.AddUint64(&as.TcpPacketsCount, 1)
+}
+
+func (as *AppStats) IncReassembledTcpPayloadsCount() {
+	atomic.AddUint64(&as.ReassembledTcpPayloadsCount, 1)
+}
+
+func (as *AppStats) IncTlsConnectionsCount() {
+	atomic.AddUint64(&as.TlsConnectionsCount, 1)
+}
+
+func (as *AppStats) UpdateProcessedBytes(size uint64) {
+	atomic.AddUint64(&as.ProcessedBytes, size)
+}
+
+func (as *AppStats) SetStartTime(startTime time.Time) {
+	as.StartTime = startTime
+}
+
+func (as *AppStats) DumpStats() *AppStats {
+	currentAppStats := &AppStats{StartTime: as.StartTime}
+
+	currentAppStats.ProcessedBytes = resetUint64(&as.ProcessedBytes)
+	currentAppStats.PacketsCount = resetUint64(&as.PacketsCount)
+	currentAppStats.TcpPacketsCount = resetUint64(&as.TcpPacketsCount)
+	currentAppStats.ReassembledTcpPayloadsCount = resetUint64(&as.ReassembledTcpPayloadsCount)
+	currentAppStats.TlsConnectionsCount = resetUint64(&as.TlsConnectionsCount)
+	currentAppStats.MatchedPairs = resetUint64(&as.MatchedPairs)
+	currentAppStats.DroppedTcpStreams = resetUint64(&as.DroppedTcpStreams)
+
+	return currentAppStats
+}
+
+func resetUint64(ref *uint64) (val uint64) {
+	val = atomic.LoadUint64(ref)
+	atomic.StoreUint64(ref, 0)
+	return
+}