1 files changed, 35 insertions, 4 deletions
diff --git a/satp/sequence-window.go b/satp/sequence-window.go
index c74ca62..94a7b0b 100644
--- a/satp/sequence-window.go
+++ b/satp/sequence-window.go
@@ -32,23 +32,43 @@ package satp
 
 import (
 	"errors"
+	"sync"
+	"sync/atomic"
 )
 
 type SequenceWindow struct {
-	size int
+	size  int
+	head  uint64
+	body  []uint32
+	mutex *sync.RWMutex
+}
+
+func (w *SequenceWindow) Size() int {
+	return w.size
+}
+
+func (w *SequenceWindow) Top() uint32 {
+	if w.size > 0 {
+		w.mutex.RLock()
+		defer w.mutex.RUnlock()
+	}
+	v := atomic.LoadUint64(&w.head)
+	return uint32(v >> 32)
 }
 
 func (w *SequenceWindow) Check(sequenceNumber uint32) (bool, error) {
-	if w.size == 0 {
+	if w.size <= 0 {
 		return false, nil
 	}
+	// TODO: implement this
 	return false, nil
 }
 
 func (w *SequenceWindow) CheckAndSet(sequenceNumber uint32) (bool, error) {
-	if w.size == 0 {
+	if w.size <= 0 {
 		return false, nil
 	}
+	// TODO: implement this
 	return false, nil
 }
 
@@ -56,6 +76,17 @@ func NewSequenceWindow(size int) (w *SequenceWindow, err error) {
 	if size < 0 {
 		return nil, errors.New("invalid sequence window size")
 	}
-	w = &SequenceWindow{size: size}
+	w = &SequenceWindow{size: size, head: 0}
+	if w.size > 0 {
+		bodyLen := (w.size / 32)
+		if (w.size % 32) != 0 {
+			bodyLen++
+		}
+		w.body = make([]uint32, bodyLen, bodyLen)
+		for i := range w.body {
+			w.body[i] = 0
+		}
+		w.mutex = &sync.RWMutex{}
+	}
 	return
 }