1 files changed, 100 insertions, 0 deletions
diff --git a/adapter/statsclient/statseg.go b/adapter/statsclient/statseg.go
new file mode 100644
index 0000000..7f1c381
--- /dev/null
+++ b/adapter/statsclient/statseg.go
@@ -0,0 +1,100 @@
+package statsclient
+
+import (
+	"sync/atomic"
+	"time"
+	"unsafe"
+)
+
+var (
+	MaxWaitInProgress    = time.Millisecond * 100
+	CheckDelayInProgress = time.Microsecond * 10
+)
+
+type sharedHeaderBase struct {
+	epoch           int64
+	inProgress      int64
+	directoryOffset int64
+	errorOffset     int64
+	statsOffset     int64
+}
+
+type statSegSharedHeader struct {
+	version uint64
+	sharedHeaderBase
+}
+
+func (h *statSegSharedHeader) legacyVersion() bool {
+	// older VPP (<=19.04) did not have version in stat segment header
+	// we try to provide fallback support by skipping it in header
+	if h.version > maxVersion && h.inProgress > 1 && h.epoch == 0 {
+		return true
+	}
+	return false
+}
+
+func statSegHeader(b []byte) (header statSegSharedHeader) {
+	h := (*statSegSharedHeader)(unsafe.Pointer(&b[0]))
+	header.version = atomic.LoadUint64(&h.version)
+	header.epoch = atomic.LoadInt64(&h.epoch)
+	header.inProgress = atomic.LoadInt64(&h.inProgress)
+	header.directoryOffset = atomic.LoadInt64(&h.directoryOffset)
+	header.errorOffset = atomic.LoadInt64(&h.errorOffset)
+	header.statsOffset = atomic.LoadInt64(&h.statsOffset)
+	return
+}
+
+func statSegHeaderLegacy(b []byte) (header statSegSharedHeader) {
+	h := (*sharedHeaderBase)(unsafe.Pointer(&b[0]))
+	header.version = 0
+	header.epoch = atomic.LoadInt64(&h.epoch)
+	header.inProgress = atomic.LoadInt64(&h.inProgress)
+	header.directoryOffset = atomic.LoadInt64(&h.directoryOffset)
+	header.errorOffset = atomic.LoadInt64(&h.errorOffset)
+	header.statsOffset = atomic.LoadInt64(&h.statsOffset)
+	return
+}
+
+type statSegAccess struct {
+	epoch int64
+}
+
+func (c *statSegment) accessStart() statSegAccess {
+	t := time.Now()
+
+	epoch, inprog := c.getEpoch()
+	for inprog {
+		if time.Since(t) > MaxWaitInProgress {
+			return statSegAccess{}
+		} else {
+			time.Sleep(CheckDelayInProgress)
+		}
+		epoch, inprog = c.getEpoch()
+	}
+	return statSegAccess{
+		epoch: epoch,
+	}
+}
+
+func (c *statSegment) accessEnd(acc *statSegAccess) bool {
+	epoch, inprog := c.getEpoch()
+	if acc.epoch != epoch || inprog {
+		return false
+	}
+	return true
+}
+
+type vecHeader struct {
+	length     uint64
+	vectorData [0]uint8
+}
+
+func vectorLen(v unsafe.Pointer) uint64 {
+	vec := *(*vecHeader)(unsafe.Pointer(uintptr(v) - unsafe.Sizeof(uintptr(0))))
+	return vec.length
+}
+
+//go:nosplit
+func statSegPointer(p unsafe.Pointer, offset uintptr) unsafe.Pointer {
+	return unsafe.Pointer(uintptr(p) + offset)
+}