StateHash method for space

app/ldiff/diff.go

@@ -7,6 +7,7 @@ package ldiff
 import (
 	"bytes"
 	"context"
+	"encoding/hex"
 	"errors"
 	"github.com/cespare/xxhash"
 	"github.com/huandu/skiplist"
@@ -89,6 +90,8 @@ type Diff interface {
 	Elements() []Element
 	// Ids retrieves ids of all elements in the Diff
 	Ids() []string
+	// Hash returns hash of all elements in the diff
+	Hash() string
 }
 
 // Remote interface for using in the Diff
@@ -169,6 +172,13 @@ func (d *diff) Elements() (elements []Element) {
 	return
 }
 
+func (d *diff) Hash() string {
+	d.mu.RLock()
+	defer d.mu.RUnlock()
+	res := d.getRange(Range{To: math.MaxUint64})
+	return hex.EncodeToString(res.Hash)
+}
+
 // RemoveId removes element by id
 func (d *diff) RemoveId(id string) error {
 	d.mu.Lock()

app/ldiff/diff_test.go

@@ -138,3 +138,13 @@ func BenchmarkDiff_Ranges(b *testing.B) {
 		resBuf = resBuf[:0]
 	}
 }
+
+func TestDiff_Hash(t *testing.T) {
+	d := New(16, 16)
+	h1 := d.Hash()
+	assert.NotEmpty(t, h1)
+	d.Set(Element{Id: "1"})
+	h2 := d.Hash()
+	assert.NotEmpty(t, h2)
+	assert.NotEqual(t, h1, h2)
+}

app/ldiff/mock_ldiff/mock_ldiff.go

@@ -66,6 +66,20 @@ func (mr *MockDiffMockRecorder) Elements() *gomock.Call {
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Elements", reflect.TypeOf((*MockDiff)(nil).Elements))
 }
 
+// Hash mocks base method.
+func (m *MockDiff) Hash() string {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Hash")
+	ret0, _ := ret[0].(string)
+	return ret0
+}
+
+// Hash indicates an expected call of Hash.
+func (mr *MockDiffMockRecorder) Hash() *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Hash", reflect.TypeOf((*MockDiff)(nil).Hash))
+}
+
 // Ids mocks base method.
 func (m *MockDiff) Ids() []string {
 	m.ctrl.T.Helper()

commonspace/headsync/headsync.go

@@ -29,6 +29,9 @@ type HeadSync interface {
 	DebugAllHeads() (res []TreeHeads)
 
 	Init(objectIds []string, deletionState deletionstate.DeletionState)
+
+	StateHash() string
+
 	Close() (err error)
 }
 
@@ -103,6 +106,10 @@ func (d *headSync) RemoveObjects(ids []string) {
 	d.syncer.RemoveObjects(ids)
 }
 
+func (d *headSync) StateHash() string {
+	return d.diff.Hash()
+}
+
 func (d *headSync) Close() (err error) {
 	d.periodicSync.Close()
 	return nil

commonspace/space.go

@@ -88,6 +88,7 @@ type Space interface {
 	BuildTree(ctx context.Context, id string, opts BuildTreeOpts) (t objecttree.ObjectTree, err error)
 	DeleteTree(ctx context.Context, id string) (err error)
 
+	HeadSync() headsync.HeadSync
 	SyncStatus() syncstatus.StatusUpdater
 	Storage() spacestorage.SpaceStorage