[#170] checksum: Drop Empty method

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

checksum/checksum.go

@@ -127,13 +127,6 @@ func (c Checksum) String() string {
 	return fmt.Sprintf("%s:%s", c.Type(), hex.EncodeToString(v2.GetSum()))
 }
 
-// Empty returns true if it is called on
-// zero checksum.
-func (c Checksum) Empty() bool {
-	v2 := (refs.Checksum)(c)
-	return v2.GetSum() == nil
-}
-
 // String implements fmt.Stringer.
 //
 // String is designed to be human-readable, and its format MAY differ between

object/fmt.go

@@ -14,9 +14,11 @@ import (
 	sigutil "github.com/nspcc-dev/neofs-sdk-go/util/signature"
 )
 
-var errCheckSumMismatch = errors.New("payload checksum mismatch")
-
-var errIncorrectID = errors.New("incorrect object identifier")
+var (
+	errCheckSumMismatch = errors.New("payload checksum mismatch")
+	errCheckSumNotSet   = errors.New("payload checksum is not set")
+	errIncorrectID      = errors.New("incorrect object identifier")
+)
 
 // CalculatePayloadChecksum calculates and returns checksum of
 // object payload bytes.
@@ -39,7 +41,13 @@ func CalculateAndSetPayloadChecksum(obj *Object) {
 // corresponds to its payload.
 func VerifyPayloadChecksum(obj *Object) error {
 	actual := CalculatePayloadChecksum(obj.Payload())
-	if !bytes.Equal(obj.PayloadChecksum().Value(), actual.Value()) {
+
+	cs, set := obj.PayloadChecksum()
+	if !set {
+		return errCheckSumNotSet
+	}
+
+	if !bytes.Equal(cs.Value(), actual.Value()) {
 		return errCheckSumMismatch
 	}
 

object/object.go

@@ -199,20 +199,22 @@ func (o *Object) SetCreationEpoch(v uint64) {
 	})
 }
 
-// PayloadChecksum returns checksum of the object payload.
+// PayloadChecksum returns checksum of the object payload and
+// bool that indicates checksum presence in the object.
 //
-// Zero Object has zero checksum.
+// Zero Object does not have payload checksum.
 //
 // See also SetPayloadChecksum.
-func (o *Object) PayloadChecksum() checksum.Checksum {
+func (o *Object) PayloadChecksum() (checksum.Checksum, bool) {
 	var v checksum.Checksum
 	v2 := (*object.Object)(o)
 
 	if hash := v2.GetHeader().GetPayloadHash(); hash != nil {
 		v.ReadFromV2(*hash)
+		return v, true
 	}
 
-	return v
+	return v, false
 }
 
 // SetPayloadChecksum sets checksum of the object payload.
@@ -228,20 +230,22 @@ func (o *Object) SetPayloadChecksum(v checksum.Checksum) {
 	})
 }
 
-// PayloadHomomorphicHash returns homomorphic hash of the object payload.
+// PayloadHomomorphicHash returns homomorphic hash of the object
+// payload and bool that indicates checksum presence in the object.
 //
-// Zero Object has zero checksum.
+// Zero Object does not have payload homomorphic checksum.
 //
 // See also SetPayloadHomomorphicHash.
-func (o *Object) PayloadHomomorphicHash() checksum.Checksum {
+func (o *Object) PayloadHomomorphicHash() (checksum.Checksum, bool) {
 	var v checksum.Checksum
 	v2 := (*object.Object)(o)
 
 	if hash := v2.GetHeader().GetHomomorphicHash(); hash != nil {
 		v.ReadFromV2(*hash)
+		return v, true
 	}
 
-	return v
+	return v, false
 }
 
 // SetPayloadHomomorphicHash sets homomorphic hash of the object payload.

object/raw_test.go

@@ -126,8 +126,10 @@ func TestObject_SetPayloadChecksum(t *testing.T) {
 	cs.SetSHA256(randSHA256Checksum(t))
 
 	obj.SetPayloadChecksum(cs)
+	cs2, set := obj.PayloadChecksum()
 
-	require.Equal(t, cs, obj.PayloadChecksum())
+	require.True(t, set)
+	require.Equal(t, cs, cs2)
 }
 
 func TestObject_SetPayloadHomomorphicHash(t *testing.T) {
@@ -137,8 +139,10 @@ func TestObject_SetPayloadHomomorphicHash(t *testing.T) {
 	cs.SetTillichZemor(randTZChecksum(t))
 
 	obj.SetPayloadHomomorphicHash(cs)
+	cs2, set := obj.PayloadHomomorphicHash()
 
-	require.Equal(t, cs, obj.PayloadHomomorphicHash())
+	require.True(t, set)
+	require.Equal(t, cs, cs2)
 }
 
 func TestObject_SetAttributes(t *testing.T) {

storagegroup/storagegroup.go

@@ -41,15 +41,18 @@ func (sg *StorageGroup) SetValidationDataSize(epoch uint64) {
 }
 
 // ValidationDataHash returns homomorphic hash from the
-// concatenation of the payloads of the storage group members.
+// concatenation of the payloads of the storage group members
+// and bool that indicates checksum presence in the storage
+// group.
 //
-// Zero StorageGroup has zero checksum.
+// Zero StorageGroup does not have validation data checksum.
 //
 // See also SetValidationDataHash.
-func (sg StorageGroup) ValidationDataHash() (v checksum.Checksum) {
+func (sg StorageGroup) ValidationDataHash() (v checksum.Checksum, isSet bool) {
 	v2 := (storagegroup.StorageGroup)(sg)
 	if checksumV2 := v2.GetValidationHash(); checksumV2 != nil {
 		v.ReadFromV2(*checksumV2)
+		isSet = true
 	}
 
 	return

storagegroup/storagegroup_test.go

@@ -21,7 +21,10 @@ func TestStorageGroup(t *testing.T) {
 
 	cs := checksumtest.Checksum()
 	sg.SetValidationDataHash(cs)
-	require.Equal(t, cs, sg.ValidationDataHash())
+	cs2, set := sg.ValidationDataHash()
+
+	require.True(t, set)
+	require.Equal(t, cs, cs2)
 
 	exp := uint64(33)
 	sg.SetExpirationEpoch(exp)
@@ -78,7 +81,8 @@ func TestNew(t *testing.T) {
 
 		// check initial values
 		require.Nil(t, sg.Members())
-		require.True(t, sg.ValidationDataHash().Empty())
+		_, set := sg.ValidationDataHash()
+		require.False(t, set)
 		require.Zero(t, sg.ExpirationEpoch())
 		require.Zero(t, sg.ValidationDataSize())