fix underflow in freezer inspect for empty ancients

Author: ucwong

core/rawdb/ancient_utils.go

@@ -34,14 +34,10 @@ type freezerInfo struct {
 	name  string      // The identifier of freezer
 	head  uint64      // The number of last stored item in the freezer
 	tail  uint64      // The number of first stored item in the freezer
+	count uint64      // The number of stored items in the freezer
 	sizes []tableSize // The storage size per table
 }
 
-// count returns the number of stored items in the freezer.
-func (info *freezerInfo) count() uint64 {
-	return info.head - info.tail + 1
-}
-
 // size returns the storage size of the entire freezer.
 func (info *freezerInfo) size() common.StorageSize {
 	var total common.StorageSize
@@ -51,6 +47,41 @@ func (info *freezerInfo) size() common.StorageSize {
 	return total
 }
 
+func inspect(name string, order map[string]freezerTableConfig, reader ctxcdb.AncientReader) (freezerInfo, error) {
+	info := freezerInfo{name: name}
+	for t := range order {
+		size, err := reader.AncientSize(t)
+		if err != nil {
+			return freezerInfo{}, err
+		}
+		info.sizes = append(info.sizes, tableSize{name: t, size: common.StorageSize(size)})
+	}
+	// Retrieve the number of last stored item
+	ancients, err := reader.Ancients()
+	if err != nil {
+		return freezerInfo{}, err
+	}
+	if ancients > 0 {
+		info.head = ancients - 1
+	} else {
+		info.head = 0
+	}
+
+	// Retrieve the number of first stored item
+	tail, err := reader.Tail()
+	if err != nil {
+		return freezerInfo{}, err
+	}
+	info.tail = tail
+
+	if ancients == 0 {
+		info.count = 0
+	} else {
+		info.count = info.head - info.tail + 1
+	}
+	return info, nil
+}
+
 // inspectFreezers inspects all freezers registered in the system.
 func inspectFreezers(db ctxcdb.Database) ([]freezerInfo, error) {
 	var infos []freezerInfo

core/rawdb/database.go

@@ -604,7 +604,7 @@ func InspectDatabase(db ctxcdb.Database, keyPrefix, keyStart []byte) error {
 				fmt.Sprintf("Ancient store (%s)", strings.Title(ancient.name)),
 				strings.Title(table.name),
 				table.size.String(),
-				fmt.Sprintf("%d", ancient.count()),
+				fmt.Sprintf("%d", ancient.count),
 			})
 		}
 		total.Add(uint64(ancient.size()))