[#61] policy: Shorten policy contract keys

* Map long entity names to 8-bytes long numbers.
* Add desctiption to docs.

Signed-off-by: Airat Arifullin <a.arifullin@yadro.com>

policy/doc.go

@@ -6,6 +6,8 @@
  |------------------------------------------|--------|-----------------------------------|
  | 'c' + uint16(len(container)) + container | []byte | Namespace chain                   |
  | 'n' + uint16(len(namespace)) + namespace | []byte | Container chain                   |
+ | 'm' + entity name (namespace/container)  | []byte | Mapped name to an encoded number  |
+ | 'counter'                                | uint64 | Integer counter used for mapping  |
 
 */
 

policy/policy_contract.go

@@ -22,6 +22,11 @@ const (
 	ownerKeyPrefix = 'o'
 )
 
+const (
+	mappingKeyPrefix = 'm'
+	counterKey       = "counter"
+)
+
 const (
 	// ErrNotAuthorized is returned when the none of the transaction signers
 	// belongs to the list of autorized keys.
@@ -44,6 +49,7 @@ func _deploy(data any, isUpdate bool) {
 		}
 		storage.Put(ctx, []byte{ownerKeyPrefix}, args.Admin)
 	}
+	storage.Put(ctx, counterKey, 0)
 }
 
 func checkAuthorization(ctx storage.Context) {
@@ -79,24 +85,61 @@ func getAdmin(ctx storage.Context) interop.Hash160 {
 	return storage.Get(ctx, []byte{ownerKeyPrefix}).(interop.Hash160)
 }
 
-func storageKey(prefix Kind, entityName string, name []byte) []byte {
+func storageKey(prefix Kind, counter int, name []byte) []byte {
-	ln := len(entityName)
+	key := append([]byte{byte(prefix)}, common.ToFixedWidth64(counter)...)
-	key := append([]byte{byte(prefix)}, byte(ln&0xFF), byte(ln>>8))
-	key = append(key, entityName...)
 	return append(key, name...)
 }
 
+// mapToNumeric maps a name to a number. That allows to keep more space in
+// a storage key shortening long names. Short entity
+// names are also mapped to prevent collisions in the map.
+func mapToNumeric(ctx storage.Context, name []byte) (mapped int, mappingExists bool) {
+	mKey := append([]byte{mappingKeyPrefix}, name...)
+	numericID := storage.Get(ctx, mKey)
+	if numericID == nil {
+		return
+	}
+	mapped = numericID.(int)
+	mappingExists = true
+	return
+}
+
+// mapToNumericCreateIfNotExists maps a name to a number. That allows to keep
+// more space in a storage key shortening long names. Short entity
+// names are also mapped to prevent collisions in the map.
+// If a mapping cannot be found, then the method creates and returns it.
+// mapToNumericCreateIfNotExists is NOT applicable for a read-only context.
+func mapToNumericCreateIfNotExists(ctx storage.Context, name []byte) int {
+	mKey := append([]byte{mappingKeyPrefix}, name...)
+	numericID := storage.Get(ctx, mKey)
+	if numericID == nil {
+		counter := storage.Get(ctx, counterKey).(int)
+		counter++
+		storage.Put(ctx, counterKey, counter)
+		storage.Put(ctx, mKey, counter)
+		return counter
+	}
+	return numericID.(int)
+}
+
 func AddChain(entity Kind, entityName string, name []byte, chain []byte) {
 	ctx := storage.GetContext()
 	checkAuthorization(ctx)
 
-	key := storageKey(entity, entityName, name)
+	entityNameBytes := mapToNumericCreateIfNotExists(ctx, []byte(entityName))
+	key := storageKey(entity, entityNameBytes, name)
 	storage.Put(ctx, key, chain)
 }
 
 func GetChain(entity Kind, entityName string, name []byte) []byte {
 	ctx := storage.GetReadOnlyContext()
-	key := storageKey(entity, entityName, name)
+
+	entityNameBytes, exists := mapToNumeric(ctx, []byte(entityName))
+	if !exists {
+		panic("not found")
+	}
+
+	key := storageKey(entity, entityNameBytes, name)
 	data := storage.Get(ctx, key).([]byte)
 	if data == nil {
 		panic("not found")
@@ -109,7 +152,12 @@ func RemoveChain(entity Kind, entityName string, name []byte) {
 	ctx := storage.GetContext()
 	checkAuthorization(ctx)
 
-	key := storageKey(entity, entityName, name)
+	entityNameBytes, exists := mapToNumeric(ctx, []byte(entityName))
+	if !exists {
+		return
+	}
+
+	key := storageKey(entity, entityNameBytes, name)
 	storage.Delete(ctx, key)
 }
 
@@ -117,7 +165,12 @@ func RemoveChainsByPrefix(entity Kind, entityName string, name []byte) {
 	ctx := storage.GetContext()
 	checkAuthorization(ctx)
 
-	key := storageKey(entity, entityName, name)
+	entityNameBytes, exists := mapToNumeric(ctx, []byte(entityName))
+	if !exists {
+		return
+	}
+
+	key := storageKey(entity, entityNameBytes, name)
 	it := storage.Find(ctx, key, storage.KeysOnly)
 	for iterator.Next(it) {
 		storage.Delete(ctx, iterator.Value(it).([]byte))
@@ -142,7 +195,12 @@ func ListChainsByPrefix(entity Kind, entityName string, prefix []byte) [][]byte
 
 	result := [][]byte{}
 
-	keyPrefix := storageKey(entity, entityName, prefix)
+	entityNameBytes, exists := mapToNumeric(ctx, []byte(entityName))
+	if !exists {
+		return result
+	}
+
+	keyPrefix := storageKey(entity, entityNameBytes, prefix)
 	it := storage.Find(ctx, keyPrefix, storage.ValuesOnly)
 	for iterator.Next(it) {
 		result = append(result, iterator.Value(it).([]byte))