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storage_key.go
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storage_key.go
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// Go Substrate RPC Client (GSRPC) provides APIs and types around Polkadot and any Substrate-based chain RPC calls
//
// Copyright 2019 Centrifuge GmbH
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package types
import (
"fmt"
"io"
"github.com/centrifuge/go-substrate-rpc-client/scale"
"github.com/pierrec/xxHash/xxHash64"
)
// StorageKey represents typically hashed storage keys of the system.
// Be careful using this in your own structs – it only works as the last value in a struct since it will consume the
// remainder of the encoded data. The reason for this is that it does not contain any length encoding, so it would
// not know where to stop.
type StorageKey []byte
// NewStorageKey creates a new StorageKey type
func NewStorageKey(b []byte) StorageKey {
return b
}
// CreateStorageKey uses the given metadata and to derive the right hashing of module, fn names and keys to create a
// hashed StorageKey
func CreateStorageKey(meta *Metadata, module string, fn string, key []byte) (StorageKey, error) {
hasher, err := meta.FindStorageKeyHasher(module, fn)
if err != nil {
return nil, err
}
afn := []byte(module + " " + fn)
if hasher != nil {
_, err = hasher.Write(append(afn, key...))
if err != nil {
return nil, err
}
return hasher.Sum(nil), nil
}
if key != nil {
return createMultiXxhash(append(afn, key...), 2)
}
return createMultiXxhash(afn, 2)
}
// Encode implements encoding for StorageKey, which just unwraps the bytes of StorageKey
func (s StorageKey) Encode(encoder scale.Encoder) error {
return encoder.Write(s)
}
// Decode implements decoding for StorageKey, which just reads all the remaining bytes into StorageKey
func (s *StorageKey) Decode(decoder scale.Decoder) error {
for i := 0; true; i++ {
b, err := decoder.ReadOneByte()
if err == io.EOF {
break
}
if err != nil {
return err
}
*s = append((*s)[:i], b)
}
return nil
}
// Hex returns a hex string representation of the value (not of the encoded value)
func (s StorageKey) Hex() string {
return fmt.Sprintf("%#x", s)
}
func createMultiXxhash(data []byte, rounds int) ([]byte, error) {
res := make([]byte, 0)
for i := 0; i < rounds; i++ {
h := xxHash64.New(uint64(i))
_, err := h.Write(data)
if err != nil {
return nil, err
}
res = append(res, h.Sum(nil)...)
}
return res, nil
}