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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/v4/scale"
"github.com/centrifuge/go-substrate-rpc-client/v4/xxhash"
)
// 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 method, prefix as well as arguments to
// create a hashed StorageKey
// Using variadic argument, so caller do not need to construct array of arguments
func CreateStorageKey(meta *Metadata, prefix, method string, args ...[]byte) (StorageKey, error) { //nolint:funlen
stringKey := []byte(prefix + " " + method)
validateAndTrimArgs := func(args [][]byte) ([][]byte, error) {
nonNilCount := -1
for i, arg := range args {
if len(arg) == 0 {
nonNilCount = i
break
}
}
if nonNilCount == -1 {
return args, nil
}
for i := nonNilCount; i < len(args); i++ {
if len(args[i]) != 0 {
return nil, fmt.Errorf("non-nil arguments cannot be preceded by nil arguments")
}
}
trimmedArgs := make([][]byte, nonNilCount)
for i := 0; i < nonNilCount; i++ {
trimmedArgs[i] = args[i]
}
return trimmedArgs, nil
}
validatedArgs, err := validateAndTrimArgs(args)
if err != nil {
return nil, err
}
entryMeta, err := meta.FindStorageEntryMetadata(prefix, method)
if err != nil {
return nil, err
}
// From metadata >= v14, there is only one representation of Map,
// which is more alike the old 'NMap': a Map with n keys (n >= 1).
// The old variants are now unified as thus IsMap() is true for all.
if entryMeta.IsMap() {
hashers, err := entryMeta.Hashers()
if err != nil {
return nil, fmt.Errorf("unable to get hashers for %s map", method)
}
if len(hashers) != len(validatedArgs) {
return nil, fmt.Errorf("%s:%s is a map, therefore requires that number of arguments should "+
"exactly match number of hashers in metadata. "+
"Expected: %d, received: %d", prefix, method, len(hashers), len(validatedArgs))
}
return createKeyMap(method, prefix, validatedArgs, entryMeta)
}
if entryMeta.IsPlain() && len(validatedArgs) != 0 {
return nil, fmt.Errorf("%s:%s is a plain key, therefore requires no argument. "+
"received: %d", prefix, method, len(validatedArgs))
}
return createKey(meta, method, prefix, stringKey, nil, entryMeta)
}
// 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)
}
// Create a key for a Map.
// The number of keys of the map should match with the number of key hashers.
func createKeyMap(method, prefix string, args [][]byte, entryMeta StorageEntryMetadata) (StorageKey, error) {
hashers, err := entryMeta.Hashers()
if err != nil {
return nil, err
}
key := createPrefixedKey(method, prefix)
for i, arg := range args {
_, err := hashers[i].Write(arg)
if err != nil {
return nil, fmt.Errorf("unable to hash args[%d]: %s Error: %v", i, arg, err)
}
key = append(key, hashers[i].Sum(nil)...)
}
return key, nil
}
// createKey creates a key for a plain value
func createKey(
meta *Metadata,
method,
prefix string,
stringKey,
arg []byte,
entryMeta StorageEntryMetadata,
) (StorageKey, error) {
hasher, err := entryMeta.Hasher()
if err != nil {
return nil, err
}
if meta.Version <= 8 {
_, err := hasher.Write(append(stringKey, arg...))
return hasher.Sum(nil), err
}
return append(createPrefixedKey(method, prefix), arg...), nil
}
func createPrefixedKey(method, prefix string) []byte {
return append(xxhash.New128([]byte(prefix)).Sum(nil), xxhash.New128([]byte(method)).Sum(nil)...)
}