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hasher.go
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hasher.go
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// Copyright 2019 Google LLC. All Rights Reserved.
//
// 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 smt
import "github.com/google/trillian/merkle/smt/node"
// Hasher provides sparse Merkle tree hash functions.
type Hasher interface {
// HashEmpty returns the hash of an empty subtree with the given root. Note
// that the empty node ID indicates the root of the entire tree.
HashEmpty(treeID int64, root node.ID) []byte
// HashChildren returns the node hash based on its children node hashes.
HashChildren(l, r []byte) []byte
}
// mapHasher is a wrapper around Hasher bound to a specific tree ID.
type mapHasher struct {
mh Hasher
treeID int64
}
// bindHasher returns a mapHasher binding the given hasher to a tree ID.
func bindHasher(hasher Hasher, treeID int64) mapHasher {
return mapHasher{mh: hasher, treeID: treeID}
}
// hashEmpty returns the hash of an empty subtree with the given root ID.
func (h mapHasher) hashEmpty(id node.ID) []byte {
return h.mh.HashEmpty(h.treeID, id)
}