// Copyright 2017 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 merkle provides Merkle tree interfaces and implementation.
package merkle

// TODO(pavelkalinnikov): Remove this root package. The only interface provided
// here does not have to exist, and can be [re-]defined on the user side, such
// as in compact or proof package.

// LogHasher provides the hash functions needed to compute dense merkle trees.
type LogHasher interface {
	// EmptyRoot supports returning a special case for the root of an empty tree.
	EmptyRoot() []byte
	// HashLeaf computes the hash of a leaf that exists.
	HashLeaf(leaf []byte) []byte
	// HashChildren computes interior nodes.
	HashChildren(l, r []byte) []byte
	// Size returns the number of bytes the Hash* functions will return.
	Size() int
}