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hashing.go
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hashing.go
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// (c) 2019-2021, Ava Labs, Inc.
//
// This file is a derived work, based on the go-ethereum library whose original
// notices appear below.
//
// It is distributed under a license compatible with the licensing terms of the
// original code from which it is derived.
//
// Much love to the original authors for their work.
// **********
// Copyright 2021 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package types
import (
"bytes"
"sync"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/rlp"
"golang.org/x/crypto/sha3"
)
// hasherPool holds LegacyKeccak256 hashers for rlpHash.
var hasherPool = sync.Pool{
New: func() interface{} { return sha3.NewLegacyKeccak256() },
}
// encodeBufferPool holds temporary encoder buffers for DeriveSha and TX encoding.
var encodeBufferPool = sync.Pool{
New: func() interface{} { return new(bytes.Buffer) },
}
// rlpHash encodes x and hashes the encoded bytes.
func rlpHash(x interface{}) (h common.Hash) {
sha := hasherPool.Get().(crypto.KeccakState)
defer hasherPool.Put(sha)
sha.Reset()
rlp.Encode(sha, x)
sha.Read(h[:])
return h
}
// prefixedRlpHash writes the prefix into the hasher before rlp-encoding x.
// It's used for typed transactions.
func prefixedRlpHash(prefix byte, x interface{}) (h common.Hash) {
sha := hasherPool.Get().(crypto.KeccakState)
defer hasherPool.Put(sha)
sha.Reset()
sha.Write([]byte{prefix})
rlp.Encode(sha, x)
sha.Read(h[:])
return h
}
// TrieHasher is the tool used to calculate the hash of derivable list.
// This is internal, do not use.
type TrieHasher interface {
Reset()
Update([]byte, []byte)
Hash() common.Hash
}
// DerivableList is the input to DeriveSha.
// It is implemented by the 'Transactions' and 'Receipts' types.
// This is internal, do not use these methods.
type DerivableList interface {
Len() int
EncodeIndex(int, *bytes.Buffer)
}
func encodeForDerive(list DerivableList, i int, buf *bytes.Buffer) []byte {
buf.Reset()
list.EncodeIndex(i, buf)
// It's really unfortunate that we need to do perform this copy.
// StackTrie holds onto the values until Hash is called, so the values
// written to it must not alias.
return common.CopyBytes(buf.Bytes())
}
// DeriveSha creates the tree hashes of transactions and receipts in a block header.
func DeriveSha(list DerivableList, hasher TrieHasher) common.Hash {
hasher.Reset()
valueBuf := encodeBufferPool.Get().(*bytes.Buffer)
defer encodeBufferPool.Put(valueBuf)
// StackTrie requires values to be inserted in increasing hash order, which is not the
// order that `list` provides hashes in. This insertion sequence ensures that the
// order is correct.
var indexBuf []byte
for i := 1; i < list.Len() && i <= 0x7f; i++ {
indexBuf = rlp.AppendUint64(indexBuf[:0], uint64(i))
value := encodeForDerive(list, i, valueBuf)
hasher.Update(indexBuf, value)
}
if list.Len() > 0 {
indexBuf = rlp.AppendUint64(indexBuf[:0], 0)
value := encodeForDerive(list, 0, valueBuf)
hasher.Update(indexBuf, value)
}
for i := 0x80; i < list.Len(); i++ {
indexBuf = rlp.AppendUint64(indexBuf[:0], uint64(i))
value := encodeForDerive(list, i, valueBuf)
hasher.Update(indexBuf, value)
}
return hasher.Hash()
}