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90 lines
2.7 KiB
90 lines
2.7 KiB
// Copyright 2023 The go-ethereum Authors
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// This file is part of go-ethereum.
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//
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// go-ethereum is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// go-ethereum is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
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package era
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import (
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"fmt"
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"math/big"
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"github.com/ethereum/go-ethereum/common"
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ssz "github.com/ferranbt/fastssz"
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)
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// ComputeAccumulator calculates the SSZ hash tree root of the Era1
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// accumulator of header records.
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func ComputeAccumulator(hashes []common.Hash, tds []*big.Int) (common.Hash, error) {
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if len(hashes) != len(tds) {
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return common.Hash{}, fmt.Errorf("must have equal number hashes as td values")
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}
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if len(hashes) > MaxEra1Size {
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return common.Hash{}, fmt.Errorf("too many records: have %d, max %d", len(hashes), MaxEra1Size)
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}
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hh := ssz.NewHasher()
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for i := range hashes {
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rec := headerRecord{hashes[i], tds[i]}
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root, err := rec.HashTreeRoot()
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if err != nil {
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return common.Hash{}, err
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}
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hh.Append(root[:])
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}
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hh.MerkleizeWithMixin(0, uint64(len(hashes)), uint64(MaxEra1Size))
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return hh.HashRoot()
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}
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// headerRecord is an individual record for a historical header.
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//
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// See https://github.com/ethereum/portal-network-specs/blob/master/history-network.md#the-header-accumulator
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// for more information.
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type headerRecord struct {
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Hash common.Hash
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TotalDifficulty *big.Int
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}
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// GetTree completes the ssz.HashRoot interface, but is unused.
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func (h *headerRecord) GetTree() (*ssz.Node, error) {
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return nil, nil
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}
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// HashTreeRoot ssz hashes the headerRecord object.
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func (h *headerRecord) HashTreeRoot() ([32]byte, error) {
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return ssz.HashWithDefaultHasher(h)
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}
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// HashTreeRootWith ssz hashes the headerRecord object with a hasher.
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func (h *headerRecord) HashTreeRootWith(hh ssz.HashWalker) (err error) {
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hh.PutBytes(h.Hash[:])
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td := bigToBytes32(h.TotalDifficulty)
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hh.PutBytes(td[:])
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hh.Merkleize(0)
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return
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}
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// bigToBytes32 converts a big.Int into a little-endian 32-byte array.
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func bigToBytes32(n *big.Int) (b [32]byte) {
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n.FillBytes(b[:])
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reverseOrder(b[:])
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return
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}
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// reverseOrder reverses the byte order of a slice.
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func reverseOrder(b []byte) []byte {
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for i := 0; i < 16; i++ {
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b[i], b[32-i-1] = b[32-i-1], b[i]
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}
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return b
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}
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