82 lines
2.4 KiB
Go
82 lines
2.4 KiB
Go
// Copyright 2021 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser 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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// The go-ethereum library 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 Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package snap
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import (
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"math/big"
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"github.com/ethereum/go-ethereum/common"
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"github.com/holiman/uint256"
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)
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// hashRange is a utility to handle ranges of hashes, Split up the
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// hash-space into sections, and 'walk' over the sections
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type hashRange struct {
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current *uint256.Int
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step *uint256.Int
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}
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// newHashRange creates a new hashRange, initiated at the start position,
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// and with the step set to fill the desired 'num' chunks
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func newHashRange(start common.Hash, num uint64) *hashRange {
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left := new(big.Int).Sub(hashSpace, start.Big())
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step := new(big.Int).Div(
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new(big.Int).Add(left, new(big.Int).SetUint64(num-1)),
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new(big.Int).SetUint64(num),
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)
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step256 := new(uint256.Int)
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step256.SetFromBig(step)
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return &hashRange{
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current: new(uint256.Int).SetBytes32(start[:]),
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step: step256,
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}
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}
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// Next pushes the hash range to the next interval.
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func (r *hashRange) Next() bool {
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next, overflow := new(uint256.Int).AddOverflow(r.current, r.step)
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if overflow {
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return false
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}
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r.current = next
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return true
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}
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// Start returns the first hash in the current interval.
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func (r *hashRange) Start() common.Hash {
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return r.current.Bytes32()
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}
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// End returns the last hash in the current interval.
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func (r *hashRange) End() common.Hash {
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// If the end overflows (non divisible range), return a shorter interval
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next, overflow := new(uint256.Int).AddOverflow(r.current, r.step)
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if overflow {
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return common.MaxHash
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}
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return next.SubUint64(next, 1).Bytes32()
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}
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// incHash returns the next hash, in lexicographical order (a.k.a plus one)
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func incHash(h common.Hash) common.Hash {
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var a uint256.Int
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a.SetBytes32(h[:])
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a.AddUint64(&a, 1)
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return common.Hash(a.Bytes32())
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}
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