82 lines
2.5 KiB
Go
82 lines
2.5 KiB
Go
// 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 snap
|
|
|
|
import (
|
|
"math/big"
|
|
|
|
"github.com/ethereum/go-ethereum/common"
|
|
"github.com/holiman/uint256"
|
|
)
|
|
|
|
// hashRange is a utility to handle ranges of hashes, Split up the
|
|
// hash-space into sections, and 'walk' over the sections
|
|
type hashRange struct {
|
|
current *uint256.Int
|
|
step *uint256.Int
|
|
}
|
|
|
|
// newHashRange creates a new hashRange, initiated at the start position,
|
|
// and with the step set to fill the desired 'num' chunks
|
|
func newHashRange(start common.Hash, num uint64) *hashRange {
|
|
left := new(big.Int).Sub(hashSpace, start.Big())
|
|
step := new(big.Int).Div(
|
|
new(big.Int).Add(left, new(big.Int).SetUint64(num-1)),
|
|
new(big.Int).SetUint64(num),
|
|
)
|
|
step256 := new(uint256.Int)
|
|
step256.SetFromBig(step)
|
|
|
|
return &hashRange{
|
|
current: new(uint256.Int).SetBytes32(start[:]),
|
|
step: step256,
|
|
}
|
|
}
|
|
|
|
// Next pushes the hash range to the next interval.
|
|
func (r *hashRange) Next() bool {
|
|
next, overflow := new(uint256.Int).AddOverflow(r.current, r.step)
|
|
if overflow {
|
|
return false
|
|
}
|
|
r.current = next
|
|
return true
|
|
}
|
|
|
|
// Start returns the first hash in the current interval.
|
|
func (r *hashRange) Start() common.Hash {
|
|
return r.current.Bytes32()
|
|
}
|
|
|
|
// End returns the last hash in the current interval.
|
|
func (r *hashRange) End() common.Hash {
|
|
// If the end overflows (non divisible range), return a shorter interval
|
|
next, overflow := new(uint256.Int).AddOverflow(r.current, r.step)
|
|
if overflow {
|
|
return common.HexToHash("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff")
|
|
}
|
|
return next.SubUint64(next, 1).Bytes32()
|
|
}
|
|
|
|
// incHash returns the next hash, in lexicographical order (a.k.a plus one)
|
|
func incHash(h common.Hash) common.Hash {
|
|
var a uint256.Int
|
|
a.SetBytes32(h[:])
|
|
a.AddUint64(&a, 1)
|
|
return common.Hash(a.Bytes32())
|
|
}
|