github.com/theQRL/go-zond@v0.1.1/zond/protocols/snap/range.go (about)

     1  // Copyright 2021 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package snap
    18  
    19  import (
    20  	"math/big"
    21  
    22  	"github.com/holiman/uint256"
    23  	"github.com/theQRL/go-zond/common"
    24  )
    25  
    26  // hashRange is a utility to handle ranges of hashes, Split up the
    27  // hash-space into sections, and 'walk' over the sections
    28  type hashRange struct {
    29  	current *uint256.Int
    30  	step    *uint256.Int
    31  }
    32  
    33  // newHashRange creates a new hashRange, initiated at the start position,
    34  // and with the step set to fill the desired 'num' chunks
    35  func newHashRange(start common.Hash, num uint64) *hashRange {
    36  	left := new(big.Int).Sub(hashSpace, start.Big())
    37  	step := new(big.Int).Div(
    38  		new(big.Int).Add(left, new(big.Int).SetUint64(num-1)),
    39  		new(big.Int).SetUint64(num),
    40  	)
    41  	step256 := new(uint256.Int)
    42  	step256.SetFromBig(step)
    43  
    44  	return &hashRange{
    45  		current: new(uint256.Int).SetBytes32(start[:]),
    46  		step:    step256,
    47  	}
    48  }
    49  
    50  // Next pushes the hash range to the next interval.
    51  func (r *hashRange) Next() bool {
    52  	next, overflow := new(uint256.Int).AddOverflow(r.current, r.step)
    53  	if overflow {
    54  		return false
    55  	}
    56  	r.current = next
    57  	return true
    58  }
    59  
    60  // Start returns the first hash in the current interval.
    61  func (r *hashRange) Start() common.Hash {
    62  	return r.current.Bytes32()
    63  }
    64  
    65  // End returns the last hash in the current interval.
    66  func (r *hashRange) End() common.Hash {
    67  	// If the end overflows (non divisible range), return a shorter interval
    68  	next, overflow := new(uint256.Int).AddOverflow(r.current, r.step)
    69  	if overflow {
    70  		return common.HexToHash("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff")
    71  	}
    72  	return next.SubUint64(next, 1).Bytes32()
    73  }
    74  
    75  // incHash returns the next hash, in lexicographical order (a.k.a plus one)
    76  func incHash(h common.Hash) common.Hash {
    77  	var a uint256.Int
    78  	a.SetBytes32(h[:])
    79  	a.AddUint64(&a, 1)
    80  	return common.Hash(a.Bytes32())
    81  }