157 lines
4.1 KiB
Go
157 lines
4.1 KiB
Go
//
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// Copyright © 2020 Vulcanize, Inc
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero 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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// This program 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 Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package iterator
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import (
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"bytes"
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"math/bits"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/core/state"
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"github.com/ethereum/go-ethereum/trie"
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)
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type PrefixBoundIterator struct {
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current trie.NodeIterator
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endKey []byte
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}
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func (it *PrefixBoundIterator) Next(descend bool) bool {
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if it.endKey == nil {
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return it.current.Next(descend)
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}
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cmp := bytes.Compare(it.current.Path(), it.endKey) // stop before endKey
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if cmp >= 0 {
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return false
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}
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return it.current.Next(descend)
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}
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func (it *PrefixBoundIterator) Error() error {
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return it.current.Error()
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}
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func (it *PrefixBoundIterator) Hash() common.Hash {
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return it.current.Hash()
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}
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func (it *PrefixBoundIterator) Path() []byte {
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return it.current.Path()
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}
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func (it *PrefixBoundIterator) Leaf() bool {
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return it.current.Leaf()
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}
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func (it *PrefixBoundIterator) LeafKey() []byte {
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return it.current.LeafKey()
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}
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func (it *PrefixBoundIterator) LeafBlob() []byte {
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return it.current.LeafBlob()
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}
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func (it *PrefixBoundIterator) LeafProof() [][]byte {
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return it.current.LeafProof()
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}
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func (it *PrefixBoundIterator) Parent() common.Hash {
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return it.current.Parent()
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}
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// Iterator with an upper bound value (hex path prefix)
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func NewPrefixBoundIterator(it trie.NodeIterator, to []byte) *PrefixBoundIterator {
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return &PrefixBoundIterator{current: it, endKey: to}
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}
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type prefixGenerator struct {
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current []byte
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step byte
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stepIndex uint
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}
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func newPrefixGenerator(nbins uint) prefixGenerator {
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if bits.OnesCount(nbins) != 1 {
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panic("nbins must be a power of 2")
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}
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// determine step dist. and path index at which to step
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var step byte
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var stepIndex uint
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for ; nbins != 0; stepIndex++ {
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divisor := byte(nbins & 0xf)
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if divisor != 0 {
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step = 0x10 / divisor
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}
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nbins = nbins >> 4
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}
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return prefixGenerator{
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current: make([]byte, stepIndex),
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step: step,
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stepIndex: stepIndex-1,
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}
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}
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func (gen *prefixGenerator) Value() []byte {
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return gen.current
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}
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func (gen *prefixGenerator) HasNext() bool {
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return gen.current[0] <= 0xf
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}
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func (gen *prefixGenerator) Next() {
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gen.current[gen.stepIndex] += gen.step
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overflow := false
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for ix := 0; ix < len(gen.current); ix++ {
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rix := len(gen.current)-1-ix // reverse
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if overflow {
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gen.current[rix]++
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overflow = false
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}
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if rix != 0 && gen.current[rix] > 0xf {
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gen.current[rix] = 0
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overflow = true
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}
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}
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}
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// Generates paths that cut the trie domain into "nbins" uniform bins, w/ optional prefix
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// eg. MakePaths([], 2) => [[0] [8]]
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// MakePaths([4], 32) => [[4 0 0] [4 0 8] [4 1 0]... [4 f 8]]
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func MakePaths(prefix []byte, nbins uint) [][]byte {
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var res [][]byte
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for it := newPrefixGenerator(nbins); it.HasNext(); it.Next() {
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next := make([]byte, len(prefix))
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copy(next, prefix)
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next = append(next, it.Value()...)
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res = append(res, next)
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}
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return res
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}
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// Cut a trie by path prefix, returning `nbins` iterators covering its subtries
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func SubtrieIterators(tree state.Trie, nbins uint) []NodeIterator {
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prefixes := MakePaths(nil, nbins)
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// pre- and postpend nil to include root & tail
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prefixes = append(prefixes, nil)
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prefixes = append([][]byte{nil}, prefixes...)
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var iters []NodeIterator
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for i := 0; i < len(prefixes)-1; i++ {
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key := prefixes[i]
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if len(key)%2 != 0 { // zero-pad for odd-length keys
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key = append(key, 0)
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}
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it := tree.NodeIterator(HexToKeyBytes(key))
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iters = append(iters, NewPrefixBoundIterator(it, prefixes[i+1]))
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}
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return iters
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}
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