improve prefix gen
use stateful iterator, and allow splitting into powers of 2 rather than 16
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c3c3195991
commit
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@ -17,10 +17,9 @@
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package iterator
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import (
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// "fmt"
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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/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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@ -69,37 +68,73 @@ func NewPrefixBoundIterator(it trie.NodeIterator, to []byte) NodeIterator {
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return &prefixBoundIterator{current: it, endKey: to}
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}
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// array of 0..f with prefix
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func prefixedNibbles(prefix []byte) [][]byte {
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var ret [][]byte
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for i := byte(0); i < 16; i++ {
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elem := make([]byte, len(prefix))
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copy(elem, prefix)
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elem = append(elem, i)
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ret = append(ret, elem)
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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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return ret
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}
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// Generates ordered cartesian product of all nibbles of given length, w/ optional prefix
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// eg. MakePaths([4], 2) => [[4 0 0] [4 0 1] ... [4 f f]]
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func MakePaths(prefix []byte, length int) [][]byte {
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paths := [][]byte{prefix}
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for depth := 0; depth < length; depth++ {
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var newPaths [][]byte
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for _, path := range paths {
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for _, newPath := range prefixedNibbles(path) {
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newPaths = append(newPaths, newPath)
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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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}
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paths = newPaths
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}
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return paths
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return res
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}
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// Apply a function to 16^cutdepth subtries divided by path prefix
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func VisitSubtries(tree state.Trie, cutDepth int, callback func(NodeIterator)) {
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prefixes := MakePaths(nil, cutDepth)
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func VisitSubtries(tree state.Trie, nbins uint, callback func(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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