prysm-pulse/beacon-chain/state/stateutil/field_root_vector.go

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package stateutil
import (
"github.com/pkg/errors"
"github.com/prysmaticlabs/prysm/crypto/hash"
"github.com/prysmaticlabs/prysm/encoding/ssz"
)
func (h *stateRootHasher) arraysRoot(input [][]byte, length uint64, fieldName string) ([32]byte, error) {
lock.Lock()
defer lock.Unlock()
hashFunc := hash.CustomSHA256Hasher()
if _, ok := layersCache[fieldName]; !ok && h.rootsCache != nil {
depth := ssz.Depth(length)
layersCache[fieldName] = make([][][32]byte, depth+1)
}
leaves := make([][32]byte, length)
for i, chunk := range input {
copy(leaves[i][:], chunk)
}
bytesProcessed := 0
changedIndices := make([]int, 0)
prevLeaves, ok := leavesCache[fieldName]
if len(prevLeaves) == 0 || h.rootsCache == nil {
prevLeaves = leaves
}
// Exit early if our previous leaves length don't match with the current set.
// This should never happen but better to be defensive here.
if len(prevLeaves) != len(leaves) {
res, err := h.merkleizeWithCache(leaves, length, fieldName, hashFunc)
if err != nil {
return [32]byte{}, err
}
if h.rootsCache != nil {
leavesCache[fieldName] = leaves
}
return res, nil
}
for i := 0; i < len(leaves); i++ {
// We check if any items changed since the roots were last recomputed.
notEqual := leaves[i] != prevLeaves[i]
if ok && h.rootsCache != nil && notEqual {
changedIndices = append(changedIndices, i)
}
bytesProcessed += 32
}
if len(changedIndices) > 0 && h.rootsCache != nil {
var rt [32]byte
var err error
// If indices did change since last computation, we only recompute
// the modified branches in the cached Merkle tree for this state field.
chunks := leaves
// We need to ensure we recompute indices of the Merkle tree which
// changed in-between calls to this function. This check adds an offset
// to the recomputed indices to ensure we do so evenly.
maxChangedIndex := changedIndices[len(changedIndices)-1]
if maxChangedIndex+2 == len(chunks) && maxChangedIndex%2 != 0 {
changedIndices = append(changedIndices, maxChangedIndex+1)
}
for i := 0; i < len(changedIndices); i++ {
rt, err = recomputeRoot(changedIndices[i], chunks, fieldName, hashFunc)
if err != nil {
return [32]byte{}, err
}
}
leavesCache[fieldName] = chunks
return rt, nil
}
res, err := h.merkleizeWithCache(leaves, length, fieldName, hashFunc)
if err != nil {
return [32]byte{}, err
}
if h.rootsCache != nil {
leavesCache[fieldName] = leaves
}
return res, nil
}
func recomputeRoot(idx int, chunks [][32]byte, fieldName string, hasher func([]byte) [32]byte) ([32]byte, error) {
items, ok := layersCache[fieldName]
if !ok {
return [32]byte{}, errors.New("could not recompute root as there was no cache found")
}
if items == nil {
return [32]byte{}, errors.New("could not recompute root as there were no items found in the layers cache")
}
layers := items
root := chunks[idx]
layers[0] = chunks
// The merkle tree structure looks as follows:
// [[r1, r2, r3, r4], [parent1, parent2], [root]]
// Using information about the index which changed, idx, we recompute
// only its branch up the tree.
currentIndex := idx
for i := 0; i < len(layers)-1; i++ {
isLeft := currentIndex%2 == 0
neighborIdx := currentIndex ^ 1
neighbor := [32]byte{}
if layers[i] != nil && len(layers[i]) != 0 && neighborIdx < len(layers[i]) {
neighbor = layers[i][neighborIdx]
}
if isLeft {
parentHash := hasher(append(root[:], neighbor[:]...))
root = parentHash
} else {
parentHash := hasher(append(neighbor[:], root[:]...))
root = parentHash
}
parentIdx := currentIndex / 2
// Update the cached layers at the parent index.
if len(layers[i+1]) == 0 {
layers[i+1] = append(layers[i+1], root)
} else {
layers[i+1][parentIdx] = root
}
currentIndex = parentIdx
}
layersCache[fieldName] = layers
// If there is only a single leaf, we return it (the identity element).
if len(layers[0]) == 1 {
return layers[0][0], nil
}
return root, nil
}
func (h *stateRootHasher) merkleizeWithCache(leaves [][32]byte, length uint64,
fieldName string, hasher func([]byte) [32]byte) ([32]byte, error) {
if len(leaves) == 0 {
return [32]byte{}, errors.New("zero leaves provided")
}
if len(leaves) == 1 {
return leaves[0], nil
}
hashLayer := leaves
layers := make([][][32]byte, ssz.Depth(length)+1)
if items, ok := layersCache[fieldName]; ok && h.rootsCache != nil {
if len(items[0]) == len(leaves) {
layers = items
}
}
layers[0] = hashLayer
var err error
layers, hashLayer, err = MerkleizeTrieLeaves(layers, hashLayer, hasher)
if err != nil {
return [32]byte{}, err
}
root := hashLayer[0]
if h.rootsCache != nil {
layersCache[fieldName] = layers
}
return root, nil
}