mirror of
https://gitlab.com/pulsechaincom/prysm-pulse.git
synced 2024-12-25 12:57:18 +00:00
288 lines
9.0 KiB
Go
288 lines
9.0 KiB
Go
package stateutil
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import (
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"bytes"
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"encoding/binary"
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"github.com/pkg/errors"
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"github.com/prysmaticlabs/prysm/shared/hashutil"
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"github.com/prysmaticlabs/prysm/shared/htrutils"
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"github.com/prysmaticlabs/prysm/shared/trieutil"
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)
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// ReturnTrieLayer returns the representation of a merkle trie when
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// provided with the elements of a fixed sized trie and the corresponding depth of
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// it.
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func ReturnTrieLayer(elements [][32]byte, length uint64) [][]*[32]byte {
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hasher := hashutil.CustomSHA256Hasher()
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leaves := elements
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if len(leaves) == 1 {
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return [][]*[32]byte{{&leaves[0]}}
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}
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hashLayer := leaves
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layers := make([][][32]byte, htrutils.Depth(length)+1)
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layers[0] = hashLayer
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layers, _ = merkleizeTrieLeaves(layers, hashLayer, hasher)
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refLayers := make([][]*[32]byte, len(layers))
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for i, val := range layers {
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refLayers[i] = make([]*[32]byte, len(val))
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for j, innerVal := range val {
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newVal := innerVal
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refLayers[i][j] = &newVal
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}
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}
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return refLayers
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}
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func merkleizeTrieLeaves(layers [][][32]byte, hashLayer [][32]byte,
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hasher func([]byte) [32]byte) ([][][32]byte, [][32]byte) {
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// We keep track of the hash layers of a Merkle trie until we reach
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// the top layer of length 1, which contains the single root element.
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// [Root] -> Top layer has length 1.
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// [E] [F] -> This layer has length 2.
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// [A] [B] [C] [D] -> The bottom layer has length 4 (needs to be a power of two).
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i := 1
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chunkBuffer := bytes.NewBuffer([]byte{})
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chunkBuffer.Grow(64)
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for len(hashLayer) > 1 && i < len(layers) {
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layer := make([][32]byte, len(hashLayer)/2)
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for j := 0; j < len(hashLayer); j += 2 {
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chunkBuffer.Write(hashLayer[j][:])
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chunkBuffer.Write(hashLayer[j+1][:])
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hashedChunk := hasher(chunkBuffer.Bytes())
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layer[j/2] = hashedChunk
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chunkBuffer.Reset()
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}
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hashLayer = layer
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layers[i] = hashLayer
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i++
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}
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return layers, hashLayer
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}
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// ReturnTrieLayerVariable returns the representation of a merkle trie when
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// provided with the elements of a variable sized trie and the corresponding depth of
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// it.
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func ReturnTrieLayerVariable(elements [][32]byte, length uint64) [][]*[32]byte {
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hasher := hashutil.CustomSHA256Hasher()
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depth := htrutils.Depth(length)
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layers := make([][]*[32]byte, depth+1)
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// Return zerohash at depth
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if len(elements) == 0 {
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zerohash := trieutil.ZeroHashes[depth]
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layers[len(layers)-1] = []*[32]byte{&zerohash}
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return layers
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}
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transformedLeaves := make([]*[32]byte, len(elements))
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for i := range elements {
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arr := elements[i]
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transformedLeaves[i] = &arr
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}
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layers[0] = transformedLeaves
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buffer := bytes.NewBuffer([]byte{})
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buffer.Grow(64)
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for i := 0; i < int(depth); i++ {
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oddNodeLength := len(layers[i])%2 == 1
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if oddNodeLength {
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zerohash := trieutil.ZeroHashes[i]
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layers[i] = append(layers[i], &zerohash)
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}
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updatedValues := make([]*[32]byte, 0, len(layers[i])/2)
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for j := 0; j < len(layers[i]); j += 2 {
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buffer.Write(layers[i][j][:])
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buffer.Write(layers[i][j+1][:])
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concat := hasher(buffer.Bytes())
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updatedValues = append(updatedValues, &concat)
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buffer.Reset()
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}
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// remove zerohash node from tree
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if oddNodeLength {
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layers[i] = layers[i][:len(layers[i])-1]
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}
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layers[i+1] = updatedValues
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}
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return layers
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}
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// RecomputeFromLayer recomputes specific branches of a fixed sized trie depending on the provided changed indexes.
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func RecomputeFromLayer(changedLeaves [][32]byte, changedIdx []uint64, layer [][]*[32]byte) ([32]byte, [][]*[32]byte, error) {
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hasher := hashutil.CustomSHA256Hasher()
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for i, idx := range changedIdx {
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layer[0][idx] = &changedLeaves[i]
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}
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if len(changedIdx) == 0 {
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return *layer[0][0], layer, nil
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}
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leaves := layer[0]
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// We need to ensure we recompute indices of the Merkle tree which
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// changed in-between calls to this function. This check adds an offset
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// to the recomputed indices to ensure we do so evenly.
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maxChangedIndex := changedIdx[len(changedIdx)-1]
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if int(maxChangedIndex+2) == len(leaves) && maxChangedIndex%2 != 0 {
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changedIdx = append(changedIdx, maxChangedIndex+1)
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}
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root := *layer[0][0]
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var err error
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for _, idx := range changedIdx {
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root, layer, err = recomputeRootFromLayer(int(idx), layer, leaves, hasher)
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if err != nil {
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return [32]byte{}, nil, err
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}
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}
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return root, layer, nil
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}
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// RecomputeFromLayerVariable recomputes specific branches of a variable sized trie depending on the provided changed indexes.
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func RecomputeFromLayerVariable(changedLeaves [][32]byte, changedIdx []uint64, layer [][]*[32]byte) ([32]byte, [][]*[32]byte, error) {
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hasher := hashutil.CustomSHA256Hasher()
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if len(changedIdx) == 0 {
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return *layer[0][0], layer, nil
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}
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root := *layer[len(layer)-1][0]
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var err error
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for i, idx := range changedIdx {
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root, layer, err = recomputeRootFromLayerVariable(int(idx), changedLeaves[i], layer, hasher)
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if err != nil {
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return [32]byte{}, nil, err
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}
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}
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return root, layer, nil
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}
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// this method assumes that the provided trie already has all its elements included
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// in the base depth.
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func recomputeRootFromLayer(idx int, layers [][]*[32]byte, chunks []*[32]byte,
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hasher func([]byte) [32]byte) ([32]byte, [][]*[32]byte, error) {
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root := *chunks[idx]
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layers[0] = chunks
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// The merkle tree structure looks as follows:
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// [[r1, r2, r3, r4], [parent1, parent2], [root]]
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// Using information about the index which changed, idx, we recompute
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// only its branch up the tree.
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currentIndex := idx
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for i := 0; i < len(layers)-1; i++ {
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isLeft := currentIndex%2 == 0
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neighborIdx := currentIndex ^ 1
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neighbor := [32]byte{}
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if layers[i] != nil && len(layers[i]) != 0 && neighborIdx < len(layers[i]) {
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neighbor = *layers[i][neighborIdx]
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}
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if isLeft {
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parentHash := hasher(append(root[:], neighbor[:]...))
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root = parentHash
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} else {
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parentHash := hasher(append(neighbor[:], root[:]...))
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root = parentHash
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}
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parentIdx := currentIndex / 2
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// Update the cached layers at the parent index.
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rootVal := root
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if len(layers[i+1]) == 0 {
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layers[i+1] = append(layers[i+1], &rootVal)
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} else {
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layers[i+1][parentIdx] = &rootVal
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}
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currentIndex = parentIdx
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}
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// If there is only a single leaf, we return it (the identity element).
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if len(layers[0]) == 1 {
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return *layers[0][0], layers, nil
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}
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return root, layers, nil
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}
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// this method assumes that the base branch does not consist of all leaves of the
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// trie. Instead missing leaves are assumed to be zerohashes, following the structure
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// of a sparse merkle trie.
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func recomputeRootFromLayerVariable(idx int, item [32]byte, layers [][]*[32]byte,
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hasher func([]byte) [32]byte) ([32]byte, [][]*[32]byte, error) {
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for idx >= len(layers[0]) {
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zerohash := trieutil.ZeroHashes[0]
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layers[0] = append(layers[0], &zerohash)
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}
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layers[0][idx] = &item
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currentIndex := idx
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root := item
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for i := 0; i < len(layers)-1; i++ {
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isLeft := currentIndex%2 == 0
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neighborIdx := currentIndex ^ 1
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neighbor := [32]byte{}
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if neighborIdx >= len(layers[i]) {
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neighbor = trieutil.ZeroHashes[i]
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} else {
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neighbor = *layers[i][neighborIdx]
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}
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if isLeft {
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parentHash := hasher(append(root[:], neighbor[:]...))
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root = parentHash
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} else {
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parentHash := hasher(append(neighbor[:], root[:]...))
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root = parentHash
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}
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parentIdx := currentIndex / 2
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if len(layers[i+1]) == 0 || parentIdx >= len(layers[i+1]) {
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newItem := root
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layers[i+1] = append(layers[i+1], &newItem)
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} else {
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newItem := root
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layers[i+1][parentIdx] = &newItem
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}
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currentIndex = parentIdx
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}
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return root, layers, nil
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}
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// AddInMixin describes a method from which a lenth mixin is added to the
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// provided root.
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func AddInMixin(root [32]byte, length uint64) ([32]byte, error) {
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rootBuf := new(bytes.Buffer)
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if err := binary.Write(rootBuf, binary.LittleEndian, length); err != nil {
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return [32]byte{}, errors.Wrap(err, "could not marshal eth1data votes length")
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}
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// We need to mix in the length of the slice.
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rootBufRoot := make([]byte, 32)
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copy(rootBufRoot, rootBuf.Bytes())
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return htrutils.MixInLength(root, rootBufRoot), nil
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}
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// Merkleize 32-byte leaves into a Merkle trie for its adequate depth, returning
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// the resulting layers of the trie based on the appropriate depth. This function
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// pads the leaves to a length of 32.
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func Merkleize(leaves [][]byte) [][][]byte {
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hashFunc := hashutil.CustomSHA256Hasher()
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layers := make([][][]byte, htrutils.Depth(uint64(len(leaves)))+1)
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for len(leaves) != 32 {
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leaves = append(leaves, make([]byte, 32))
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}
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currentLayer := leaves
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layers[0] = currentLayer
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// We keep track of the hash layers of a Merkle trie until we reach
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// the top layer of length 1, which contains the single root element.
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// [Root] -> Top layer has length 1.
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// [E] [F] -> This layer has length 2.
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// [A] [B] [C] [D] -> The bottom layer has length 4 (needs to be a power of two).
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i := 1
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for len(currentLayer) > 1 && i < len(layers) {
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layer := make([][]byte, 0)
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for i := 0; i < len(currentLayer); i += 2 {
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hashedChunk := hashFunc(append(currentLayer[i], currentLayer[i+1]...))
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layer = append(layer, hashedChunk[:])
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}
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currentLayer = layer
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layers[i] = currentLayer
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i++
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}
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return layers
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}
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