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259 lines
5.4 KiB
259 lines
5.4 KiB
package merkle
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import (
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"bytes"
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"crypto/sha256"
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"fmt"
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. "github.com/tendermint/tendermint/binary"
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)
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func HashFromTwoHashes(left []byte, right []byte) []byte {
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var n int64
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var err error
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var hasher = sha256.New()
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WriteByteSlice(hasher, left, &n, &err)
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WriteByteSlice(hasher, right, &n, &err)
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if err != nil {
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panic(err)
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}
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return hasher.Sum(nil)
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}
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/*
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Computes a deterministic minimal height merkle tree hash.
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If the number of items is not a power of two, some leaves
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will be at different levels.
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*
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/ \
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/ \
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/ \
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/ \
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* *
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/ \ / \
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/ \ / \
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/ \ / \
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* h2 * *
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/ \ / \ / \
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h0 h1 h3 h4 h5 h6
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*/
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func HashFromHashes(hashes [][]byte) []byte {
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switch len(hashes) {
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case 0:
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panic("Cannot compute hash of empty slice")
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case 1:
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return hashes[0]
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default:
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left := HashFromHashes(hashes[:len(hashes)/2])
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right := HashFromHashes(hashes[len(hashes)/2:])
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return HashFromTwoHashes(left, right)
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}
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}
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// Convenience for HashFromHashes.
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func HashFromBinaries(items []Binary) []byte {
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hashes := [][]byte{}
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for _, item := range items {
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hasher := sha256.New()
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_, err := item.WriteTo(hasher)
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if err != nil {
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panic(err)
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}
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hash := hasher.Sum(nil)
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hashes = append(hashes, hash)
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}
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return HashFromHashes(hashes)
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}
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// Convenience for HashFromHashes.
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func HashFromHashables(items []Hashable) []byte {
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hashes := [][]byte{}
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for _, item := range items {
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hash := item.Hash()
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hashes = append(hashes, hash)
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}
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return HashFromHashes(hashes)
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}
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/*
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Calculates an array of hashes, useful for deriving hash trails.
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7
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/ \
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/ \
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/ \
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/ \
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3 11
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/ \ / \
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/ \ / \
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/ \ / \
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1 5 9 13
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/ \ / \ / \ / \
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0 2 4 6 8 10 12 14
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h0 h1 h2 h3 h4 h5 h6 h7
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(diagram and idea borrowed from libswift)
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The hashes provided get assigned to even indices.
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The derived merkle hashes get assigned to odd indices.
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If "hashes" is not of length power of 2, it is padded
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with blank (zeroed) hashes.
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*/
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func HashTreeFromHashes(hashes [][]byte) [][]byte {
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// Make length of "hashes" a power of 2
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hashesLen := uint32(len(hashes))
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fullLen := uint32(1)
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for {
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if fullLen >= hashesLen {
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break
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} else {
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fullLen <<= 1
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}
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}
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blank := make([]byte, len(hashes[0]))
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for i := hashesLen; i < fullLen; i++ {
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hashes = append(hashes, blank)
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}
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// The result is twice the length minus one.
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res := make([][]byte, len(hashes)*2-1)
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for i, hash := range hashes {
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res[i*2] = hash
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}
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// Fill all the hashes recursively.
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fillTreeRoot(res, 0, len(res)-1)
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return res
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}
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// Fill in the blanks.
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func fillTreeRoot(res [][]byte, start, end int) []byte {
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if start == end {
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return res[start]
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} else {
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mid := (start + end) / 2
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left := fillTreeRoot(res, start, mid-1)
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right := fillTreeRoot(res, mid+1, end)
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root := HashFromTwoHashes(left, right)
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res[mid] = root
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return root
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}
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}
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// Convenience for HashTreeFromHashes.
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func HashTreeFromHashables(items []Hashable) [][]byte {
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hashes := [][]byte{}
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for _, item := range items {
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hash := item.Hash()
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hashes = append(hashes, hash)
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}
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return HashTreeFromHashes(hashes)
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}
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/*
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Given the original index of an item,
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(e.g. for h5 in the diagram above, the index is 5, not 10)
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returns a trail of hashes, which along with the index can be
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used to calculate the merkle root.
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See VerifyHashTrailForIndex()
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*/
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func HashTrailForIndex(hashTree [][]byte, index int) [][]byte {
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trail := [][]byte{}
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index *= 2
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// We start from the leaf layer and work our way up.
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// Notice the indices in the diagram:
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// 0 2 4 ... offset 0, stride 2
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// 1 5 9 ... offset 1, stride 4
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// 3 11 19 ... offset 3, stride 8
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// 7 23 39 ... offset 7, stride 16 etc.
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offset := 0
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stride := 2
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for {
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// Calculate sibling of index.
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var next int
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if ((index-offset)/stride)%2 == 0 {
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next = index + stride
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} else {
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next = index - stride
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}
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if next >= len(hashTree) {
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break
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}
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// Insert sibling hash to trail.
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trail = append(trail, hashTree[next])
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index = (index + next) / 2
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offset += stride
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stride *= 2
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}
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return trail
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}
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// Ensures that leafHash is part of rootHash.
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func VerifyHashTrailForIndex(index int, leafHash []byte, trail [][]byte, rootHash []byte) bool {
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index *= 2
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offset := 0
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stride := 2
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tempHash := make([]byte, len(leafHash))
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copy(tempHash, leafHash)
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for i := 0; i < len(trail); i++ {
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var next int
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if ((index-offset)/stride)%2 == 0 {
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next = index + stride
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tempHash = HashFromTwoHashes(tempHash, trail[i])
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} else {
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next = index - stride
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tempHash = HashFromTwoHashes(trail[i], tempHash)
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}
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index = (index + next) / 2
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offset += stride
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stride *= 2
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}
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return bytes.Equal(rootHash, tempHash)
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}
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//-----------------------------------------------------------------------------
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func PrintIAVLNode(node *IAVLNode) {
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fmt.Println("==== NODE")
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if node != nil {
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printIAVLNode(node, 0)
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}
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fmt.Println("==== END")
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}
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func printIAVLNode(node *IAVLNode, indent int) {
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indentPrefix := ""
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for i := 0; i < indent; i++ {
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indentPrefix += " "
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}
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if node.right != nil {
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printIAVLNode(node.rightFilled(nil), indent+1)
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}
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fmt.Printf("%s%v:%v\n", indentPrefix, node.key, node.height)
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if node.left != nil {
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printIAVLNode(node.leftFilled(nil), indent+1)
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}
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}
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func maxUint8(a, b uint8) uint8 {
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if a > b {
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return a
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}
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return b
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}
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