trie: add merkle proof functions
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Felix Lange
parent
a2d5a60418
commit
c1a352c108
122
trie/proof.go
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122
trie/proof.go
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@ -0,0 +1,122 @@
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package trie
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import (
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"bytes"
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"errors"
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"fmt"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/crypto/sha3"
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"github.com/ethereum/go-ethereum/rlp"
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)
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// Prove constructs a merkle proof for key. The result contains all
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// encoded nodes on the path to the value at key. The value itself is
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// also included in the last node and can be retrieved by verifying
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// the proof.
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//
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// The returned proof is nil if the trie does not contain a value for key.
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// For existing keys, the proof will have at least one element.
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func (t *Trie) Prove(key []byte) []rlp.RawValue {
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// Collect all nodes on the path to key.
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key = compactHexDecode(key)
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nodes := []node{}
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tn := t.root
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for len(key) > 0 {
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switch n := tn.(type) {
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case shortNode:
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if len(key) < len(n.Key) || !bytes.Equal(n.Key, key[:len(n.Key)]) {
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// The trie doesn't contain the key.
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return nil
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}
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tn = n.Val
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key = key[len(n.Key):]
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nodes = append(nodes, n)
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case fullNode:
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tn = n[key[0]]
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key = key[1:]
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nodes = append(nodes, n)
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case nil:
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return nil
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case hashNode:
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tn = t.resolveHash(n)
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default:
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panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
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}
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}
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if t.hasher == nil {
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t.hasher = newHasher()
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}
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proof := make([]rlp.RawValue, 0, len(nodes))
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for i, n := range nodes {
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// Don't bother checking for errors here since hasher panics
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// if encoding doesn't work and we're not writing to any database.
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n, _ = t.hasher.replaceChildren(n, nil)
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hn, _ := t.hasher.store(n, nil, false)
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if _, ok := hn.(hashNode); ok || i == 0 {
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// If the node's database encoding is a hash (or is the
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// root node), it becomes a proof element.
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enc, _ := rlp.EncodeToBytes(n)
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proof = append(proof, enc)
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}
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}
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return proof
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}
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// VerifyProof checks merkle proofs. The given proof must contain the
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// value for key in a trie with the given root hash. VerifyProof
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// returns an error if the proof contains invalid trie nodes or the
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// wrong value.
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func VerifyProof(rootHash common.Hash, key []byte, proof []rlp.RawValue) (value []byte, err error) {
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key = compactHexDecode(key)
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sha := sha3.NewKeccak256()
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wantHash := rootHash.Bytes()
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for i, buf := range proof {
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sha.Reset()
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sha.Write(buf)
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if !bytes.Equal(sha.Sum(nil), wantHash) {
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return nil, fmt.Errorf("bad proof node %d: hash mismatch", i)
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}
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n, err := decodeNode(buf)
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if err != nil {
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return nil, fmt.Errorf("bad proof node %d: %v", i, err)
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}
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keyrest, cld := get(n, key)
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switch cld := cld.(type) {
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case nil:
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return nil, fmt.Errorf("key mismatch at proof node %d", i)
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case hashNode:
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key = keyrest
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wantHash = cld
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case valueNode:
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if i != len(proof)-1 {
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return nil, errors.New("additional nodes at end of proof")
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}
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return cld, nil
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}
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}
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return nil, errors.New("unexpected end of proof")
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}
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func get(tn node, key []byte) ([]byte, node) {
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for len(key) > 0 {
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switch n := tn.(type) {
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case shortNode:
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if len(key) < len(n.Key) || !bytes.Equal(n.Key, key[:len(n.Key)]) {
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return nil, nil
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}
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tn = n.Val
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key = key[len(n.Key):]
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case fullNode:
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tn = n[key[0]]
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key = key[1:]
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case hashNode:
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return key, n
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case nil:
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return key, nil
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default:
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panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
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}
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}
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return nil, tn.(valueNode)
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}
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139
trie/proof_test.go
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139
trie/proof_test.go
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@ -0,0 +1,139 @@
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package trie
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import (
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"bytes"
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crand "crypto/rand"
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mrand "math/rand"
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"testing"
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"time"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/rlp"
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)
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func init() {
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mrand.Seed(time.Now().Unix())
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}
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func TestProof(t *testing.T) {
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trie, vals := randomTrie(500)
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root := trie.Hash()
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for _, kv := range vals {
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proof := trie.Prove(kv.k)
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if proof == nil {
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t.Fatalf("missing key %x while constructing proof", kv.k)
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}
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val, err := VerifyProof(root, kv.k, proof)
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if err != nil {
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t.Fatalf("VerifyProof error for key %x: %v\nraw proof: %x", kv.k, err, proof)
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}
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if !bytes.Equal(val, kv.v) {
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t.Fatalf("VerifyProof returned wrong value for key %x: got %x, want %x", kv.k, val, kv.v)
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}
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}
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}
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func TestOneElementProof(t *testing.T) {
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trie := new(Trie)
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updateString(trie, "k", "v")
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proof := trie.Prove([]byte("k"))
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if proof == nil {
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t.Fatal("nil proof")
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}
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if len(proof) != 1 {
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t.Error("proof should have one element")
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}
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val, err := VerifyProof(trie.Hash(), []byte("k"), proof)
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if err != nil {
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t.Fatalf("VerifyProof error: %v\nraw proof: %x", err, proof)
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}
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if !bytes.Equal(val, []byte("v")) {
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t.Fatalf("VerifyProof returned wrong value: got %x, want 'k'", val)
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}
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}
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func TestVerifyBadProof(t *testing.T) {
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trie, vals := randomTrie(800)
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root := trie.Hash()
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for _, kv := range vals {
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proof := trie.Prove(kv.k)
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if proof == nil {
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t.Fatal("nil proof")
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}
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mutateByte(proof[mrand.Intn(len(proof))])
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if _, err := VerifyProof(root, kv.k, proof); err == nil {
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t.Fatalf("expected proof to fail for key %x", kv.k)
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}
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}
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}
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// mutateByte changes one byte in b.
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func mutateByte(b []byte) {
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for r := mrand.Intn(len(b)); ; {
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new := byte(mrand.Intn(255))
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if new != b[r] {
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b[r] = new
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break
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}
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}
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}
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func BenchmarkProve(b *testing.B) {
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trie, vals := randomTrie(100)
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var keys []string
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for k := range vals {
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keys = append(keys, k)
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}
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b.ResetTimer()
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for i := 0; i < b.N; i++ {
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kv := vals[keys[i%len(keys)]]
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if trie.Prove(kv.k) == nil {
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b.Fatalf("nil proof for %x", kv.k)
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}
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}
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}
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func BenchmarkVerifyProof(b *testing.B) {
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trie, vals := randomTrie(100)
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root := trie.Hash()
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var keys []string
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var proofs [][]rlp.RawValue
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for k := range vals {
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keys = append(keys, k)
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proofs = append(proofs, trie.Prove([]byte(k)))
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}
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b.ResetTimer()
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for i := 0; i < b.N; i++ {
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im := i % len(keys)
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if _, err := VerifyProof(root, []byte(keys[im]), proofs[im]); err != nil {
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b.Fatalf("key %x: error", keys[im], err)
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}
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}
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}
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func randomTrie(n int) (*Trie, map[string]*kv) {
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trie := new(Trie)
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vals := make(map[string]*kv)
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for i := byte(0); i < 100; i++ {
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value := &kv{common.LeftPadBytes([]byte{i}, 32), []byte{i}, false}
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value2 := &kv{common.LeftPadBytes([]byte{i + 10}, 32), []byte{i}, false}
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trie.Update(value.k, value.v)
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trie.Update(value2.k, value2.v)
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vals[string(value.k)] = value
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vals[string(value2.k)] = value2
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}
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for i := 0; i < n; i++ {
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value := &kv{randBytes(32), randBytes(20), false}
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trie.Update(value.k, value.v)
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vals[string(value.k)] = value
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}
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return trie, vals
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}
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func randBytes(n int) []byte {
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r := make([]byte, n)
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crand.Read(r)
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return r
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}
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