store/rootmulti: add SimpleProofsFromMap (#6481)

* add sipleproofs from map to sdk

* bring changes from tendermint pr

* bring back tmhash

* add changelog

* Update CHANGELOG.md

Co-authored-by: Federico Kunze <31522760+fedekunze@users.noreply.github.com>

CHANGELOG.md

@@ -296,6 +296,7 @@ pagination.
 * (types) [\#6128](https://github.com/cosmos/cosmos-sdk/pull/6137) Add `String()` method to `GasMeter`.
 * (types) [\#6195](https://github.com/cosmos/cosmos-sdk/pull/6195) Add codespace to broadcast(sync/async) response.
 * (baseapp) [\#6053](https://github.com/cosmos/cosmos-sdk/pull/6053) Customizable panic recovery handling added for `app.runTx()` method (as proposed in the [ADR 22](https://github.com/cosmos/cosmos-sdk/blob/master/docs/architecture/adr-022-custom-panic-handling.md)). Adds ability for developers to register custom panic handlers extending standard ones.
+* (store) [\#6481](https://github.com/cosmos/cosmos-sdk/pull/6481) Move `SimpleProofsFromMap` from Tendermint into the SDK.
 
 ## [v0.38.4] - 2020-05-21
 

store/rootmulti/map.go

@@ -100,3 +100,91 @@ func hashKVPairs(kvs kv.Pairs) []byte {
 
 	return merkle.SimpleHashFromByteSlices(kvsH)
 }
+
+// ---------------------------------------------
+
+// Merkle tree from a map.
+// Leaves are `hash(key) | hash(value)`.
+// Leaves are sorted before Merkle hashing.
+type simpleMap struct {
+	kvs    kv.Pairs
+	sorted bool
+}
+
+func newSimpleMap() *simpleMap {
+	return &simpleMap{
+		kvs:    nil,
+		sorted: false,
+	}
+}
+
+// Set creates a kv pair of the key and the hash of the value,
+// and then appends it to simpleMap's kv pairs.
+func (sm *simpleMap) Set(key string, value []byte) {
+	sm.sorted = false
+
+	// The value is hashed, so you can
+	// check for equality with a cached value (say)
+	// and make a determination to fetch or not.
+	vhash := tmhash.Sum(value)
+
+	sm.kvs = append(sm.kvs, kv.Pair{
+		Key:   []byte(key),
+		Value: vhash,
+	})
+}
+
+// Hash Merkle root hash of items sorted by key
+// (UNSTABLE: and by value too if duplicate key).
+func (sm *simpleMap) Hash() []byte {
+	sm.Sort()
+	return hashKVPairs(sm.kvs)
+}
+
+func (sm *simpleMap) Sort() {
+	if sm.sorted {
+		return
+	}
+	sm.kvs.Sort()
+	sm.sorted = true
+}
+
+// Returns a copy of sorted KVPairs.
+// NOTE these contain the hashed key and value.
+func (sm *simpleMap) KVPairs() kv.Pairs {
+	sm.Sort()
+	kvs := make(kv.Pairs, len(sm.kvs))
+	copy(kvs, sm.kvs)
+	return kvs
+}
+
+//----------------------------------------
+
+// A local extension to KVPair that can be hashed.
+// Key and value are length prefixed and concatenated,
+// then hashed.
+type KVPair kv.Pair
+
+// NewKVPair takes in a key and value and creates a kv.Pair
+// wrapped in the local extension KVPair
+func NewKVPair(key, value []byte) KVPair {
+	return KVPair(kv.Pair{
+		Key:   key,
+		Value: value,
+	})
+}
+
+// Bytes returns key || value, with both the
+// key and value length prefixed.
+func (kv KVPair) Bytes() []byte {
+	var b bytes.Buffer
+	err := encodeByteSlice(&b, kv.Key)
+	if err != nil {
+		panic(err)
+	}
+	err = encodeByteSlice(&b, kv.Value)
+	if err != nil {
+		panic(err)
+	}
+	return b.Bytes()
+}

store/rootmulti/map_test.go

@@ -7,7 +7,7 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func TestSimpleMap(t *testing.T) {
+func TestMerkleMap(t *testing.T) {
 	tests := []struct {
 		keys   []string
 		values []string // each string gets converted to []byte in test
@@ -48,3 +48,44 @@ func TestSimpleMap(t *testing.T) {
 		assert.Equal(t, tc.want, fmt.Sprintf("%x", got), "Hash didn't match on tc %d", i)
 	}
 }
+
+func TestSimpleMap(t *testing.T) {
+	tests := []struct {
+		keys   []string
+		values []string // each string gets converted to []byte in test
+		want   string
+	}{
+		{[]string{"key1"}, []string{"value1"}, "a44d3cc7daba1a4600b00a2434b30f8b970652169810d6dfa9fb1793a2189324"},
+		{[]string{"key1"}, []string{"value2"}, "0638e99b3445caec9d95c05e1a3fc1487b4ddec6a952ff337080360b0dcc078c"},
+		// swap order with 2 keys
+		{
+			[]string{"key1", "key2"},
+			[]string{"value1", "value2"},
+			"8fd19b19e7bb3f2b3ee0574027d8a5a4cec370464ea2db2fbfa5c7d35bb0cff3",
+		},
+		{
+			[]string{"key2", "key1"},
+			[]string{"value2", "value1"},
+			"8fd19b19e7bb3f2b3ee0574027d8a5a4cec370464ea2db2fbfa5c7d35bb0cff3",
+		},
+		// swap order with 3 keys
+		{
+			[]string{"key1", "key2", "key3"},
+			[]string{"value1", "value2", "value3"},
+			"1dd674ec6782a0d586a903c9c63326a41cbe56b3bba33ed6ff5b527af6efb3dc",
+		},
+		{
+			[]string{"key1", "key3", "key2"},
+			[]string{"value1", "value3", "value2"},
+			"1dd674ec6782a0d586a903c9c63326a41cbe56b3bba33ed6ff5b527af6efb3dc",
+		},
+	}
+	for i, tc := range tests {
+		db := newSimpleMap()
+		for i := 0; i < len(tc.keys); i++ {
+			db.Set(tc.keys[i], []byte(tc.values[i]))
+		}
+		got := db.Hash()
+		assert.Equal(t, tc.want, fmt.Sprintf("%x", got), "Hash didn't match on tc %d", i)
+	}
+}

store/rootmulti/store.go

@@ -613,13 +613,13 @@ func (ci commitInfo) Hash() []byte {
 	if len(ci.StoreInfos) == 0 {
 		return nil
 	}
-	rootHash, _, _ := merkle.SimpleProofsFromMap(ci.toMap())
+	rootHash, _, _ := SimpleProofsFromMap(ci.toMap())
 	return rootHash
 }
 
 func (ci commitInfo) ProofOp(storeName string) merkle.ProofOp {
 	cmap := ci.toMap()
-	_, proofs, _ := merkle.SimpleProofsFromMap(cmap)
+	_, proofs, _ := SimpleProofsFromMap(cmap)
 	proof := proofs[storeName]
 	if proof == nil {
 		panic(fmt.Sprintf("ProofOp for %s but not registered store name", storeName))
@@ -793,3 +793,28 @@ func SimpleHashFromMap(m map[string][]byte) []byte {
 
 	return mm.hash()
 }
+
+// SimpleProofsFromMap generates proofs from a map. The keys/values of the map will be used as the keys/values
+// in the underlying key-value pairs.
+// The keys are sorted before the proofs are computed.
+func SimpleProofsFromMap(m map[string][]byte) (rootHash []byte, proofs map[string]*merkle.SimpleProof, keys []string) {
+	sm := newSimpleMap()
+	for k, v := range m {
+		sm.Set(k, v)
+	}
+	sm.Sort()
+	kvs := sm.kvs
+	kvsBytes := make([][]byte, len(kvs))
+	for i, kvp := range kvs {
+		kvsBytes[i] = KVPair(kvp).Bytes()
+	}
+
+	rootHash, proofList := merkle.SimpleProofsFromByteSlices(kvsBytes)
+	proofs = make(map[string]*merkle.SimpleProof)
+	keys = make([]string, len(proofList))
+	for i, kvp := range kvs {
+		proofs[string(kvp.Key)] = proofList[i]
+		keys[i] = string(kvp.Key)
+	}
+	return
+}