perf: limit use of unsafe UnsafeBytesToStr

Unsafe []byte to string conversion is not required for map lookups,
because the Go compiler does the conversion in a garbage-free way.

Limit the scope of the unsafe strings in the few places it is needed
(map deletion).

WriteDOTGraph doesn't seem performance sensitive, so tolerate the extra
garbage there.

cache/cache.go

@@ -61,16 +61,15 @@ func New(maxElementCount int) Cache {
 }
 
 func (c *lruCache) Add(node Node) Node {
-	keyStr := ibytes.UnsafeBytesToStr(node.GetKey())
-	if e, exists := c.dict[keyStr]; exists {
+	if e, exists := c.dict[string(node.GetKey())]; exists {
 		c.ll.MoveToFront(e)
 		old := e.Value
 		e.Value = node
 		return old.(Node)
 	}
 
 	elem := c.ll.PushFront(node)
-	c.dict[keyStr] = elem
+	c.dict[string(node.GetKey())] = elem
 
 	if c.ll.Len() > c.maxElementCount {
 		oldest := c.ll.Back()
@@ -80,15 +79,15 @@ func (c *lruCache) Add(node Node) Node {
 }
 
 func (c *lruCache) Get(key []byte) Node {
-	if ele, hit := c.dict[ibytes.UnsafeBytesToStr(key)]; hit {
+	if ele, hit := c.dict[string(key)]; hit {
 		c.ll.MoveToFront(ele)
 		return ele.Value.(Node)
 	}
 	return nil
 }
 
 func (c *lruCache) Has(key []byte) bool {
-	_, exists := c.dict[ibytes.UnsafeBytesToStr(key)]
+	_, exists := c.dict[string(key)]
 	return exists
 }
 
@@ -97,7 +96,7 @@ func (c *lruCache) Len() int {
 }
 
 func (c *lruCache) Remove(key []byte) Node {
-	if elem, exists := c.dict[ibytes.UnsafeBytesToStr(key)]; exists {
+	if elem, exists := c.dict[string(key)]; exists {
 		return c.remove(elem)
 	}
 	return nil

cmd/iaviewer/main.go

@@ -14,7 +14,6 @@ import (
 	dbm "github.com/cosmos/cosmos-db"
 
 	"github.com/cosmos/iavl"
-	ibytes "github.com/cosmos/iavl/internal/bytes"
 )
 
 // TODO: make this configurable?
@@ -102,8 +101,8 @@ func PrintDBStats(db dbm.DB) {
 
 	defer itr.Close()
 	for ; itr.Valid(); itr.Next() {
-		key := ibytes.UnsafeBytesToStr(itr.Key()[:1])
-		prefix[key]++
+		key := itr.Key()[:1]
+		prefix[string(key)]++
 		count++
 	}
 	if err := itr.Error(); err != nil {

mutable_tree.go

@@ -138,7 +138,7 @@ func (tree *MutableTree) Get(key []byte) ([]byte, error) {
 	}
 
 	if !tree.skipFastStorageUpgrade {
-		if fastNode, ok := tree.unsavedFastNodeAdditions[ibytes.UnsafeBytesToStr(key)]; ok {
+		if fastNode, ok := tree.unsavedFastNodeAdditions[string(key)]; ok {
 			return fastNode.GetValue(), nil
 		}
 		// check if node was deleted
@@ -770,9 +770,8 @@ func (tree *MutableTree) getUnsavedFastNodeRemovals() map[string]interface{} {
 }
 
 func (tree *MutableTree) addUnsavedAddition(key []byte, node *fastnode.Node) {
-	skey := ibytes.UnsafeBytesToStr(key)
-	delete(tree.unsavedFastNodeRemovals, skey)
-	tree.unsavedFastNodeAdditions[skey] = node
+	delete(tree.unsavedFastNodeRemovals, ibytes.UnsafeBytesToStr(key))
+	tree.unsavedFastNodeAdditions[string(key)] = node
 }
 
 func (tree *MutableTree) saveFastNodeAdditions(batchCommmit bool) error {

tree_dotgraph.go

@@ -8,7 +8,6 @@ import (
 	"os"
 	"text/template"
 
-	ibytes "github.com/cosmos/iavl/internal/bytes"
 	"github.com/emicklei/dot"
 )
 
@@ -61,12 +60,12 @@ func WriteDOTGraph(w io.Writer, tree *ImmutableTree, paths []PathToLeaf) {
 		}
 		shortHash := graphNode.Hash[:7]
 
-		graphNode.Label = mkLabel(ibytes.UnsafeBytesToStr(node.key), 16, "sans-serif")
+		graphNode.Label = mkLabel(string(node.key), 16, "sans-serif")
 		graphNode.Label += mkLabel(shortHash, 10, "monospace")
 		graphNode.Label += mkLabel(fmt.Sprintf("nodeKey=%v", node.nodeKey), 10, "monospace")
 
 		if node.value != nil {
-			graphNode.Label += mkLabel(ibytes.UnsafeBytesToStr(node.value), 10, "sans-serif")
+			graphNode.Label += mkLabel(string(node.value), 10, "sans-serif")
 		}
 
 		if node.subtreeHeight == 0 {