refactor(Store): remove abci query req and res deps from store (#16321)

store/internal/tree/hash.go

@@ -0,0 +1,68 @@
+package tree
+
+import (
+	"crypto/sha256"
+	"hash"
+	"math/bits"
+)
+
+var (
+	leafPrefix  = []byte{0}
+	innerPrefix = []byte{1}
+)
+
+// HashFromByteSlices computes a Merkle tree where the leaves are the byte slice,
+// in the provided order. It follows RFC-6962.
+func HashFromByteSlices(items [][]byte) []byte {
+	return hashFromByteSlices(sha256.New(), items)
+}
+
+func hashFromByteSlices(sha hash.Hash, items [][]byte) []byte {
+	switch len(items) {
+	case 0:
+		return emptyHash()
+	case 1:
+		return leafHashOpt(sha, items[0])
+	default:
+		k := getSplitPoint(int64(len(items)))
+		left := hashFromByteSlices(sha, items[:k])
+		right := hashFromByteSlices(sha, items[k:])
+		return innerHashOpt(sha, left, right)
+	}
+}
+
+// returns tmhash(0x00 || leaf)
+func leafHashOpt(s hash.Hash, leaf []byte) []byte {
+	s.Reset()
+	s.Write(leafPrefix)
+	s.Write(leaf)
+	return s.Sum(nil)
+}
+
+func innerHashOpt(s hash.Hash, left, right []byte) []byte {
+	s.Reset()
+	s.Write(innerPrefix)
+	s.Write(left)
+	s.Write(right)
+	return s.Sum(nil)
+}
+
+// returns tmhash(<empty>)
+func emptyHash() []byte {
+	h := sha256.Sum256([]byte{})
+	return h[:]
+}
+
+// getSplitPoint returns the largest power of 2 less than length
+func getSplitPoint(length int64) int64 {
+	if length < 1 {
+		panic("Trying to split a tree with size < 1")
+	}
+	uLength := uint(length)
+	bitlen := bits.Len(uLength)
+	k := int64(1 << uint(bitlen-1))
+	if k == length {
+		k >>= 1
+	}
+	return k
+}