Merkle hash calculation for chunks and empty tests

swarm/storage/binarymerkle.go

@@ -0,0 +1,27 @@
+package storage
+
+// This implementation does not take advantage of any paralellisms and uses
+// far more memory than necessary, but it is easy to see that it is correct.
+// It can be used for generating test cases for optimized implementations.
+
+func BinaryMerkle(chunk []byte, hasher Hasher) []byte {
+	hash := hasher()
+	section := 2 * hash.Size()
+	l := len(chunk)
+	if l > section {
+		n := l / section
+		r := l - n*section
+		hash.Write(chunk[0:r])
+		next := hash.Sum(nil)
+		for r < l {
+			hash.Reset()
+			hash.Write(chunk[r : r+section])
+			next = hash.Sum(next)
+			r += section
+		}
+		return BinaryMerkle(next, hasher)
+	} else {
+		hash.Write(chunk)
+		return hash.Sum(nil)
+	}
+}

swarm/storage/binarymerkle_test.go

@@ -0,0 +1,42 @@
+package storage
+
+import (
+	"bytes"
+	"testing"
+)
+
+// tests the hashing of an empty slice; not even a valid chunk
+func TestEmpty(t *testing.T) {
+	// obtained from
+	// true | sha256sum
+	expected := []byte{
+		0xe3, 0xb0, 0xc4, 0x42, 0x98, 0xfc, 0x1c, 0x14, 0x9a, 0xfb, 0xf4, 0xc8,
+		0x99, 0x6f, 0xb9, 0x24, 0x27, 0xae, 0x41, 0xe4, 0x64, 0x9b, 0x93, 0x4c,
+		0xa4, 0x95, 0x99, 0x1b, 0x78, 0x52, 0xb8, 0x55,
+	}
+	empty := []byte{}
+	hasher := MakeHashFunc(NewChunkerParams().Hash)
+	hash := BinaryMerkle(empty, hasher)
+	t.Logf("Empty slice hash: %x", hash)
+	if !bytes.Equal(hash, expected) {
+		t.Errorf("Expected: %x", expected)
+	}
+}
+
+// tests the hashing of an empty chunk
+func TestEmptyChunk(t *testing.T) {
+	// obtained from
+	// head -c8 /dev/zero |sha256sum
+	expected := []byte{
+		0xaf, 0x55, 0x70, 0xf5, 0xa1, 0x81, 0x0b, 0x7a, 0xf7, 0x8c, 0xaf, 0x4b,
+		0xc7, 0x0a, 0x66, 0x0f, 0x0d, 0xf5, 0x1e, 0x42, 0xba, 0xf9, 0x1d, 0x4d,
+		0xe5, 0xb2, 0x32, 0x8d, 0xe0, 0xe8, 0x3d, 0xfc,
+	}
+	empty := []byte{0, 0, 0, 0, 0, 0, 0, 0}
+	hasher := MakeHashFunc(NewChunkerParams().Hash)
+	hash := BinaryMerkle(empty, hasher)
+	t.Logf("Empty chunk hash: %x", hash)
+	if !bytes.Equal(hash, expected) {
+		t.Errorf("Expected: %x", expected)
+	}
+}