Detect nonstandard hash algo and stop folder (ref #2314)

lib/protocol/hashalgorithm_test.go

@@ -0,0 +1,35 @@
+// Copyright (C) 2016 The Protocol Authors.
+
+package protocol
+
+import "testing"
+
+/*
+   0                   1                   2                   3
+    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+   |                       Reserved                  | Hash  |D|P|R|
+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+*/
+func TestHashAlgorithmFromFlagBits(t *testing.T) {
+	// SHA256 is algorithm zero, shifted three bits to the left (for clarity,
+	// I know it doesn't actually do anything).
+
+	sha256 := uint32(0 << 3)
+
+	h, err := HashAlgorithmFromFlagBits(sha256)
+	if err != nil {
+		t.Error(err)
+	}
+	if h != SHA256 {
+		t.Error("Zero should have unmarshalled as SHA256")
+	}
+
+	// Any other algorithm is unknown
+	unknown := uint32(1 << 3)
+
+	_, err = HashAlgorithmFromFlagBits(unknown)
+	if err == nil {
+		t.Error("Unknown algo should not have unmarshalled")
+	}
+}