Note values should be little-endian byte order.

src/zcash/util.cpp

@@ -0,0 +1,12 @@
+#include "zcash/util.h"
+#include <algorithm>
+
+std::vector<unsigned char> convertIntToVectorLE(const uint64_t val_int) {
+    std::vector<unsigned char> bytes;
+
+    for(size_t i = 0; i < 8; i++) {
+        bytes.push_back(val_int >> (i * 8));
+    }
+
+    return bytes;
+}