Introduce new libzcash Zcash protocol API and crypto constructions surrounding the zkSNARK circuit.

src/zcash/circuit/gadget.tcc

@@ -0,0 +1,44 @@
+template<typename FieldT, size_t NumInputs, size_t NumOutputs>
+class joinsplit_gadget : gadget<FieldT> {
+public:
+    joinsplit_gadget(protoboard<FieldT> &pb) : gadget<FieldT>(pb) {
+        pb_variable_array<FieldT> test;
+        test.allocate(pb, 1);
+        pb.set_input_sizes(1);
+
+        // TODO!
+    }
+
+    void generate_r1cs_constraints() {
+        // TODO!
+    }
+
+    void generate_r1cs_witness(
+        const uint256& phi,
+        const uint256& rt,
+        const uint256& h_sig,
+        const boost::array<JSInput, NumInputs>& inputs,
+        const boost::array<Note, NumOutputs>& outputs,
+        uint64_t vpub_old,
+        uint64_t vpub_new
+    ) {
+        // TODO!
+    }
+
+    static r1cs_primary_input<FieldT> witness_map(
+        const uint256& rt,
+        const uint256& h_sig,
+        const boost::array<uint256, NumInputs>& hmacs,
+        const boost::array<uint256, NumInputs>& nullifiers,
+        const boost::array<uint256, NumOutputs>& commitments,
+        uint64_t vpub_old,
+        uint64_t vpub_new
+    ) {
+        // todo
+
+        std::vector<FieldT> input_as_field_elements;
+        input_as_field_elements.push_back(FieldT::zero());
+
+        return input_as_field_elements;
+    }
+};