From 685c0ab07fd90b244dac5e2cb1f069ac6151ec5c Mon Sep 17 00:00:00 2001
From: Sean Bowe <ewillbefull@gmail.com>
Date: Sat, 17 Nov 2018 15:47:35 -0700
Subject: [PATCH] Allow user to ask server to save the Sprout R1CS out during
 startup.

---
 src/init.cpp            | 10 ++++++++++
 src/zcash/JoinSplit.cpp | 10 ++++++++++
 src/zcash/JoinSplit.hpp |  2 ++
 3 files changed, 22 insertions(+)

diff --git a/src/init.cpp b/src/init.cpp
index add2fc1b1..8ce766e5c 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -842,6 +842,8 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
             return InitError(_("Payment disclosure requires -experimentalfeatures."));
         } else if (mapArgs.count("-zmergetoaddress")) {
             return InitError(_("RPC method z_mergetoaddress requires -experimentalfeatures."));
+        } else if (mapArgs.count("-savesproutr1cs")) {
+            return InitError(_("Saving the Sprout R1CS requires -experimentalfeatures."));
         }
     }
 
@@ -1221,6 +1223,14 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
     // Initialize Zcash circuit parameters
     ZC_LoadParams(chainparams);
 
+    if (GetBoolArg("-savesproutr1cs", false)) {
+        boost::filesystem::path r1cs_path = ZC_GetParamsDir() / "r1cs";
+
+        LogPrintf("Saving Sprout R1CS to %s\n", r1cs_path.string());
+
+        pzcashParams->saveR1CS(r1cs_path.string());
+    }
+
     /* Start the RPC server already.  It will be started in "warmup" mode
      * and not really process calls already (but it will signify connections
      * that the server is there and will be ready later).  Warmup mode will
diff --git a/src/zcash/JoinSplit.cpp b/src/zcash/JoinSplit.cpp
index 0772ecb67..669b5f63a 100644
--- a/src/zcash/JoinSplit.cpp
+++ b/src/zcash/JoinSplit.cpp
@@ -101,6 +101,16 @@ public:
         saveToFile(pkPath, keypair.pk);
     }
 
+    void saveR1CS(std::string path)
+    {
+        protoboard<FieldT> pb;
+        joinsplit_gadget<FieldT, NumInputs, NumOutputs> g(pb);
+        g.generate_r1cs_constraints();
+        r1cs_constraint_system<FieldT> r1cs = pb.get_constraint_system();
+
+        saveToFile(path, r1cs);
+    }
+
     bool verify(
         const PHGRProof& proof,
         ProofVerifier& verifier,
diff --git a/src/zcash/JoinSplit.hpp b/src/zcash/JoinSplit.hpp
index c37926ede..2d3a61a6d 100644
--- a/src/zcash/JoinSplit.hpp
+++ b/src/zcash/JoinSplit.hpp
@@ -67,6 +67,8 @@ public:
                          const uint256& joinSplitPubKey
                         );
 
+    virtual void saveR1CS(std::string path) = 0;
+
     // Compute nullifiers, macs, note commitments & encryptions, and SNARK proof
     virtual SproutProof prove(
         bool makeGrothProof,