From 6fdcc6f75b89ca4536a819da00c9e5f009b9a5bd Mon Sep 17 00:00:00 2001
From: Sean Bowe <ewillbefull@gmail.com>
Date: Wed, 14 Sep 2016 11:15:53 -0600
Subject: [PATCH] Refactor dummy CS instance creation.

---
 snark/src/lib.rs           |  4 +--
 snark/src/libsnarkwrap.cpp | 63 +++++++++++++++++++++++---------------
 2 files changed, 40 insertions(+), 27 deletions(-)

diff --git a/snark/src/lib.rs b/snark/src/lib.rs
index b6ad548..7278a1d 100644
--- a/snark/src/lib.rs
+++ b/snark/src/lib.rs
@@ -9,7 +9,7 @@ use bn::*;
 
 extern "C" {
     fn libsnarkwrap_init();
-    fn libsnarkwrap_getcs(d: *mut libc::uint64_t, vars: *mut libc::uint64_t, inputs: *mut libc::uint64_t, omega: *mut Fr) -> *mut libc::c_void;
+    fn libsnarkwrap_getcs_dummy(d: *mut libc::uint64_t, vars: *mut libc::uint64_t, inputs: *mut libc::uint64_t, omega: *mut Fr) -> *mut libc::c_void;
     fn libsnarkwrap_dropcs(cs: *mut libc::c_void);
     fn libsnarkwrap_dropkeypair(kp: *mut libc::c_void);
     fn libsnarkwrap_eval(
@@ -204,7 +204,7 @@ impl CS {
         let mut num_inputs = 0;
         let mut o = Fr::zero();
 
-        let cs = unsafe { libsnarkwrap_getcs(&mut d, &mut vars, &mut num_inputs, &mut o) };
+        let cs = unsafe { libsnarkwrap_getcs_dummy(&mut d, &mut vars, &mut num_inputs, &mut o) };
 
         CS {
             ptr: cs,
diff --git a/snark/src/libsnarkwrap.cpp b/snark/src/libsnarkwrap.cpp
index c51172f..ba09931 100644
--- a/snark/src/libsnarkwrap.cpp
+++ b/snark/src/libsnarkwrap.cpp
@@ -39,35 +39,48 @@ extern "C" void libsnarkwrap_init() {
 
 // QAP
 
-extern "C" void* libsnarkwrap_getcs(uint64_t *d, uint64_t *vars, uint64_t *num_inputs, curve_Fr *omega)
+void* libsnark_cs_return(
+    uint64_t *d, uint64_t *vars, uint64_t *num_inputs, curve_Fr *omega,
+    r1cs_constraint_system<curve_Fr> cs
+)
+{
+    // A/B swap
+    cs.swap_AB_if_beneficial();
+
+    // QAP reduction
+    auto qap = r1cs_to_qap_instance_map(cs);
+
+    *vars = cs.num_variables()+1;
+    *d = qap.degree();
+
+    // Sanity checks
+    assert(qap.A_in_Lagrange_basis.size() == *vars);
+    assert(qap.B_in_Lagrange_basis.size() == *vars);
+    assert(qap.C_in_Lagrange_basis.size() == *vars);
+
+    // Degree of the QAP must be a power of 2
+    assert(*d >= 2);
+    assert(((*d / 2) * 2) == *d);
+    
+    // Assume radix2 evaluation domain
+    *omega = std::static_pointer_cast<basic_radix2_domain<curve_Fr>>(qap.domain)->omega;
+    *num_inputs = cs.num_inputs();
+
+    return new r1cs_constraint_system<curve_Fr>(cs);
+}
+
+extern "C" void* libsnarkwrap_getcs_dummy(uint64_t *d, uint64_t *vars, uint64_t *num_inputs, curve_Fr *omega)
 {
     // Generate a dummy circuit
     auto example = generate_r1cs_example_with_field_input<curve_Fr>(250, 4);
 
-    // A/B swap
-    example.constraint_system.swap_AB_if_beneficial();
-
-    {
-        // QAP reduction
-        auto qap = r1cs_to_qap_instance_map(example.constraint_system);
-
-        // Sanity checks
-        assert(qap.A_in_Lagrange_basis.size() == example.constraint_system.num_variables()+1);
-        assert(qap.B_in_Lagrange_basis.size() == example.constraint_system.num_variables()+1);
-        assert(qap.C_in_Lagrange_basis.size() == example.constraint_system.num_variables()+1);
-
-        // Degree of the QAP must be a power of 2
-        assert(qap.degree() == 256);
-        
-        // Assume radix2 evaluation domain
-        *omega = std::static_pointer_cast<basic_radix2_domain<curve_Fr>>(qap.domain)->omega;
-
-        *d = qap.degree();
-        *vars = example.constraint_system.num_variables()+1;
-        *num_inputs = example.constraint_system.num_inputs();
-    }
-    
-    return new r1cs_constraint_system<curve_Fr>(example.constraint_system);
+    return libsnark_cs_return(
+        d,
+        vars,
+        num_inputs,
+        omega,
+        example.constraint_system
+    );
 }
 
 extern "C" void libsnarkwrap_dropcs(r1cs_constraint_system<curve_Fr> *cs)