Carry the constraint system through and compute QAP reduction whenever necessary.

snark/src/lib.rs

@@ -18,8 +18,8 @@ pub use self::g2::G2;
 extern "C" {
     fn libsnarkwrap_init();
     fn libsnarkwrap_pairing(p: *const G1, q: *const G2) -> Gt;
-    fn libsnarkwrap_getqap(d: *mut libc::uint32_t, omega: *mut Fr) -> *mut libc::c_void;
-    fn libsnarkwrap_dropqap(qap: *mut libc::c_void);
+    fn libsnarkwrap_getcs(d: *mut libc::uint32_t, omega: *mut Fr) -> *mut libc::c_void;
+    fn libsnarkwrap_dropcs(cs: *mut libc::c_void);
     fn libsnarkwrap_test_compare_tau(
         i: *const G1,
         tau: *const Fr,
@@ -41,29 +41,28 @@ pub fn initialize() {
     }
 }
 
-pub struct QAP(*mut libc::c_void);
+pub struct CS(*mut libc::c_void);
 
-impl Drop for QAP {
+impl Drop for CS {
     fn drop(&mut self) {
-        unsafe { libsnarkwrap_dropqap(self.0) }
+        unsafe { libsnarkwrap_dropcs(self.0) }
     }
 }
 
 /// Get the QAP info for the generation routines
-pub fn getqap() -> (usize, Fr, QAP) {
+pub fn getqap() -> (usize, Fr, CS) {
     let mut d = 0;
     let mut o = Fr::zero();
 
+    let cs = unsafe { libsnarkwrap_getcs(&mut d, &mut o) };
 
-    let qap = unsafe { libsnarkwrap_getqap(&mut d, &mut o) };
-
-    (d as usize, o, QAP(qap))
+    (d as usize, o, CS(cs))
 }
 
 /// Check that the lagrange coefficients computed by tau over
 /// G1 equal the expected vector.
-pub fn compare_tau(v: &[G1], tau: &Fr, qap: &QAP) -> bool {
-    unsafe { libsnarkwrap_test_compare_tau(&v[0], tau, v.len() as u32, qap.0) }
+pub fn compare_tau(v: &[G1], tau: &Fr, cs: &CS) -> bool {
+    unsafe { libsnarkwrap_test_compare_tau(&v[0], tau, v.len() as u32, cs.0) }
 }
 
 pub trait Pairing<Other: Group> {

snark/src/libsnarkwrap.cpp

@@ -172,7 +172,7 @@ extern "C" curve_GT libsnarkwrap_pairing(const curve_G1 *p, const curve_G2 *q) {
 
 // QAP
 
-qap_instance<curve_Fr> get_qap()
+extern "C" void* libsnarkwrap_getcs(uint32_t *d, curve_Fr *omega)
 {
     // Generate a dummy circuit
     auto example = generate_r1cs_example_with_field_input<curve_Fr>(250, 4);
@@ -180,41 +180,38 @@ qap_instance<curve_Fr> get_qap()
     // A/B swap
     example.constraint_system.swap_AB_if_beneficial();
 
-    // QAP reduction
-    auto qap = r1cs_to_qap_instance_map(example.constraint_system);
+    {
+        // QAP reduction
+        auto qap = r1cs_to_qap_instance_map(example.constraint_system);
 
-    // Degree of the QAP must be a power of 2
-    assert(qap.degree() == 256);
+        // 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;
 
-    return qap;
+        *d = qap.degree();
+    }
+    
+    return new r1cs_constraint_system<curve_Fr>(example.constraint_system);
 }
 
-extern "C" void* libsnarkwrap_getqap(uint32_t *d, curve_Fr *omega)
+extern "C" void libsnarkwrap_dropcs(r1cs_constraint_system<curve_Fr> *cs)
 {
-    auto qap = new qap_instance<curve_Fr>(get_qap());
-    
-    // Assume radix2 evaluation domain
-    *omega = std::static_pointer_cast<basic_radix2_domain<curve_Fr>>(qap->domain)->omega;
-    *d = qap->degree();
-    
-    return qap;
-}
-
-extern "C" void libsnarkwrap_dropqap(qap_instance<curve_Fr> *qap)
-{
-    delete qap;
+    delete cs;
 }
 
 extern "C" bool libsnarkwrap_test_compare_tau(
     const curve_G1 *inputs,
     const curve_Fr *tau,
     uint32_t d,
-    const qap_instance<curve_Fr> *qap
+    const r1cs_constraint_system<curve_Fr> *cs
 )
 {
-    auto coeffs = qap->domain->lagrange_coeffs(*tau);
+    auto qap = r1cs_to_qap_instance_map(*cs);
+    auto coeffs = qap.domain->lagrange_coeffs(*tau);
     assert(coeffs.size() == d);
-    assert(qap->degree() == d);
+    assert(qap.degree() == d);
 
     bool res = true;
     for (size_t i = 0; i < d; i++) {

src/fft.rs

@@ -46,7 +46,7 @@ mod test {
         initialize();
 
         // Get the QAP degree and omega (for FFT evaluation)
-        let (d, omega, qap) = getqap();
+        let (d, omega, cs) = getqap();
 
         // Sample a random tau
         let tau = Fr::random();
@@ -62,9 +62,9 @@ mod test {
                     .collect::<Vec<_>>();
 
         // Compare against libsnark
-        assert!(compare_tau(&lc, &tau, &qap));
+        assert!(compare_tau(&lc, &tau, &cs));
 
         // Wrong tau
-        assert!(!compare_tau(&lc, &Fr::random(), &qap));
+        assert!(!compare_tau(&lc, &Fr::random(), &cs));
     }
 }