From bc6fd2683ecf0f4aee6d9a3154498e646cbd091a Mon Sep 17 00:00:00 2001
From: Ariel Gabizon <ariel.gabizon@gmail.com>
Date: Fri, 5 Aug 2016 20:30:52 +0300
Subject: [PATCH] returning qap

---
 snark/src/lib.rs           | 28 +++++++++++++++++++++-------
 snark/src/libsnarkwrap.cpp | 34 +++++++++++++++++-----------------
 src/fft.rs                 |  6 +++---
 3 files changed, 41 insertions(+), 27 deletions(-)

diff --git a/snark/src/lib.rs b/snark/src/lib.rs
index 5642852..825184b 100644
--- a/snark/src/lib.rs
+++ b/snark/src/lib.rs
@@ -18,8 +18,13 @@ 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);
-    fn libsnarkwrap_test_compare_tau(i: *const G1, tau: *const Fr, d: libc::uint32_t) -> bool;
+    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_test_compare_tau(
+        i: *const G1,
+        tau: *const Fr,
+        d: libc::uint32_t,
+        qap: *const libc::c_void) -> bool;
 }
 
 lazy_static! {
@@ -36,20 +41,29 @@ pub fn initialize() {
     }
 }
 
+pub struct QAP(*mut libc::c_void);
+
+impl Drop for QAP {
+    fn drop(&mut self) {
+        unsafe { libsnarkwrap_dropqap(self.0) }
+    }
+}
+
 /// Get the QAP info for the generation routines
-pub fn getqap() -> (usize, Fr) {
+pub fn getqap() -> (usize, Fr, QAP) {
     let mut d = 0;
     let mut o = Fr::zero();
 
-    unsafe { libsnarkwrap_getqap(&mut d, &mut o); }
 
-    (d as usize, o)
+    let qap = unsafe { libsnarkwrap_getqap(&mut d, &mut o) };
+
+    (d as usize, o, QAP(qap))
 }
 
 /// Check that the lagrange coefficients computed by tau over
 /// G1 equal the expected vector.
-pub fn compare_tau(v: &[G1], tau: &Fr) -> bool {
-    unsafe { libsnarkwrap_test_compare_tau(&v[0], tau, v.len() as u32) }
+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 trait Pairing<Other: Group> {
diff --git a/snark/src/libsnarkwrap.cpp b/snark/src/libsnarkwrap.cpp
index f90cfa4..c566da6 100644
--- a/snark/src/libsnarkwrap.cpp
+++ b/snark/src/libsnarkwrap.cpp
@@ -172,9 +172,7 @@ extern "C" curve_GT libsnarkwrap_pairing(const curve_G1 *p, const curve_G2 *q) {
 
 // QAP
 
-qap_instance<curve_Fr> get_qap(
-    std::shared_ptr<basic_radix2_domain<curve_Fr>> &domain
-)
+qap_instance<curve_Fr> get_qap()
 {
     // Generate a dummy circuit
     auto example = generate_r1cs_example_with_field_input<curve_Fr>(250, 4);
@@ -188,33 +186,35 @@ qap_instance<curve_Fr> get_qap(
     // Degree of the QAP must be a power of 2
     assert(qap.degree() == 256);
 
-    // Assume radix2 evaluation domain
-    domain = std::static_pointer_cast<basic_radix2_domain<curve_Fr>>(qap.domain);
-
     return qap;
 }
 
-extern "C" void libsnarkwrap_getqap(uint32_t *d, curve_Fr *omega)
+extern "C" void* libsnarkwrap_getqap(uint32_t *d, curve_Fr *omega)
 {
-    std::shared_ptr<basic_radix2_domain<curve_Fr>> domain;
-    auto qap = get_qap(domain);
+    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;
+}
 
-    *omega = domain->omega;
-    *d = qap.degree();
+extern "C" void libsnarkwrap_dropqap(qap_instance<curve_Fr> *qap)
+{
+    delete qap;
 }
 
 extern "C" bool libsnarkwrap_test_compare_tau(
     const curve_G1 *inputs,
     const curve_Fr *tau,
-    uint32_t d
+    uint32_t d,
+    const qap_instance<curve_Fr> *qap
 )
 {
-    std::shared_ptr<basic_radix2_domain<curve_Fr>> domain;
-    auto qap = get_qap(domain);
-
-    auto coeffs = domain->lagrange_coeffs(*tau);
+    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++) {
diff --git a/src/fft.rs b/src/fft.rs
index 24e58a5..23f5f8a 100644
--- a/src/fft.rs
+++ b/src/fft.rs
@@ -46,7 +46,7 @@ mod test {
         initialize();
 
         // Get the QAP degree and omega (for FFT evaluation)
-        let (d, omega) = getqap();
+        let (d, omega, qap) = 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));
+        assert!(compare_tau(&lc, &tau, &qap));
 
         // Wrong tau
-        assert!(!compare_tau(&lc, &Fr::random()));
+        assert!(!compare_tau(&lc, &Fr::random(), &qap));
     }
 }