From 977a8e8daba41b912e07ad059ce4a3d0a2b331ca Mon Sep 17 00:00:00 2001
From: Sean Bowe <ewillbefull@gmail.com>
Date: Thu, 4 Aug 2016 20:22:31 -0600
Subject: [PATCH] Add Fr::inverse

---
 Cargo.lock                 |  4 ++++
 snark/Cargo.lock           | 24 ------------------------
 snark/src/fr.rs            | 18 ++++++++++++++++++
 snark/src/libsnarkwrap.cpp |  4 ++++
 4 files changed, 26 insertions(+), 24 deletions(-)
 delete mode 100644 snark/Cargo.lock

diff --git a/Cargo.lock b/Cargo.lock
index 7cefcdf..c8b9f1e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -29,3 +29,7 @@ dependencies = [
  "libc 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[metadata]
+"checksum gcc 0.3.32 (registry+https://github.com/rust-lang/crates.io-index)" = "dcb000abd6df9df4c637f75190297ebe56c1d7e66b56bbf3b4aa7aece15f61a2"
+"checksum lazy_static 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)" = "cf186d1a8aa5f5bee5fd662bc9c1b949e0259e1bcc379d1f006847b0080c7417"
+"checksum libc 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)" = "39dfaaa0f4da0f1a06876c5d94329d739ad0150868069cc235f1ddf80a0480e7"
diff --git a/snark/Cargo.lock b/snark/Cargo.lock
deleted file mode 100644
index 9d0bfe6..0000000
--- a/snark/Cargo.lock
+++ /dev/null
@@ -1,24 +0,0 @@
-[root]
-name = "snark"
-version = "0.0.1"
-dependencies = [
- "gcc 0.3.32 (registry+https://github.com/rust-lang/crates.io-index)",
- "lazy_static 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
-[[package]]
-name = "gcc"
-version = "0.3.32"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-
-[[package]]
-name = "lazy_static"
-version = "0.1.16"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-
-[[package]]
-name = "libc"
-version = "0.2.14"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-
diff --git a/snark/src/fr.rs b/snark/src/fr.rs
index 7daf521..51cd4ee 100644
--- a/snark/src/fr.rs
+++ b/snark/src/fr.rs
@@ -17,6 +17,7 @@ extern "C" {
     fn libsnarkwrap_Fr_mul(a: *const Fr, b: *const Fr) -> Fr;
     fn libsnarkwrap_Fr_sub(a: *const Fr, b: *const Fr) -> Fr;
     fn libsnarkwrap_Fr_neg(a: *const Fr) -> Fr;
+    fn libsnarkwrap_Fr_inverse(a: *const Fr) -> Fr;
     fn libsnarkwrap_Fr_is_zero(a: *const Fr) -> bool;
 }
 
@@ -33,6 +34,10 @@ impl Fr {
         unsafe { libsnarkwrap_Fr_random() }
     }
 
+    pub fn inverse(&self) -> Self {
+        unsafe { libsnarkwrap_Fr_inverse(self) }
+    }
+
     pub fn is_zero(&self) -> bool {
         unsafe { libsnarkwrap_Fr_is_zero(self) }
     }
@@ -105,6 +110,19 @@ impl Neg for Fr {
     }
 }
 
+#[test]
+fn test_inverses() {
+    super::initialize();
+
+    for _ in 0..50 {
+        let a = Fr::random();
+        assert!(a != Fr::zero());
+        let b = a.inverse();
+
+        assert!(a * b == Fr::one());
+    }
+}
+
 #[test]
 fn test_basic_arith() {
     super::initialize();
diff --git a/snark/src/libsnarkwrap.cpp b/snark/src/libsnarkwrap.cpp
index b2626bf..761d640 100644
--- a/snark/src/libsnarkwrap.cpp
+++ b/snark/src/libsnarkwrap.cpp
@@ -75,6 +75,10 @@ extern "C" curve_Fr libsnarkwrap_Fr_neg(const curve_Fr *a) {
     return -(*a);
 }
 
+extern "C" curve_Fr libsnarkwrap_Fr_inverse(const curve_Fr *a) {
+    return a->inverse();
+}
+
 extern "C" bool libsnarkwrap_Fr_is_zero(const curve_Fr *a) {
     return a->is_zero();
 }