From bce3026b6d499b049e03c44094437cdf8bee92ee Mon Sep 17 00:00:00 2001
From: MITSUNARI Shigeo <herumi@nifty.com>
Date: Mon, 8 Feb 2016 23:30:58 +0900
Subject: [PATCH] test of addNC/subNC

---
 include/mcl/fp.hpp    |  8 ++++++++
 src/fp.cpp            |  7 ++++---
 test/mont_fp_test.cpp | 10 ++++++++--
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/include/mcl/fp.hpp b/include/mcl/fp.hpp
index 09f5909..9387355 100644
--- a/include/mcl/fp.hpp
+++ b/include/mcl/fp.hpp
@@ -129,6 +129,14 @@ public:
 	{
 		Gmp::getStr(pstr, op_.mp);
 	}
+	/*
+		binary patter of p
+		@note the value of p is zero
+	*/
+	static inline const FpT& getP()
+	{
+		return *reinterpret_cast<const FpT*>(op_.p);
+	}
 	static inline bool isOdd(const FpT& x)
 	{
 		fp::Block b;
diff --git a/src/fp.cpp b/src/fp.cpp
index 08b7b53..1fc761f 100644
--- a/src/fp.cpp
+++ b/src/fp.cpp
@@ -122,12 +122,12 @@ struct OpeFunc {
 		}
 		Gmp::getArray(z, N, mz);
 	}
-	// z = x + y
+	// z = x + y without carry
 	static inline void fp_addNCC(Unit *z, const Unit *x, const Unit *y)
 	{
-		Unit ret[N + 2]; // not N + 1
+		Unit ret[N + 1];
 		mpz_t mz, mx, my;
-		set_zero(mz, ret, N + 2);
+		set_zero(mz, ret, N + 1);
 		set_mpz_t(mx, x);
 		set_mpz_t(my, y);
 		mpz_add(mz, mx, my);
@@ -140,6 +140,7 @@ struct OpeFunc {
 		set_zero(mz, ret, N + 1);
 		set_mpz_t(mx, x);
 		set_mpz_t(my, y);
+		assert(mx >= my);
 		mpz_sub(mz, mx, my);
 		Gmp::getArray(z, N, mz);
 	}
diff --git a/test/mont_fp_test.cpp b/test/mont_fp_test.cpp
index 7336314..e7927f6 100644
--- a/test/mont_fp_test.cpp
+++ b/test/mont_fp_test.cpp
@@ -459,9 +459,15 @@ struct Test {
 		{
 			Fp x(5), y(3), z;
 			Fp::addNC(z, x, y);
+			if (Fp::compareRaw(z, Fp::getP()) >= 0) {
+				Fp::subNC(z, z, Fp::getP());
+			}
 			CYBOZU_TEST_EQUAL(z, Fp(8));
-//			Fp::subNC(z, x, y);
-//			CYBOZU_TEST_EQUAL(z, Fp(2));
+			if (Fp::compareRaw(x, y) < 0) {
+				Fp::addNC(x, x, Fp::getP());
+			}
+			Fp::subNC(x, x, y);
+			CYBOZU_TEST_EQUAL(x, Fp(2));
 		}
 	}
 	void power()