From 1c2e807f69e563f7a133737a6ab6bebf43a563da Mon Sep 17 00:00:00 2001
From: Mirek Kratochvil <exa.exa@gmail.com>
Date: Sun, 13 May 2012 00:17:12 +0200
Subject: [PATCH] debugging stash 1

---
 include/codecrypt.h |  1 +
 lib/bvector.cpp     | 12 ++++++++--
 lib/gf2m.cpp        |  2 +-
 lib/polynomial.cpp  | 56 ++++++++++++++++++++++-----------------------
 4 files changed, 39 insertions(+), 32 deletions(-)

diff --git a/include/codecrypt.h b/include/codecrypt.h
index 0d248b8..b30ba1f 100644
--- a/include/codecrypt.h
+++ b/include/codecrypt.h
@@ -38,6 +38,7 @@ public:
 	bool operator* (const bvector&); //dot product
 	bool zero() const;
 	void to_poly (polynomial&, gf2m&);
+	void from_poly (const polynomial&, gf2m&);
 };
 
 /*
diff --git a/lib/bvector.cpp b/lib/bvector.cpp
index 04179c4..9630af7 100644
--- a/lib/bvector.cpp
+++ b/lib/bvector.cpp
@@ -34,8 +34,16 @@ bool bvector::zero() const
 void bvector::to_poly (polynomial&r, gf2m&fld)
 {
 	r.clear();
-	if(size() % fld.m) return; //impossible
+	if (size() % fld.m) return; //impossible
 	r.resize (size() / fld.m, 0);
 	for (uint i = 0; i < size(); ++i)
-		if (item (i) ) r[i/fld.m] |= 1 << (i % fld.m);
+		if (item (i) ) r[i/fld.m] |= (1 << (i % fld.m) );
+}
+
+void bvector::from_poly (const polynomial&r, gf2m&fld)
+{
+	clear();
+	resize (r.size() *fld.m, 0);
+	for (uint i = 0; i < size(); ++i)
+		item (i) = (r[i/fld.m] >> (i % fld.m) ) & 1;
 }
diff --git a/lib/gf2m.cpp b/lib/gf2m.cpp
index b8858d2..038cb37 100644
--- a/lib/gf2m.cpp
+++ b/lib/gf2m.cpp
@@ -76,7 +76,7 @@ bool gf2m::create (uint M)
 	m = M;
 	n = 1 << m;
 	if (!n) return false; //too big.
-	for (uint t = 1 + (1 << m), e = 1 << (1 + m); t < e; t += 2)
+	for (uint t = (1 << m)+1, e = 1 << (m+1); t < e; t += 2)
 		if (is_irreducible_gf2_poly (t) ) {
 			poly = t;
 			return true;
diff --git a/lib/polynomial.cpp b/lib/polynomial.cpp
index 451e84d..ca484f2 100644
--- a/lib/polynomial.cpp
+++ b/lib/polynomial.cpp
@@ -67,15 +67,14 @@ void polynomial::mod (const polynomial&f, gf2m&fld)
 void polynomial::mult (const polynomial&b, gf2m&fld)
 {
 	polynomial a = *this;
-	clear();
 	uint i, j;
 	int da, db;
 	da = a.degree();
 	db = b.degree();
-	if ( (da < 0) || (db < 0) ) { //multiply by zero
-		clear();
+
+	clear();
+	if ( (da < 0) || (db < 0) ) //multiply by zero
 		return;
-	}
 
 	resize (da + db + 1, 0);
 	for (i = 0; i <= da; ++i)
@@ -113,7 +112,7 @@ bool polynomial::is_irreducible (gf2m&fld) const
 	xmodf.mod (*this, fld); //mod f
 
 	uint d = degree();
-	for (uint i = 1; i <= d / 2; ++i) {
+	for (uint i = 1; i <= (d / 2); ++i) {
 		for (uint j = 0; j < fld.m; ++j) {
 			t = xi;
 			t.mult (xi, fld);
@@ -124,7 +123,7 @@ bool polynomial::is_irreducible (gf2m&fld) const
 		t.add (xmodf, fld);
 
 		t = t.gcd (*this, fld);
-		if (t.degree() > 0) //gcd(f,x^2^i - x mod f) != const
+		if (!t.one() )
 			return false;
 	}
 	return true;
@@ -228,7 +227,7 @@ void polynomial::compute_goppa_check_matrix (matrix&r, gf2m&fld)
 {
 	if (degree() < 0) return; //wrongly initialized polynomial
 	uint t = degree();
-	vector<vector<uint> > vd, h;
+	vector<polynomial> vd, h; //matrix over fld
 	uint i, j, k;
 
 	//construction from Barreto's slides with maximal support L=[0..fld.n)
@@ -246,20 +245,18 @@ void polynomial::compute_goppa_check_matrix (matrix&r, gf2m&fld)
 	for (i = 0; i < fld.n; ++i) {
 		h[i].resize (t);
 		for (j = 0; j < t; ++j) { //computing the element h[i][j]
-			h[i][j]=0;
+			h[i][j] = 0;
 			for (k = 0; k <= j; ++k) //k = column index of t
 				h[i][j] = fld.add (h[i][j],
-				                   fld.mult (item (t - j + k),
+				                   fld.mult (item (t + k - j),
 				                             vd[i][k]) );
+		}
 	}
 
 	//now convert to binary
 	r.resize (fld.n);
-	for (i = 0; i < fld.n; ++i) {
-		r[i].resize (fld.m * t);
-		for (j = 0; j < fld.m * t; ++j)
-			r[i][j] = (h[i][j/fld.m] >> (j % fld.m) ) & 1;
-	}
+	for (i = 0; i < fld.n; ++i)
+		r[i].from_poly (h[i], fld);
 }
 
 void polynomial::make_monic (gf2m&fld)
@@ -279,7 +276,7 @@ void polynomial::shift (uint n)
 void polynomial::square (gf2m&fld)
 {
 	polynomial a = *this;
-	this->mult (a, fld);
+	mult (a, fld);
 }
 
 void polynomial::sqrt (vector<polynomial>& sqInv, gf2m&fld)
@@ -329,10 +326,7 @@ void polynomial::div (polynomial&p, polynomial&m, gf2m&fld)
 	}
 
 	*this = s0;
-	if (r0.degree() >= 0) {
-		uint m = fld.inv (r0[r0.degree() ]);
-		for (uint i = 0; i < size(); ++i) item (i) = fld.mult (item (i), m);
-	}
+	make_monic(fld);
 }
 
 void polynomial::divmod (polynomial&d, polynomial&res, polynomial&rem, gf2m&fld)
@@ -356,31 +350,35 @@ void polynomial::divmod (polynomial&d, polynomial&res, polynomial&rem, gf2m&fld)
 void polynomial::inv (polynomial&m, gf2m&fld)
 {
 	polynomial a = *this;
-	this->resize (1);
+	resize (1);
 	item (0) = 1;
 	div (a, m, fld);
 }
 
-void polynomial::mod_to_fracton (polynomial&a, polynomial&b, polynomial&m, gf2m&fld)
+void polynomial::mod_to_fracton (polynomial&a, polynomial&b,
+                                 polynomial&m, gf2m&fld)
 {
 	int deg = m.degree() / 2;
-	polynomial a0, a1, b0, b1, t1, t2;
+	polynomial a0, a1, b0, b1, q, r;
 	a0 = m;
 	a1 = *this;
 	a1.mod (m, fld);
-	b0.resize (1, 0);
+
+	b0.clear();
+	b1.clear();
 	b1.resize (1, 1);
+
 	while (a1.degree() > deg) {
 
-		a0.divmod (a1, t1, t2, fld);
+		a0.divmod (a1, q, r, fld);
 		a0.swap (a1);
-		a1.swap (t2);
+		a1.swap (r);
 
-		t1.mult (b1, fld);
-		t1.mod (m, fld);
-		t1.add (b0, fld);
+		q.mult (b1, fld);
+		q.mod (m, fld);
+		q.add (b0, fld);
 		b0.swap (b1);
-		b1.swap (t1);
+		b1.swap (q);
 	}
 	a = a1;
 	b = b1;