From 595cf80cc5e31fcaa871766a231113908c2f2f08 Mon Sep 17 00:00:00 2001
From: Ahmet Inan <inan@aicodix.de>
Date: Fri, 21 Apr 2023 09:00:19 +0200
Subject: [PATCH] degree of poly is always larger than of the element

---
 galois_field.hh | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/galois_field.hh b/galois_field.hh
index 8ac3713..b54229c 100644
--- a/galois_field.hh
+++ b/galois_field.hh
@@ -393,14 +393,19 @@ GaloisFieldReference<M, POLY, TYPE> rcp(GaloisFieldReference<M, POLY, TYPE> a)
 {
 	assert(a.v);
 #if 1
-	uint32_t r = POLY, newr = a.v;
-	uint32_t t = 0, newt = 1;
+	if (a.v == 1)
+		return a;
+	uint32_t newr = POLY, r = a.v;
+	uint32_t newt = 0, t = 1;
 	auto degree = [](uint32_t a) {
 		int d = 0;
 		while (a >>= 1)
 			++d;
 		return d;
 	};
+	int j = M - degree(r);
+	newr ^= r << j;
+	newt ^= t << j;
 	while (newr != 1) {
 		int j = degree(newr) - degree(r);
 		if (j < 0) {