From 0ef4c578d372f00d0eedac154e279acbd2646f8a Mon Sep 17 00:00:00 2001
From: Ludovic 'Archivist' Lagouardette
 <archivist@172-0-0-153.lightspeed.brhmal.sbcglobal.net>
Date: Wed, 5 Feb 2020 18:54:27 +0100
Subject: [PATCH] More RC6 fixes

---
 include/rc6_generic.hpp | 46 ++++++++++++++++++++++-------------------
 1 file changed, 25 insertions(+), 21 deletions(-)

diff --git a/include/rc6_generic.hpp b/include/rc6_generic.hpp
index 5322583..3a804e2 100644
--- a/include/rc6_generic.hpp
+++ b/include/rc6_generic.hpp
@@ -66,18 +66,21 @@ class RC6 {
 
 
 	class RC6_KeySched {
+		using sched_t = std::array<word_t, 2*r+4>;
 	public:
 		static constexpr size_t c = (b+word_size-1)/word_size;
 		static constexpr size_t v_3 = std::max(c, 2*r+4);
 		static constexpr size_t v = v_3*3;
 	private:
-		std::array<word_t, 2*r+4> S;
+		sched_t S;
 	public:
-		RC6_KeySched(std::array<word_t, c> L)
+		constexpr RC6_KeySched(std::array<word_t, c> L)
 		{
 			assert(r_l(r_r(13,13),13) == 13);
-			S[0] = P;
-			for(auto it = S.begin()+1; it < S.end(); ++it)
+
+			auto it = S.begin();
+			*(it++) = P;
+			for(; it != S.end(); ++it)
 			{
 				*it = *(it-1) + Q;
 			}
@@ -88,10 +91,11 @@ class RC6 {
 
 			for(size_t s = 0; s < v; ++s)
 			{
-				i = s % (2*r+4);
-				j = s % c;
 				A = S[i] = r_l( S[i] + A + B, 3 );
 				B = L[j] = r_l( L[j] + A + B, (A + B)%(word_size));
+
+				i = s % S.size();
+				j = s % L.size();
 			}
 		}
 
@@ -99,24 +103,24 @@ class RC6 {
 			return S[pos];
 		}
 
-		auto begin()
+		const auto cbegin()
 		{
-			return S.begin();
+			return S.cbegin();
 		}
 
-		auto end()
+		const auto cend()
 		{
-			return S.end();
+			return S.cend();
 		}
 
-		auto rbegin()
+		const auto crbegin()
 		{
-			return S.rbegin();
+			return S.crbegin();
 		}
 
-		auto rend()
+		const auto crend()
 		{
-			return S.rend();
+			return S.crend();
 		}
 	};
 
@@ -127,17 +131,17 @@ public:
 	typedef std::array<word_t, RC6_KeySched::c> key_type;
 	typedef std::array<word_t, 4> block_type;
 
-	RC6(const key_type& key)
+	constexpr RC6(const key_type& key)
 	: S(key)
 	{}
 
-	block_type encrypt(block_type plaintext) {
+	constexpr const block_type encrypt(block_type plaintext) {
 		auto& A = plaintext[0];
 		auto& B = plaintext[1];
 		auto& C = plaintext[2];
 		auto& D = plaintext[3];
 
-		auto it = S.begin();
+		auto it = S.cbegin();
 
 		B += *(it++);
 		D += *(it++);
@@ -153,16 +157,16 @@ public:
 
 		A += *(it++);
 		C += *(it++);
-		assert(it == S.end());
+		assert(it == S.cend());
 		return plaintext;
 	}
 
-	block_type decrypt(block_type plaintext) {
+	constexpr const block_type decrypt(block_type plaintext) {
 		auto& A = plaintext[0];
 		auto& B = plaintext[1];
 		auto& C = plaintext[2];
 		auto& D = plaintext[3];
-		auto it = S.rbegin();
+		auto it = S.crbegin();
 
 		C -= *(it++);
 		A -= *(it++);
@@ -178,7 +182,7 @@ public:
 
 		D -= *(it++);
 		B -= *(it++);
-		assert(it == S.rend());
+		assert(it == S.crend());
 		return plaintext;
 	}