From c0efa75c1adce9f4bfe6e36d50e57935a0d13f16 Mon Sep 17 00:00:00 2001
From: surtur <a_mirre@utb.cz>
Date: Tue, 26 Oct 2021 15:59:22 +0200
Subject: [PATCH] switch to using {tuples,128bit int for ctr}

multiple changes combined in a single commit, I know...

also, a move towards the use of OOP paradigm is imminent as we now have
to do rewrites at multiple places in the code for any minor change
---
 generator.cpp | 25 +++++++++++++++++--------
 generator.h   |  7 ++++---
 2 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/generator.cpp b/generator.cpp
index bb2d234..3ee3c3b 100644
--- a/generator.cpp
+++ b/generator.cpp
@@ -1,14 +1,14 @@
 #include <cmath>
 #include <cassert>
 #include <stdexcept>
+#include <tuple>
 #include "generator.h"
 
 using namespace std;
 
 struct G_state{
 	long k;
-	// TODO: use __int128 for ctr eventually;
-	unsigned long ctr;
+	unsigned __int128 ctr;
 };
 
 G_state *initialize_generator(){
@@ -18,7 +18,7 @@ G_state *initialize_generator(){
 	return G;
 };
 
-string do_crypto(long k, unsigned long ctr){
+string do_crypto(long k, unsigned __int128 ctr){
 	/* this function calls the block cipher
 	   do whatever atm */
 	k = 0;
@@ -26,17 +26,19 @@ string do_crypto(long k, unsigned long ctr){
 	return "";
 }
 
-G_state generate_blocks(G_state G, int k_blocks){
+/* lacking objects, we have to return both the state and the string */
+tuple<string, G_state> generate_blocks(G_state G, int k_blocks){
 	assert (G.ctr!=0);
 	string r = "";
 	for (int i = 0; i < k_blocks; ++i) {
 		r += do_crypto(G.k, G.ctr);
 		G.ctr += 1;
 	}
-	return G;
+	return {r, G};
 }
 
-string generate_random_data(G_state G, uint n){
+/* n is number of random bytes to generate */
+tuple<string, G_state> generate_random_data(G_state G, uint n){
 	string r = "";
 	if (n < 0){
 		/* this should not be possible */
@@ -48,8 +50,15 @@ string generate_random_data(G_state G, uint n){
 	}
 	/* do magic to compute r
 	 * r ← first-n-bytes(GenerateBlocks(G, ceil(n/16) )) */
-	string rr = to_string(generate_blocks(G,ceil(n/16)).ctr);
+	string rr = std::get<0>(generate_blocks(G,ceil(n/16)));
 	r = rr.substr(0,n);
-	return r;
+
+	/* re-key */
+	// TODO: check conversions
+	G.k = stoul(std::get<0>(generate_blocks(G, 2)));
+	// returning just r throws away our state, this should be reworked
+	// using OOP
+	// return r;
+	return {r, G};
 };
 
diff --git a/generator.h b/generator.h
index 470af3b..53304e7 100644
--- a/generator.h
+++ b/generator.h
@@ -3,17 +3,18 @@
 
 #include <string>
 #include <cstring>
+#include <tuple>
 
 struct G_state;
 
 /* initializes generator */
 G_state *initialize_generator();
 
-std::string do_crypto(long k, unsigned long ctr);
+std::string do_crypto(long k, unsigned __int128 ctr);
 
-G_state generate_blocks(G_state G, int k_blocks);
+std::tuple<std::string, G_state> generate_blocks(G_state G, int k_blocks);
 
 /* returns output of 0 <= n <= 2^20 bytes */
-std::string generate_random_data(G_state G, int n);
+std::tuple<std::string, G_state> generate_random_data(G_state G, int n);
 
 #endif//FORTUNA_GENERATOR_H