From 7d91d4bc01b9c13cc70a9ced3161b69667d96728 Mon Sep 17 00:00:00 2001
From: Laurian-Dufrechou <lauriandugers@hotmail.fr>
Date: Wed, 26 Oct 2022 16:13:54 +0200
Subject: [PATCH] RemoveNullChar

fonction qui enleve le dernier charactere si il est null
---
 src/cryptography/Des.java | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/cryptography/Des.java b/src/cryptography/Des.java
index 5c9a01e..692617a 100644
--- a/src/cryptography/Des.java
+++ b/src/cryptography/Des.java
@@ -121,6 +121,7 @@ public class Des {
         // On découpe en bloc de 8bits
         int[][] blocsOfOctet = decoupage(blocs, blocs.length / 8);
 
+
         StringBuilder resultat = new StringBuilder();
         for (int[] octet : blocsOfOctet) {
             // Convertis l'octet en chaine de caractère
@@ -363,6 +364,32 @@ public class Des {
         return recollageBloc(msg_crypte_bit);
     }
 
+    /**
+     * Remove the last character if it contains only zeros
+     * @param message_decrypte
+     *
+     * @return int[] = array without the last 8 bits if they were all zeroes
+     */
+    public static int[] removeCharNull (int[] message_decrypte){
+
+        int[][] blocsOfOctet = decoupage(message_decrypte, message_decrypte.length / 8);
+
+
+        int[] octet = blocsOfOctet[blocsOfOctet.length-1];
+        StringBuilder stringBuilderOctet = new StringBuilder();
+        for (int i : octet) stringBuilderOctet.append(i);
+        String stringOctet = stringBuilderOctet.toString();
+        int c = Integer.parseInt(stringOctet, 2);
+
+        if ((char) c == 0){
+            int[] newTab = new int[message_decrypte.length-8];
+            System.arraycopy(message_decrypte, 0, newTab, 0, newTab.length);
+            return newTab;
+        }else{
+            return message_decrypte;
+        }
+     }
+
     public String decrypte(int[] messageCode) {
         int[][] decoupe = decoupage(messageCode, messageCode.length / TAILLE_BLOC);
 
@@ -381,7 +408,8 @@ public class Des {
             invPermutation(PERM_INITIALE, decoupe[i]);
         }
         int[] message_decrypte = recollageBloc(decoupe);
-        return bitsToString(message_decrypte);
+
+        return bitsToString(removeCharNull(message_decrypte));
     }
 }