From c4535aefbea7b22f5f9abe894527fc10962e17c0 Mon Sep 17 00:00:00 2001
From: Michael Schierl <schierlm@gmx.de>
Date: Thu, 7 Sep 2017 22:13:26 +0200
Subject: [PATCH] Avoid copying from Array to list and back

As Java's Lists use boxed Integers, we try to avoid the memory
consumption, GC pressure and time overhead caused by copying an int[]
into a List<Integer> and back again.
---
 src/main/java/jota/utils/Signing.java | 21 ++++-----------------
 1 file changed, 4 insertions(+), 17 deletions(-)

diff --git a/src/main/java/jota/utils/Signing.java b/src/main/java/jota/utils/Signing.java
index e03543c..19cba57 100644
--- a/src/main/java/jota/utils/Signing.java
+++ b/src/main/java/jota/utils/Signing.java
@@ -54,29 +54,16 @@ public class Signing {
         curl.reset();
         curl.absorb(seed, 0, seed.length);
 
-        final List<Integer> key = new ArrayList<>();
-        int[] buffer = new int[seed.length];
+        final int[] key = new int[length * seed.length * 27];
         int offset = 0;
 
         while (length-- > 0) {
-
             for (int i = 0; i < 27; i++) {
-                curl.squeeze(buffer, offset, buffer.length);
-                for (int j = 0; j < 243; j++) {
-                    key.add(buffer[j]);
-                }
+                curl.squeeze(key, offset, seed.length);
+                offset += seed.length;
             }
         }
-        return to(key);
-    }
-
-    private int[] to(List<Integer> key) {
-        int a[] = new int[key.size()];
-        int i = 0;
-        for (Integer v : key) {
-            a[i++] = v;
-        }
-        return a;
+        return key;
     }
 
     public int[] signatureFragment(int[] normalizedBundleFragment, int[] keyFragment) {