From 319e37be1303cf29b35b6100a3775ee6aea39dac Mon Sep 17 00:00:00 2001
From: Vincent Rabaud <vrabaud@google.com>
Date: Fri, 24 Jun 2016 16:11:25 +0200
Subject: [PATCH] Improve lossless compression.

This is essentially a revert of a3611513d2bf465fd282d9dc45b3f72c79c232ad
and cfbcc5ece022fc74ae9b987e05c2807df0d82ec5.
Here is what happened: there was a corruption bug that eventually
got fixed by 0174d18d8b51f6c9228c70066a987c30a8132995.
But before finding the root, a3611513d2bf465fd282d9dc45b3f72c79c232ad
and cfbcc5ece022fc74ae9b987e05c2807df0d82ec5 hid the bug
by not imposing length of 1 when it was actually 2 or 3 (which does help
compression as a litteral is more efficient than an offset and a length
of size 2 or 3).

Change-Id: I6f18fc1f583a51ac9d8aab2508458264047cd493
---
 src/enc/backward_references.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/enc/backward_references.c b/src/enc/backward_references.c
index e3c2a357..34036640 100644
--- a/src/enc/backward_references.c
+++ b/src/enc/backward_references.c
@@ -442,7 +442,7 @@ static int BackwardReferencesLz77(int xsize, int ysize,
     int len = 0;
     int j;
     HashChainFindCopy(hash_chain, i, &offset, &len);
-    if (len > MIN_LENGTH) {
+    if (len > MIN_LENGTH + 1) {
       const int len_ini = len;
       int max_reach = 0;
       assert(i + len < pix_count);
@@ -464,7 +464,7 @@ static int BackwardReferencesLz77(int xsize, int ysize,
         }
       }
     } else {
-      len = (len == 0) ? 1 : len;
+      len = 1;
     }
     // Go with literal or backward reference.
     assert(len > 0);