From 9997c1c0437c53cf0e16d7da388bce825f02b23d Mon Sep 17 00:00:00 2001
From: Lam Pham-Sy <lam.pham-sy@scality.com>
Date: Fri, 22 Jun 2018 12:37:07 +0200
Subject: [PATCH] FEC NF4: fix

---
 src/fec_rs_nf4.h | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/src/fec_rs_nf4.h b/src/fec_rs_nf4.h
index ec0d8007..a8387be9 100644
--- a/src/fec_rs_nf4.h
+++ b/src/fec_rs_nf4.h
@@ -305,26 +305,36 @@ class RsNf4 : public FecCode<T> {
         for (unsigned i = 0; i < this->n_data; ++i) {
             const int frag_id = fragments_ids.get(i);
             T* chunk = words->get(i);
-            size_t curr_frag_index = 0;
-            // loop over marked symbols
+
+            // the vector will contain marked symbols that will be packed
+            // firstly. Since locations are stored in unordered map, the vector
+            // will be sorted later to facilitate packing un-marked symbols
+            std::vector<size_t> packed_symbs;
+            // pack marked symbols
             for (auto const& data : props[frag_id].get_map()) {
                 off_t loc_offset = data.first.get_offset();
                 if (loc_offset >= offset && loc_offset < offset_max) {
                     // As loc.offset := offset + j * this->word_size
                     const size_t j = (loc_offset - offset) / this->word_size;
-
-                    // pack symbols from `curr_frag_index` to `j-1`
-                    for (; curr_frag_index < j; ++curr_frag_index) {
-                        chunk[curr_frag_index] =
-                            ngff4->pack(chunk[curr_frag_index]);
-                    }
-                    // increment curr_frag_index to pass found index `j`
-                    curr_frag_index++;
+                    packed_symbs.push_back(j);
                     // pack symbol at index `j`
                     uint32_t flag = std::stoul(data.second);
                     chunk[j] = ngff4->pack(chunk[j], flag);
                 }
             }
+            // sort the list of packed symbols
+            std::sort(packed_symbs.begin(), packed_symbs.end());
+
+            // pack un-marked symbols
+            size_t curr_frag_index = 0;
+            for (auto const& done_id : packed_symbs) {
+                // pack symbols from `curr_frag_index` to `j-1`
+                for (; curr_frag_index < done_id; ++curr_frag_index) {
+                    chunk[curr_frag_index] =
+                        ngff4->pack(chunk[curr_frag_index]);
+                }
+                curr_frag_index++;
+            }
             // pack last symbols from `curr_frag_index` to `this->pkt_size-1`
             for (; curr_frag_index < this->pkt_size; ++curr_frag_index) {
                 chunk[curr_frag_index] = ngff4->pack(chunk[curr_frag_index]);