serialize/save: add RLE for empty tiles

3 files changed, 31 insertions, 1 deletions

diff --git a/serialize/world-impl.hpp b/serialize/world-impl.hpp
index a869e022..ea7e8792 100644
--- a/serialize/world-impl.hpp
+++ b/serialize/world-impl.hpp
@@ -23,6 +23,7 @@
  *  8) Entity subtypes.
  *  9) Interned strings.
  * 10) Chunk Z level.
+ * 11) RLE empty tiles.
  */
 
 namespace floormat {
@@ -49,7 +50,7 @@ constexpr inline auto null_atlas = (atlasid)-1LL;
 constexpr inline size_t character_name_max = 128;
 constexpr inline size_t string_max = 512;
 
-constexpr inline proto_t proto_version = 10;
+constexpr inline proto_t proto_version = 11;
 constexpr inline proto_t min_proto_version = 1;
 constexpr inline auto chunk_magic = (uint16_t)~0xc0d3;
 constexpr inline auto scenery_magic = (uint16_t)~0xb00b;
@@ -76,6 +77,8 @@ enum : tilemeta {
     meta_ground         = 1 << 2,
     meta_wall_n         = 1 << 3,
     meta_wall_w         = 1 << 4,
+    meta_rle            = 1 << 7,
+
     meta_short_atlasid_ = 1 << 5,
     meta_short_variant_ = 1 << 6,
     meta_scenery_       = 1 << 7,
diff --git a/serialize/world-reader.cpp b/serialize/world-reader.cpp
index 05add388..90b040f3 100644
--- a/serialize/world-reader.cpp
+++ b/serialize/world-reader.cpp
@@ -184,6 +184,15 @@ void reader_state::read_chunks(reader_t& s)
         {
             SET_CHUNK_SIZE();
             const tilemeta flags = s.read<tilemeta>();
+
+            if (PROTO >= 11) [[likely]]
+                if (flags & meta_rle)
+                {
+                    auto j = flags & 0x7fuz;
+                    i += j;
+                    continue;
+                }
+
             tile_ref t = c[i];
             using uchar = uint8_t;
             const auto make_atlas = [&]() -> tile_image_proto {
diff --git a/serialize/world-writer.cpp b/serialize/world-writer.cpp
index ee955c47..8ffe1883 100644
--- a/serialize/world-writer.cpp
+++ b/serialize/world-writer.cpp
@@ -422,6 +422,24 @@ void writer_state::serialize_chunk(const chunk& c, chunk_coords_ coord)
         auto img_n = maybe_intern_atlas(wall_north);
         auto img_w = maybe_intern_atlas(wall_west);
 
+        if (img_g == null_atlas && img_n == null_atlas && img_w == null_atlas)
+        {
+            size_t j, max = std::min(TILE_COUNT, i + 0x80);
+            for (j = i+1; j < max; j++)
+            {
+                auto tile = c[j];
+                if (tile.ground_atlas || tile.wall_north_atlas || tile.wall_west_atlas)
+                    break;
+            }
+            j -= i + 1;
+            fm_assert(j == (j & 0x7fuz));
+            i += j;
+            tilemeta flags = meta_rle | (tilemeta)j;
+            s << flags;
+
+            continue;
+        }
+
         tilemeta flags = {};
         flags |= meta_ground  * (img_g != null_atlas);
         flags |= meta_wall_n  * (img_n != null_atlas);