From 7a28fe8cc39880025c83a81cf88797aa5f174b0d Mon Sep 17 00:00:00 2001
From: tatiana-kondakova <tatiana.kondakova@gmail.com>
Date: Tue, 24 Apr 2018 18:16:41 +0300
Subject: [PATCH] [geocoder] Use delta coding for borders

---
 generator/feature_builder.cpp |  8 +++++++-
 indexer/borders.cpp           | 17 ++++++++++++-----
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/generator/feature_builder.cpp b/generator/feature_builder.cpp
index 0aaf0bbe2b..55e6a52b40 100644
--- a/generator/feature_builder.cpp
+++ b/generator/feature_builder.cpp
@@ -419,11 +419,17 @@ void FeatureBuilder1::SerializeBorder(serial::GeometryCodingParams const & param
   CHECK_GREATER(m_polygons.size(), 0, ());
 
   WriteToSink(sink, m_polygons.size() - 1);
+
+  auto toU = [&params](m2::PointD const & p) { return PointDToPointU(p, params.GetCoordBits()); };
   for (auto const & polygon : m_polygons)
   {
     WriteToSink(sink, polygon.size());
+    auto last = params.GetBasePoint();
     for (auto const & p : polygon)
-      serial::SavePoint(sink, p, params);
+    {
+      coding::EncodePointDelta(sink, toU(last), toU(p));
+      last = p;
+    }
   }
 }
 
diff --git a/indexer/borders.cpp b/indexer/borders.cpp
index 0702ae728f..81946e145a 100644
--- a/indexer/borders.cpp
+++ b/indexer/borders.cpp
@@ -25,6 +25,16 @@ public:
     m_recordReader.ForEachRecord([&](uint32_t pos, char const * data, uint32_t /*size*/) {
       ArrayByteSource src(data);
       serial::GeometryCodingParams cp = {};
+
+      auto readPoly = [&cp, &src](vector<m2::PointD> & poly) {
+        m2::PointU base = PointDToPointU(cp.GetBasePoint(), cp.GetCoordBits());
+        for (auto & point : poly)
+        {
+          base = coding::DecodePointDelta(src, base);
+          point = PointUToPointD(base, cp.GetCoordBits());
+        }
+      };
+
       uint64_t id;
       ReadPrimitiveFromSource(src, id);
       size_t size;
@@ -32,9 +42,7 @@ public:
       size_t outerSize;
       ReadPrimitiveFromSource(src, outerSize);
       vector<m2::PointD> outer(outerSize);
-      // todo:(@t.yan) consider delta coding techniques.
-      for (auto & point : outer)
-        point = serial::LoadPoint(src, cp);
+      readPoly(outer);
 
       vector<vector<m2::PointD>> inners(size);
       for (auto & inner : inners)
@@ -42,8 +50,7 @@ public:
         size_t innerSize;
         ReadPrimitiveFromSource(src, innerSize);
         inner = vector<m2::PointD>(innerSize);
-        for (auto & point : inner)
-          point = serial::LoadPoint(src, cp);
+        readPoly(inner);
       }
       toDo(id, outer, inners);
     });