From c8d53fa85cc413f6a1c3dfbdb1bf15a71792f265 Mon Sep 17 00:00:00 2001
From: Vladimir Byko-Ianko <v.bykoianko@corp.mail.ru>
Date: Fri, 29 Jul 2016 10:59:18 +0300
Subject: [PATCH] Separating preparing altitudes for saving and writing them.
 Using bit writer to save them.

---
 indexer/feature_altitude.cpp | 58 ++++++++++++++++++++++++++++++++++++
 indexer/feature_altitude.hpp | 44 +++++++++++----------------
 indexer/indexer.pro          |  1 +
 3 files changed, 76 insertions(+), 27 deletions(-)
 create mode 100644 indexer/feature_altitude.cpp

diff --git a/indexer/feature_altitude.cpp b/indexer/feature_altitude.cpp
new file mode 100644
index 0000000000..2cff07fc39
--- /dev/null
+++ b/indexer/feature_altitude.cpp
@@ -0,0 +1,58 @@
+#include "indexer/feature_altitude.hpp"
+
+#include "base/bits.hpp"
+
+namespace feature
+{
+void Altitudes::PrepareSerializationData(TAltitude minAltitude, vector<uint32_t> & deviations) const
+{
+  CHECK(!m_altitudes.empty(), ());
+
+  deviations.clear();
+  uint32_t const firstPntDeviation =
+      bits::ZigZagEncode(static_cast<int32_t>(m_altitudes[0]) -
+      static_cast<int32_t>(minAltitude)) + 1 /* making it more than zero */;
+  CHECK_LESS(0, firstPntDeviation, ());
+  deviations.push_back(firstPntDeviation);
+  for (size_t i = 1; i < m_altitudes.size(); ++i)
+  {
+    uint32_t const nextPntDeviation = bits::ZigZagEncode(static_cast<int32_t>(m_altitudes[i]) -
+        static_cast<int32_t>(m_altitudes[i - 1])) + 1 /* making it more than zero */;
+    CHECK_LESS(0, nextPntDeviation, ());
+    deviations.push_back(nextPntDeviation);
+  }
+}
+
+bool Altitudes::FillAltitudesByDeserializedDate(TAltitude minAltitude, vector<uint32_t> const & deviations)
+{
+  m_altitudes.clear();
+  if (deviations.size() == 0)
+  {
+    ASSERT(false, ());
+    return false;
+  }
+
+  m_altitudes.resize(deviations.size());
+  TAltitude prevAltitude = minAltitude;
+  for (size_t i = 0; i < deviations.size(); ++i)
+  {
+    if (deviations[i] == 0)
+    {
+      ASSERT(false, (i));
+      m_altitudes.clear();
+      return false;
+    }
+
+    m_altitudes[i] = static_cast<TAltitude>(bits::ZigZagDecode(deviations[i] -
+                                                               1 /* Recovering value */) + prevAltitude);
+    if (m_altitudes[i] < minAltitude)
+    {
+      ASSERT(false, (i));
+      m_altitudes.clear();
+      return false;
+    }
+    prevAltitude = m_altitudes[i];
+  }
+  return true;
+}
+}  // namespace feature
diff --git a/indexer/feature_altitude.hpp b/indexer/feature_altitude.hpp
index 81b0c918ed..755ecb0be3 100644
--- a/indexer/feature_altitude.hpp
+++ b/indexer/feature_altitude.hpp
@@ -1,4 +1,6 @@
 #pragma once
+#include "coding/bit_streams.hpp"
+#include "coding/elias_coder.hpp"
 #include "coding/reader.hpp"
 #include "coding/varint.hpp"
 #include "coding/write_to_sink.hpp"
@@ -51,7 +53,7 @@ struct AltitudeHeader
 
   size_t GetFeatureTableSize() const { return m_altitudesOffset - m_featureTableOffset; }
 
-  size_t GetAltitudeInfo() const { return m_endOffset - m_altitudesOffset; }
+  size_t GetAltitudeInfoSize() const { return m_endOffset - m_altitudesOffset; }
 
   void Reset()
   {
@@ -81,40 +83,24 @@ public:
   template <class TSink>
   void Serialize(TAltitude minAltitude, TSink & sink) const
   {
-    CHECK(!m_altitudes.empty(), ());
+    vector<uint32_t> deviations;
+    PrepareSerializationData(minAltitude, deviations);
 
-    WriteVarInt(sink, static_cast<int32_t>(m_altitudes[0]) - static_cast<int32_t>(minAltitude));
-    for (size_t i = 1; i < m_altitudes.size(); ++i)
-    {
-      WriteVarInt(sink,
-                  static_cast<int32_t>(m_altitudes[i]) - static_cast<int32_t>(m_altitudes[i - 1]));
-    }
+    BitWriter<TSink> bits(sink);
+    for (auto const d : deviations)
+      coding::DeltaCoder::Encode(bits, d);
   }
 
   template <class TSource>
   bool Deserialize(TAltitude minAltitude, size_t pointCount, TSource & src)
   {
-    m_altitudes.clear();
-    if (pointCount == 0)
-    {
-      ASSERT(false, ());
-      return false;
-    }
+    vector<uint32_t> deviations(pointCount);
+    BitReader<TSource> bits(src);
 
-    m_altitudes.resize(pointCount);
-    TAltitude prevAltitude = minAltitude;
     for (size_t i = 0; i < pointCount; ++i)
-    {
-      m_altitudes[i] = static_cast<TAltitude>(ReadVarInt<int32_t>(src) + prevAltitude);
-      if (m_altitudes[i] < minAltitude)
-      {
-        ASSERT(false, ());
-        m_altitudes.clear();
-        return false;
-      }
-      prevAltitude = m_altitudes[i];
-    }
-    return true;
+      deviations[i] = coding::DeltaCoder::Decode(bits);
+
+    return FillAltitudesByDeserializedDate(minAltitude, deviations);
   }
 
   /// \note |m_altitudes| is a vector of feature point altitudes. There's two possibilities:
@@ -122,5 +108,9 @@ public:
   /// * size of |m_pointAlt| is equal to the number of this feature's points. If so
   ///   all items of |m_altitudes| have valid value.
   TAltitudes m_altitudes;
+
+private:
+  void PrepareSerializationData(TAltitude minAltitude, vector<uint32_t> & deviations) const;
+  bool FillAltitudesByDeserializedDate(TAltitude minAltitude, vector<uint32_t> const & deviations);
 };
 }  // namespace feature
diff --git a/indexer/indexer.pro b/indexer/indexer.pro
index f5b6d8e255..905a1f3c0c 100644
--- a/indexer/indexer.pro
+++ b/indexer/indexer.pro
@@ -29,6 +29,7 @@ SOURCES += \
     edits_migration.cpp \
     feature.cpp \
     feature_algo.cpp \
+    feature_altitude.cpp \
     feature_covering.cpp \
     feature_data.cpp \
     feature_decl.cpp \