[core] Fix int overflow issue in GridIndex

2 files changed, 18 insertions, 16 deletions

diff --git a/src/mbgl/util/grid_index.cpp b/src/mbgl/util/grid_index.cpp
index f6b59b1bac..f33e889ddb 100644
--- a/src/mbgl/util/grid_index.cpp
+++ b/src/mbgl/util/grid_index.cpp
@@ -9,14 +9,16 @@ namespace mbgl {
 
 
 template <class T>
-GridIndex<T>::GridIndex(const float width_, const float height_, const int16_t cellSize_) :
+GridIndex<T>::GridIndex(const float width_, const float height_, const uint32_t cellSize_) :
     width(width_),
     height(height_),
-    xCellCount(std::ceil(width_ / cellSize_)),
-    yCellCount(std::ceil(height_ / cellSize_)),
-    xScale(xCellCount / width_),
-    yScale(yCellCount / height_)
+    xCellCount(std::ceil(width / cellSize_)),
+    yCellCount(std::ceil(height / cellSize_)),
+    xScale(xCellCount / width),
+    yScale(yCellCount / height)
     {
+        assert(width > 0.0f);
+        assert(height > 0.0f);
         boxCells.resize(xCellCount * yCellCount);
         circleCells.resize(xCellCount * yCellCount);
     }
@@ -30,7 +32,7 @@ void GridIndex<T>::insert(T&& t, const BBox& bbox) {
     auto cx2 = convertToXCellCoord(bbox.max.x);
     auto cy2 = convertToYCellCoord(bbox.max.y);
 
-    int16_t x, y, cellIndex;
+    std::size_t x, y, cellIndex;
     for (x = cx1; x <= cx2; ++x) {
         for (y = cy1; y <= cy2; ++y) {
             cellIndex = xCellCount * y + x;
@@ -50,7 +52,7 @@ void GridIndex<T>::insert(T&& t, const BCircle& bcircle) {
     auto cx2 = convertToXCellCoord(bcircle.center.x + bcircle.radius);
     auto cy2 = convertToYCellCoord(bcircle.center.y + bcircle.radius);
 
-    int16_t x, y, cellIndex;
+    std::size_t x, y, cellIndex;
     for (x = cx1; x <= cx2; ++x) {
         for (y = cy1; y <= cy2; ++y) {
             cellIndex = xCellCount * y + x;
@@ -151,7 +153,7 @@ void GridIndex<T>::query(const BBox& queryBBox, std::function<bool (const T&, co
     auto cx2 = convertToXCellCoord(queryBBox.max.x);
     auto cy2 = convertToYCellCoord(queryBBox.max.y);
 
-    int16_t x, y, cellIndex;
+    std::size_t x, y, cellIndex;
     for (x = cx1; x <= cx2; ++x) {
         for (y = cy1; y <= cy2; ++y) {
             cellIndex = xCellCount * y + x;
@@ -214,7 +216,7 @@ void GridIndex<T>::query(const BCircle& queryBCircle, std::function<bool (const
     auto cx2 = convertToXCellCoord(queryBCircle.center.x + queryBCircle.radius);
     auto cy2 = convertToYCellCoord(queryBCircle.center.y + queryBCircle.radius);
 
-    int16_t x, y, cellIndex;
+    std::size_t x, y, cellIndex;
     for (x = cx1; x <= cx2; ++x) {
         for (y = cy1; y <= cy2; ++y) {
             cellIndex = xCellCount * y + x;
@@ -252,12 +254,12 @@ void GridIndex<T>::query(const BCircle& queryBCircle, std::function<bool (const
 }
 
 template <class T>
-int16_t GridIndex<T>::convertToXCellCoord(const float x) const {
+std::size_t GridIndex<T>::convertToXCellCoord(const float x) const {
     return util::max(0.0, util::min(xCellCount - 1.0, std::floor(x * xScale)));
 }
 
 template <class T>
-int16_t GridIndex<T>::convertToYCellCoord(const float y) const {
+std::size_t GridIndex<T>::convertToYCellCoord(const float y) const {
     return util::max(0.0, util::min(yCellCount - 1.0, std::floor(y * yScale)));
 }
 
diff --git a/src/mbgl/util/grid_index.hpp b/src/mbgl/util/grid_index.hpp
index 4c2d7dccc8..cb38023e59 100644
--- a/src/mbgl/util/grid_index.hpp
+++ b/src/mbgl/util/grid_index.hpp
@@ -57,7 +57,7 @@ template <class T>
 class GridIndex {
 public:
 
-    GridIndex(const float width_, const float height_, const int16_t cellSize_);
+    GridIndex(const float width_, const float height_, const uint32_t cellSize_);
 
     using BBox = mapbox::geometry::box<float>;
     using BCircle = geometry::circle<float>;
@@ -81,8 +81,8 @@ private:
     void query(const BBox&, std::function<bool (const T&, const BBox&)>) const;
     void query(const BCircle&, std::function<bool (const T&, const BBox&)>) const;
 
-    int16_t convertToXCellCoord(const float x) const;
-    int16_t convertToYCellCoord(const float y) const;
+    std::size_t convertToXCellCoord(const float x) const;
+    std::size_t convertToYCellCoord(const float y) const;
     
     bool boxesCollide(const BBox&, const BBox&) const;
     bool circlesCollide(const BCircle&, const BCircle&) const;
@@ -91,8 +91,8 @@ private:
     const float width;
     const float height;
     
-    const int16_t xCellCount;
-    const int16_t yCellCount;
+    const std::size_t xCellCount;
+    const std::size_t yCellCount;
     const double xScale;
     const double yScale;