Fast tileCount with help from @mapbox/sphericalmercator module

2 files changed, 27 insertions, 10 deletions

diff --git a/platform/default/mbgl/storage/offline.cpp b/platform/default/mbgl/storage/offline.cpp
index fd2d47819b..644684c8a6 100644
--- a/platform/default/mbgl/storage/offline.cpp
+++ b/platform/default/mbgl/storage/offline.cpp
@@ -1,6 +1,7 @@
 #include <mbgl/storage/offline.hpp>
 #include <mbgl/util/tile_cover.hpp>
 #include <mbgl/util/tileset.hpp>
+#include <mbgl/util/projection.hpp>
 
 #include <rapidjson/document.h>
 #include <rapidjson/stringbuffer.h>
@@ -24,17 +25,11 @@ OfflineTilePyramidRegionDefinition::OfflineTilePyramidRegionDefinition(
 }
 
 std::vector<CanonicalTileID> OfflineTilePyramidRegionDefinition::tileCover(SourceType type, uint16_t tileSize, const Range<uint8_t>& zoomRange) const {
-    double minZ = std::max<double>(util::coveringZoomLevel(minZoom, type, tileSize), zoomRange.min);
-    double maxZ = std::min<double>(util::coveringZoomLevel(maxZoom, type, tileSize), zoomRange.max);
-
-    assert(minZ >= 0);
-    assert(maxZ >= 0);
-    assert(minZ < std::numeric_limits<uint8_t>::max());
-    assert(maxZ < std::numeric_limits<uint8_t>::max());
+    const Range<uint8_t> clampedZoomRange = coveringZoomRange(type, tileSize, zoomRange);
 
     std::vector<CanonicalTileID> result;
 
-    for (uint8_t z = minZ; z <= maxZ; z++) {
+    for (uint8_t z = clampedZoomRange.min; z <= clampedZoomRange.max; z++) {
         for (const auto& tile : util::tileCover(bounds, z)) {
             result.emplace_back(tile.canonical);
         }
@@ -43,6 +38,28 @@ std::vector<CanonicalTileID> OfflineTilePyramidRegionDefinition::tileCover(Sourc
     return result;
 }
 
+unsigned long OfflineTilePyramidRegionDefinition::tileCount(SourceType type, uint16_t tileSize, const Range<uint8_t>& zoomRange) const {
+    
+    const Range<uint8_t> clampedZoomRange = coveringZoomRange(type, tileSize, zoomRange);
+    unsigned long result = 0;;
+    for (uint8_t z = clampedZoomRange.min; z <= clampedZoomRange.max; z++) {
+        result +=  util::tileCount(bounds, z, tileSize);
+    }
+
+    return result;
+}
+
+Range<uint8_t> OfflineTilePyramidRegionDefinition::coveringZoomRange(SourceType type, uint16_t tileSize, const Range<uint8_t>& zoomRange) const {
+    double minZ = std::max<double>(util::coveringZoomLevel(minZoom, type, tileSize), zoomRange.min);
+    double maxZ = std::min<double>(util::coveringZoomLevel(maxZoom, type, tileSize), zoomRange.max);
+
+    assert(minZ >= 0);
+    assert(maxZ >= 0);
+    assert(minZ < std::numeric_limits<uint8_t>::max());
+    assert(maxZ < std::numeric_limits<uint8_t>::max());
+    return { static_cast<uint8_t>(minZ), static_cast<uint8_t>(maxZ) };
+}
+
 OfflineRegionDefinition decodeOfflineRegionDefinition(const std::string& region) {
     rapidjson::GenericDocument<rapidjson::UTF8<>, rapidjson::CrtAllocator> doc;
     doc.Parse<0>(region.c_str());
diff --git a/platform/default/mbgl/storage/offline_download.cpp b/platform/default/mbgl/storage/offline_download.cpp
index 7f0001f64b..ff61114888 100644
--- a/platform/default/mbgl/storage/offline_download.cpp
+++ b/platform/default/mbgl/storage/offline_download.cpp
@@ -80,7 +80,7 @@ OfflineRegionStatus OfflineDownload::getStatus() const {
         auto handleTiledSource = [&] (const variant<std::string, Tileset>& urlOrTileset, const uint16_t tileSize) {
             if (urlOrTileset.is<Tileset>()) {
                 result.requiredResourceCount +=
-                    definition.tileCover(type, tileSize, urlOrTileset.get<Tileset>().zoomRange).size();
+                    definition.tileCount(type, tileSize, urlOrTileset.get<Tileset>().zoomRange);
             } else {
                 result.requiredResourceCount += 1;
                 const auto& url = urlOrTileset.get<std::string>();
@@ -90,7 +90,7 @@ OfflineRegionStatus OfflineDownload::getStatus() const {
                     optional<Tileset> tileset = style::conversion::convertJSON<Tileset>(*sourceResponse->data, error);
                     if (tileset) {
                         result.requiredResourceCount +=
-                            definition.tileCover(type, tileSize, (*tileset).zoomRange).size();
+                            definition.tileCount(type, tileSize, (*tileset).zoomRange);
                     }
                 } else {
                     result.requiredResourceCountIsPrecise = false;