feat(traffictile.h): Adds versioning checks

Allocates one of the spare fields in the TrafficTileHeader
for versioning data, with the version being made up of
the first four bytes of the MD5 checksum of baldr/traffictile.h

scripts/build_traffic_tile_version.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+# Builds the traffic_tile_version.h header
+
+set -o errexit -o pipefail -o nounset
+
+readonly VALHALLA_SOURCE_DIR="${1:-NONE}"
+
+if [ "$VALHALLA_SOURCE_DIR" = NONE ]; then
+  echo "Must specify path to root folder"
+  exit 1
+fi
+
+printf "const uint32_t TRAFFIC_TILE_VERSION = 0x%s;" $(
+  # Grab only four bytes because space constraints
+  sha1sum ${VALHALLA_SOURCE_DIR}/valhalla/baldr/traffictile.h | head -c4
+)

src/baldr/CMakeLists.txt

@@ -25,12 +25,22 @@ add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/date_time_windows_zones.h
 
 file(GLOB headers ${VALHALLA_SOURCE_DIR}/valhalla/baldr/*.h)
 
+# Builds a checksum of the traffictile header and store it in `traffic_tile_version.h`
+set(GENERATED_VERSION_HEADER "${CMAKE_CURRENT_BINARY_DIR}/traffic_tile_version.h")
+add_custom_command(OUTPUT "${GENERATED_VERSION_HEADER}"
+    COMMENT "Generating the traffic-tile version"
+    COMMAND ${VALHALLA_SOURCE_DIR}/scripts/build_traffic_tile_version.sh  ${VALHALLA_SOURCE_DIR} > "${GENERATED_VERSION_HEADER}"
+    DEPENDS ${VALHALLA_SOURCE_DIR}/valhalla/baldr/traffictile.h
+    )
+
 set(includes
     ${VALHALLA_SOURCE_DIR}
      ${VALHALLA_SOURCE_DIR}/valhalla
      $<$<BOOL:${MSVC}>:${VALHALLA_SOURCE_DIR}/third_party/dirent/include>
      ${VALHALLA_SOURCE_DIR}/third_party/rapidjson/include
-     ${VALHALLA_SOURCE_DIR}/third_party/date/include)
+     ${VALHALLA_SOURCE_DIR}/third_party/date/include
+     ${CMAKE_CURRENT_BINARY_DIR}/src/baldr
+     )
 
 set(sources
     accessrestriction.cc
@@ -69,8 +79,9 @@ set(sources
     verbal_text_formatter_us_tx.cc
     verbal_text_formatter_factory.cc)
 
-#basic timezone stuff
 list(APPEND sources
+    ${GENERATED_VERSION_HEADER}
+    #basic timezone stuff
     ${CMAKE_CURRENT_BINARY_DIR}/date_time_africa.h
     ${CMAKE_CURRENT_BINARY_DIR}/date_time_antarctica.h
     ${CMAKE_CURRENT_BINARY_DIR}/date_time_asia.h

test/gurka/test_traffic.cc

@@ -86,7 +86,8 @@ void update_all_edges_but_bd(const valhalla::gurka::map& map, uint16_t new_speed
   update_all_edges_but_bd(map, ts);
 }
 
-void blank_traffic(const valhalla::gurka::map& map) {
+void blank_traffic(const valhalla::gurka::map& map,
+                   uint32_t traffic_tile_version = TRAFFIC_TILE_VERSION) {
   const auto& traffic_extract = map.config.get<std::string>("mjolnir.traffic_extract");
   mtar_t tar;
   auto tar_open_result = mtar_open(&tar, traffic_extract.c_str(), "w");
@@ -109,6 +110,7 @@ void blank_traffic(const valhalla::gurka::map& map) {
     std::stringstream buffer;
     baldr::TrafficTileHeader header = {};
     header.tile_id = tile_id;
+    header.traffic_tile_version = traffic_tile_version;
     std::vector<baldr::TrafficSpeed> speeds;
     header.directed_edge_count = tile->header()->directededgecount();
     buffer.write(reinterpret_cast<char*>(&header), sizeof(header));

test/traffictile.cc

@@ -18,6 +18,7 @@ TEST(Traffic, TileConstruction) {
   TestTile testdata = {};
 
   testdata.header.directed_edge_count = 3;
+  testdata.header.traffic_tile_version = TRAFFIC_TILE_VERSION;
   testdata.speed3.overall_speed = 98 >> 1;
   testdata.speed3.speed1 = 98 >> 1;
   testdata.speed3.speed2 = UNKNOWN_TRAFFIC_SPEED_RAW;
@@ -32,6 +33,13 @@ TEST(Traffic, TileConstruction) {
   EXPECT_EQ(speed.get_overall_speed(), 98);
   EXPECT_EQ(speed.get_speed(0), 98);
   EXPECT_EQ(speed.get_speed(1), UNKNOWN_TRAFFIC_SPEED_RAW << 1);
+
+  // Verify the version (Expect this value to change when traffictile.h is updated)
+  EXPECT_EQ(0x4c91, TRAFFIC_TILE_VERSION);
+  // Test with an invalid version
+  testdata.header.traffic_tile_version = 78;
+  auto const volatile& invalid_speed = tile.trafficspeed(2);
+  EXPECT_FALSE(invalid_speed.valid());
 }
 
 TEST(Traffic, NullTileConstruction) {

valhalla/baldr/traffictile.h

@@ -17,6 +17,7 @@
 #else
 #include <stdint.h>
 #endif
+#include "baldr/traffic_tile_version.h"
 
 #ifndef C_ONLY_INTERFACE
 namespace valhalla {
@@ -69,6 +70,7 @@ struct TrafficSpeed {
         assert(false);
     }
   }
+
   /// Returns overall speed in kph across edge
   inline uint8_t get_overall_speed() const volatile {
     return overall_speed << 1;
@@ -102,7 +104,7 @@ struct TrafficTileHeader {
   uint64_t tile_id;
   uint64_t last_update; // seconds since epoch
   uint32_t directed_edge_count;
-  uint32_t spare1;
+  uint32_t traffic_tile_version;
   uint32_t spare2;
   uint32_t spare3;
 };
@@ -149,8 +151,11 @@ class TrafficTile {
   }
 
   const volatile TrafficSpeed& trafficspeed(const uint32_t directed_edge_offset) const {
-    if (header == nullptr)
+    if (header == nullptr) {
+      return INVALID_SPEED;
+    } else if (header->traffic_tile_version != TRAFFIC_TILE_VERSION) {
       return INVALID_SPEED;
+    }
     if (directed_edge_offset >= header->directed_edge_count)
       throw std::runtime_error("TrafficSpeed requested for edgeid beyond bounds of tile (offset: " +
                                std::to_string(directed_edge_offset) +