Merge pull request #114 from johnathanchann/feature/hashing

Hashing implementation for the Coordinate class.

Author: rozukke

include/mcpp/coordinate.h

@@ -74,6 +74,15 @@ struct Coordinate {
    */
   Coordinate operator-(const Coordinate& obj) const;
 
+  /**
+   * @brief Implements hash algorithm for Coordinate object using non-negative
+   * mapping and weighted coordinate values.
+   *
+   * @param obj The Coordinate object to hash.
+   * @return Hash of Coordinate object.
+   */
+  std::size_t operator()(const Coordinate& obj) const;
+
   /**
    * @brief Outputs the Coordinate object to an ostream.
    *

src/coordinate.cpp

@@ -24,6 +24,17 @@ Coordinate Coordinate::operator-(const Coordinate& obj) const {
   return result;
 }
 
+std::size_t Coordinate::operator()(const mcpp::Coordinate& obj) const {
+  int lower = -3e7, upper = 3e7;
+  size_t base = upper - lower + 1;
+
+  size_t nx = obj.x - lower;
+  size_t ny = obj.y - lower;
+  size_t nz = obj.z - lower;
+
+  return nx * base * base + ny * base + nz;
+}
+
 std::string to_string(const Coordinate& coord) {
   using std::to_string;
   return "(" + to_string(coord.x) + "," + to_string(coord.y) + "," + to_string(coord.z) + ")";

test/local_tests.cpp

@@ -3,6 +3,7 @@
 #include "../include/mcpp/block.h"
 #include "../include/mcpp/coordinate.h"
 #include "doctest.h"
+#include <random>
 
 // NOLINTBEGIN
 
@@ -22,6 +23,22 @@ TEST_CASE("Test Coordinate class") {
     CHECK_EQ(test_coord.z, 0);
   }
 
+  SUBCASE("Test hash no collision") {
+    const int seed = 12345;
+    std::set<size_t> hashes;
+    std::mt19937 gen(seed);
+    std::uniform_int_distribution<int> dis(-3e7, 3e7);
+    std::uniform_int_distribution<int> dis2(-64, 256);
+
+    Coordinate hashing;
+    for (int i = 0; i < 100; i++) {
+      Coordinate testCoord(dis(gen), dis2(gen), dis(gen));
+      size_t hash = hashing(testCoord);
+      hashes.insert(hash);
+    }
+    CHECK_EQ(hashes.size(), 100);
+  }
+
   SUBCASE("Test double init") {
     Coordinate test_coord(1.5, 2.5, 3.5);
     Coordinate test_coord_float(1.5F, 2.5F, 3.5F);