test: add cases from C++ deserialize

Author: proost

src/test/java/org/apache/datasketches/req/ReqSketchCrossLanguageTest.java

@@ -99,4 +99,47 @@ public void deserializeFromCpp() throws IOException {
     }
   }
 
+  @Test(groups = {CHECK_CPP_FILES})
+  public void deserializeNegativeFromCpp() throws IOException {
+    final int[] nArr = {1, 10};
+    for (final int n: nArr) {
+      final byte[] bytes = getFileBytes(cppPath, "req_float_negative_n" + n + "_cpp.sk");
+      final ReqSketch sk = ReqSketch.heapify(MemorySegment.ofArray(bytes));
+      assertTrue(!sk.isEmpty());
+      assertEquals(sk.getN(), n);
+      assertEquals(sk.getMinItem(), -n);
+      assertEquals(sk.getMaxItem(), -1);
+      final QuantilesFloatsSketchIterator it = sk.iterator();
+      long weight = 0;
+      while(it.next()) {
+        assertTrue(it.getQuantile() >= sk.getMinItem());
+        assertTrue(it.getQuantile() <= sk.getMaxItem());
+        weight += it.getWeight();
+      }
+      assertEquals(weight, n);
+    }
+  }
+
+  @Test(groups = {CHECK_CPP_FILES})
+  public void deserializeMixedFromCpp() throws IOException {
+    final int[] nArr = {1, 10};
+    for (final int n: nArr) {
+      final byte[] bytes = getFileBytes(cppPath, "req_float_mixed_n" + n + "_cpp.sk");
+      final ReqSketch sk = ReqSketch.heapify(MemorySegment.ofArray(bytes));
+      assertTrue(!sk.isEmpty());
+      final int expectedN = 2 * n + 1; // range -n to n inclusive
+      assertEquals(sk.getN(), expectedN);
+      assertEquals(sk.getMinItem(), -n);
+      assertEquals(sk.getMaxItem(), (float) n);
+      final QuantilesFloatsSketchIterator it = sk.iterator();
+      long weight = 0;
+      while(it.next()) {
+        assertTrue(it.getQuantile() >= sk.getMinItem());
+        assertTrue(it.getQuantile() <= sk.getMaxItem());
+        weight += it.getWeight();
+      }
+      assertEquals(weight, expectedN);
+    }
+  }
+
 }