Reorder if/else, add javadoc, add tests.

apache · Jul 30, 2019 · c48c149 · c48c149
1 parent fcaa7f8
commit c48c149
Show file tree

Hide file tree

Showing 2 changed files with 38 additions and 6 deletions.
diff --git a/src/main/java/org/apache/datasketches/memory/UnsafeUtil.java b/src/main/java/org/apache/datasketches/memory/UnsafeUtil.java
@@ -157,15 +157,14 @@ static long getFieldOffset(final Class<?> c, final String fieldName) {
     }
   }
 
+  /**
+   * Like {@link Unsafe#arrayBaseOffset(Class)}, but caches return values for common array types. Useful because
+   * calling {@link Unsafe#arrayBaseOffset(Class)} directly incurs more overhead.
+   */
   static long getArrayBaseOffset(final Class<?> c) {
+    // Ordering here is roughly in order of what we expect to be most popular.
     if (c == byte[].class) {
       return ARRAY_BYTE_BASE_OFFSET;
-    } else if (c == boolean[].class) {
-      return ARRAY_BOOLEAN_BASE_OFFSET;
-    } else if (c == short[].class) {
-      return ARRAY_SHORT_BASE_OFFSET;
-    } else if (c == char[].class) {
-      return ARRAY_CHAR_BASE_OFFSET;
     } else if (c == int[].class) {
       return ARRAY_INT_BASE_OFFSET;
     } else if (c == long[].class) {
@@ -174,6 +173,12 @@ static long getArrayBaseOffset(final Class<?> c) {
       return ARRAY_FLOAT_BASE_OFFSET;
     } else if (c == double[].class) {
       return ARRAY_DOUBLE_BASE_OFFSET;
+    } else if (c == boolean[].class) {
+      return ARRAY_BOOLEAN_BASE_OFFSET;
+    } else if (c == short[].class) {
+      return ARRAY_SHORT_BASE_OFFSET;
+    } else if (c == char[].class) {
+      return ARRAY_CHAR_BASE_OFFSET;
     } else if (c == Object[].class) {
       return ARRAY_OBJECT_BASE_OFFSET;
     } else {

diff --git a/src/test/java/org/apache/datasketches/memory/UnsafeUtilTest.java b/src/test/java/org/apache/datasketches/memory/UnsafeUtilTest.java
@@ -23,6 +23,9 @@
 import static org.testng.Assert.assertTrue;
 import static org.testng.Assert.fail;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import org.testng.annotations.Test;
 
 
@@ -122,6 +125,30 @@ public void checkInts() {
     Ints.checkedCast(1L << 32);
   }
 
+  @Test
+  public void checkArrayBaseOffset()
+  {
+    final List<Class<?>> classes = new ArrayList<>();
+    classes.add(byte[].class);
+    classes.add(int[].class);
+    classes.add(long[].class);
+    classes.add(float[].class);
+    classes.add(double[].class);
+    classes.add(boolean[].class);
+    classes.add(short[].class);
+    classes.add(char[].class);
+    classes.add(Object[].class);
+    classes.add(byte[][].class); // An array type that is not cached
+
+    for (Class<?> clazz : classes) {
+      assertEquals(
+          UnsafeUtil.getArrayBaseOffset(clazz),
+          UnsafeUtil.unsafe.arrayBaseOffset(clazz),
+          clazz.getTypeName()
+      );
+    }
+  }
+
   @Test
   public void printlnTest() {
     println("PRINTING: "+this.getClass().getName());