Introduce .first and .last to 64 implementation RoaringBitmap#583

RoaringBitmap/src/main/java/org/roaringbitmap/longlong/HighLowContainer.java

@@ -6,13 +6,10 @@
 import java.io.DataOutput;
 import java.io.IOException;
 import java.nio.ByteBuffer;
+import java.util.NoSuchElementException;
+
 import org.roaringbitmap.Container;
-import org.roaringbitmap.art.Art;
-import org.roaringbitmap.art.ContainerIterator;
-import org.roaringbitmap.art.Containers;
-import org.roaringbitmap.art.KeyIterator;
-import org.roaringbitmap.art.LeafNodeIterator;
-import org.roaringbitmap.art.Node;
+import org.roaringbitmap.art.*;
 
 public class HighLowContainer {
 
@@ -111,6 +108,44 @@ public boolean isEmpty() {
     return art.isEmpty();
   }
 
+  private void assertNonEmpty() {
+    if(isEmpty()) {
+      throw new NoSuchElementException("Empty HighLowContainer");
+    }
+  }
+
+  /**
+   * Gets the first value in the array
+   * @return the first value in the array
+   * @throws NoSuchElementException if empty
+   */
+  public long first() {
+    assertNonEmpty();
+
+    LeafNode firstNode = highKeyLeafNodeIterator(false).next();
+    long containerIdx = firstNode.getContainerIdx();
+    Container container = getContainer(containerIdx);
+    byte[] high = firstNode.getKeyBytes();
+    int low = container.first();
+    return LongUtils.toLong(high, low);
+  }
+
+  /**
+   * Gets the last value in the array
+   * @return the last value in the array
+   * @throws NoSuchElementException if empty
+   */
+  public long last() {
+    assertNonEmpty();
+
+    LeafNode firstNode = highKeyLeafNodeIterator(true).next();
+    long containerIdx = firstNode.getContainerIdx();
+    Container container = getContainer(containerIdx);
+    byte[] high = firstNode.getKeyBytes();
+    int low = container.last();
+    return LongUtils.toLong(high, low);
+  }
+
   /**
    * serialize into the ByteBuffer in little endian
    * @param buffer the ByteBuffer should be large enough to hold the data

RoaringBitmap/src/main/java/org/roaringbitmap/longlong/ImmutableLongBitmapDataProvider.java

@@ -6,6 +6,7 @@
 
 import java.io.DataOutput;
 import java.io.IOException;
+import java.util.NoSuchElementException;
 import java.util.PrimitiveIterator;
 import java.util.Spliterator;
 import java.util.Spliterators;
@@ -142,6 +143,22 @@ public default LongStream reverseStream() {
    */
   public long select(long j);
 
+  /**
+   * Get the first (smallest) integer in this RoaringBitmap,
+   * that is, returns the minimum of the set.
+   * @return the first (smallest) integer
+   * @throws NoSuchElementException if empty
+   */
+  long first();
+
+  /**
+   * Get the last (largest) integer in this RoaringBitmap,
+   * that is, returns the maximum of the set.
+   * @return the last (largest) integer
+   * @throws NoSuchElementException if empty
+   */
+  long last();
+
   /**
    * Serialize this bitmap.
    *

RoaringBitmap/src/main/java/org/roaringbitmap/longlong/LongUtils.java

@@ -37,7 +37,7 @@ public static char lowPart(long num) {
    * @param low the low 16 bit
    * @return the long data
    */
-  public static long toLong(byte[] high, char low) {
+  public static long toLong(byte[] high, int low) {
     byte byte6 = (byte) (low >>> 8 & 0xFFL);
     byte byte7 = (byte) low;
     return (high[0] & 0xFFL) << 56

RoaringBitmap/src/main/java/org/roaringbitmap/longlong/Roaring64Bitmap.java

@@ -10,6 +10,7 @@
 import java.nio.ByteOrder;
 import java.util.Arrays;
 import java.util.Iterator;
+import java.util.NoSuchElementException;
 import java.util.Objects;
 
 import org.roaringbitmap.*;
@@ -127,6 +128,28 @@ private long throwSelectInvalidIndex(long j) {
         "select " + j + " when the cardinality is " + this.getLongCardinality());
   }
 
+  /**
+   * Get the first (smallest) integer in this RoaringBitmap,
+   * that is, returns the minimum of the set.
+   * @return the first (smallest) integer
+   * @throws NoSuchElementException if empty
+   */
+  @Override
+  public long first() {
+    return highLowContainer.first();
+  }
+
+  /**
+   * Get the last (largest) integer in this RoaringBitmap,
+   * that is, returns the maximum of the set.
+   * @return the last (largest) integer
+   * @throws NoSuchElementException if empty
+   */
+  @Override
+  public long last() {
+    return highLowContainer.last();
+  }
+
   /**
    * For better performance, consider the Use the {@link #forEach forEach} method.
    *

RoaringBitmap/src/main/java/org/roaringbitmap/longlong/Roaring64NavigableMap.java

@@ -1454,4 +1454,24 @@ public void flip(final long x) {
 
     invalidateAboveHigh(high);
   }
+
+  private void assertNonEmpty() {
+    if(isEmpty()) {
+      throw new NoSuchElementException("Empty " + this.getClass().getSimpleName());
+    }
+  }
+
+  @Override
+  public long first() {
+    Map.Entry<Integer, BitmapDataProvider> firstEntry = highToBitmap.firstEntry();
+
+    return RoaringIntPacking.pack(firstEntry.getKey(), firstEntry.getValue().first());
+  }
+
+  @Override
+  public long last() {
+    Map.Entry<Integer, BitmapDataProvider> lastEntry = highToBitmap.lastEntry();
+
+    return RoaringIntPacking.pack(lastEntry.getKey(), lastEntry.getValue().last());
+  }
 }

RoaringBitmap/src/test/java/org/roaringbitmap/longlong/TestRoaring64Bitmap.java

@@ -9,7 +9,6 @@
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
-import org.junit.jupiter.api.function.Executable;
 import static org.roaringbitmap.Util.toUnsignedLong;
 
 import com.google.common.primitives.Ints;
@@ -33,6 +32,7 @@
 import static org.roaringbitmap.ValidationRangeConsumer.Value.PRESENT;
 import org.roaringbitmap.art.LeafNode;
 import org.roaringbitmap.art.LeafNodeIterator;
+import org.roaringbitmap.buffer.MutableRoaringBitmap;
 
 public class TestRoaring64Bitmap {
 
@@ -2201,4 +2201,50 @@ public void testIssue580() {
     assertEquals(count, 7);
 
   }
+
+  @Test
+  public void testEmptyFirst() {
+    assertThrows(NoSuchElementException.class, () -> new MutableRoaringBitmap().first());
+  }
+
+  @Test
+  public void testEmptyLast() {
+    assertThrows(NoSuchElementException.class, () -> new MutableRoaringBitmap().last());
+  }
+
+  @Test
+  public void testFirstLast_32b() {
+    Roaring64Bitmap rb = newDefaultCtor();
+
+    rb.add(2);
+    rb.add(4);
+    rb.add(8);
+    assertEquals(2, rb.first());
+    assertEquals(8, rb.last());
+  }
+
+  @Test
+  public void testFirstLast_64b() {
+    Roaring64Bitmap rb = newDefaultCtor();
+
+    rb.add(-128);
+    rb.add(-64);
+    rb.add(-32);
+    assertEquals(-128, rb.first());
+    assertEquals(-32, rb.last());
+  }
+
+  @Test
+  public void testFirstLast_32_64b() {
+    Roaring64Bitmap rb = newDefaultCtor();
+
+    rb.add(2);
+    rb.add(4);
+    rb.add(8);
+    rb.add(-128);
+    rb.add(-64);
+    rb.add(-32);
+    assertEquals(2, rb.first());
+    assertEquals(-32, rb.last());
+  }
 }

RoaringBitmap/src/test/java/org/roaringbitmap/longlong/TestRoaring64NavigableMap.java

@@ -1648,4 +1648,39 @@ public void testNaivelazyor_ImplicitRoaringBitmap() {
     }
   }
 
+  @Test
+  public void testFirstLast_32b() {
+    Roaring64NavigableMap rb = newDefaultCtor();
+
+    rb.add(2);
+    rb.add(4);
+    rb.add(8);
+    assertEquals(2, rb.first());
+    assertEquals(8, rb.last());
+  }
+
+  @Test
+  public void testFirstLast_64b() {
+    Roaring64NavigableMap rb = newDefaultCtor();
+
+    rb.add(-128);
+    rb.add(-64);
+    rb.add(-32);
+    assertEquals(-128, rb.first());
+    assertEquals(-32, rb.last());
+  }
+
+  @Test
+  public void testFirstLast_32_64b() {
+    Roaring64NavigableMap rb = newDefaultCtor();
+
+    rb.add(2);
+    rb.add(4);
+    rb.add(8);
+    rb.add(-128);
+    rb.add(-64);
+    rb.add(-32);
+    assertEquals(2, rb.first());
+    assertEquals(-32, rb.last());
+  }
 }