Merge pull request #674 from apache/ffm_phase6

FFM Phase 6: KLL Sketches

Author: leerho

src/main/java/org/apache/datasketches/common/MemorySegmentRequest.java

@@ -0,0 +1,65 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.datasketches.common;
+
+import java.lang.foreign.MemorySegment;
+
+/**
+ * This is a callback interface to provide a means to request a new MemorySegment of a specified size.
+ *
+ * @author Lee Rhodes
+ */
+public interface MemorySegmentRequest {
+
+  /**
+   * Request a new MemorySegment with the given <i>newByteSize</i>.
+   * Because we do not have a reference to an Arena, the default here is to
+   * allocate a new MemorySegment on the heap.  It is up to the user to override this as appropriate.
+   * @param prevSeg the previous MemorySegment to be possibly closed here or by using the separate
+   * {@link #requestClose requestClose} method. This is included for convenience, it may be null.
+   * @param newByteSize The new <i>byteSize</i> being requested.
+   * @return new MemorySegment with the requested <i>byteSize</i>.
+   */
+  default MemorySegment request(final MemorySegment prevSeg, final long newByteSize) {
+    if (newByteSize > Integer.MAX_VALUE) {
+      throw new SketchesArgumentException("Requested size in bytes exceeds Integer.MAX_VALUE.");
+    }
+    return MemorySegment.ofArray(new byte[(int)newByteSize]);
+  }
+
+  /**
+   * Request to close the given MemorySegment.
+   * Because we do not have a reference to an Arena, the default here is to do nothing.
+   * It is up to the user to override this as appropriate.
+   * @param prevSeg the previous MemorySegment to be closed.
+   */
+  default void requestClose(final MemorySegment prevSeg) { }
+
+  /**
+   * This class implements the defaults
+   */
+  public static class Default implements MemorySegmentRequest { }
+
+  /**
+   * Create Default as static member.
+   */
+  Default DEFAULT = new Default();
+
+}

src/main/java/org/apache/datasketches/common/MemorySegmentRequestExtension.java

@@ -0,0 +1,78 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.datasketches.common;
+
+import java.lang.foreign.Arena;
+import java.lang.foreign.MemorySegment;
+import java.util.Enumeration;
+import java.util.Hashtable;
+
+/**
+ * This is just an example of a possible extension of the MemorySegmentRequest interface.
+   * You may want to enable the println statements to track the state of the Hashtable.
+ */
+public final class MemorySegmentRequestExtension implements MemorySegmentRequest {
+  private final Hashtable<MemorySegment, Arena> table = new Hashtable<>();
+
+  @Override
+  public synchronized MemorySegment request(final MemorySegment prevSeg, final long newByteSize) {
+    if (prevSeg.isNative()) {
+      final Arena arena = Arena.ofConfined();
+      final MemorySegment seg = arena.allocate(newByteSize);
+      table.put(seg, arena);  //println("Add");
+      return seg;
+    } else {
+      if (newByteSize > Integer.MAX_VALUE) {
+        throw new SketchesArgumentException("Requested byteSize is greater than Integer.MAX_VALUE.");
+      }
+      return MemorySegment.ofArray(new byte[(int)newByteSize]);
+    }
+  }
+
+  @Override
+  public synchronized void requestClose(final MemorySegment prevSeg) {
+    final Arena arena = table.get(prevSeg);
+    if ((arena != null) && arena.scope().isAlive()) {
+      arena.close();
+      table.remove(prevSeg); //println("Remove");
+    } //else ignore
+  }
+
+  /**
+   * This cleans up any unclosed off-heap MemorySegments.
+   */
+  public synchronized void cleanup() {
+    for (final Enumeration<Arena> e = table.elements(); e.hasMoreElements();) {
+      final Arena arena = e.nextElement();
+      if (arena.scope().isAlive()) {
+        arena.close(); //println("Closed remaining Arenas in the Hashtable");
+      }
+    }
+  }
+
+//  /**
+//   * Println Object o
+//   * @param o object to print
+//   */
+//  private static void println(final Object o) {
+//    System.out.println(o.toString());
+//  }
+
+}