API for creating and processing heap dumps fully in memory

visualvm/libs.profiler/lib.profiler/src/org/graalvm/visualvm/lib/jfluid/heap/HeapFactory.java

@@ -32,6 +32,7 @@
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.ByteBuffer;
 
 
 /**
@@ -87,6 +88,22 @@ public static Heap createHeap(File heapDump, int segment)
         return new HprofHeap(heapDump, segment, cacheDir);
 
     }
+
+    /** Factory method for processing heap dumps in memory. When heap data
+     * aren't available on disk, but only in memory, create a {@link ByteBuffer}
+     * from them and use this factory method to create their {@link Heap}
+     * representation.
+     * 
+     * @param buffer data representing the heap dump
+     * @param segment select corresponding dump from multi-dump file
+     * @return implementation of {@link Heap} corresponding to the memory dump
+     * passed in the {@code buffer} parameter
+     * @throws IOException if the access to the buffer fails or data are corrupted
+     * @since 2.2
+     */
+    public static Heap createHeap(ByteBuffer buffer, int segment) throws IOException {
+        return new HprofHeap(buffer, segment, new CacheDirectory(null));
+    }
 
     static Heap loadHeap(CacheDirectory cacheDir)
                            throws FileNotFoundException, IOException {

visualvm/libs.profiler/lib.profiler/src/org/graalvm/visualvm/lib/jfluid/heap/HprofByteBuffer.java

@@ -27,6 +27,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import java.util.Date;
 import java.util.ResourceBundle;
 
@@ -84,6 +85,10 @@ static HprofByteBuffer createHprofByteBuffer(File dumpFile)
         }
     }
 
+    static HprofByteBuffer createHprofByteBuffer(ByteBuffer bb) throws IOException {
+        return new HprofMappedByteBuffer(bb);
+    }
+
     abstract char getChar(long index);
 
     abstract double getDouble(long index);

visualvm/libs.profiler/lib.profiler/src/org/graalvm/visualvm/lib/jfluid/heap/HprofHeap.java

@@ -32,6 +32,7 @@
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -128,11 +129,11 @@ class HprofHeap implements Heap {
     private boolean retainedSizeByClassComputed;
     private final Object retainedSizeByClassLock = new Object();
     private int idMapSize;
-    private int segment;
+    private final int segment;
 
     // for serialization
-    File heapDumpFile;
-    CacheDirectory cacheDirectory;
+    final File heapDumpFile;
+    final CacheDirectory cacheDirectory;
 
     //~ Constructors -------------------------------------------------------------------------------------------------------------
 
@@ -153,6 +154,23 @@ class HprofHeap implements Heap {
         heapDumpFile = dumpFile;
     }
 
+    HprofHeap(ByteBuffer bb, int seg, CacheDirectory cacheDir) throws IOException {
+        cacheDirectory = cacheDir;
+        dumpBuffer = HprofByteBuffer.createHprofByteBuffer(bb);
+        segment = seg;
+        fillTagBounds(dumpBuffer.getHeaderSize());
+        heapDumpSegment = computeHeapDumpStart();
+
+        if (heapDumpSegment != null) {
+            fillHeapTagBounds();
+        }
+
+        idToOffsetMap = new LongMap(idMapSize,dumpBuffer.getIDSize(),dumpBuffer.getFoffsetSize(), cacheDirectory);
+        nearestGCRoot = new NearestGCRoot(this);
+        gcRoots = new HprofGCRoots(this);
+        heapDumpFile = null;
+    }
+
     //~ Methods ------------------------------------------------------------------------------------------------------------------
 
     public List<JavaClass> getAllClasses() {

visualvm/libs.profiler/lib.profiler/src/org/graalvm/visualvm/lib/jfluid/heap/HprofMappedByteBuffer.java

@@ -27,7 +27,9 @@
 
 import java.io.File;
 import java.io.FileInputStream;
+import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import java.nio.MappedByteBuffer;
 import java.nio.channels.FileChannel;
 
@@ -39,16 +41,17 @@
 class HprofMappedByteBuffer extends HprofByteBuffer {
     //~ Instance fields ----------------------------------------------------------------------------------------------------------
 
-    private MappedByteBuffer dumpBuffer;
+    private final ByteBuffer dumpBuffer;
 
     //~ Constructors -------------------------------------------------------------------------------------------------------------
 
     HprofMappedByteBuffer(File dumpFile) throws IOException {
-        FileInputStream fis = new FileInputStream(dumpFile);
-        FileChannel channel = fis.getChannel();
-        length = channel.size();
-        dumpBuffer = channel.map(FileChannel.MapMode.READ_ONLY, 0, length);
-        channel.close();
+        this(mmap(dumpFile));
+    }
+
+    HprofMappedByteBuffer(ByteBuffer buffer) throws IOException {
+        this.dumpBuffer = buffer;
+        this.length = buffer.capacity();
         readHeader();
     }
 
@@ -87,4 +90,12 @@ synchronized void get(long position, byte[] chars) {
         dumpBuffer.position((int) position);
         dumpBuffer.get(chars);
     }
+
+    private static MappedByteBuffer mmap(File dumpFile) throws IOException, FileNotFoundException {
+        FileInputStream fis = new FileInputStream(dumpFile);
+        FileChannel channel = fis.getChannel();
+        MappedByteBuffer d = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size());
+        channel.close();
+        return d;
+    }
 }

visualvm/libs.profiler/lib.profiler/test/unit/src/org/graalvm/visualvm/lib/jfluid/heap/HeapFromBufferTest.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2010, 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package org.graalvm.visualvm.lib.jfluid.heap;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+import org.junit.Before;
+
+public class HeapFromBufferTest extends HeapTest {
+    public HeapFromBufferTest() {
+    }
+
+    @Before
+    public void setUp() throws IOException, URISyntaxException {
+        URL url = getClass().getResource("small_heap.bin");
+        File heapFile = new File(url.toURI());
+        ByteBuffer buffer = ByteBuffer.allocate((int) heapFile.length());
+        try (FileChannel ch = new FileInputStream(heapFile).getChannel()) {
+            while (buffer.remaining() > 0) {
+                int len = ch.read(buffer);
+                if (len == -1) {
+                    break;
+                }
+            }
+        }
+        heap = HeapFactory.createHeap(buffer, 0);
+    }
+
+}

visualvm/libs.profiler/lib.profiler/test/unit/src/org/graalvm/visualvm/lib/jfluid/heap/HeapTest.java

@@ -48,9 +48,7 @@
 import java.util.Properties;
 import java.util.TimeZone;
 import org.junit.After;
-import org.junit.AfterClass;
 import org.junit.Before;
-import org.junit.BeforeClass;
 import org.junit.Test;
 import static org.junit.Assert.*;
 
@@ -59,19 +57,11 @@
  * @author Tomas Hurka
  */
 public class HeapTest {
-    private Heap heap;
+    Heap heap;
 
     public HeapTest() {
     }
 
-    @BeforeClass
-    public static void setUpClass() throws Exception {
-    }
-
-    @AfterClass
-    public static void tearDownClass() throws Exception {
-    }
-
     @Before
     public void setUp() throws IOException, URISyntaxException {
         URL url = getClass().getResource("small_heap.bin");