--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.jfr/share/classes/jdk/jfr/internal/cmd/ReconstructCommand.java	Tue May 15 20:24:34 2018 +0200
@@ -0,0 +1,131 @@
+/*
+ * Copyright (c) 2016, 2018, 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 jdk.jfr.internal.cmd;
+
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.nio.channels.FileChannel;
+import java.nio.file.DirectoryStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.Deque;
+import java.util.List;
+
+final class ReconstructCommand extends Command {
+
+    @Override
+    public String getOptionSyntax() {
+        return "<repository> <file>";
+    }
+
+    @Override
+    public String getName() {
+        return "reconstruct";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Assemble leftover chunks, from a disk repository, into a recording file (.jfr)";
+    }
+
+    @Override
+    public void displayOptionUsage() {
+        println("  <repository>   Directory where the repository is located");
+        println();
+        println("  <file>         Name of the recording file (.jfr) to create");
+    }
+
+    @Override
+    public void execute(Deque<String> options) {
+        ensureMinArgumentCount(options, 2);
+        ensureMaxArgumentCount(options, 2);
+
+        Path repository = Paths.get(options.pop()).toAbsolutePath();
+        if (!Files.exists(repository)) {
+            userFailed("Could not find disk repository at " + repository);
+        }
+        if (!Files.isDirectory(repository)) {
+            userFailed("Must specify a directory as disk repository");
+        }
+        Path output = Paths.get(options.pop());
+        ensureFileDoesNotExist(output);
+        ensureJFRFile(output);
+
+        try (FileOutputStream fos = new FileOutputStream(output.toFile())) {
+            List<Path> files = listJFRFiles(repository);
+            if (files.isEmpty()) {
+                throw new IllegalStateException("No *.jfr files found at " + repository);
+            }
+            println();
+            println("Combining files... ");
+            println();
+            transferTo(files, output, fos.getChannel());
+            println();
+            println("Reconstruction complete.");
+        } catch (IOException e) {
+            userFailed("Could not open destination file " + output + ". " + e.getMessage());
+        }
+    }
+
+    private List<Path> listJFRFiles(Path path) throws IOException {
+        try {
+            List<Path> files = new ArrayList<>();
+            if (Files.isDirectory(path)) {
+                try (DirectoryStream<Path> stream = Files.newDirectoryStream(path, "*.jfr")) {
+                    for (Path p : stream) {
+                        if (!Files.isDirectory(p) && Files.isReadable(p)) {
+                            files.add(p);
+                        }
+                    }
+                }
+            }
+            files.sort((u, v) -> u.getFileName().compareTo(v.getFileName()));
+            return files;
+        } catch (IOException ioe) {
+            throw new IllegalStateException("Could not list *.jfr for directory " + path + ". " + ioe.getMessage());
+        }
+    }
+
+    private void transferTo(List<Path> sourceFiles, Path output, FileChannel out) {
+        long pos = 0;
+        for (Path p : sourceFiles) {
+            println(" " + p.toString());
+            try (FileChannel sourceChannel = FileChannel.open(p)) {
+                long rem = Files.size(p);
+                while (rem > 0) {
+                    long n = Math.min(rem, 1024 * 1024);
+                    long w = out.transferFrom(sourceChannel, pos, n);
+                    pos += w;
+                    rem -= w;
+                }
+            } catch (IOException ioe) {
+                throw new IllegalStateException("Could not copy recording chunk " + p + " to new file. " + ioe.getMessage());
+            }
+        }
+    }
+}