--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/test/testlibrary/com/oracle/java/testlibrary/InMemoryJavaCompiler.java	Wed Aug 07 16:47:32 2013 +0200
@@ -0,0 +1,154 @@
+/*
+ * Copyright (c) 2013, 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.
+ *
+ * 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 com.oracle.java.testlibrary;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+
+import java.net.URI;
+import java.util.Arrays;
+
+import javax.tools.ForwardingJavaFileManager;
+import javax.tools.ForwardingJavaFileManager;
+import javax.tools.FileObject;
+import javax.tools.JavaCompiler;
+import javax.tools.JavaCompiler.CompilationTask;
+import javax.tools.JavaFileManager;
+import javax.tools.JavaFileObject;
+import javax.tools.JavaFileObject.Kind;
+import javax.tools.SimpleJavaFileObject;
+import javax.tools.ToolProvider;
+
+/**
+ * {@code InMemoryJavaCompiler} can be used for compiling a {@link
+ * CharSequence} to a {@code byte[]}.
+ *
+ * The compiler will not use the file system at all, instead using a {@link
+ * ByteArrayOutputStream} for storing the byte code. For the source code, any
+ * kind of {@link CharSequence} can be used, e.g. {@link String}, {@link
+ * StringBuffer} or {@link StringBuilder}.
+ *
+ * The {@code InMemoryCompiler} can easily be used together with a {@code
+ * ByteClassLoader} to easily compile and load source code in a {@link String}:
+ *
+ * <pre>
+ * {@code
+ * import com.oracle.java.testlibrary.InMemoryJavaCompiler;
+ * import com.oracle.java.testlibrary.ByteClassLoader;
+ *
+ * class Example {
+ *     public static void main(String[] args) {
+ *         String className = "Foo";
+ *         String sourceCode = "public class " + className + " {" +
+ *                             "    public void bar() {" +
+ *                             "        System.out.println("Hello from bar!");" +
+ *                             "    }" +
+ *                             "}";
+ *         byte[] byteCode = InMemoryJavaCompiler.compile(className, sourceCode);
+ *         Class fooClass = ByteClassLoader.load(className, byteCode);
+ *     }
+ * }
+ * }
+ * </pre>
+ */
+public class InMemoryJavaCompiler {
+    private static class MemoryJavaFileObject extends SimpleJavaFileObject {
+        private final String className;
+        private final CharSequence sourceCode;
+        private final ByteArrayOutputStream byteCode;
+
+        public MemoryJavaFileObject(String className, CharSequence sourceCode) {
+            super(URI.create("string:///" + className.replace('.','/') + Kind.SOURCE.extension), Kind.SOURCE);
+            this.className = className;
+            this.sourceCode = sourceCode;
+            this.byteCode = new ByteArrayOutputStream();
+        }
+
+        @Override
+        public CharSequence getCharContent(boolean ignoreEncodingErrors) {
+            return sourceCode;
+        }
+
+        @Override
+        public OutputStream openOutputStream() throws IOException {
+            return byteCode;
+        }
+
+        public byte[] getByteCode() {
+            return byteCode.toByteArray();
+        }
+
+        public String getClassName() {
+            return className;
+        }
+    }
+
+    private static class FileManagerWrapper extends ForwardingJavaFileManager {
+        private MemoryJavaFileObject file;
+
+        public FileManagerWrapper(MemoryJavaFileObject file) {
+            super(getCompiler().getStandardFileManager(null, null, null));
+            this.file = file;
+        }
+
+        @Override
+        public JavaFileObject getJavaFileForOutput(Location location, String className,
+                                                   Kind kind, FileObject sibling)
+            throws IOException {
+            if (!file.getClassName().equals(className)) {
+                throw new IOException("Expected class with name " + file.getClassName() +
+                                      ", but got " + className);
+            }
+            return file;
+        }
+    }
+
+    /**
+     * Compiles the class with the given name and source code.
+     *
+     * @param className The name of the class
+     * @param sourceCode The source code for the class with name {@code className}
+     * @throws RuntimeException if the compilation did not succeed
+     * @return The resulting byte code from the compilation
+     */
+    public static byte[] compile(String className, CharSequence sourceCode) {
+        MemoryJavaFileObject file = new MemoryJavaFileObject(className, sourceCode);
+        CompilationTask task = getCompilationTask(file);
+
+        if(!task.call()) {
+            throw new RuntimeException("Could not compile " + className + " with source code " + sourceCode);
+        }
+
+        return file.getByteCode();
+    }
+
+    private static JavaCompiler getCompiler() {
+        return ToolProvider.getSystemJavaCompiler();
+    }
+
+    private static CompilationTask getCompilationTask(MemoryJavaFileObject file) {
+        return getCompiler().getTask(null, new FileManagerWrapper(file), null, null, null, Arrays.asList(file));
+    }
+}