--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/java.base/share/classes/sun/security/provider/FileInputStreamPool.java Wed Jan 21 12:49:53 2015 +0100
@@ -0,0 +1,159 @@
+/*
+ * Copyright (c) 2014, 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 sun.security.provider;
+
+import java.io.*;
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.WeakReference;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+
+/**
+ * A pool of {@code InputStream}s opened from distinct files. Only a single
+ * instance is ever opened from the same file. This is used to read special
+ * infinite files like {@code /dev/random} where the current file pointer is not
+ * relevant, so multiple readers can share the same file descriptor and
+ * consequently the same {@code InputStream}.
+ */
+class FileInputStreamPool {
+
+ /**
+ * a pool of: StreamRef -> UnclosableInputStream -> FileInputStream(s)
+ */
+ private static final ConcurrentMap<File, StreamRef> pool =
+ new ConcurrentHashMap<>();
+
+ /**
+ * a reference queue of cleared StreamRef(s)
+ */
+ private static final ReferenceQueue<UnclosableInputStream> refQueue =
+ new ReferenceQueue<>();
+
+ /**
+ * This method opens an underlying {@link java.io.FileInputStream} for a
+ * given {@code file} and returns a wrapper over it. The wrapper is shared
+ * among multiple readers of the same {@code file} and ignores
+ * {@link java.io.InputStream#close()} requests. The underlying stream is
+ * closed when all references to the wrapper are relinquished.
+ *
+ * @param file the file to be opened for reading.
+ * @return a shared {@link java.io.InputStream} instance opened from given
+ * file.
+ * @throws FileNotFoundException if the file does not exist, is a directory
+ * rather than a regular file, or for some
+ * other reason cannot be opened for reading.
+ * @throws SecurityException if a security manager exists and its
+ * <code>checkRead</code> method denies read
+ * access to the file.
+ */
+ static InputStream getInputStream(File file) throws IOException {
+
+ // expunge any cleared references
+ StreamRef oldRref;
+ while ((oldRref = (StreamRef) refQueue.poll()) != null) {
+ pool.remove(oldRref.file, oldRref);
+ }
+
+ // canonicalize the path
+ // (this also checks the read permission on the file if SecurityManager
+ // is present, so no checking is needed later when we just return the
+ // already opened stream)
+ File cfile = file.getCanonicalFile();
+
+ // check if it exists in pool
+ oldRref = pool.get(cfile);
+ UnclosableInputStream oldStream = (oldRref == null)
+ ? null
+ : oldRref.get();
+ StreamRef newRef = null;
+ UnclosableInputStream newStream = null;
+
+ // retry loop
+ while (true) {
+ if (oldStream != null) {
+ // close our optimistically opened stream 1st (if we opened it)
+ if (newStream != null) {
+ try {
+ newStream.getWrappedStream().close();
+ } catch (IOException ignore) {
+ // can't do anything here
+ }
+ }
+ // return it
+ return oldStream;
+ } else {
+ // we need to open new stream optimistically (if not already)
+ if (newStream == null) {
+ newStream = new UnclosableInputStream(
+ new FileInputStream(cfile));
+ newRef = new StreamRef(cfile, newStream, refQueue);
+ }
+ // either try to install newRef or replace oldRef with newRef
+ if (oldRref == null) {
+ oldRref = pool.putIfAbsent(cfile, newRef);
+ } else {
+ oldRref = pool.replace(cfile, oldRref, newRef)
+ ? null
+ : pool.get(cfile);
+ }
+ if (oldRref == null) {
+ // success
+ return newStream;
+ } else {
+ // lost race
+ oldStream = oldRref.get();
+ // another loop
+ }
+ }
+ }
+ }
+
+ private static class StreamRef extends WeakReference<UnclosableInputStream> {
+ final File file;
+
+ StreamRef(File file,
+ UnclosableInputStream stream,
+ ReferenceQueue<UnclosableInputStream> refQueue) {
+ super(stream, refQueue);
+ this.file = file;
+ }
+ }
+
+ private static final class UnclosableInputStream extends FilterInputStream {
+ UnclosableInputStream(InputStream in) {
+ super(in);
+ }
+
+ @Override
+ public void close() throws IOException {
+ // Ignore close attempts since underlying InputStream is shared.
+ }
+
+ InputStream getWrappedStream() {
+ return in;
+ }
+ }
+}