8295803: Console should be usable in jshell and other environments

Reviewed-by: jlaskey, alanb

src/java.base/share/classes/java/io/ProxyingConsole.java

@@ -0,0 +1,198 @@
+/*
+ * Copyright (c) 2022, 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 java.io;
+
+import java.nio.charset.Charset;
+import jdk.internal.io.JdkConsole;
+
+/**
+ * Console implementation for internal use. Custom Console delegate may be
+ * provided with jdk.internal.io.JdkConsoleProvider.
+ */
+final class ProxyingConsole extends Console {
+    private final JdkConsole delegate;
+    private final Object readLock;
+    private final Object writeLock;
+    private final Reader reader;
+    private final PrintWriter printWriter;
+
+    ProxyingConsole(JdkConsole delegate) {
+        this.delegate = delegate;
+        readLock = new Object();
+        writeLock = new Object();
+        reader = new WrappingReader(delegate.reader(), readLock);
+        printWriter = new WrappingWriter(delegate.writer(), writeLock);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public PrintWriter writer() {
+        return printWriter;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public Reader reader() {
+        return reader;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public Console format(String fmt, Object ... args) {
+        synchronized (writeLock) {
+            delegate.format(fmt, args);
+        }
+        return this;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public Console printf(String format, Object ... args) {
+        synchronized (writeLock) {
+            delegate.printf(format, args);
+        }
+        return this;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public String readLine(String fmt, Object ... args) {
+        synchronized (writeLock) {
+            synchronized (readLock) {
+                return delegate.readLine(fmt, args);
+            }
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public String readLine() {
+        synchronized (readLock) {
+            return delegate.readLine();
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public char[] readPassword(String fmt, Object ... args) {
+        synchronized (writeLock) {
+            synchronized (readLock) {
+                return delegate.readPassword(fmt, args);
+            }
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public char[] readPassword() {
+        synchronized (readLock) {
+            return delegate.readPassword();
+        }
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public void flush() {
+        delegate.flush();
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public Charset charset() {
+        return delegate.charset();
+    }
+
+    private static class WrappingReader extends Reader {
+        private final Reader r;
+        private final Object lock;
+
+        WrappingReader(Reader r, Object lock) {
+            super(lock);
+            this.r = r;
+            this.lock = lock;
+        }
+
+        @Override
+        public int read(char[] cbuf, int off, int len) throws IOException {
+            synchronized (lock) {
+                return r.read(cbuf, off, len);
+            }
+        }
+
+        @Override
+        public void close() {
+            // no-op, per Console's spec
+        }
+    }
+
+    private static class WrappingWriter extends PrintWriter {
+        private final PrintWriter pw;
+        private final Object lock;
+
+        public WrappingWriter(PrintWriter pw, Object lock) {
+            super(pw, lock);
+            this.pw = pw;
+            this.lock = lock;
+        }
+
+        @Override
+        public void write(char[] cbuf, int off, int len) {
+            synchronized (lock) {
+                pw.write(cbuf, off, len);
+            }
+        }
+
+        @Override
+        public void flush() {
+            pw.flush();
+        }
+
+        @Override
+        public void close() {
+            // no-op, per Console's spec
+        }
+    }
+}