SmartWriter.java revision 3266:8ea3f9487e89 
1/*
2 * Copyright (c) 2012, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package com.sun.tools.sjavac.comp;
27
28import com.sun.tools.sjavac.Log;
29
30import java.io.*;
31import javax.tools.JavaFileObject;
32
33/**
34 * The SmartWriter will cache the written data and when the writer is closed,
35 * then it will compare the cached data with the old_content string.
36 * If different, then it will write all the new content to the file.
37 * If not, the file is not touched.
38 *
39 *  <p><b>This is NOT part of any supported API.
40 *  If you write code that depends on this, you do so at your own risk.
41 *  This code and its internal interfaces are subject to change or
42 *  deletion without notice.</b>
43 */
44public class SmartWriter extends Writer {
45
46    String name;
47    JavaFileObject file;
48    String oldContent;
49    StringWriter newContent = new StringWriter();
50    boolean closed;
51
52    public SmartWriter(JavaFileObject f, String s, String n) {
53        name = n;
54        file = f;
55        oldContent = s;
56        newContent = new StringWriter();
57        closed = false;
58    }
59
60    public void write(char[] chars, int i, int i1) {
61        newContent.write(chars, i, i1);
62    }
63
64    public void close() throws IOException {
65        if (closed) return;
66        closed = true;
67        String s = newContent.toString();
68        if (!oldContent.equals(s)) {
69            int p = file.getName().lastIndexOf(File.separatorChar);
70            try (Writer writer = file.openWriter()) {
71                writer.write(s);
72            }
73            Log.debug("Writing " + file.getName().substring(p + 1));
74        }
75    }
76
77    public void flush() throws IOException {
78    }
79}
80