WrappedIndentingWriter.java revision 373ff22ec69bb6e93646994347b6d80502be1588 
1/*
2 * Copyright 2013, Google Inc.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met:
8 *
9 *     * Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 *     * Redistributions in binary form must reproduce the above
12 * copyright notice, this list of conditions and the following disclaimer
13 * in the documentation and/or other materials provided with the
14 * distribution.
15 *     * Neither the name of Google Inc. nor the names of its
16 * contributors may be used to endorse or promote products derived from
17 * this software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 */
31
32package org.jf.util;
33
34import java.io.FilterWriter;
35import java.io.IOException;
36import java.io.Writer;
37
38/**
39 * Writer that wraps another writer and passes width-limited and
40 * optionally-prefixed output to its subordinate. When lines are
41 * wrapped they are automatically indented based on the start of the
42 * line.
43 */
44public final class WrappedIndentingWriter extends FilterWriter {
45    /** null-ok; optional prefix for every line */
46    private final String prefix;
47
48    /** > 0; the maximum output width */
49    private final int width;
50
51    /** > 0; the maximum indent */
52    private final int maxIndent;
53
54    /** >= 0; current output column (zero-based) */
55    private int column;
56
57    /** whether indent spaces are currently being collected */
58    private boolean collectingIndent;
59
60    /** >= 0; current indent amount */
61    private int indent;
62
63    /**
64     * Constructs an instance.
65     *
66     * @param out non-null; writer to send final output to
67     * @param width >= 0; the maximum output width (not including
68     * <code>prefix</code>), or <code>0</code> for no maximum
69     * @param prefix non-null; the prefix for each line
70     */
71    public WrappedIndentingWriter(Writer out, int width, String prefix) {
72        super(out);
73
74        if (out == null) {
75            throw new NullPointerException("out == null");
76        }
77
78        if (width < 0) {
79            throw new IllegalArgumentException("width < 0");
80        }
81
82        if (prefix == null) {
83            throw new NullPointerException("prefix == null");
84        }
85
86        this.width = (width != 0) ? width : Integer.MAX_VALUE;
87        this.maxIndent = width >> 1;
88        this.prefix = (prefix.length() == 0) ? null : prefix;
89
90        bol();
91    }
92
93    /**
94     * Constructs a no-prefix instance.
95     *
96     * @param out non-null; writer to send final output to
97     * @param width &gt;= 0; the maximum output width (not including
98     * <code>prefix</code>), or <code>0</code> for no maximum
99     */
100    public WrappedIndentingWriter(Writer out, int width) {
101        this(out, width, "");
102    }
103
104    /** {@inheritDoc} */
105    @Override
106    public void write(int c) throws IOException {
107        synchronized (lock) {
108            if (collectingIndent) {
109                if (c == ' ') {
110                    indent++;
111                    if (indent >= maxIndent) {
112                        indent = maxIndent;
113                        collectingIndent = false;
114                    }
115                } else {
116                    collectingIndent = false;
117                }
118            }
119
120            if ((column == width) && (c != '\n')) {
121                out.write('\n');
122                column = 0;
123                /*
124                 * Note: No else, so this should fall through to the next
125                 * if statement.
126                 */
127            }
128
129            if (column == 0) {
130                if (prefix != null) {
131                    out.write(prefix);
132                }
133
134                if (!collectingIndent) {
135                    for (int i = 0; i < indent; i++) {
136                        out.write(' ');
137                    }
138                    column = indent;
139                }
140            }
141
142            out.write(c);
143
144            if (c == '\n') {
145                bol();
146            } else {
147                column++;
148            }
149        }
150    }
151
152    /** {@inheritDoc} */
153    @Override
154    public void write(char[] cbuf, int off, int len) throws IOException {
155        synchronized (lock) {
156            while (len > 0) {
157                write(cbuf[off]);
158                off++;
159                len--;
160            }
161        }
162    }
163
164    /** {@inheritDoc} */
165    @Override
166    public void write(String str, int off, int len) throws IOException {
167        synchronized (lock) {
168            while (len > 0) {
169                write(str.charAt(off));
170                off++;
171                len--;
172            }
173        }
174    }
175
176    /**
177     * Indicates that output is at the beginning of a line.
178     */
179    private void bol() {
180        column = 0;
181        collectingIndent = (maxIndent != 0);
182        indent = 0;
183    }
184}
185