IndentingWriter.java revision 579d7739c53a2707ad711a2d2cae46d7d782f061 
1/*
2 * Copyright (C) 2007 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.dx.util;
18
19import java.io.FilterWriter;
20import java.io.IOException;
21import java.io.Writer;
22
23/**
24 * Writer that wraps another writer and passes width-limited and
25 * optionally-prefixed output to its subordinate. When lines are
26 * wrapped they are automatically indented based on the start of the
27 * line.
28 */
29public final class IndentingWriter extends FilterWriter {
30    /** {@code null-ok;} optional prefix for every line */
31    private final String prefix;
32
33    /** {@code > 0;} the maximum output width */
34    private final int width;
35
36    /** {@code > 0;} the maximum indent */
37    private final int maxIndent;
38
39    /** {@code >= 0;} current output column (zero-based) */
40    private int column;
41
42    /** whether indent spaces are currently being collected */
43    private boolean collectingIndent;
44
45    /** {@code >= 0;} current indent amount */
46    private int indent;
47
48    /**
49     * Constructs an instance.
50     *
51     * @param out {@code non-null;} writer to send final output to
52     * @param width {@code >= 0;} the maximum output width (not including
53     * {@code prefix}), or {@code 0} for no maximum
54     * @param prefix {@code non-null;} the prefix for each line
55     */
56    public IndentingWriter(Writer out, int width, String prefix) {
57        super(out);
58
59        if (out == null) {
60            throw new NullPointerException("out == null");
61        }
62
63        if (width < 0) {
64            throw new IllegalArgumentException("width < 0");
65        }
66
67        if (prefix == null) {
68            throw new NullPointerException("prefix == null");
69        }
70
71        this.width = (width != 0) ? width : Integer.MAX_VALUE;
72        this.maxIndent = width >> 1;
73        this.prefix = (prefix.length() == 0) ? null : prefix;
74
75        bol();
76    }
77
78    /**
79     * Constructs a no-prefix instance.
80     *
81     * @param out {@code non-null;} writer to send final output to
82     * @param width {@code >= 0;} the maximum output width (not including
83     * {@code prefix}), or {@code 0} for no maximum
84     */
85    public IndentingWriter(Writer out, int width) {
86        this(out, width, "");
87    }
88
89    /** {@inheritDoc} */
90    @Override
91    public void write(int c) throws IOException {
92        synchronized (lock) {
93            if (collectingIndent) {
94                if (c == ' ') {
95                    indent++;
96                    if (indent >= maxIndent) {
97                        indent = maxIndent;
98                        collectingIndent = false;
99                    }
100                } else {
101                    collectingIndent = false;
102                }
103            }
104
105            if ((column == width) && (c != '\n')) {
106                out.write('\n');
107                column = 0;
108                /*
109                 * Note: No else, so this should fall through to the next
110                 * if statement.
111                 */
112            }
113
114            if (column == 0) {
115                if (prefix != null) {
116                    out.write(prefix);
117                }
118
119                if (!collectingIndent) {
120                    for (int i = 0; i < indent; i++) {
121                        out.write(' ');
122                    }
123                    column = indent;
124                }
125            }
126
127            out.write(c);
128
129            if (c == '\n') {
130                bol();
131            } else {
132                column++;
133            }
134        }
135    }
136
137    /** {@inheritDoc} */
138    @Override
139    public void write(char[] cbuf, int off, int len) throws IOException {
140        synchronized (lock) {
141            while (len > 0) {
142                write(cbuf[off]);
143                off++;
144                len--;
145            }
146        }
147    }
148
149    /** {@inheritDoc} */
150    @Override
151    public void write(String str, int off, int len) throws IOException {
152        synchronized (lock) {
153            while (len > 0) {
154                write(str.charAt(off));
155                off++;
156                len--;
157            }
158        }
159    }
160
161    /**
162     * Indicates that output is at the beginning of a line.
163     */
164    private void bol() {
165        column = 0;
166        collectingIndent = (maxIndent != 0);
167        indent = 0;
168    }
169}
170