1 /*
2  * Copyright (C) 2012 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 
17 package com.android.internal.util;
18 
19 import java.io.PrintWriter;
20 import java.io.Writer;
21 import java.util.Arrays;
22 
23 /**
24  * Lightweight wrapper around {@link PrintWriter} that automatically indents
25  * newlines based on internal state. It also automatically wraps long lines
26  * based on given line length.
27  * <p>
28  * Delays writing indent until first actual write on a newline, enabling indent
29  * modification after newline.
30  */
31 public class IndentingPrintWriter extends PrintWriter {
32     private final String mSingleIndent;
33     private final int mWrapLength;
34 
35     /** Mutable version of current indent */
36     private StringBuilder mIndentBuilder = new StringBuilder();
37     /** Cache of current {@link #mIndentBuilder} value */
38     private char[] mCurrentIndent;
39     /** Length of current line being built, excluding any indent */
40     private int mCurrentLength;
41 
42     /**
43      * Flag indicating if we're currently sitting on an empty line, and that
44      * next write should be prefixed with the current indent.
45      */
46     private boolean mEmptyLine = true;
47 
48     private char[] mSingleChar = new char[1];
49 
IndentingPrintWriter(Writer writer, String singleIndent)50     public IndentingPrintWriter(Writer writer, String singleIndent) {
51         this(writer, singleIndent, -1);
52     }
53 
IndentingPrintWriter(Writer writer, String singleIndent, int wrapLength)54     public IndentingPrintWriter(Writer writer, String singleIndent, int wrapLength) {
55         super(writer);
56         mSingleIndent = singleIndent;
57         mWrapLength = wrapLength;
58     }
59 
setIndent(String indent)60     public IndentingPrintWriter setIndent(String indent) {
61         mIndentBuilder.setLength(0);
62         mIndentBuilder.append(indent);
63         mCurrentIndent = null;
64         return this;
65     }
66 
setIndent(int indent)67     public IndentingPrintWriter setIndent(int indent) {
68         mIndentBuilder.setLength(0);
69         for (int i = 0; i < indent; i++) {
70             increaseIndent();
71         }
72         return this;
73     }
74 
increaseIndent()75     public IndentingPrintWriter increaseIndent() {
76         mIndentBuilder.append(mSingleIndent);
77         mCurrentIndent = null;
78         return this;
79     }
80 
decreaseIndent()81     public IndentingPrintWriter decreaseIndent() {
82         mIndentBuilder.delete(0, mSingleIndent.length());
83         mCurrentIndent = null;
84         return this;
85     }
86 
printPair(String key, Object value)87     public IndentingPrintWriter printPair(String key, Object value) {
88         print(key + "=" + String.valueOf(value) + " ");
89         return this;
90     }
91 
printPair(String key, Object[] value)92     public IndentingPrintWriter printPair(String key, Object[] value) {
93         print(key + "=" + Arrays.toString(value) + " ");
94         return this;
95     }
96 
printHexPair(String key, int value)97     public IndentingPrintWriter printHexPair(String key, int value) {
98         print(key + "=0x" + Integer.toHexString(value) + " ");
99         return this;
100     }
101 
102     @Override
println()103     public void println() {
104         write('\n');
105     }
106 
107     @Override
write(int c)108     public void write(int c) {
109         mSingleChar[0] = (char) c;
110         write(mSingleChar, 0, 1);
111     }
112 
113     @Override
write(String s, int off, int len)114     public void write(String s, int off, int len) {
115         final char[] buf = new char[len];
116         s.getChars(off, len - off, buf, 0);
117         write(buf, 0, len);
118     }
119 
120     @Override
write(char[] buf, int offset, int count)121     public void write(char[] buf, int offset, int count) {
122         final int indentLength = mIndentBuilder.length();
123         final int bufferEnd = offset + count;
124         int lineStart = offset;
125         int lineEnd = offset;
126 
127         // March through incoming buffer looking for newlines
128         while (lineEnd < bufferEnd) {
129             char ch = buf[lineEnd++];
130             mCurrentLength++;
131             if (ch == '\n') {
132                 maybeWriteIndent();
133                 super.write(buf, lineStart, lineEnd - lineStart);
134                 lineStart = lineEnd;
135                 mEmptyLine = true;
136                 mCurrentLength = 0;
137             }
138 
139             // Wrap if we've pushed beyond line length
140             if (mWrapLength > 0 && mCurrentLength >= mWrapLength - indentLength) {
141                 if (!mEmptyLine) {
142                     // Give ourselves a fresh line to work with
143                     super.write('\n');
144                     mEmptyLine = true;
145                     mCurrentLength = lineEnd - lineStart;
146                 } else {
147                     // We need more than a dedicated line, slice it hard
148                     maybeWriteIndent();
149                     super.write(buf, lineStart, lineEnd - lineStart);
150                     super.write('\n');
151                     mEmptyLine = true;
152                     lineStart = lineEnd;
153                     mCurrentLength = 0;
154                 }
155             }
156         }
157 
158         if (lineStart != lineEnd) {
159             maybeWriteIndent();
160             super.write(buf, lineStart, lineEnd - lineStart);
161         }
162     }
163 
maybeWriteIndent()164     private void maybeWriteIndent() {
165         if (mEmptyLine) {
166             mEmptyLine = false;
167             if (mIndentBuilder.length() != 0) {
168                 if (mCurrentIndent == null) {
169                     mCurrentIndent = mIndentBuilder.toString().toCharArray();
170                 }
171                 super.write(mCurrentIndent, 0, mCurrentIndent.length);
172             }
173         }
174     }
175 }
176