1 /*
2  * Copyright (C) 2016 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.voicemail.impl.utils;
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 newlines based on
25  * internal state. It also automatically wraps long lines based on given line length.
26  *
27  * <p>Delays writing indent until first actual write on a newline, enabling indent modification
28  * after newline.
29  */
30 public class IndentingPrintWriter extends PrintWriter {
31 
32   private final String singleIndent;
33   private final int wrapLength;
34 
35   /** Mutable version of current indent */
36   private StringBuilder indentBuilder = new StringBuilder();
37   /** Cache of current {@link #indentBuilder} value */
38   private char[] currentIndent;
39   /** Length of current line being built, excluding any indent */
40   private int currentLength;
41 
42   /**
43    * Flag indicating if we're currently sitting on an empty line, and that next write should be
44    * prefixed with the current indent.
45    */
46   private boolean emptyLine = true;
47 
48   private char[] singleChar = 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     this.singleIndent = singleIndent;
57     this.wrapLength = wrapLength;
58   }
59 
increaseIndent()60   public void increaseIndent() {
61     indentBuilder.append(singleIndent);
62     currentIndent = null;
63   }
64 
decreaseIndent()65   public void decreaseIndent() {
66     indentBuilder.delete(0, singleIndent.length());
67     currentIndent = null;
68   }
69 
printPair(String key, Object value)70   public void printPair(String key, Object value) {
71     print(key + "=" + String.valueOf(value) + " ");
72   }
73 
printPair(String key, Object[] value)74   public void printPair(String key, Object[] value) {
75     print(key + "=" + Arrays.toString(value) + " ");
76   }
77 
printHexPair(String key, int value)78   public void printHexPair(String key, int value) {
79     print(key + "=0x" + Integer.toHexString(value) + " ");
80   }
81 
82   @Override
println()83   public void println() {
84     write('\n');
85   }
86 
87   @Override
write(int c)88   public void write(int c) {
89     singleChar[0] = (char) c;
90     write(singleChar, 0, 1);
91   }
92 
93   @Override
write(String s, int off, int len)94   public void write(String s, int off, int len) {
95     final char[] buf = new char[len];
96     s.getChars(off, len - off, buf, 0);
97     write(buf, 0, len);
98   }
99 
100   @Override
write(char[] buf, int offset, int count)101   public void write(char[] buf, int offset, int count) {
102     final int indentLength = indentBuilder.length();
103     final int bufferEnd = offset + count;
104     int lineStart = offset;
105     int lineEnd = offset;
106 
107     // March through incoming buffer looking for newlines
108     while (lineEnd < bufferEnd) {
109       char ch = buf[lineEnd++];
110       currentLength++;
111       if (ch == '\n') {
112         maybeWriteIndent();
113         super.write(buf, lineStart, lineEnd - lineStart);
114         lineStart = lineEnd;
115         emptyLine = true;
116         currentLength = 0;
117       }
118 
119       // Wrap if we've pushed beyond line length
120       if (wrapLength > 0 && currentLength >= wrapLength - indentLength) {
121         if (!emptyLine) {
122           // Give ourselves a fresh line to work with
123           super.write('\n');
124           emptyLine = true;
125           currentLength = lineEnd - lineStart;
126         } else {
127           // We need more than a dedicated line, slice it hard
128           maybeWriteIndent();
129           super.write(buf, lineStart, lineEnd - lineStart);
130           super.write('\n');
131           emptyLine = true;
132           lineStart = lineEnd;
133           currentLength = 0;
134         }
135       }
136     }
137 
138     if (lineStart != lineEnd) {
139       maybeWriteIndent();
140       super.write(buf, lineStart, lineEnd - lineStart);
141     }
142   }
143 
maybeWriteIndent()144   private void maybeWriteIndent() {
145     if (emptyLine) {
146       emptyLine = false;
147       if (indentBuilder.length() != 0) {
148         if (currentIndent == null) {
149           currentIndent = indentBuilder.toString().toCharArray();
150         }
151         super.write(currentIndent, 0, currentIndent.length);
152       }
153     }
154   }
155 }
156