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 
increaseIndent()60     public void increaseIndent() {
61         mIndentBuilder.append(mSingleIndent);
62         mCurrentIndent = null;
63     }
64 
decreaseIndent()65     public void decreaseIndent() {
66         mIndentBuilder.delete(0, mSingleIndent.length());
67         mCurrentIndent = 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         mSingleChar[0] = (char) c;
90         write(mSingleChar, 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 = mIndentBuilder.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             mCurrentLength++;
111             if (ch == '\n') {
112                 maybeWriteIndent();
113                 super.write(buf, lineStart, lineEnd - lineStart);
114                 lineStart = lineEnd;
115                 mEmptyLine = true;
116                 mCurrentLength = 0;
117             }
118 
119             // Wrap if we've pushed beyond line length
120             if (mWrapLength > 0 && mCurrentLength >= mWrapLength - indentLength) {
121                 if (!mEmptyLine) {
122                     // Give ourselves a fresh line to work with
123                     super.write('\n');
124                     mEmptyLine = true;
125                     mCurrentLength = 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                     mEmptyLine = true;
132                     lineStart = lineEnd;
133                     mCurrentLength = 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 (mEmptyLine) {
146             mEmptyLine = false;
147             if (mIndentBuilder.length() != 0) {
148                 if (mCurrentIndent == null) {
149                     mCurrentIndent = mIndentBuilder.toString().toCharArray();
150                 }
151                 super.write(mCurrentIndent, 0, mCurrentIndent.length);
152             }
153         }
154     }
155 }
156