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      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 
     50     public IndentingPrintWriter(Writer writer, String singleIndent) {
     51         this(writer, singleIndent, -1);
     52     }
     53 
     54     public IndentingPrintWriter(Writer writer, String singleIndent, int wrapLength) {
     55         super(writer);
     56         mSingleIndent = singleIndent;
     57         mWrapLength = wrapLength;
     58     }
     59 
     60     public IndentingPrintWriter setIndent(String indent) {
     61         mIndentBuilder.setLength(0);
     62         mIndentBuilder.append(indent);
     63         mCurrentIndent = null;
     64         return this;
     65     }
     66 
     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 
     75     public IndentingPrintWriter increaseIndent() {
     76         mIndentBuilder.append(mSingleIndent);
     77         mCurrentIndent = null;
     78         return this;
     79     }
     80 
     81     public IndentingPrintWriter decreaseIndent() {
     82         mIndentBuilder.delete(0, mSingleIndent.length());
     83         mCurrentIndent = null;
     84         return this;
     85     }
     86 
     87     public IndentingPrintWriter printPair(String key, Object value) {
     88         print(key + "=" + String.valueOf(value) + " ");
     89         return this;
     90     }
     91 
     92     public IndentingPrintWriter printPair(String key, Object[] value) {
     93         print(key + "=" + Arrays.toString(value) + " ");
     94         return this;
     95     }
     96 
     97     public IndentingPrintWriter printHexPair(String key, int value) {
     98         print(key + "=0x" + Integer.toHexString(value) + " ");
     99         return this;
    100     }
    101 
    102     @Override
    103     public void println() {
    104         write('\n');
    105     }
    106 
    107     @Override
    108     public void write(int c) {
    109         mSingleChar[0] = (char) c;
    110         write(mSingleChar, 0, 1);
    111     }
    112 
    113     @Override
    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
    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 
    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