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      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 
     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     this.singleIndent = singleIndent;
     57     this.wrapLength = wrapLength;
     58   }
     59 
     60   public void increaseIndent() {
     61     indentBuilder.append(singleIndent);
     62     currentIndent = null;
     63   }
     64 
     65   public void decreaseIndent() {
     66     indentBuilder.delete(0, singleIndent.length());
     67     currentIndent = null;
     68   }
     69 
     70   public void printPair(String key, Object value) {
     71     print(key + "=" + String.valueOf(value) + " ");
     72   }
     73 
     74   public void printPair(String key, Object[] value) {
     75     print(key + "=" + Arrays.toString(value) + " ");
     76   }
     77 
     78   public void printHexPair(String key, int value) {
     79     print(key + "=0x" + Integer.toHexString(value) + " ");
     80   }
     81 
     82   @Override
     83   public void println() {
     84     write('\n');
     85   }
     86 
     87   @Override
     88   public void write(int c) {
     89     singleChar[0] = (char) c;
     90     write(singleChar, 0, 1);
     91   }
     92 
     93   @Override
     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
    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 
    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