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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 
     22 /**
     23  * Lightweight wrapper around {@link PrintWriter} that automatically indents
     24  * newlines based on internal state. Delays writing indent until first actual
     25  * write on a newline, enabling indent modification after newline.
     26  */
     27 public class IndentingPrintWriter extends PrintWriter {
     28     private final String mIndent;
     29 
     30     private StringBuilder mBuilder = new StringBuilder();
     31     private char[] mCurrent;
     32     private boolean mEmptyLine = true;
     33 
     34     public IndentingPrintWriter(Writer writer, String indent) {
     35         super(writer);
     36         mIndent = indent;
     37     }
     38 
     39     public void increaseIndent() {
     40         mBuilder.append(mIndent);
     41         mCurrent = null;
     42     }
     43 
     44     public void decreaseIndent() {
     45         mBuilder.delete(0, mIndent.length());
     46         mCurrent = null;
     47     }
     48 
     49     public void printPair(String key, Object value) {
     50         print(key + "=" + String.valueOf(value) + " ");
     51     }
     52 
     53     @Override
     54     public void write(char[] buf, int offset, int count) {
     55         final int bufferEnd = offset + count;
     56         int lineStart = offset;
     57         int lineEnd = offset;
     58         while (lineEnd < bufferEnd) {
     59             char ch = buf[lineEnd++];
     60             if (ch == '\n') {
     61                 writeIndent();
     62                 super.write(buf, lineStart, lineEnd - lineStart);
     63                 lineStart = lineEnd;
     64                 mEmptyLine = true;
     65             }
     66         }
     67 
     68         if (lineStart != lineEnd) {
     69             writeIndent();
     70             super.write(buf, lineStart, lineEnd - lineStart);
     71         }
     72     }
     73 
     74     private void writeIndent() {
     75         if (mEmptyLine) {
     76             mEmptyLine = false;
     77             if (mBuilder.length() != 0) {
     78                 if (mCurrent == null) {
     79                     mCurrent = mBuilder.toString().toCharArray();
     80                 }
     81                 super.write(mCurrent, 0, mCurrent.length);
     82             }
     83         }
     84     }
     85 }
     86