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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. It also automatically wraps long lines
     25  * based on given line length.
     26  * <p>
     27  * Delays writing indent until first actual write on a newline, enabling indent
     28  * modification after newline.
     29  */
     30 public class IndentingPrintWriter extends PrintWriter {
     31     private final String mSingleIndent;
     32     private final int mWrapLength;
     33 
     34     /** Mutable version of current indent */
     35     private StringBuilder mIndentBuilder = new StringBuilder();
     36     /** Cache of current {@link #mIndentBuilder} value */
     37     private char[] mCurrentIndent;
     38     /** Length of current line being built, excluding any indent */
     39     private int mCurrentLength;
     40 
     41     /**
     42      * Flag indicating if we're currently sitting on an empty line, and that
     43      * next write should be prefixed with the current indent.
     44      */
     45     private boolean mEmptyLine = true;
     46 
     47     public IndentingPrintWriter(Writer writer, String singleIndent) {
     48         this(writer, singleIndent, -1);
     49     }
     50 
     51     public IndentingPrintWriter(Writer writer, String singleIndent, int wrapLength) {
     52         super(writer);
     53         mSingleIndent = singleIndent;
     54         mWrapLength = wrapLength;
     55     }
     56 
     57     public void increaseIndent() {
     58         mIndentBuilder.append(mSingleIndent);
     59         mCurrentIndent = null;
     60     }
     61 
     62     public void decreaseIndent() {
     63         mIndentBuilder.delete(0, mSingleIndent.length());
     64         mCurrentIndent = null;
     65     }
     66 
     67     public void printPair(String key, Object value) {
     68         print(key + "=" + String.valueOf(value) + " ");
     69     }
     70 
     71     @Override
     72     public void write(char[] buf, int offset, int count) {
     73         final int indentLength = mIndentBuilder.length();
     74         final int bufferEnd = offset + count;
     75         int lineStart = offset;
     76         int lineEnd = offset;
     77 
     78         // March through incoming buffer looking for newlines
     79         while (lineEnd < bufferEnd) {
     80             char ch = buf[lineEnd++];
     81             mCurrentLength++;
     82             if (ch == '\n') {
     83                 maybeWriteIndent();
     84                 super.write(buf, lineStart, lineEnd - lineStart);
     85                 lineStart = lineEnd;
     86                 mEmptyLine = true;
     87                 mCurrentLength = 0;
     88             }
     89 
     90             // Wrap if we've pushed beyond line length
     91             if (mWrapLength > 0 && mCurrentLength >= mWrapLength - indentLength) {
     92                 if (!mEmptyLine) {
     93                     // Give ourselves a fresh line to work with
     94                     super.write('\n');
     95                     mEmptyLine = true;
     96                     mCurrentLength = lineEnd - lineStart;
     97                 } else {
     98                     // We need more than a dedicated line, slice it hard
     99                     maybeWriteIndent();
    100                     super.write(buf, lineStart, lineEnd - lineStart);
    101                     super.write('\n');
    102                     mEmptyLine = true;
    103                     lineStart = lineEnd;
    104                     mCurrentLength = 0;
    105                 }
    106             }
    107         }
    108 
    109         if (lineStart != lineEnd) {
    110             maybeWriteIndent();
    111             super.write(buf, lineStart, lineEnd - lineStart);
    112         }
    113     }
    114 
    115     private void maybeWriteIndent() {
    116         if (mEmptyLine) {
    117             mEmptyLine = false;
    118             if (mIndentBuilder.length() != 0) {
    119                 if (mCurrentIndent == null) {
    120                     mCurrentIndent = mIndentBuilder.toString().toCharArray();
    121                 }
    122                 super.write(mCurrentIndent, 0, mCurrentIndent.length);
    123             }
    124         }
    125     }
    126 }
    127