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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 void increaseIndent() {
     61         mIndentBuilder.append(mSingleIndent);
     62         mCurrentIndent = null;
     63     }
     64 
     65     public void decreaseIndent() {
     66         mIndentBuilder.delete(0, mSingleIndent.length());
     67         mCurrentIndent = 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         mSingleChar[0] = (char) c;
     90         write(mSingleChar, 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 = 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 
    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