Home | History | Annotate | Download | only in util 
      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     public IndentingPrintWriter(Writer writer, String singleIndent) {
     49         this(writer, singleIndent, -1);
     50     }
     51 
     52     public IndentingPrintWriter(Writer writer, String singleIndent, int wrapLength) {
     53         super(writer);
     54         mSingleIndent = singleIndent;
     55         mWrapLength = wrapLength;
     56     }
     57 
     58     public void increaseIndent() {
     59         mIndentBuilder.append(mSingleIndent);
     60         mCurrentIndent = null;
     61     }
     62 
     63     public void decreaseIndent() {
     64         mIndentBuilder.delete(0, mSingleIndent.length());
     65         mCurrentIndent = null;
     66     }
     67 
     68     public void printPair(String key, Object value) {
     69         print(key + "=" + String.valueOf(value) + " ");
     70     }
     71 
     72     public void printPair(String key, Object[] value) {
     73         print(key + "=" + Arrays.toString(value) + " ");
     74     }
     75 
     76     public void printHexPair(String key, int value) {
     77         print(key + "=0x" + Integer.toHexString(value) + " ");
     78     }
     79 
     80     @Override
     81     public void write(char[] buf, int offset, int count) {
     82         final int indentLength = mIndentBuilder.length();
     83         final int bufferEnd = offset + count;
     84         int lineStart = offset;
     85         int lineEnd = offset;
     86 
     87         // March through incoming buffer looking for newlines
     88         while (lineEnd < bufferEnd) {
     89             char ch = buf[lineEnd++];
     90             mCurrentLength++;
     91             if (ch == '\n') {
     92                 maybeWriteIndent();
     93                 super.write(buf, lineStart, lineEnd - lineStart);
     94                 lineStart = lineEnd;
     95                 mEmptyLine = true;
     96                 mCurrentLength = 0;
     97             }
     98 
     99             // Wrap if we've pushed beyond line length
    100             if (mWrapLength > 0 && mCurrentLength >= mWrapLength - indentLength) {
    101                 if (!mEmptyLine) {
    102                     // Give ourselves a fresh line to work with
    103                     super.write('\n');
    104                     mEmptyLine = true;
    105                     mCurrentLength = lineEnd - lineStart;
    106                 } else {
    107                     // We need more than a dedicated line, slice it hard
    108                     maybeWriteIndent();
    109                     super.write(buf, lineStart, lineEnd - lineStart);
    110                     super.write('\n');
    111                     mEmptyLine = true;
    112                     lineStart = lineEnd;
    113                     mCurrentLength = 0;
    114                 }
    115             }
    116         }
    117 
    118         if (lineStart != lineEnd) {
    119             maybeWriteIndent();
    120             super.write(buf, lineStart, lineEnd - lineStart);
    121         }
    122     }
    123 
    124     private void maybeWriteIndent() {
    125         if (mEmptyLine) {
    126             mEmptyLine = false;
    127             if (mIndentBuilder.length() != 0) {
    128                 if (mCurrentIndent == null) {
    129                     mCurrentIndent = mIndentBuilder.toString().toCharArray();
    130                 }
    131                 super.write(mCurrentIndent, 0, mCurrentIndent.length);
    132             }
    133         }
    134     }
    135 }
    136