IndentingPrintWriter.java revision 1b8ef7e3165ff9aa52a4905dafc8d0f83e7403f9
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 17package com.android.internal.util; 18 19import java.io.PrintWriter; 20import java.io.Writer; 21import 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 */ 31public 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