1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.fileupload.util.mime; 18 19 import java.io.IOException; 20 import java.io.OutputStream; 21 22 /** 23 * @since 1.3 24 */ 25 final class QuotedPrintableDecoder { 26 27 /** 28 * Carriage return character '{@value}'. 29 */ 30 private static final char CR = '\r'; 31 32 /** 33 * Equal character '{@value}'. 34 */ 35 private static final char EQUAL = '='; 36 37 /** 38 * Line feed character '{@value}'. 39 */ 40 private static final char LF = '\n'; 41 42 /** 43 * Space character '{@value}'. 44 */ 45 private static final char SP = ' '; 46 47 /** 48 * Underscore character '{@value}'. 49 */ 50 private static final char UNDERSCORE = '_'; 51 52 /** 53 * The shift value required to create the upper nibble 54 * from the first of 2 byte values converted from ASCII hex. 55 */ 56 private static final int UPPER_NIBBLE_SHIFT = Byte.SIZE / 2; 57 58 /** 59 * Decode the encoded byte data writing it to the given output stream. 60 * 61 * @param data The array of byte data to decode. 62 * @param out The output stream used to return the decoded data. 63 * @return the number of bytes produced. 64 * @throws IOException if an IO error occurs 65 */ 66 public static int decode(final byte[] data, final OutputStream out) throws IOException { 67 int off = 0; 68 final int length = data.length; 69 final int endOffset = off + length; 70 int bytesWritten = 0; 71 72 while (off < endOffset) { 73 final byte ch = data[off++]; 74 75 // space characters were translated to '_' on encode, so we need to translate them back. 76 if (ch == UNDERSCORE) { 77 out.write(SP); 78 } else if (ch == EQUAL) { 79 // we found an encoded character. Reduce the 3 char sequence to one. 80 // but first, make sure we have two characters to work with. 81 if (off + 1 >= endOffset) { 82 throw new IOException("Invalid quoted printable encoding; truncated escape sequence"); 83 } 84 85 final byte b1 = data[off++]; 86 final byte b2 = data[off++]; 87 88 // we've found an encoded carriage return. The next char needs to be a newline 89 if (b1 == CR) { 90 if (b2 != LF) { 91 throw new IOException("Invalid quoted printable encoding; CR must be followed by LF"); 92 } 93 // this was a soft linebreak inserted by the encoding. We just toss this away 94 // on decode. 95 } else { 96 // this is a hex pair we need to convert back to a single byte. 97 final int c1 = hexToBinary(b1); 98 final int c2 = hexToBinary(b2); 99 out.write(c1 << UPPER_NIBBLE_SHIFT | c2); 100 // 3 bytes in, one byte out 101 bytesWritten++; 102 } 103 } else { 104 // simple character, just write it out. 105 out.write(ch); 106 bytesWritten++; 107 } 108 } 109 110 return bytesWritten; 111 } 112 113 /** 114 * Convert a hex digit to the binary value it represents. 115 * 116 * @param b the ASCII hex byte to convert (0-0, A-F, a-f) 117 * @return the int value of the hex byte, 0-15 118 * @throws IOException if the byte is not a valid hex digit. 119 */ 120 private static int hexToBinary(final byte b) throws IOException { 121 // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE 122 final int i = Character.digit((char) b, 16); 123 if (i == -1) { 124 throw new IOException("Invalid quoted printable encoding: not a valid hex digit: " + b); 125 } 126 return i; 127 } 128 129 /** 130 * Hidden constructor, this class must not be instantiated. 131 */ 132 private QuotedPrintableDecoder() { 133 // do nothing 134 } 135 136 }