| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.commons.fileupload.util.mime; |
| |
| import java.io.IOException; |
| import java.io.OutputStream; |
| |
| /** |
| * @since 1.3 |
| */ |
| final class QuotedPrintableDecoder { |
| |
| /** |
| * The shift value required to create the upper nibble |
| * from the first of 2 byte values converted from ascii hex. |
| */ |
| private static final int UPPER_NIBBLE_SHIFT = Byte.SIZE / 2; |
| |
| /** |
| * Hidden constructor, this class must not be instantiated. |
| */ |
| private QuotedPrintableDecoder() { |
| // do nothing |
| } |
| |
| /** |
| * Decode the encoded byte data writing it to the given output stream. |
| * |
| * @param data The array of byte data to decode. |
| * @param out The output stream used to return the decoded data. |
| * |
| * @return the number of bytes produced. |
| * @exception IOException |
| */ |
| public static int decode(byte[] data, OutputStream out) throws IOException { |
| int off = 0; |
| int length = data.length; |
| int endOffset = off + length; |
| int bytesWritten = 0; |
| |
| while (off < endOffset) { |
| byte ch = data[off++]; |
| |
| // space characters were translated to '_' on encode, so we need to translate them back. |
| if (ch == '_') { |
| out.write(' '); |
| } else if (ch == '=') { |
| // we found an encoded character. Reduce the 3 char sequence to one. |
| // but first, make sure we have two characters to work with. |
| if (off + 1 >= endOffset) { |
| throw new IOException("Invalid quoted printable encoding; truncated escape sequence"); |
| } |
| |
| byte b1 = data[off++]; |
| byte b2 = data[off++]; |
| |
| // we've found an encoded carriage return. The next char needs to be a newline |
| if (b1 == '\r') { |
| if (b2 != '\n') { |
| throw new IOException("Invalid quoted printable encoding; CR must be followed by LF"); |
| } |
| // this was a soft linebreak inserted by the encoding. We just toss this away |
| // on decode. |
| } else { |
| // this is a hex pair we need to convert back to a single byte. |
| int c1 = hexToBinary(b1); |
| int c2 = hexToBinary(b2); |
| out.write((c1 << UPPER_NIBBLE_SHIFT) | c2); |
| // 3 bytes in, one byte out |
| bytesWritten++; |
| } |
| } else { |
| // simple character, just write it out. |
| out.write(ch); |
| bytesWritten++; |
| } |
| } |
| |
| return bytesWritten; |
| } |
| |
| /** |
| * Convert a hex digit to the binary value it represents. |
| * |
| * @param b the ascii hex byte to convert (0-0, A-F, a-f) |
| * @return the int value of the hex byte, 0-15 |
| * @throws IOException if the byte is not a valid hex digit. |
| */ |
| private static int hexToBinary(final byte b) throws IOException { |
| // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE |
| final int i = Character.digit((char) b, 16); |
| if (i == -1) { |
| throw new IOException("Invalid quoted printable encoding: not a valid hex digit: " + b); |
| } |
| return i; |
| } |
| |
| } |