QuotedPrintableDecoder.java
- /*
- * 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.fileupload2.core;
- import java.io.IOException;
- import java.io.OutputStream;
- /**
- */
- 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;
- /**
- * Decodes 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.
- * @throws IOException if an IO error occurs
- */
- public static int decode(final byte[] data, final OutputStream out) throws IOException {
- var off = 0;
- final var length = data.length;
- final var endOffset = off + length;
- var bytesWritten = 0;
- while (off < endOffset) {
- final var 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");
- }
- final var b1 = data[off++];
- final var 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.
- final var c1 = hexToBinary(b1);
- final var 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;
- }
- /**
- * Converts a hexadecimal digit to the binary value it represents.
- *
- * @param b the ASCII hexadecimal byte to convert (0-0, A-F, a-f)
- * @return the int value of the hexadecimal byte, 0-15
- * @throws IOException if the byte is not a valid hexadecimal digit.
- */
- private static int hexToBinary(final byte b) throws IOException {
- // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE
- final var i = Character.digit((char) b, 16);
- if (i == -1) {
- throw new IOException("Invalid quoted printable encoding: not a valid hex digit: " + b);
- }
- return i;
- }
- /**
- * Hidden constructor, this class must not be instantiated.
- */
- private QuotedPrintableDecoder() {
- // do nothing
- }
- }