| /* |
| * 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 Base64Decoder { |
| |
| /** |
| * Set up the encoding table. |
| */ |
| private static final byte[] ENCODING_TABLE = { |
| (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G', |
| (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N', |
| (byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', |
| (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z', |
| (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g', |
| (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n', |
| (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u', |
| (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z', |
| (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6', |
| (byte) '7', (byte) '8', (byte) '9', |
| (byte) '+', (byte) '/' |
| }; |
| |
| /** |
| * The padding byte. |
| */ |
| private static final byte PADDING = (byte) '='; |
| |
| /** |
| * Set up the decoding table; this is indexed by a byte converted to an int, |
| * so must be at least as large as the number of different byte values, |
| * positive and negative and zero. |
| */ |
| private static final byte[] DECODING_TABLE = new byte[Byte.MAX_VALUE - Byte.MIN_VALUE + 1]; |
| |
| static { |
| for (int i = 0; i < ENCODING_TABLE.length; i++) { |
| DECODING_TABLE[ENCODING_TABLE[i]] = (byte) i; |
| } |
| } |
| |
| /** |
| * Hidden constructor, this class must not be instantiated. |
| */ |
| private Base64Decoder() { |
| // do nothing |
| } |
| |
| /** |
| * Checks if the input char must be skipped from the decode. |
| * The method skips whitespace characters LF, CR, horizontal tab and space. |
| * |
| * @param c the char to be checked. |
| * @return true, if the input char has to be skipped, false otherwise. |
| */ |
| private static boolean ignore(char c) { |
| return (c == '\n' || c == '\r' || c == '\t' || c == ' '); |
| } |
| |
| /** |
| * Decode the base 64 encoded byte data writing it to the given output stream, |
| * whitespace characters will be ignored. |
| * |
| * @param data the buffer containing the Base64-encoded data |
| * @param off the start offset (zero-based) |
| * @param length the number of bytes to convert |
| * @param out the output stream to hold the decoded bytes |
| * |
| * @return the number of bytes produced. |
| */ |
| public static int decode(byte[] data, int off, int length, OutputStream out) throws IOException { |
| byte b1, b2, b3, b4; |
| int outLen = 0; |
| |
| int end = off + length; |
| |
| while (end > 0) { |
| if (!ignore((char) data[end - 1])) { |
| break; |
| } |
| |
| end--; |
| } |
| |
| int i = off; |
| // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE |
| int finish = end - 4; // last set of 4 bytes might include padding |
| |
| while (i < finish) { |
| while ((i < finish) && ignore((char) data[i])) { |
| i++; |
| } |
| |
| b1 = DECODING_TABLE[data[i++]]; |
| |
| while ((i < finish) && ignore((char) data[i])) { |
| i++; |
| } |
| |
| b2 = DECODING_TABLE[data[i++]]; |
| |
| while ((i < finish) && ignore((char) data[i])) { |
| i++; |
| } |
| |
| b3 = DECODING_TABLE[data[i++]]; |
| |
| while ((i < finish) && ignore((char) data[i])) { |
| i++; |
| } |
| |
| b4 = DECODING_TABLE[data[i++]]; |
| |
| // Convert 4 6-bit bytes to 3 8-bit bytes |
| // CHECKSTYLE IGNORE MagicNumber FOR NEXT 3 LINES |
| out.write((b1 << 2) | (b2 >> 4)); // 6 bits of b1 plus 2 bits of b2 |
| out.write((b2 << 4) | (b3 >> 2)); // 4 bits of b2 plus 4 bits of b3 |
| out.write((b3 << 6) | b4); // 2 bits of b3 plus 6 bits of b4 |
| |
| // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE |
| outLen += 3; |
| } |
| |
| // Get the last 4 bytes; only last two can be padding |
| b1 = DECODING_TABLE[data[i++]]; |
| b2 = DECODING_TABLE[data[i++]]; |
| |
| // always write the first byte |
| // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE |
| out.write((b1 << 2) | (b2 >> 4)); // 6 bits of b1 plus 2 bits of b2 |
| outLen++; |
| |
| byte p1 = data[i++]; |
| byte p2 = data[i++]; |
| |
| b3 = DECODING_TABLE[p1]; // may be needed later |
| |
| if (p1 != PADDING) { // Nothing more to do if p1 == PADDING |
| // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE |
| out.write((b2 << 4) | (b3 >> 2)); // 4 bits of b2 plus 4 bits of b3 |
| outLen++; |
| } else if (p2 != PADDING) { // Nothing more to do if p2 == PADDING |
| b4 = DECODING_TABLE[p2]; |
| // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE |
| out.write((b3 << 6) | b4); // 2 bits of b3 plus 6 bits of b4 |
| outLen++; |
| } |
| |
| return outLen; |
| } |
| |
| } |