Coverage Report - org.apache.commons.fileupload.util.mime.Base64Decoder
 
Classes in this File Line Coverage Branch Coverage Complexity
Base64Decoder
94%
37/39
94%
17/18
7
 
 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 Base64Decoder {
 26  
 
 27  
     /**
 28  
      * Decoding table value for invalid bytes.
 29  
      */
 30  
     private static final int INVALID_BYTE = -1; // must be outside range 0-63
 31  
 
 32  
     /**
 33  
      * Decoding table value for padding bytes, so can detect PAD afer conversion.
 34  
      */
 35  
     private static final int PAD_BYTE = -2; // must be outside range 0-63
 36  
 
 37  
     /**
 38  
      * Mask to treat byte as unsigned integer.
 39  
      */
 40  
     private static final int MASK_BYTE_UNSIGNED = 0xFF;
 41  
 
 42  
     /**
 43  
      * Number of bytes per encoded chunk - 4 6bit bytes produce 3 8bit bytes on output.
 44  
      */
 45  
     private static final int INPUT_BYTES_PER_CHUNK = 4;
 46  
 
 47  
     /**
 48  
      * Set up the encoding table.
 49  
      */
 50  1
     private static final byte[] ENCODING_TABLE = {
 51  
         (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G',
 52  
         (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N',
 53  
         (byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U',
 54  
         (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z',
 55  
         (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g',
 56  
         (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n',
 57  
         (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u',
 58  
         (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z',
 59  
         (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6',
 60  
         (byte) '7', (byte) '8', (byte) '9',
 61  
         (byte) '+', (byte) '/'
 62  
     };
 63  
 
 64  
     /**
 65  
      * The padding byte.
 66  
      */
 67  
     private static final byte PADDING = (byte) '=';
 68  
 
 69  
     /**
 70  
      * Set up the decoding table; this is indexed by a byte converted to an unsigned int,
 71  
      * so must be at least as large as the number of different byte values,
 72  
      * positive and negative and zero.
 73  
      */
 74  1
     private static final byte[] DECODING_TABLE = new byte[Byte.MAX_VALUE - Byte.MIN_VALUE + 1];
 75  
 
 76  
     static {
 77  
         // Initialise as all invalid characters
 78  257
         for (int i = 0; i < DECODING_TABLE.length; i++) {
 79  256
             DECODING_TABLE[i] = INVALID_BYTE;
 80  
         }
 81  
         // set up valid characters
 82  65
         for (int i = 0; i < ENCODING_TABLE.length; i++) {
 83  64
             DECODING_TABLE[ENCODING_TABLE[i]] = (byte) i;
 84  
         }
 85  
         // Allow pad byte to be easily detected after conversion
 86  1
         DECODING_TABLE[PADDING] = PAD_BYTE;
 87  1
     }
 88  
 
 89  
     /**
 90  
      * Hidden constructor, this class must not be instantiated.
 91  
      */
 92  0
     private Base64Decoder() {
 93  
         // do nothing
 94  0
     }
 95  
 
 96  
     /**
 97  
      * Decode the base 64 encoded byte data writing it to the given output stream,
 98  
      * whitespace characters will be ignored.
 99  
      *
 100  
      * @param data the buffer containing the Base64-encoded data
 101  
      * @param out the output stream to hold the decoded bytes
 102  
      *
 103  
      * @return the number of bytes produced.
 104  
      * @throws IOException thrown when the padding is incorrect or the input is truncated.
 105  
      */
 106  
     public static int decode(byte[] data, OutputStream out) throws IOException {
 107  28
         int        outLen = 0;
 108  28
         byte [] cache = new byte[INPUT_BYTES_PER_CHUNK];
 109  28
         int cachedBytes = 0;
 110  
 
 111  418
         for (byte b : data) {
 112  393
             final byte d = DECODING_TABLE[MASK_BYTE_UNSIGNED & b];
 113  393
             if (d == INVALID_BYTE) {
 114  14
                 continue; // Ignore invalid bytes
 115  
             }
 116  379
             cache[cachedBytes++] = d;
 117  379
             if (cachedBytes == INPUT_BYTES_PER_CHUNK) {
 118  
                 // CHECKSTYLE IGNORE MagicNumber FOR NEXT 4 LINES
 119  92
                 final byte b1 = cache[0];
 120  92
                 final byte b2 = cache[1];
 121  92
                 final byte b3 = cache[2];
 122  92
                 final byte b4 = cache[3];
 123  92
                 if (b1 == PAD_BYTE || b2 == PAD_BYTE) {
 124  2
                     throw new IOException("Invalid Base64 input: incorrect padding, first two bytes cannot be padding");
 125  
                 }
 126  
                 // Convert 4 6-bit bytes to 3 8-bit bytes
 127  
                 // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE
 128  90
                 out.write((b1 << 2) | (b2 >> 4)); // 6 bits of b1 plus 2 bits of b2
 129  90
                 outLen++;
 130  90
                 if (b3 != PAD_BYTE) {
 131  
                     // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE
 132  82
                     out.write((b2 << 4) | (b3 >> 2)); // 4 bits of b2 plus 4 bits of b3
 133  82
                     outLen++;
 134  82
                     if (b4 != PAD_BYTE) {
 135  
                         // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE
 136  72
                         out.write((b3 << 6) | b4);        // 2 bits of b3 plus 6 bits of b4
 137  72
                         outLen++;
 138  
                     }
 139  8
                 } else if (b4 != PAD_BYTE) { // if byte 3 is pad, byte 4 must be pad too
 140  1
                     throw new // line wrap to avoid 120 char limit
 141  
                     IOException("Invalid Base64 input: incorrect padding, 4th byte must be padding if 3rd byte is");
 142  
                 }
 143  89
                 cachedBytes = 0;
 144  
             }
 145  
         }
 146  
         // Check for anything left over
 147  25
         if (cachedBytes != 0) {
 148  6
             throw new IOException("Invalid Base64 input: truncated");
 149  
         }
 150  19
         return outLen;
 151  
     }
 152  
 }