src/be/nikiroo/utils/streams/Base64InputStream.java

   1 /*
   2  * Copyright (C) 2010 The Android Open Source Project
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *      http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 package be.nikiroo.utils.streams;
  18
  19 import java.io.FilterInputStream;
  20 import java.io.IOException;
  21 import java.io.InputStream;
  22
  23 /**
  24  * An InputStream that does Base64 decoding on the data read through
  25  * it.
  26  */
  27 public class Base64InputStream extends FilterInputStream {
  28     private final Base64.Coder coder;
  29
  30     private static byte[] EMPTY = new byte[0];
  31
  32     private static final int BUFFER_SIZE = 2048;
  33     private boolean eof;
  34     private byte[] inputBuffer;
  35     private int outputStart;
  36     private int outputEnd;
  37
  38     /**
  39      * An InputStream that performs Base64 decoding on the data read
  40      * from the wrapped stream.
  41      *
  42      * @param in the InputStream to read the source data from
  43      */
  44     public Base64InputStream(InputStream in) {
  45         this(in, false);
  46     }
  47
  48     /**
  49      * Performs Base64 encoding or decoding on the data read from the
  50      * wrapped InputStream.
  51      *
  52      * @param in the InputStream to read the source data from
  53      * @param flags bit flags for controlling the decoder; see the
  54      *        constants in {@link Base64}
  55      * @param encode true to encode, false to decode
  56      *
  57      * @hide
  58      */
  59     public Base64InputStream(InputStream in, boolean encode) {
  60         super(in);
  61         eof = false;
  62         inputBuffer = new byte[BUFFER_SIZE];
  63         if (encode) {
  64             coder = new Base64.Encoder(Base64.NO_WRAP, null);
  65         } else {
  66             coder = new Base64.Decoder(Base64.NO_WRAP, null);
  67         }
  68         coder.output = new byte[coder.maxOutputSize(BUFFER_SIZE)];
  69         outputStart = 0;
  70         outputEnd = 0;
  71     }
  72
  73     public boolean markSupported() {
  74         return false;
  75     }
  76
  77     public void mark(int readlimit) {
  78         throw new UnsupportedOperationException();
  79     }
  80
  81     public void reset() {
  82         throw new UnsupportedOperationException();
  83     }
  84
  85     public void close() throws IOException {
  86         in.close();
  87         inputBuffer = null;
  88     }
  89
  90     public int available() {
  91         return outputEnd - outputStart;
  92     }
  93
  94     public long skip(long n) throws IOException {
  95         if (outputStart >= outputEnd) {
  96             refill();
  97         }
  98         if (outputStart >= outputEnd) {
  99             return 0;
 100         }
 101         long bytes = Math.min(n, outputEnd-outputStart);
 102         outputStart += bytes;
 103         return bytes;
 104     }
 105
 106     public int read() throws IOException {
 107         if (outputStart >= outputEnd) {
 108             refill();
 109         }
 110         if (outputStart >= outputEnd) {
 111             return -1;
 112         } else {
 113             return coder.output[outputStart++] & 0xff;
 114         }
 115     }
 116
 117     public int read(byte[] b, int off, int len) throws IOException {
 118         if (outputStart >= outputEnd) {
 119             refill();
 120         }
 121         if (outputStart >= outputEnd) {
 122             return -1;
 123         }
 124         int bytes = Math.min(len, outputEnd-outputStart);
 125         System.arraycopy(coder.output, outputStart, b, off, bytes);
 126         outputStart += bytes;
 127         return bytes;
 128     }
 129
 130     /**
 131      * Read data from the input stream into inputBuffer, then
 132      * decode/encode it into the empty coder.output, and reset the
 133      * outputStart and outputEnd pointers.
 134      */
 135     private void refill() throws IOException {
 136         if (eof) return;
 137         int bytesRead = in.read(inputBuffer);
 138         boolean success;
 139         if (bytesRead == -1) {
 140             eof = true;
 141             success = coder.process(EMPTY, 0, 0, true);
 142         } else {
 143             success = coder.process(inputBuffer, 0, bytesRead, false);
 144         }
 145         if (!success) {
 146             throw new IOException("bad base-64");
 147         }
 148         outputEnd = coder.op;
 149         outputStart = 0;
 150     }
 151 }