1 | /*
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2 | * To change this template, choose Tools | Templates
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3 | * and open the template in the editor.
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4 | */
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5 |
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6 | package com.kitfox.svg.xml;
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7 |
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8 | import java.io.FilterInputStream;
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9 | import java.io.IOException;
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10 | import java.io.InputStream;
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11 |
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12 | /**
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13 | *
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14 | * @author kitfox
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15 | */
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16 | public class Base64InputStream extends FilterInputStream
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17 | {
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18 | int buf; //Cached bytes to read
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19 | int bufSize; //Number of bytes waiting to be read from buffer
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20 | boolean drain = false; //After set, read no more chunks
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21 |
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22 | public Base64InputStream(InputStream in)
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23 | {
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24 | super(in);
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25 | }
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26 |
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27 | public int read() throws IOException
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28 | {
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29 | if (drain && bufSize == 0)
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30 | {
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31 | return -1;
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32 | }
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33 |
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34 | if (bufSize == 0)
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35 | {
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36 | //Read next chunk into 4 byte buffer
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37 | int chunk = in.read();
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38 | if (chunk == -1)
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39 | {
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40 | drain = true;
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41 | return -1;
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42 | }
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43 |
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44 | //get remaining 3 bytes
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45 | for (int i = 0; i < 3; ++i)
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46 | {
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47 | int value = in.read();
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48 | if (value == -1)
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49 | {
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50 | throw new IOException("Early termination of base64 stream");
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51 | }
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52 | chunk = (chunk << 8) | (value & 0xff);
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53 | }
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54 |
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55 | //Check for special termination characters
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56 | if ((chunk & 0xffff) == (((byte)'=' << 8) | (byte)'='))
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57 | {
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58 | bufSize = 1;
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59 | drain = true;
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60 | }
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61 | else if ((chunk & 0xff) == (byte)'=')
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62 | {
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63 | bufSize = 2;
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64 | drain = true;
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65 | }
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66 | else
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67 | {
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68 | bufSize = 3;
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69 | }
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70 |
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71 | //Fill buffer with decoded characters
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72 | for (int i = 0; i < bufSize + 1; ++i)
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73 | {
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74 | buf = (buf << 6) | Base64Util.decodeByte((chunk >> 24) & 0xff);
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75 | chunk <<= 8;
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76 | }
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77 | }
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78 |
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79 | //Return nth remaing bte & decrement counter
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80 | return (buf >> (--bufSize * 8)) & 0xff;
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81 | }
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82 | }
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