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1 #include <stdlib.h>
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2 #include <stdio.h>
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3 #include <string.h>
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4
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5 struct tagTT
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6 {
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7 unsigned char buf;
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8 char *cont;
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9 int nlen;
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10 };
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11
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12 unsigned char CtoNum( int c );
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13 int GetNumB64( struct tagTT *pWork );
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14
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15 int decode(char *cont, FILE *outfile)
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16 {
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17 int rw;
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18 struct tagTT work;
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19
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20 work.buf = 0;
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21 work.nlen = 0;
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22 work.cont = cont;
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23
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24 rw = GetNumB64( &work );
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25 while ( rw != -1 )
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26 {
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27 putc( rw, outfile );
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28 rw = GetNumB64( &work );
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29 }
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30 return 0;
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31 }
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32
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33
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34 int GetNumB64( struct tagTT *pWork )
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35 {
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36 int wr;
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37 unsigned char w;
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38 unsigned char r;
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39
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40 wr = *pWork->cont;
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41 pWork->cont++;
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42 if ( wr == '\0' || wr == '=' )
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43 return -1;
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44
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45 while(wr == '\n' || wr == '\t')
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46 {
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47 wr = *pWork->cont;
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48 pWork->cont++;
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49 }
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50
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51 w = CtoNum( wr );
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52 if ( pWork->nlen == 0 )
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53 {
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54 unsigned char w2;
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55
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56 wr = *pWork->cont;
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57 pWork->cont++;
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58 if ( wr != '\0' && wr != '=' )
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59 w2 = CtoNum( wr );
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60 else
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61 w2 = 0;
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62
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63 pWork->buf = w << 2;
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64 w = w2;
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65 pWork->nlen = 6;
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66 }
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67
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68 pWork->nlen -= 2;
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69
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70 r = pWork->buf | ( w >> pWork->nlen );
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71
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72 pWork->buf = ( w << ( 8 - pWork->nlen ) );
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73 return r;
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74 }
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75
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76 unsigned char CtoNum( int c )
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77 {
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78 if ( c >= 'A' && c <= 'Z' ) return c - 'A';
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79 if ( c >= 'a' && c <= 'z' ) return ( c - 'a' ) + 26;
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80 if ( c >= '0' && c <= '9' ) return ( c - '0' ) + 52;
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81 if ( c == '+' ) return 62;
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82 if ( c == '/' ) return 63;
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83 return -1;
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84 }
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