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comparison b64_de.c @ 0:01387a2e419e

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initial version
author Shinji KONO <kono@ie.u-ryukyu.ac.jp>
date Tue, 07 Dec 2010 15:39:45 +0900
parents
children 972a7f233b23
comparison
equal deleted inserted replaced
-1:000000000000 0:01387a2e419e
1 #include <stdlib.h>
2 #include <stdio.h>
3 #include <string.h>
4
5 struct tagTT
6 {
7 unsigned char buf;
8 char *cont;
9 int nlen;
10 };
11
12 unsigned char CtoNum( int c );
13 int GetNumB64( struct tagTT *pWork );
14
15 int decode(char *cont, FILE *outfile)
16 {
17 unsigned int rw;
18 struct tagTT work;
19
20 work.buf = 0;
21 work.nlen = 0;
22 work.cont = cont;
23
24 rw = GetNumB64( &work );
25 while ( rw != -1 )
26 {
27 putc( rw, outfile );
28 rw = GetNumB64( &work );
29 }
30 return 0;
31 }
32
33
34 int GetNumB64( struct tagTT *pWork )
35 {
36 int wr;
37 unsigned char w;
38 unsigned char r;
39
40 wr = *pWork->cont;
41 pWork->cont++;
42 if ( wr == '\0' || wr == '=' )
43 return -1;
44
45 while(wr == '\n' || wr == '\t')
46 {
47 wr = *pWork->cont;
48 pWork->cont++;
49 }
50
51 w = CtoNum( wr );
52 if ( pWork->nlen == 0 )
53 {
54 unsigned char w2;
55
56 wr = *pWork->cont;
57 pWork->cont++;
58 if ( wr != '\0' && wr != '=' )
59 w2 = CtoNum( wr );
60 else
61 w2 = 0;
62
63 pWork->buf = w << 2;
64 w = w2;
65 pWork->nlen = 6;
66 }
67
68 pWork->nlen -= 2;
69
70 r = pWork->buf | ( w >> pWork->nlen );
71
72 pWork->buf = ( w << ( 8 - pWork->nlen ) );
73 return r;
74 }
75
76 unsigned char CtoNum( int c )
77 {
78 if ( c >= 'A' && c <= 'Z' ) return c - 'A';
79 if ( c >= 'a' && c <= 'z' ) return ( c - 'a' ) + 26;
80 if ( c >= '0' && c <= '9' ) return ( c - '0' ) + 52;
81 if ( c == '+' ) return 62;
82 if ( c == '/' ) return 63;
83 return -1;
84 }