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2 - 1 
#include <u.h>
2 
#include <libc.h>
3 
 
4 
enum {
5 
	INVAL=	255
6 
};
7 
 
8 
static uchar t64d[256] = {
9 
   INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
10 
   INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
11 
   INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,   62,INVAL,INVAL,INVAL,   63,
12 
      52,   53,   54,   55,   56,   57,   58,   59,   60,   61,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
13 
   INVAL,    0,    1,    2,    3,    4,    5,    6,    7,    8,    9,   10,   11,   12,   13,   14,
14 
      15,   16,   17,   18,   19,   20,   21,   22,   23,   24,   25,INVAL,INVAL,INVAL,INVAL,INVAL,
15 
   INVAL,   26,   27,   28,   29,   30,   31,   32,   33,   34,   35,   36,   37,   38,   39,   40,
16 
      41,   42,   43,   44,   45,   46,   47,   48,   49,   50,   51,INVAL,INVAL,INVAL,INVAL,INVAL,
17 
   INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
18 
   INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
19 
   INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
20 
   INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
21 
   INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
22 
   INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
23 
   INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,
24 
   INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL
25 
};
26 
static char t64e[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
27 
 
28 
int
29 
dec64(uchar *out, int lim, char *in, int n)
30 
{
31 
	ulong b24;
32 
	uchar *start = out;
33 
	uchar *e = out + lim;
34 
	int i, c;
35 
 
36 
	b24 = 0;
37 
	i = 0;
38 
	while(n-- > 0){
39 
 
40 
		c = t64d[*(uchar*)in++];
41 
		if(c == INVAL)
42 
			continue;
43 
		switch(i){
44 
		case 0:
45 
			b24 = c<<18;
46 
			break;
47 
		case 1:
48 
			b24 |= c<<12;
49 
			break;
50 
		case 2:
51 
			b24 |= c<<6;
52 
			break;
53 
		case 3:
54 
			if(out + 3 > e)
55 
				goto exhausted;
56 
 
57 
			b24 |= c;
58 
			*out++ = b24>>16;
59 
			*out++ = b24>>8;
60 
			*out++ = b24;
61 
			i = -1;
62 
			break;
63 
		}
64 
		i++;
65 
	}
66 
	switch(i){
67 
	case 2:
68 
		if(out + 1 > e)
69 
			goto exhausted;
70 
		*out++ = b24>>16;
71 
		break;
72 
	case 3:
73 
		if(out + 2 > e)
74 
			goto exhausted;
75 
		*out++ = b24>>16;
76 
		*out++ = b24>>8;
77 
		break;
78 
	}
79 
exhausted:
80 
	return out - start;
81 
}
82 
 
83 
int
84 
enc64(char *out, int lim, uchar *in, int n)
85 
{
86 
	int i;
87 
	ulong b24;
88 
	char *start = out;
89 
	char *e = out + lim;
90 
 
91 
	for(i = n/3; i > 0; i--){
92 
		b24 = (*in++)<<16;
93 
		b24 |= (*in++)<<8;
94 
		b24 |= *in++;
95 
		if(out + 4 >= e)
96 
			goto exhausted;
97 
		*out++ = t64e[(b24>>18)];
98 
		*out++ = t64e[(b24>>12)&0x3f];
99 
		*out++ = t64e[(b24>>6)&0x3f];
100 
		*out++ = t64e[(b24)&0x3f];
101 
	}
102 
 
103 
	switch(n%3){
104 
	case 2:
105 
		b24 = (*in++)<<16;
106 
		b24 |= (*in)<<8;
107 
		if(out + 4 >= e)
108 
			goto exhausted;
109 
		*out++ = t64e[(b24>>18)];
110 
		*out++ = t64e[(b24>>12)&0x3f];
111 
		*out++ = t64e[(b24>>6)&0x3f];
112 
		*out++ = '=';
113 
		break;
114 
	case 1:
115 
		b24 = (*in)<<16;
116 
		if(out + 4 >= e)
117 
			goto exhausted;
118 
		*out++ = t64e[(b24>>18)];
119 
		*out++ = t64e[(b24>>12)&0x3f];
120 
		*out++ = '=';
121 
		*out++ = '=';
122 
		break;
123 
	}
124 
exhausted:
125 
	*out = 0;
126 
	return out - start;
127 
}