u32.c - 9base - revived minimalist port of Plan 9 userland to Unix
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u32.c (2399B)
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1 #include <lib9.h>
2
3 int
4 dec32(uchar *dest, int ndest, char *src, int nsrc)
5 {
6 char *s, *tab;
7 uchar *start;
8 int i, u[8];
9
10 if(ndest+1 < (5*nsrc+7)/8)
11 return -1;
12 start = dest;
13 tab = "23456789abcdefghijkmnpqrstuvwxyz";
14 while(nsrc>=8){
15 for(i=0; i<8; i++){
16 s = strchr(tab,(int)src[i]);
17 u[i] = s ? s-tab : 0;
18 }
19 *dest++ = (u[0]<<3) | (0x7 & (u[1]>>2));
20 *dest++ = ((0x3 & u[1])<<6) | (u[2]<<1) | (0x1 & (u[3]>>4));
21 *dest++ = ((0xf & u[3])<<4) | (0xf & (u[4]>>1));
22 *dest++ = ((0x1 & u[4])<<7) | (u[5]<<2) | (0x3 & (u[6]>>3));
23 *dest++ = ((0x7 & u[6])<<5) | u[7];
24 src += 8;
25 nsrc -= 8;
26 }
27 if(nsrc > 0){
28 if(nsrc == 1 || nsrc == 3 || nsrc == 6)
29 return -1;
30 for(i=0; i<nsrc; i++){
31 s = strchr(tab,(int)src[i]);
32 u[i] = s ? s-tab : 0;
33 }
34 *dest++ = (u[0]<<3) | (0x7 & (u[1]>>2));
35 if(nsrc == 2)
36 goto out;
37 *dest++ = ((0x3 & u[1])<<6) | (u[2]<<1) | (0x1 & (u[3]>>4));
38 if(nsrc == 4)
39 goto out;
40 *dest++ = ((0xf & u[3])<<4) | (0xf & (u[4]>>1));
41 if(nsrc == 5)
42 goto out;
43 *dest++ = ((0x1 & u[4])<<7) | (u[5]<<2) | (0x3 & (u[6]>>3));
44 }
45 out:
46 return dest-start;
47 }
48
49 int
50 enc32(char *dest, int ndest, uchar *src, int nsrc)
51 {
52 char *tab, *start;
53 int j;
54
55 if(ndest <= (8*nsrc+4)/5 )
56 return -1;
57 start = dest;
58 tab = "23456789abcdefghijkmnpqrstuvwxyz";
59 while(nsrc>=5){
60 j = (0x1f & (src[0]>>3));
61 *dest++ = tab[j];
62 j = (0x1c & (src[0]<<2)) | (0x03 & (src[1]>>6));
63 *dest++ = tab[j];
64 j = (0x1f & (src[1]>>1));
65 *dest++ = tab[j];
66 j = (0x10 & (src[1]<<4)) | (0x0f & (src[2]>>4));
67 *dest++ = tab[j];
68 j = (0x1e & (src[2]<<1)) | (0x01 & (src[3]>>7));
69 *dest++ = tab[j];
70 j = (0x1f & (src[3]>>2));
71 *dest++ = tab[j];
72 j = (0x18 & (src[3]<<3)) | (0x07 & (src[4]>>5));
73 *dest++ = tab[j];
74 j = (0x1f & (src[4]));
75 *dest++ = tab[j];
76 src += 5;
77 nsrc -= 5;
78 }
79 if(nsrc){
80 j = (0x1f & (src[0]>>3));
81 *dest++ = tab[j];
82 j = (0x1c & (src[0]<<2));
83 if(nsrc == 1)
84 goto out;
85 j |= (0x03 & (src[1]>>6));
86 *dest++ = tab[j];
87 j = (0x1f & (src[1]>>1));
88 if(nsrc == 2)
89 goto out;
90 *dest++ = tab[j];
91 j = (0x10 & (src[1]<<4));
92 if(nsrc == 3)
93 goto out;
94 j |= (0x0f & (src[2]>>4));
95 *dest++ = tab[j];
96 j = (0x1e & (src[2]<<1));
97 if(nsrc == 4)
98 goto out;
99 j |= (0x01 & (src[3]>>7));
100 *dest++ = tab[j];
101 j = (0x1f & (src[3]>>2));
102 *dest++ = tab[j];
103 j = (0x18 & (src[3]<<3));
104 out:
105 *dest++ = tab[j];
106 }
107 *dest = 0;
108 return dest-start;
109 }