2 * basE91 encoding/decoding routines
4 * Copyright (c) 2000-2006 Joachim Henke
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8 * modification, are permitted provided that the following conditions are met:
10 * - Redistributions of source code must retain the above copyright notice,
11 * this list of conditions and the following disclaimer.
12 * - Redistributions in binary form must reproduce the above copyright notice,
13 * this list of conditions and the following disclaimer in the documentation
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16 * be used to endorse or promote products derived from this software without
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34 const unsigned char enctab[91] = {
35 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
36 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
37 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
38 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
39 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '!', '#', '$',
40 '%', '&', '(', ')', '*', '+', ',', '.', '/', ':', ';', '<', '=',
41 '>', '?', '@', '[', ']', '^', '_', '`', '{', '|', '}', '~', '"'
43 const unsigned char dectab[256] = {
44 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91,
45 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91,
46 91, 62, 90, 63, 64, 65, 66, 91, 67, 68, 69, 70, 71, 91, 72, 73,
47 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 74, 75, 76, 77, 78, 79,
48 80, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
49 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 81, 91, 82, 83, 84,
50 85, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
51 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 86, 87, 88, 89, 91,
52 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91,
53 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91,
54 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91,
55 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91,
56 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91,
57 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91,
58 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91,
59 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91, 91
62 void basE91_init(struct basE91 *b)
69 size_t basE91_encode(struct basE91 *b, const void *i, size_t len, void *o)
71 const unsigned char *ib = i;
72 unsigned char *ob = o;
76 b->queue |= *ib++ << b->nbits;
78 if (b->nbits > 13) { /* enough bits in queue */
79 unsigned int val = b->queue & 8191;
84 } else { /* we can take 14 bits */
85 val = b->queue & 16383;
89 ob[n++] = enctab[val % 91];
90 ob[n++] = enctab[val / 91];
97 /* process remaining bits from bit queue; write up to 2 bytes */
99 size_t basE91_encode_end(struct basE91 *b, void *o)
101 unsigned char *ob = o;
105 ob[n++] = enctab[b->queue % 91];
106 if (b->nbits > 7 || b->queue > 90)
107 ob[n++] = enctab[b->queue / 91];
116 /* return maximum length that an input of length i could encode to
117 * (this is a maximum, not a precise figure, because the actual
118 * size depends on the precise data */
120 size_t basE91_encode_maxlen(size_t i /* must be < SIZE_T_MAX/8 */)
123 size_t pairs = bits / 13;
124 size_t leftover = bits % 13;
125 return 2*pairs + (leftover==0 ? 0 : leftover<=6 ? 1 : 2);
128 size_t basE91_decode(struct basE91 *b, const void *i, size_t len, void *o)
130 const unsigned char *ib = i;
131 unsigned char *ob = o;
138 continue; /* ignore non-alphabet chars */
140 b->val = d; /* start next value */
143 b->queue |= b->val << b->nbits;
144 b->nbits += (b->val & 8191) > 88 ? 13 : 14;
149 } while (b->nbits > 7);
150 b->val = -1; /* mark value complete */
157 /* process remaining bits; write at most 1 byte */
159 size_t basE91_decode_end(struct basE91 *b, void *o)
161 unsigned char *ob = o;
165 ob[n++] = b->queue | b->val << b->nbits;
173 /* return maximum length that an input of length i could decode to
174 * (this is a maximum, not a precise figure, because the actual
175 * size depends on the precise data */
177 size_t basE91_decode_maxlen(size_t i /* must be < SIZE_T_MAX/7 */)
179 size_t pairs = i / 2;
180 size_t bits = pairs * 14;
181 size_t bytes = bits / 8;
182 size_t leftover = i % 2;
183 return bytes + !!leftover;