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DEFINITIONS
This source file includes following definitions.
- lsqlite3_base160
- lsqlite3_base160Next
1 /*
2 base160 code used by ldb_sqlite3
3
4 Copyright (C) 2004 Derrell Lipman
5
6 This library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 3 of the License, or (at your option) any later version.
10
11 This library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with this library; if not, see <http://www.gnu.org/licenses/>.
18 */
19
20
21 /*
22 * ldb_sqlite3_base160()
23 *
24 * Convert an integer value to a string containing the base 160 representation
25 * of the integer. We always convert to a string representation that is 4
26 * bytes in length, and we always null terminate.
27 *
28 * Parameters:
29 * val --
30 * The value to be converted
31 *
32 * result --
33 * Buffer in which the result is to be placed
34 *
35 * Returns:
36 * nothing
37 */
38 static unsigned char base160tab[161] =
39 {
40 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , /* 0-9 */
41 58 , 59 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , /* : ; A-H */
42 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , /* I-R */
43 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 97 , 98 , /* S-Z , a-b */
44 99 , 100, 101, 102, 103, 104, 105, 106, 107, 108, /* c-l */
45 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, /* m-v */
46 119, 120, 121, 122, 160, 161, 162, 163, 164, 165, /* w-z, latin1 */
47 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, /* latin1 */
48 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, /* latin1 */
49 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, /* latin1 */
50 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, /* latin1 */
51 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, /* latin1 */
52 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, /* latin1 */
53 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, /* latin1 */
54 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, /* latin1 */
55 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, /* latin1 */
56 '\0'
57 };
58
59
60 /*
61 * lsqlite3_base160()
62 *
63 * Convert an unsigned long integer into a base160 representation of the
64 * number.
65 *
66 * Parameters:
67 * val --
68 * value to be converted
69 *
70 * result --
71 * character array, 5 bytes long, into which the base160 representation
72 * will be placed. The result will be a four-digit representation of the
73 * number (with leading zeros prepended as necessary), and null
74 * terminated.
75 *
76 * Returns:
77 * Nothing
78 */
79 void
80 lsqlite3_base160(unsigned long val,
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81 unsigned char result[5])
82 {
83 int i;
84
85 for (i = 3; i >= 0; i--) {
86
87 result[i] = base160tab[val % 160];
88 val /= 160;
89 }
90
91 result[4] = '\0';
92 }
93
94
95 /*
96 * lsqlite3_base160Next()
97 *
98 * Retrieve the next-greater number in the base160 sequence for the terminal
99 * tree node (the last four digits). Only one tree level (four digits) are
100 * operated on.
101 *
102 * Parameters:
103 * base160 -- a character array containing either an empty string (in which
104 * case no operation is performed), or a string of base160 digits
105 * with a length of a multiple of four digits.
106 *
107 * Upon return, the trailing four digits (one tree level) will
108 * have been incremented by 1.
109 *
110 * Returns:
111 * base160 -- the modified array
112 */
113 char *
114 lsqlite3_base160Next(char base160[])
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115 {
116 int i;
117 int len;
118 unsigned char * pTab;
119 char * pBase160 = base160;
120
121 /*
122 * We need a minimum of four digits, and we will always get a multiple of
123 * four digits.
124 */
125 if (len = strlen(pBase160)) >= 4)
126 {
127 pBase160 += strlen(pBase160) - 1;
128
129 /* We only carry through four digits: one level in the tree */
130 for (i = 0; i < 4; i++) {
131
132 /* What base160 value does this digit have? */
133 pTab = strchr(base160tab, *pBase160);
134
135 /* Is there a carry? */
136 if (pTab < base160tab + sizeof(base160tab) - 1) {
137
138 /* Nope. Just increment this value and we're done. */
139 *pBase160 = *++pTab;
140 break;
141 } else {
142
143 /*
144 * There's a carry. This value gets base160tab[0], we
145 * decrement the buffer pointer to get the next higher-order
146 * digit, and continue in the loop.
147 */
148 *pBase160-- = base160tab[0];
149 }
150 }
151 }
152
153 return base160;
154 }