460b9539 |
1 | /* |
2 | * This file is part of DisOrder. |
3 | * Copyright (C) 2005 Richard Kettlewell |
4 | * |
5 | * This program is free software; you can redistribute it and/or modify |
6 | * it under the terms of the GNU General Public License as published by |
7 | * the Free Software Foundation; either version 2 of the License, or |
8 | * (at your option) any later version. |
9 | * |
10 | * This program is distributed in the hope that it will be useful, but |
11 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | * General Public License for more details. |
14 | * |
15 | * You should have received a copy of the GNU General Public License |
16 | * along with this program; if not, write to the Free Software |
17 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 |
18 | * USA |
19 | */ |
20 | |
21 | #include <config.h> |
22 | #include "types.h" |
23 | |
24 | #include <string.h> |
25 | |
26 | #include "basen.h" |
27 | |
d7b6f0d1 |
28 | /** @brief Test whether v is 0 |
29 | * @param v Pointer to bigendian bignum |
30 | * @param nwords Length of bignum |
31 | * @return !v |
32 | */ |
460b9539 |
33 | static int zero(const unsigned long *v, int nwords) { |
34 | int n; |
35 | |
36 | for(n = 0; n < nwords && !v[n]; ++n) |
37 | ; |
38 | return n == nwords; |
39 | } |
40 | |
d7b6f0d1 |
41 | /** @brief Divide v by m returning the remainder. |
42 | * @param v Pointer to bigendian bignum |
43 | * @param nwords Length of bignum |
44 | * @param m Divisor (must not be 0) |
45 | * @return Remainder |
46 | * |
47 | * The quotient is stored in @p v. |
48 | */ |
460b9539 |
49 | static unsigned divide(unsigned long *v, int nwords, unsigned long m) { |
50 | unsigned long r = 0, a, b; |
51 | int n; |
52 | |
53 | /* we do the divide 16 bits at a time */ |
54 | for(n = 0; n < nwords; ++n) { |
55 | a = v[n] >> 16; |
56 | b = v[n] & 0xFFFF; |
57 | a += r << 16; |
58 | r = a % m; |
59 | a /= m; |
60 | b += r << 16; |
61 | r = b % m; |
62 | b /= m; |
63 | v[n] = (a << 16) + b; |
64 | } |
65 | return r; |
66 | } |
67 | |
d7b6f0d1 |
68 | /** @brief Convert v to a chosen base |
69 | * @param v Pointer to bigendian bignum |
70 | * @param nwords Length of bignum |
71 | * @param buffer Output buffer |
72 | * @param bufsize Size of output buffer |
73 | * @param base Number base (2..62) |
74 | * @return 0 on success, -1 if the buffer is too small |
75 | * |
76 | * Converts @p v to a string in the given base using decimal digits, lower case |
77 | * letter sand upper case letters as digits. |
78 | */ |
460b9539 |
79 | int basen(unsigned long *v, |
80 | int nwords, |
81 | char buffer[], |
82 | size_t bufsize, |
83 | unsigned base) { |
84 | size_t i = bufsize; |
85 | static const char chars[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"; |
86 | |
87 | do { |
88 | if(i <= 1) return -1; /* overflow */ |
89 | buffer[--i] = chars[divide(v, nwords, base)]; |
90 | } while(!zero(v, nwords)); |
91 | memmove(buffer, buffer + i, bufsize - i); |
92 | buffer[bufsize - i] = 0; |
93 | return 0; |
94 | } |
95 | |
96 | /* |
97 | Local Variables: |
98 | c-basic-offset:2 |
99 | comment-column:40 |
100 | fill-column:79 |
101 | End: |
102 | */ |