74cb8366d4a24967ace7b610d62846e46c47e07d
2 * This file is part of DisOrder.
3 * Copyright (C) 2005, 2007, 2008 Richard Kettlewell
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.
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.
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
20 /** @file lib/basen.c @brief Arbitrary base conversion
22 * The functions in this file handle arbitrary-size non-negative integers,
23 * represented as a bigendian (MSW first) sequence of @c unsigned @c long
24 * words. The words themselves use the native byte order.
34 /** @brief Test whether v is 0
35 * @param v Pointer to bigendian bignum
36 * @param nwords Length of bignum
39 static int zero(const unsigned long *v
, int nwords
) {
42 for(n
= 0; n
< nwords
&& !v
[n
]; ++n
)
47 /** @brief Divide v by m returning the remainder.
48 * @param v Pointer to bigendian bignum
49 * @param nwords Length of bignum
50 * @param m Divisor (must not be 0)
53 * The quotient is stored in @p v.
55 static unsigned divide(unsigned long *v
, int nwords
, unsigned long m
) {
56 unsigned long r
= 0, a
, b
;
59 /* we do the divide 16 bits at a time */
60 for(n
= 0; n
< nwords
; ++n
) {
74 /** @brief Convert v to a chosen base
75 * @param v Pointer to bigendian bignum (modified!)
76 * @param nwords Length of bignum
77 * @param buffer Output buffer
78 * @param bufsize Size of output buffer
79 * @param base Number base (2..62)
80 * @return 0 on success, -1 if the buffer is too small
82 * Converts @p v to a string in the given base using decimal digits, lower case
83 * letter sand upper case letters as digits.
85 int basen(unsigned long *v
,
91 static const char chars
[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
95 return -1; /* overflow */
96 buffer
[--i
] = chars
[divide(v
, nwords
, base
)];
97 } while(!zero(v
, nwords
));
98 memmove(buffer
, buffer
+ i
, bufsize
- i
);
99 buffer
[bufsize
- i
] = 0;