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.
31 /** @brief Test whether v is 0
32 * @param v Pointer to bigendian bignum
33 * @param nwords Length of bignum
36 static int zero(const unsigned long *v, int nwords) {
39 for(n = 0; n < nwords && !v[n]; ++n)
44 /** @brief Divide v by m returning the remainder.
45 * @param v Pointer to bigendian bignum
46 * @param nwords Length of bignum
47 * @param m Divisor (must not be 0)
50 * The quotient is stored in @p v.
52 static unsigned divide(unsigned long *v, int nwords, unsigned long m) {
53 unsigned long r = 0, a, b;
56 /* we do the divide 16 bits at a time */
57 for(n = 0; n < nwords; ++n) {
71 /** @brief Convert v to a chosen base
72 * @param v Pointer to bigendian bignum (modified!)
73 * @param nwords Length of bignum
74 * @param buffer Output buffer
75 * @param bufsize Size of output buffer
76 * @param base Number base (2..62)
77 * @return 0 on success, -1 if the buffer is too small
79 * Converts @p v to a string in the given base using decimal digits, lower case
80 * letter sand upper case letters as digits.
82 int basen(unsigned long *v,
88 static const char chars[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
92 return -1; /* overflow */
93 buffer[--i] = chars[divide(v, nwords, base)];
94 } while(!zero(v, nwords));
95 memmove(buffer, buffer + i, bufsize - i);
96 buffer[bufsize - i] = 0;