/*
* This file is part of DisOrder.
- * Copyright (C) 2005 Richard Kettlewell
+ * Copyright (C) 2005, 2007, 2008 Richard Kettlewell
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*/
+/** @file lib/basen.c @brief Arbitrary base conversion
+ *
+ * The functions in this file handle arbitrary-size non-negative integers,
+ * represented as a bigendian (MSW first) sequence of @c unsigned @c long
+ * words. The words themselves use the native byte order.
+ */
#include <config.h>
#include "types.h"
#include "basen.h"
-/* test whether v is 0 */
+/** @brief Test whether v is 0
+ * @param v Pointer to bigendian bignum
+ * @param nwords Length of bignum
+ * @return !v
+ */
static int zero(const unsigned long *v, int nwords) {
int n;
return n == nwords;
}
-/* divide v by m returning the remainder */
+/** @brief Divide v by m returning the remainder.
+ * @param v Pointer to bigendian bignum
+ * @param nwords Length of bignum
+ * @param m Divisor (must not be 0)
+ * @return Remainder
+ *
+ * The quotient is stored in @p v.
+ */
static unsigned divide(unsigned long *v, int nwords, unsigned long m) {
unsigned long r = 0, a, b;
int n;
return r;
}
+/** @brief Convert v to a chosen base
+ * @param v Pointer to bigendian bignum (modified!)
+ * @param nwords Length of bignum
+ * @param buffer Output buffer
+ * @param bufsize Size of output buffer
+ * @param base Number base (2..62)
+ * @return 0 on success, -1 if the buffer is too small
+ *
+ * Converts @p v to a string in the given base using decimal digits, lower case
+ * letter sand upper case letters as digits.
+ */
int basen(unsigned long *v,
int nwords,
char buffer[],
static const char chars[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
do {
- if(i <= 1) return -1; /* overflow */
+ if(i <= 1)
+ return -1; /* overflow */
buffer[--i] = chars[divide(v, nwords, base)];
} while(!zero(v, nwords));
memmove(buffer, buffer + i, bufsize - i);
fill-column:79
End:
*/
-/* arch-tag:iGDXjhkM2cdyv0RSlftgGQ */