/*
* 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
+ * 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
- * the Free Software Foundation; either version 2 of the License, or
+ * the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * General Public License for more details.
- *
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
* You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
- * USA
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+/** @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 <string.h>
+#include "common.h"
#include "basen.h"
-/* test whether v is 0 */
-static int zero(const unsigned long *v, int nwords) {
+/** @brief Test whether v is 0
+ * @param v Pointer to bigendian bignum
+ * @param nwords Length of bignum
+ * @return !v
+ */
+static int zero(const uint32_t *v, int nwords) {
int n;
for(n = 0; n < nwords && !v[n]; ++n)
return n == nwords;
}
-/* divide v by m returning the remainder */
-static unsigned divide(unsigned long *v, int nwords, unsigned long m) {
+/** @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(uint32_t *v, int nwords, unsigned long m) {
unsigned long r = 0, a, b;
int n;
return r;
}
-int basen(unsigned long *v,
+/** @brief Multiple v by m and add a
+ * @param v Pointer to bigendian bignum
+ * @param nwords Length of bignum
+ * @param m Value to multiply by
+ * @param a Value to add
+ * @return 0 on success, non-0 on overflow
+ *
+ * Does v = m * v + a.
+ */
+static int mla(uint32_t *v, int nwords, uint32_t m, uint32_t a) {
+ int n = nwords - 1;
+ uint32_t carry = a;
+
+ while(n >= 0) {
+ const uint64_t p = (uint64_t)v[n] * m + carry;
+ carry = (uint32_t)(p >> 32);
+ v[n] = (uint32_t)p;
+ --n;
+ }
+ /* If there is still a carry then we overflowed */
+ return !!carry;
+}
+
+static const char basen_chars[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+/** @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
+ * letters and upper case letters as digits.
+ *
+ * The inverse of nesab().
+ */
+int basen(uint32_t *v,
int nwords,
char buffer[],
size_t bufsize,
unsigned base) {
size_t i = bufsize;
- static const char chars[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
do {
- if(i <= 1) return -1; /* overflow */
- buffer[--i] = chars[divide(v, nwords, base)];
+ if(i <= 1)
+ return -1; /* overflow */
+ buffer[--i] = basen_chars[divide(v, nwords, base)];
} while(!zero(v, nwords));
memmove(buffer, buffer + i, bufsize - i);
buffer[bufsize - i] = 0;
return 0;
}
+/** @brief Convert a string back to a large integer in an arbitrary base
+ * @param v Where to store result as a bigendian bignum
+ * @param nwords Space available in @p v
+ * @param s Input string
+ * @param base Number base (2..62)
+ * @return 0 on success, non-0 on overflow or invalid input
+ *
+ * The inverse of basen(). If the number is much smaller than the buffer then
+ * the first words will be 0.
+ */
+int nesab(uint32_t *v,
+ int nwords,
+ const char *s,
+ unsigned base) {
+ /* Initialize to 0 */
+ memset(v, 0, nwords * sizeof *v);
+ while(*s) {
+ const char *dp = strchr(basen_chars, *s++);
+ if(!dp)
+ return -1;
+ if(mla(v, nwords, base, dp - basen_chars))
+ return -1;
+ }
+ return 0;
+}
+
/*
Local Variables:
c-basic-offset:2
fill-column:79
End:
*/
-/* arch-tag:iGDXjhkM2cdyv0RSlftgGQ */
~mdw / disorder / blobdiff