X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~mdw/git/disorder/blobdiff_plain/763d5e6ad88ef3ba1cd1d7742d060e4f1e54c6b8..ec57f6c97b41d54ade912f7e3b9f727b40e38e16:/lib/basen.c

diff --git a/lib/basen.c b/lib/basen.c
index 69ab273..87d2795 100644
--- a/lib/basen.c
+++ b/lib/basen.c
@@ -1,31 +1,36 @@
 /*
  * 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 */
+/** @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;
 
@@ -34,7 +39,14 @@ static int zero(const unsigned long *v, int nwords) {
   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;
@@ -54,6 +66,17 @@ static unsigned divide(unsigned long *v, int nwords, unsigned long m) {
   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[],
@@ -63,7 +86,8 @@ int basen(unsigned long *v,
   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);