summaryrefslogtreecommitdiffstats
path: root/libtommath/bn_mp_count_bits.c
diff options
context:
space:
mode:
Diffstat (limited to 'libtommath/bn_mp_count_bits.c')
-rw-r--r--libtommath/bn_mp_count_bits.c41
1 files changed, 41 insertions, 0 deletions
diff --git a/libtommath/bn_mp_count_bits.c b/libtommath/bn_mp_count_bits.c
new file mode 100644
index 0000000..f3f85ac
--- /dev/null
+++ b/libtommath/bn_mp_count_bits.c
@@ -0,0 +1,41 @@
+#include <tommath.h>
+#ifdef BN_MP_COUNT_BITS_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis
+ *
+ * LibTomMath is a library that provides multiple-precision
+ * integer arithmetic as well as number theoretic functionality.
+ *
+ * The library was designed directly after the MPI library by
+ * Michael Fromberger but has been written from scratch with
+ * additional optimizations in place.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, tomstdenis@iahu.ca, http://math.libtomcrypt.org
+ */
+
+/* returns the number of bits in an int */
+int
+mp_count_bits (mp_int * a)
+{
+ int r;
+ mp_digit q;
+
+ /* shortcut */
+ if (a->used == 0) {
+ return 0;
+ }
+
+ /* get number of digits and add that */
+ r = (a->used - 1) * DIGIT_BIT;
+
+ /* take the last digit and count the bits in it */
+ q = a->dp[a->used - 1];
+ while (q > ((mp_digit) 0)) {
+ ++r;
+ q >>= ((mp_digit) 1);
+ }
+ return r;
+}
+#endif