1 files changed, 83 insertions, 0 deletions
diff --git a/libtommath/bn_mp_radix_size.c b/libtommath/bn_mp_radix_size.c
new file mode 100644
index 0000000..40c4d04
--- /dev/null
+++ b/libtommath/bn_mp_radix_size.c
@@ -0,0 +1,83 @@
+#include <tommath.h>
+#ifdef BN_MP_RADIX_SIZE_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@gmail.com, http://math.libtomcrypt.com
+ */
+
+/* returns size of ASCII reprensentation */
+int mp_radix_size (mp_int * a, int radix, int *size)
+{
+  int     res, digs;
+  mp_int  t;
+  mp_digit d;
+
+  *size = 0;
+
+  /* special case for binary */
+  if (radix == 2) {
+    *size = mp_count_bits (a) + (a->sign == MP_NEG ? 1 : 0) + 1;
+    return MP_OKAY;
+  }
+
+  /* make sure the radix is in range */
+  if (radix < 2 || radix > 64) {
+    return MP_VAL;
+  }
+
+  if (mp_iszero(a) == MP_YES) {
+    *size = 2;
+    return MP_OKAY;
+  }
+
+  /* digs is the digit count */
+  digs = 0;
+
+  /* if it's negative add one for the sign */
+  if (a->sign == MP_NEG) {
+    ++digs;
+  }
+
+  /* init a copy of the input */
+  if ((res = mp_init_copy (&t, a)) != MP_OKAY) {
+    return res;
+  }
+
+  /* force temp to positive */
+  t.sign = MP_ZPOS; 
+
+  /* fetch out all of the digits */
+  while (mp_iszero (&t) == MP_NO) {
+    if ((res = mp_div_d (&t, (mp_digit) radix, &t, &d)) != MP_OKAY) {
+      mp_clear (&t);
+      return res;
+    }
+    ++digs;
+  }
+  mp_clear (&t);
+
+  /* 
+   * return digs + 1, the 1 is for the NULL byte that would be required.
+   * mp_toradix_n requires a minimum of 3 bytes, so never report less than
+   * that.
+   */
+
+  if ( digs >= 2 ) {
+      *size = digs + 1;
+  } else {
+      *size = 3;
+  }
+  return MP_OKAY;
+}
+
+#endif