--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/der_length_integer.c	Sun Dec 19 11:34:45 2004 +0000
@@ -0,0 +1,54 @@
+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, [email protected], http://libtomcrypt.org
+ */
+
+#include "mycrypt.h"
+
+/* Gets length of DER encoding of num */
+
+int der_length_integer(mp_int *num, unsigned long *outlen)
+{
+   unsigned long z, len;
+   int           leading_zero;
+
+   _ARGCHK(num     != NULL);
+   _ARGCHK(outlen  != NULL);
+
+   /* we only need a leading zero if the msb of the first byte is one */
+   if ((mp_count_bits(num) & 7) == 7 || mp_iszero(num) == MP_YES) {
+      leading_zero = 1;
+   } else {
+      leading_zero = 0;
+   }
+
+   /* size for bignum */
+   z = len = leading_zero + mp_unsigned_bin_size(num);
+
+   /* we need a 0x02 */
+   ++len;
+
+   /* now we need a length */
+   if (z < 128) {
+      /* short form */
+      ++len;
+   } else {
+      /* long form (relies on z != 0) */
+      ++len;
+
+      while (z) {
+         ++len;
+         z >>= 8;
+      }
+   }
+
+   *outlen = len; 
+   return CRYPT_OK;
+}
+