version 0.3.33

[fms.git] / libs / libtomcrypt / pk / asn1 / der / short_integer / der_length_short_integer.c

diff --git a/libs/libtomcrypt/pk/asn1/der/short_integer/der_length_short_integer.c b/libs/libtomcrypt/pk/asn1/der/short_integer/der_length_short_integer.c
new file mode 100644 (file)
index 0000000..073e294
--- /dev/null
+++ b/libs/libtomcrypt/pk/asn1/der/short_integer/der_length_short_integer.c
@@ -0,0 +1,70 @@
+/* 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, tomstdenis@gmail.com, http://libtomcrypt.com
+ */
+#include "tomcrypt.h"
+
+/**
+  @file der_length_short_integer.c
+  ASN.1 DER, get length of encoding, Tom St Denis
+*/
+
+
+#ifdef LTC_DER
+/**
+  Gets length of DER encoding of num 
+  @param num    The integer to get the size of 
+  @param outlen [out] The length of the DER encoding for the given integer
+  @return CRYPT_OK if successful
+*/
+int der_length_short_integer(unsigned long num, unsigned long *outlen)
+{
+   unsigned long z, y, len;
+
+   LTC_ARGCHK(outlen  != NULL);
+
+   /* force to 32 bits */
+   num &= 0xFFFFFFFFUL;
+
+   /* get the number of bytes */
+   z = 0;
+   y = num;
+   while (y) {
+     ++z;
+     y >>= 8;
+   }
+   
+   /* handle zero */
+   if (z == 0) {
+      z = 1;
+   }
+
+   /* we need a 0x02 to indicate it's INTEGER */
+   len = 1;
+
+   /* length byte */
+   ++len;
+
+   /* bytes in value */
+   len += z;
+
+   /* see if msb is set */
+   len += (num&(1UL<<((z<<3) - 1))) ? 1 : 0;
+
+   /* return length */
+   *outlen = len; 
+   
+   return CRYPT_OK;
+}
+
+#endif
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/short_integer/der_length_short_integer.c,v $ */
+/* $Revision: 1.5 $ */
+/* $Date: 2006/03/31 14:15:35 $ */