1 files changed, 97 insertions, 0 deletions
diff --git a/libtomcrypt/src/pk/asn1/der/short_integer/der_encode_short_integer.c b/libtomcrypt/src/pk/asn1/der/short_integer/der_encode_short_integer.c
new file mode 100644
index 0000000..eb94d38
--- /dev/null
+++ b/libtomcrypt/src/pk/asn1/der/short_integer/der_encode_short_integer.c
@@ -0,0 +1,97 @@
+/* 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.org
+ */
+#include "tomcrypt.h"
+
+/**
+  @file der_encode_short_integer.c
+  ASN.1 DER, encode an integer, Tom St Denis
+*/
+
+
+#ifdef LTC_DER
+
+/* Exports a positive integer as DER format (upto 32-bits in size) */
+/**
+  Store a mp_int integer
+  @param num      The integer to encode
+  @param out      [out] The destination for the DER encoded integers
+  @param outlen   [in/out] The max size and resulting size of the DER encoded integers
+  @return CRYPT_OK if successful
+*/
+int der_encode_short_integer(unsigned long num, unsigned char *out, unsigned long *outlen)
+{  
+   unsigned long len, x, y, z;
+   int           err;
+   
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+
+   /* force to 32 bits */
+   num &= 0xFFFFFFFFUL;
+
+   /* find out how big this will be */
+   if ((err = der_length_short_integer(num, &len)) != CRYPT_OK) {
+      return err;
+   }
+
+   if (*outlen < len) {
+      return CRYPT_BUFFER_OVERFLOW;
+   }
+
+   /* get len of output */
+   z = 0;
+   y = num;
+   while (y) {
+     ++z;
+     y >>= 8;
+   }
+
+   /* handle zero */
+   if (z == 0) {
+      z = 1;
+   }
+
+   /* see if msb is set */
+   z += (num&(1UL<<((z<<3) - 1))) ? 1 : 0;
+
+   /* adjust the number so the msB is non-zero */
+   for (x = 0; (z <= 4) && (x < (4 - z)); x++) {
+      num <<= 8;
+   }
+
+   /* store header */
+   x = 0;
+   out[x++] = 0x02;
+   out[x++] = z;
+
+   /* if 31st bit is set output a leading zero and decrement count */
+   if (z == 5) {
+      out[x++] = 0;
+      --z;
+   }
+
+   /* store values */
+   for (y = 0; y < z; y++) {
+      out[x++] = (num >> 24) & 0xFF;
+      num    <<= 8;
+   }
+
+   /* we good */
+   *outlen = x;
+ 
+   return CRYPT_OK;
+}
+
+#endif
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/short_integer/der_encode_short_integer.c,v $ */
+/* $Revision: 1.3 $ */
+/* $Date: 2005/05/23 01:27:03 $ */