Import code from previous AssetBuilder version

thirdparty/libtomcrypt/pk/dh/dh_export_key.c

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+/* 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.
+ */
+
+#include "tomcrypt.h"
+
+#ifdef LTC_MDH
+
+/**
+  Binary export a DH key to a buffer
+  @param out    [out] The destination for the key
+  @param outlen [in/out] The max size and resulting size of the DH key
+  @param type   Which type of key (PK_PRIVATE or PK_PUBLIC)
+  @param key    The key you wish to export
+  @return CRYPT_OK if successful
+*/
+int dh_export_key(void *out, unsigned long *outlen, int type, dh_key *key)
+{
+   unsigned long len;
+   void *k;
+
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+   LTC_ARGCHK(key    != NULL);
+
+   k = (type == PK_PRIVATE) ? key->x : key->y;
+   len = mp_unsigned_bin_size(k);
+
+   if (*outlen < len) {
+      *outlen = len;
+      return CRYPT_BUFFER_OVERFLOW;
+   }
+   *outlen = len;
+
+   return mp_to_unsigned_bin(k, out);
+}
+
+#endif /* LTC_MDH */
+
+/* ref:         HEAD -> master, tag: v1.18.2 */
+/* git commit:  7e7eb695d581782f04b24dc444cbfde86af59853 */
+/* commit time: 2018-07-01 22:49:01 +0200 */