Added a init_role_mapping function to be used for later

sql/sql_acl.cc

@@ -549,6 +549,44 @@ static uchar* acl_role_map_get_key(ROLE_GRANT_PAIR *entry, size_t *length,
   return (uchar*) entry->hashkey.str;
 }
 
+static void init_role_grant_pair(MEM_ROOT *mem, ROLE_GRANT_PAIR *entry,
+                                 char *username, char *hostname, char *rolename)
+{
+      size_t len[3] = {username ? strlen(username) : 0,
+                       hostname ? strlen(hostname) : 0,
+                       rolename ? strlen(rolename) : 0};
+      /*
+        Create a buffer that holds all 3 NULL terminated strings in succession
+        To save memory space, the same buffer is used as the hashkey
+      */
+      size_t bufflen = len[0] + len[1] + len[2] + 3; //add the '\0' aswell
+      char *buff= (char *)alloc_root(mem, bufflen);
+      /*
+        Offsets in the buffer for all 3 strings
+      */
+      char *username_pos= buff;
+      char *hostname_pos= buff + len[0] + 1;
+      char *rolename_pos= buff + len[0] + len[1] + 2;
+
+      if (username)
+        memcpy(username_pos, username, len[0]);
+      username_pos[len[0]]= '\0';         //#1 string terminator
+      entry->u_uname= username_pos;
+
+      if (hostname)
+        memcpy(hostname_pos, hostname, len[1]);
+      hostname_pos[len[1]]= '\0';         //#2 string terminator
+      entry->u_hname= hostname_pos;
+
+      if (rolename)
+        memcpy(rolename_pos, rolename, len[2]);
+      rolename_pos[len[2]]= '\0';         //#3 string terminator
+      entry->r_uname= rolename_pos;
+
+      entry->hashkey.str = buff;
+      entry->hashkey.length = bufflen;
+}
+
 #define IP_ADDR_STRLEN (3 + 1 + 3 + 1 + 3 + 1 + 3)
 #define ACL_KEY_LENGTH (IP_ADDR_STRLEN + 1 + NAME_LEN + \
                         1 + USERNAME_LENGTH + 1)