Remove temporary std::string creation in some hex->bin calls

contrib/epee/include/string_tools.h

@@ -42,6 +42,7 @@
 #include <type_traits>
 #include <boost/lexical_cast.hpp>
 #include <boost/algorithm/string/predicate.hpp>
+#include <boost/utility/string_ref.hpp>
 #include "misc_log_ex.h"
 #include "storages/parserse_base_utils.h"
 #include "hex.h"
@@ -69,7 +70,7 @@ namespace string_tools
     return to_hex::string(to_byte_span(to_span(src)));
   }
   //----------------------------------------------------------------------------
-  inline bool parse_hexstr_to_binbuff(const epee::span<const char> s, epee::span<char>& res)
+  inline bool parse_hexstr_to_binbuff(const boost::string_ref s, epee::span<char> res)
   {
       if (s.size() != res.size() * 2)
         return false;
@@ -90,7 +91,7 @@ namespace string_tools
       return true;
   }
   //----------------------------------------------------------------------------
-  inline bool parse_hexstr_to_binbuff(const std::string& s, std::string& res)
+  inline bool parse_hexstr_to_binbuff(const boost::string_ref s, std::string& res)
   {
     if (s.size() & 1)
       return false;
@@ -303,7 +304,7 @@ POP_WARNINGS
   }
   //----------------------------------------------------------------------------
   template<class t_pod_type>
-  bool hex_to_pod(const std::string& hex_str, t_pod_type& s)
+  bool hex_to_pod(const boost::string_ref hex_str, t_pod_type& s)
   {
     static_assert(std::is_pod<t_pod_type>::value, "expected pod type");
     if(sizeof(s)*2 != hex_str.size())
@@ -313,13 +314,13 @@ POP_WARNINGS
   }
   //----------------------------------------------------------------------------
   template<class t_pod_type>
-  bool hex_to_pod(const std::string& hex_str, tools::scrubbed<t_pod_type>& s)
+  bool hex_to_pod(const boost::string_ref hex_str, tools::scrubbed<t_pod_type>& s)
   {
     return hex_to_pod(hex_str, unwrap(s));
   }
   //----------------------------------------------------------------------------
   template<class t_pod_type>
-  bool hex_to_pod(const std::string& hex_str, epee::mlocked<t_pod_type>& s)
+  bool hex_to_pod(const boost::string_ref hex_str, epee::mlocked<t_pod_type>& s)
   {
     return hex_to_pod(hex_str, unwrap(s));
   }