Optimize logging for const char* messages

include/spdlog/details/fmt_helper.h

@@ -22,12 +22,8 @@ inline void append_str(const std::string &str, fmt::basic_memory_buffer<char, Bu
 template<size_t Buffer_Size>
 inline void append_c_str(const char *c_str, fmt::basic_memory_buffer<char, Buffer_Size> &dest)
 {
-    char ch;
-    while ((ch = *c_str) != '\0')
-    {
-        dest.push_back(ch);
-        ++c_str;
-    }
+	auto len = std::char_traits<char>::length(c_str);
+	dest.append(c_str, c_str + len);   
 }
 
 template<size_t Buffer_Size1, size_t Buffer_Size2>

include/spdlog/details/logger_impl.h

@@ -5,9 +5,12 @@
 
 #pragma once
 
+#include "spdlog/details/fmt_helper.h"
+
 #include <memory>
 #include <string>
 
+
 // create logger with given name, sinks and the default pattern formatter
 // all other ctors will call this one
 template<typename It>
@@ -76,8 +79,8 @@ inline void spdlog::logger::log(level::level_enum lvl, const char *msg)
     }
     try
     {
-        details::log_msg log_msg(&name_, lvl);
-        fmt::format_to(log_msg.raw, "{}", msg);
+        details::log_msg log_msg(&name_, lvl);        
+		details::fmt_helper::append_c_str(msg, log_msg.raw);
         sink_it_(log_msg);
     }
     SPDLOG_CATCH_AND_HANDLE