Improvements to print overloads and add support for printing std::string_view - develop

libraries/eosiolib/core/eosio/print.hpp

@@ -5,8 +5,8 @@
 #pragma once
 #include <utility>
 #include <string>
-
-
+#include <string_view>
+#include <type_traits>
 
 namespace eosio {
  namespace internal_use_do_not_use {
@@ -44,6 +44,7 @@ namespace eosio {
  __attribute__((eosio_wasm_import))
  void printhex(const void*, uint32_t);
  }
+
  };
 
  /**
@@ -86,7 +87,7 @@ namespace eosio {
  * @param len - number of chars to print
  */
  inline void printl( const char* ptr, size_t len ) {
- internal_use_do_not_use::prints_l(ptr, len);
+  internal_use_do_not_use::prints_l(ptr, len);
  }
 
  /**
@@ -96,7 +97,27 @@ namespace eosio {
  * @param ptr - a null terminated string
  */
  inline void print( const char* ptr ) {
- internal_use_do_not_use::prints(ptr);
+ internal_use_do_not_use::prints(ptr);
+ }
+
+ /**
+ * Prints string
+ *
+ * @ingroup console
+ * @param str - an std::string
+ */
+ inline void print( const std::string& str ) {
+ internal_use_do_not_use::prints_l(str.c_str(), str.size());
+ }
+
+ /**
+ * Prints string
+ *
+ * @ingroup console
+ * @param str - an std::string_view
+ */
+ inline void print( std::string_view str ) {
+ internal_use_do_not_use::prints_l(str.data(), str.size());
  }
 
  /**
@@ -160,16 +181,12 @@ namespace eosio {
  *
  * @ingroup console
  * @param t to be printed
- * @pre T must implements print() function
+ * @pre T must implement print() function
  */
- template<typename T, std::enable_if_t<!std::is_integral<std::decay_t<T>>::value, int> = 0>
- inline void print( T&& t ) {
- if constexpr (std::is_same<std::decay_t<T>, std::string>::value)
- internal_use_do_not_use::prints_l( t.c_str(), t.size() );
- else if constexpr (std::is_same<std::decay_t<T>, char*>::value)
- internal_use_do_not_use::prints(t);
- else
- t.print();
+ template <typename T>
+ inline auto print(T&& t) -> std::void_t<decltype(t.print())> 
+ {
+ std::forward<T>(t).print();
  }
 
  /**
@@ -179,7 +196,7 @@ namespace eosio {
  * @param s null terminated string to be printed
  */
  inline void print_f( const char* s ) {
- internal_use_do_not_use::prints(s);
+  internal_use_do_not_use::prints(s);
  }
 
  /**
@@ -229,7 +246,8 @@ namespace eosio {
  * @endcode
  */
  template<typename Arg, typename... Args>
- void print( Arg&& a, Args&&... args ) {
+ auto print( Arg&& a, Args&&... args ) -> std::enable_if_t<sizeof...(Args) != 0, void>
+ {
  print(std::forward<Arg>(a));
  print(std::forward<Args>(args)...);
  }