feat: add ""_toml literal

toml.hpp

@@ -34,6 +34,7 @@
 #endif
 
 #include "toml/parser.hpp"
+#include "toml/literal.hpp"
 #include "toml/serializer.hpp"
 #include "toml/from_toml.hpp"
 #include "toml/get.hpp"

toml/literal.hpp

@@ -0,0 +1,55 @@
+//     Copyright Toru Niina 2019.
+// Distributed under the MIT License.
+#ifndef TOML11_LITERAL_HPP
+#define TOML11_LITERAL_HPP
+#include "parser.hpp"
+
+namespace toml
+{
+inline namespace literals
+{
+inline namespace toml_literals
+{
+
+inline ::toml::value operator""_toml(const char* str, std::size_t len)
+{
+    ::toml::detail::location<std::vector<char>>
+        loc(/* filename = */ std::string("TOML literal encoded in a C++ code"),
+            /* contents = */ std::vector<char>(str, str + len));
+
+    // if there are some comments or empty lines, skip them.
+    using skip_line = ::toml::detail::repeat<toml::detail::sequence<
+            ::toml::detail::maybe<::toml::detail::lex_ws>,
+            ::toml::detail::maybe<::toml::detail::lex_comment>,
+            ::toml::detail::lex_newline
+        >, ::toml::detail::at_least<1>>;
+    skip_line::invoke(loc);
+
+    // if there are some whitespaces before a value, skip them.
+    using skip_ws = ::toml::detail::repeat<
+        ::toml::detail::lex_ws, ::toml::detail::at_least<1>>;
+    skip_ws::invoke(loc);
+
+    // literal may be a bare value. try them first.
+    if(auto data = ::toml::detail::parse_value(loc))
+    {
+        return data.unwrap();
+    }
+
+    // literal is a TOML file (i.e. multiline table).
+    if(auto data = ::toml::detail::parse_toml_file(loc))
+    {
+        loc.iter() = loc.begin(); // rollback to the top of the literal
+        return ::toml::value(std::move(data.unwrap()),
+                ::toml::detail::region<std::vector<char>>(std::move(loc)));
+    }
+    else // none of them.
+    {
+        throw ::toml::syntax_error(data.unwrap_err());
+    }
+}
+
+} // toml_literals
+} // literals
+} // toml
+#endif//TOML11_LITERAL_HPP