feat: add source_location for error message generation.

toml/source_location.hpp

@@ -0,0 +1,82 @@
+//     Copyright Toru Niina 2019.
+// Distributed under the MIT License.
+#ifndef TOML11_SOURCE_LOCATION_HPP
+#define TOML11_SOURCE_LOCATION_HPP
+#include "region.hpp"
+#include <cstdint>
+
+namespace toml
+{
+
+// A struct to contain location in a toml file.
+// The interface imitates std::experimental::source_location,
+// but not completely the same.
+//
+// It would be constructed by toml::value. It can be used to generate
+// user-defined error messages.
+//
+// - std::uint_least32_t line() const noexcept
+//   - returns the line number where the region is on.
+// - std::uint_least32_t column() const noexcept
+//   - returns the column number where the region starts.
+// - std::uint_least32_t region() const noexcept
+//   - returns the size of the region.
+//
+// +-- line()       +-- region of interest (region() == 9)
+// v            .---+---.
+// 12 | value = "foo bar"
+//              ^
+//              +-- column()
+//
+// - std::string const& file_name() const noexcept;
+//   - name of the file.
+// - std::string const& line_str() const noexcept;
+//   - the whole line that contains the region of interest.
+//
+struct source_location
+{
+  public:
+
+    source_location()
+        : line_num_(0), column_num_(0), region_size_(0),
+          file_name_("unknown file"), line_str_("")
+    {}
+
+    explicit source_location(const detail::region_base* reg)
+        : line_num_(0), column_num_(0), region_size_(0),
+          file_name_("unknown file"), line_str_("")
+    {
+        if(reg)
+        {
+            line_num_    = std::stoul(reg->line_num());
+            column_num_  = reg->before() + 1;
+            region_size_ = reg->size();
+            file_name_   = reg->name();
+            line_str_    = reg->line();
+        }
+    }
+
+    ~source_location() = default;
+    source_location(source_location const&) = default;
+    source_location(source_location &&)     = default;
+    source_location& operator=(source_location const&) = default;
+    source_location& operator=(source_location &&)     = default;
+
+    std::uint_least32_t line()      const noexcept {return line_num_;}
+    std::uint_least32_t column()    const noexcept {return column_num_;}
+    std::uint_least32_t region()    const noexcept {return region_size_;}
+
+    std::string const&  file_name() const noexcept {return file_name_;}
+    std::string const&  line_str()  const noexcept {return line_str_;}
+
+  private:
+
+    std::uint_least32_t line_num_;
+    std::uint_least32_t column_num_;
+    std::uint_least32_t region_size_;
+    std::string         file_name_;
+    std::string         line_str_;
+};
+
+} // toml
+#endif// TOML11_SOURCE_LOCATION_HPP