List delimiting primitive for output streams.

delimited_list.cc

@@ -0,0 +1,79 @@
+static_assert( __cplusplus > 2020'99 );
+
+#include "delimited_list.h"
+
+#include <Alepha/error.h>
+
+#include <Alepha/IOStreams/StreamState.h>
+
+namespace Alepha::Hydrogen  ::detail::  delimited_list_m
+{
+
+	namespace
+	{
+		namespace C
+		{
+			const bool debug= false;
+		}
+
+		namespace impl_cc
+		{
+			struct DelimitedListStreambuf;
+		}
+
+		IOStreams::StreamState< impl_cc::DelimitedListStreambuf * > tracker{ [] { return nullptr; } };
+	}
+
+	struct impl_cc::DelimitedListStreambuf
+		: virtual public IOStreams::StackableStreambuf, virtual public std::streambuf
+	{
+		private:
+			std::string delim;
+			bool first= true;
+
+		public:
+			explicit
+			DelimitedListStreambuf( std::ios &is, const std::string delim )
+				: StackableStreambuf( is ), delim( delim )
+			{
+				tracker.get( is )= this;
+				if( C::debug ) error() << "Streambuf adapted." << std::endl;
+			}
+
+			void
+			doNext()
+			{
+				if( C::debug ) error() << "Do Next called" << std::endl;
+				if( not first ) out() << delim;
+				first= false;
+			}
+
+		private:
+			void writeChar( char ) override { throw "Unimpl"; }
+			void drain() override { throw "Unimpl"; }
+
+			int
+			overflow( const int ch ) override
+			{
+				if( C::debug ) error() << "Overflow called" << std::endl;
+				return forwardOverflow( ch );
+			}
+	};
+
+
+	std::ostream &
+	impl::operator << ( std::ostream &os, MarkItem_t )
+	{
+		if( C::debug ) error() << "Marker called" << std::endl;
+		auto thisTracker= tracker.get( os );
+		if( thisTracker != nullptr ) thisTracker->doNext();
+
+		return os;
+	}
+
+	void
+	impl::build_streambuf( std::ostream &os, StartDelimitedList &&params )
+	{
+		new impl_cc::DelimitedListStreambuf( os, params.delimiter );
+	}
+}