IOStream filter stage.

This permits creation of custom filtration stages in the IOStream
streambuf stack.

IOStreams/Filter.test/0.cc

@@ -0,0 +1,128 @@
+static_assert( __cplusplus > 2020'99 );
+
+#include "../Filter.h"
+
+#include <Alepha/Testing/test.h>
+#include <Alepha/Testing/TableTest.h>
+
+#include <sstream>
+#include <iostream>
+
+static auto init= Alepha::Utility::enroll <=[]
+{
+	using namespace std::literals::string_literals;
+	using namespace Alepha::Testing::literals;
+
+	using namespace Alepha::Testing::exports;
+
+	[]( const std::string &s )
+	{
+		std::stringstream iss{ s };
+
+		//iss >> Filter{ std::make_unique< CapitalizationFilter >() };
+
+		std::string rv;
+		iss << "bob";
+		int x;
+		iss >> x;
+	};
+
+	"Simple Filter"_test <=TableTest
+	<
+		[]( const std::string &s )
+				-> std::string
+		{
+			using namespace Alepha::IOStreams::exports::Filter_m;
+			struct CapitalizationFilter : StreamFilter
+			{
+				public:
+					Emitter
+					nextChar( const char ch ) override
+					{
+						struct EmitterImpl
+							: public Emitter::Impl
+						{
+							char ch;
+							bool read= false;
+
+							explicit EmitterImpl( const char ch ) : ch( ch ) {}
+
+							bool empty() const final { return read; }
+							char
+							next() final
+							{
+								read= true;
+								std::cerr << "Emitted `" << ch << "`" << std::endl;
+								return ch;
+							}
+						};
+
+						std::cerr << "Emitter built for `" << ch << "`" << std::endl;
+						return Emitter{ std::make_unique< EmitterImpl >( ::toupper( ch ) ) };
+					}
+			};
+
+			std::ostringstream oss;
+
+			oss << Filter{ std::make_unique< CapitalizationFilter >() };
+
+			oss << s;
+
+			oss << Alepha::IOStreams::PopStack{};
+
+			return oss.str();
+		}
+	>
+	::Cases
+	{
+		{ "Hello", { "hello" }, "HELLO" },
+	};
+
+	auto streamWriter= []( const std::string &s )
+	{
+		using namespace Alepha::IOStreams::exports::Filter_m;
+		struct CapitalizationFilter : StreamFilter
+		{
+			public:
+				Emitter
+				nextChar( const char ch ) override
+				{
+					struct EmitterImpl
+						: public Emitter::Impl
+					{
+						char ch;
+						bool read= false;
+
+						explicit EmitterImpl( const char ch ) : ch( ch ) {}
+
+						bool empty() const final { return read; }
+						char
+						next() final
+						{
+							read= true;
+							std::cerr << "Emitted `" << ch << "`" << std::endl;
+							return ch;
+						}
+					};
+					std::cerr << "Emitter built for `" << ch << "`" << std::endl;
+					return Emitter{ std::make_unique< EmitterImpl >( ::toupper( ch ) ) };
+				}
+		};
+
+		std::stringstream iss{ s };
+
+		iss >> Filter{ std::make_unique< CapitalizationFilter >() };
+
+		std::string rv;
+		iss >> rv;
+
+		iss >> Alepha::IOStreams::PopStack{};
+
+		return rv;
+	};
+
+	"Simple Input Filter"_test <=TableTest< streamWriter >::Cases
+	{
+		{ "Hello", { "hello" }, "HELLO" },
+	};
+};

IOStreams/Filter.test/CMakeLists.txt

@@ -0,0 +1 @@
+unit_test( 0 )