Put nested_output in it's own file

base/nested_output.h

@@ -0,0 +1,94 @@
+#ifndef BASE_NESTED_OUTPUT_H
+#define BASE_NESTED_OUTPUT_H
+
+#include <iostream>
+
+//----------------------------------------------------------------
+
+namespace base {
+	class end_message {};
+
+	class nested_output {
+	public:
+		nested_output(std::ostream &out, unsigned step)
+			: out_(out),
+			  step_(step),
+			  beginning_of_line_(true),
+			  enabled_(true),
+			  indent_(0) {
+		}
+
+		template <typename T>
+		nested_output &operator <<(T const &t) {
+			if (beginning_of_line_) {
+				beginning_of_line_ = false;
+				indent();
+			}
+
+			if (enabled_)
+				out_ << t;
+
+			return *this;
+		}
+
+		nested_output &operator <<(end_message const &m) {
+			beginning_of_line_ = true;
+
+			if (enabled_)
+				out_ << std::endl;
+
+			return *this;
+		}
+
+		void inc_indent() {
+			indent_ += step_;
+		}
+
+		void dec_indent() {
+			indent_ -= step_;
+		}
+
+		struct nest {
+			nest(nested_output &out)
+			: out_(out) {
+				out_.inc_indent();
+			}
+
+			~nest() {
+				out_.dec_indent();
+			}
+
+			nested_output &out_;
+		};
+
+		nest push() {
+			return nest(*this);
+		}
+
+		void enable() {
+			enabled_ = true;
+		}
+
+		void disable() {
+			enabled_ = false;
+		}
+
+	private:
+		void indent() {
+			if (enabled_)
+				for (unsigned i = 0; i < indent_; i++)
+					out_ << ' ';
+		}
+
+		std::ostream &out_;
+		unsigned step_;
+
+		bool beginning_of_line_;
+		bool enabled_;
+		unsigned indent_;
+	};
+}
+
+//----------------------------------------------------------------
+
+#endif