Initial commit

First commit with most of the main features implemented. May still need
some bug fixes here and there.

include/progress_bar.hpp

@@ -0,0 +1,59 @@
+#include <cmath>
+#include <iomanip>
+#include <ostream>
+#include <string>
+
+class progress_bar
+{
+	static const auto overhead = sizeof " [100%]";
+
+	std::ostream& os;
+	const std::size_t bar_width;
+	std::string message;
+	const std::string full_bar;
+
+ public:
+	progress_bar(std::ostream& os, std::size_t line_width,
+				 std::string message_, const char symbol = '.')
+		: os{os},
+		  bar_width{line_width - overhead},
+		  message{std::move(message_)},
+		  full_bar{std::string(bar_width, symbol) + std::string(bar_width, ' ')}
+	{
+		if (message.size()+1 >= bar_width || message.find('\n') != message.npos) {
+			os << message << '\n';
+			message.clear();
+		} else {
+			message += ' ';
+		}
+		write(0.0);
+	}
+
+	// not copyable
+	progress_bar(const progress_bar&) = delete;
+	progress_bar& operator=(const progress_bar&) = delete;
+
+	~progress_bar()
+	{
+		write(1.0);
+		os << '\n';
+	}
+
+	void write(double fraction);
+};
+
+void progress_bar::write(double fraction)
+{
+	// clamp fraction to valid range [0,1]
+	if (fraction < 0)
+		fraction = 0;
+	else if (fraction > 1)
+		fraction = 1;
+
+	auto width = bar_width - message.size();
+	auto offset = bar_width - static_cast<unsigned>(width * fraction);
+
+	os << '\r' << message;
+	os.write(full_bar.data() + offset, width);
+	os << " [" << std::setw(3) << static_cast<int>(100*fraction) << "%] " << std::flush;
+}