libutil++/generic_spec.h

/**
 * @file generic_spec.h
 * Container holding an item or a special "match all" item
 *
 * @remark Copyright 2003 OProfile authors
 * @remark Read the file COPYING
 *
 * @author John Levon
 * @author Philippe Elie
 */

#ifndef GENERIC_SPEC_H
#define GENERIC_SPEC_H

#include <stdexcept>
#include <string>
#include <sstream>

#include "string_manip.h"


/**
 * used to hold something like { int cpu_nr, bool is_all };
 * to store a sub part of a samples filename see PP:3.21.
 */
template <class T>
class generic_spec
{
public:
	/**
	 * build a default spec which match anything
	 */
	generic_spec();

	/// build a spec from a string, valid argument are "all"
	/// or a string convertible to T through istringtream(str) >> data
	/// conversion is strict, no space are allowed at begin or end of str
	void set(std::string const &);

	/// return true if a specific value is held by this container
	bool is_set() const {
		return !is_all;
	}

	/// return the specific value (only if is_set() == true)
	T const value() const {
		if (!is_all)
			return data;
		throw std::out_of_range("generic_spec holds no value");
	}

	/// return true if rhs match this spec. Sub part of PP:3.24
	bool match(T const & rhs) const {
		return rhs == data;
	}

	/// return true if rhs match this spec. Sub part of PP:3.24
	bool match(generic_spec<T> const & rhs) const {
		return is_all || rhs.is_all || rhs.data == data;
	}

private:
	T data;
	bool is_all;
};


template <class T>
generic_spec<T>::generic_spec()
	:
	data(T()),
	is_all(true)
{
}


template <class T>
void generic_spec<T>::set(std::string const & str)
{
	if (str == "all") {
		is_all = true;
		return;
	}

	is_all = false;
	data = op_lexical_cast<T>(str);
}


/// We don't use generic_spec<string>, since it's probably an error to try
/// to use generic_spec<string> we specialize but don't define it to get a
/// link error (using generic_spec<string> is problematic because g.set("all")
/// is ambiguous)
template <>
void generic_spec<std::string>::set(std::string const & str);

#endif /* !GENERIC_SPEC_H */