Boost C++ Libraries

boost/units/io.hpp

// Boost.Units - A C++ library for zero-overhead dimensional analysis and 
// unit/quantity manipulation and conversion
//
// Copyright (C) 2003-2008 Matthias Christian Schabel
// Copyright (C) 2007-2008 Steven Watanabe
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)

#ifndef BOOST_UNITS_IO_HPP
#define BOOST_UNITS_IO_HPP

#include <cassert>
#include <string>
#include <iosfwd>
#include <ios>
#include <sstream>

#include <boost/mpl/size.hpp>
#include <boost/mpl/begin.hpp>
#include <boost/mpl/next.hpp>
#include <boost/mpl/deref.hpp>
#include <boost/serialization/nvp.hpp>

#include <boost/units/units_fwd.hpp>
#include <boost/units/heterogeneous_system.hpp>
#include <boost/units/quantity.hpp>
#include <boost/units/scale.hpp>
#include <boost/units/static_rational.hpp>
#include <boost/units/unit.hpp>
#include <boost/units/detail/utility.hpp>

namespace boost {

namespace serialization {

/// Boost Serialization library support for units.
template<class Archive,class System,class Dim>
inline void serialize(Archive& ar,boost::units::unit<Dim,System>&,const unsigned int /*version*/)
{ }

/// Boost Serialization library support for quantities.
template<class Archive,class Unit,class Y>
inline void serialize(Archive& ar,boost::units::quantity<Unit,Y>& q,const unsigned int /*version*/)
{
    ar & boost::serialization::make_nvp("value", units::quantity_cast<Y&>(q));
}
        
} // namespace serialization

namespace units {

// get string representation of arbitrary type
template<class T> std::string to_string(const T& t)
{
    std::stringstream sstr;
    
    sstr << t;
    
    return sstr.str();
}

// get string representation of integral-valued @c static_rational
template<integer_type N> std::string to_string(const static_rational<N>&)
{
    return to_string(N);
}

// get string representation of @c static_rational
template<integer_type N, integer_type D> std::string to_string(const static_rational<N,D>&)
{
    return '(' + to_string(N) + '/' + to_string(D) + ')';
}

/// Write @c static_rational to @c std::basic_ostream.
template<class Char, class Traits, integer_type N, integer_type D>
inline std::basic_ostream<Char, Traits>& operator<<(std::basic_ostream<Char, Traits>& os,const static_rational<N,D>& r)
{
    os << to_string(r);
    return os;
}

/// traits template for unit names
template<class BaseUnit>
struct base_unit_info
{
    /// The full name of the unit (returns BaseUnit::name() by default)
    static std::string name()
    {
        return(BaseUnit::name());
    }
    
    /// The symbol for the base unit (Returns BaseUnit::symbol() by default)
    static std::string symbol()
    {
        return(BaseUnit::symbol());
    }
};

enum format_mode 
{
    symbol_fmt = 0,     // default - reduces unit names to known symbols for both base and derived units
    name_fmt,           // output full unit names for base and derived units
    raw_fmt,            // output only symbols for base units 
    typename_fmt        // output demangled typenames
};

namespace detail {

template<bool>
struct xalloc_key_holder 
{
    static int value;
    static bool initialized;
};

template<bool b>
int xalloc_key_holder<b>::value = 0;

template<bool b>
bool xalloc_key_holder<b>::initialized = 0;

struct xalloc_key_initializer_t 
{
    xalloc_key_initializer_t() 
    {
        if (!xalloc_key_holder<true>::initialized) 
        {
            xalloc_key_holder<true>::value = std::ios_base::xalloc();
            xalloc_key_holder<true>::initialized = true;
        }
    }
};

namespace /**/ {
    
xalloc_key_initializer_t xalloc_key_initializer;

} // namespace

} // namespace detail

inline format_mode get_format(std::ios_base& ios) 
{
    return(static_cast<format_mode>(ios.iword(detail::xalloc_key_holder<true>::value)));
}

inline void set_format(std::ios_base& ios, format_mode new_mode) 
{
    ios.iword(detail::xalloc_key_holder<true>::value) = static_cast<long>(new_mode);
}

inline std::ios_base& typename_format(std::ios_base& ios) 
{
    (set_format)(ios, typename_fmt);
    return(ios);
}

inline std::ios_base& raw_format(std::ios_base& ios) 
{
    (set_format)(ios, raw_fmt);
    return(ios);
}

inline std::ios_base& symbol_format(std::ios_base& ios) 
{
    (set_format)(ios, symbol_fmt);
    return(ios);
}

inline std::ios_base& name_format(std::ios_base& ios) 
{
    (set_format)(ios, name_fmt);
    return(ios);
}

namespace detail {

template<integer_type N, integer_type D>
inline std::string exponent_string(const static_rational<N,D>& r)
{
    return '^' + to_string(r);
}

template<>
inline std::string exponent_string(const static_rational<1>&)
{
    return "";
}

template<class T>
inline std::string base_unit_symbol_string(const T&)
{
    return base_unit_info<typename T::tag_type>::symbol() + exponent_string(typename T::value_type());
}

template<class T>    
inline std::string base_unit_name_string(const T&)
{
    return base_unit_info<typename T::tag_type>::name() + exponent_string(typename T::value_type());
}

// stringify with symbols
template<int N>
struct symbol_string_impl
{
    template<class Begin>
    struct apply
    {
        typedef typename symbol_string_impl<N-1>::template apply<typename Begin::next> next;
        static void value(std::string& str)
        {
            str += base_unit_symbol_string(typename Begin::item()) + ' ';
            next::value(str);
        }
    };
};

template<>
struct symbol_string_impl<1>
{
    template<class Begin>
    struct apply
    {
        static void value(std::string& str)
        {
            str += base_unit_symbol_string(typename Begin::item());
        };
    };
};

template<>
struct symbol_string_impl<0>
{
    template<class Begin>
    struct apply
    {
        static void value(std::string& str)
        {
            // better shorthand for dimensionless?
            str += "dimensionless";
        }
    };
};

template<int N>
struct scale_symbol_string_impl 
{
    template<class Begin>
    struct apply 
    {
        static void value(std::string& str) 
        {
            str += Begin::item::symbol();
            scale_symbol_string_impl<N - 1>::template apply<typename Begin::next>::value(str);
        }
    };
};

template<>
struct scale_symbol_string_impl<0>
{
    template<class Begin>
    struct apply 
    {
        static void value(std::string&) { }
    };
};

// stringify with names
template<int N>
struct name_string_impl
{
    template<class Begin>
    struct apply
    {
        typedef typename name_string_impl<N-1>::template apply<typename Begin::next> next;
        static void value(std::string& str)
        {
            str += base_unit_name_string(typename Begin::item()) + ' ';
            next::value(str);
        }
    };
};

template<>
struct name_string_impl<1>
{
    template<class Begin>
    struct apply
    {
        static void value(std::string& str)
        {
            str += base_unit_name_string(typename Begin::item());
        };
    };
};

template<>
struct name_string_impl<0>
{
    template<class Begin>
    struct apply
    {
        static void value(std::string& str)
        {
            str += "dimensionless";
        }
    };
};

template<int N>
struct scale_name_string_impl 
{
    template<class Begin>
    struct apply 
    {
        static void value(std::string& str) 
        {
            str += Begin::item::name();
            scale_name_string_impl<N - 1>::template apply<typename Begin::next>::value(str);
        }
    };
};

template<>
struct scale_name_string_impl<0>
{
    template<class Begin>
    struct apply 
    {
        static void value(std::string&) { }
    };
};

} // namespace detail

namespace detail {

// These two overloads of symbol_string and name_string will
// will pick up homogeneous_systems.  They simply call the
// appropriate function with a heterogeneous_system.
template<class Dimension,class System, class SubFormatter>
inline std::string
to_string_impl(const unit<Dimension,System>&, SubFormatter f)
{
    return f(typename reduce_unit<unit<Dimension, System> >::type());
}

/// INTERNAL ONLY
// this overload picks up heterogeneous units that are not scaled.
template<class Dimension,class Units, class Subformatter>
inline std::string
to_string_impl(const unit<Dimension, heterogeneous_system<heterogeneous_system_impl<Units, Dimension, dimensionless_type> > >&, Subformatter f)
{
    std::string str;
    f.template append_units_to<Units>(str);
    return(str);
}

// This overload is a special case for heterogeneous_system which
// is really unitless
/// INTERNAL ONLY
template<class Subformatter>
inline std::string
to_string_impl(const unit<dimensionless_type, heterogeneous_system<heterogeneous_system_impl<dimensionless_type, dimensionless_type, dimensionless_type> > >&, Subformatter)
{
    return("dimensionless");
}

// this overload deals with heterogeneous_systems which are unitless
// but scaled.
/// INTERNAL ONLY
template<class Scale, class Subformatter>
inline std::string
to_string_impl(const unit<dimensionless_type, heterogeneous_system<heterogeneous_system_impl<dimensionless_type, dimensionless_type, Scale> > >&, Subformatter f)
{
    std::string str;
    f.template append_scale_to<Scale>(str);
    return(str);
}

// this overload deals with scaled units.
/// INTERNAL ONLY
template<class Dimension,class Units,class Scale, class Subformatter>
inline std::string
to_string_impl(const unit<Dimension, heterogeneous_system<heterogeneous_system_impl<Units, Dimension, Scale> > >&, Subformatter f)
{
    std::string str;

    f.template append_scale_to<Scale>(str);

    std::string without_scale = f(unit<Dimension, heterogeneous_system<heterogeneous_system_impl<Units, Dimension, dimensionless_type> > >());
    
    if (f.is_default_string(without_scale, unit<Dimension, heterogeneous_system<heterogeneous_system_impl<Units, Dimension, dimensionless_type> > >()))
    {
        str += "(";
        str += without_scale;
        str += ")";
    } 
    else 
    {
        str += without_scale;
    }

    return(str);
}

// this overload catches scaled units that have a single base unit
// raised to the first power.  It causes si::nano * si::meters to not
// put parentheses around the meters.  i.e. nm rather than n(m)
/// INTERNAL ONLY
template<class Dimension,class Unit,class Scale, class Subformatter>
inline std::string
to_string_impl(const unit<Dimension, heterogeneous_system<heterogeneous_system_impl<list<heterogeneous_system_dim<Unit, static_rational<1> >,dimensionless_type>, Dimension, Scale> > >&, Subformatter f)
{
    std::string str;

    f.template append_scale_to<Scale>(str);
    str += f(unit<Dimension, heterogeneous_system<heterogeneous_system_impl<list<heterogeneous_system_dim<Unit, static_rational<1> >, dimensionless_type>, Dimension, dimensionless_type> > >());

    return(str);
}

// this overload is necessary to disambiguate.
// it catches units that are unscaled and have a single
// base unit raised to the first power.  It is treated the
// same as any other unscaled unit.
/// INTERNAL ONLY
template<class Dimension,class Unit,class Subformatter>
inline std::string
to_string_impl(const unit<Dimension, heterogeneous_system<heterogeneous_system_impl<list<heterogeneous_system_dim<Unit, static_rational<1> >,dimensionless_type>, Dimension, dimensionless_type> > >&, Subformatter f)
{
    std::string str;
    f.template append_units_to<list<heterogeneous_system_dim<Unit, static_rational<1> >,dimensionless_type> >(str);
    return(str);
}


// this overload catches scaled units that have a single scaled base unit
// raised to the first power.  It moves that scaling on the base unit
// to the unit level scaling and recurses.  By doing this we make sure that
// si::milli * si::kilograms will print g rather than mkg
//
/// INTERNAL ONLY
template<class Dimension,class Unit,class UnitScale, class Scale, class Subformatter>
inline std::string
to_string_impl(const unit<Dimension, heterogeneous_system<heterogeneous_system_impl<list<heterogeneous_system_dim<scaled_base_unit<Unit, UnitScale>, static_rational<1> >, dimensionless_type>, Dimension, Scale> > >&, Subformatter f)
{
    return(f(
        unit<
            Dimension,
            heterogeneous_system<
                heterogeneous_system_impl<
                    list<heterogeneous_system_dim<Unit, static_rational<1> >, dimensionless_type>,
                    Dimension,
                    typename mpl::times<Scale, list<UnitScale, dimensionless_type> >::type
                >
            >
        >()));
}

// this overload disambuguates between the overload for an unscaled unit
// and the overload for a scaled base unit raised to the first power.
/// INTERNAL ONLY
template<class Dimension,class Unit,class UnitScale,class Subformatter>
inline std::string
to_string_impl(const unit<Dimension, heterogeneous_system<heterogeneous_system_impl<list<heterogeneous_system_dim<scaled_base_unit<Unit, UnitScale>, static_rational<1> >, dimensionless_type>, Dimension, dimensionless_type> > >&, Subformatter f)
{
    std::string str;
    f.template append_units_to<list<heterogeneous_system_dim<scaled_base_unit<Unit, UnitScale>, static_rational<1> >, dimensionless_type> >(str);
    return(str);
}

struct format_raw_symbol_impl {
    template<class Units>
    void append_units_to(std::string& str) {
        detail::symbol_string_impl<Units::size::value>::template apply<Units>::value(str);
    }
    template<class Scale>
    void append_scale_to(std::string& str) {
        detail::scale_symbol_string_impl<Scale::size::value>::template apply<Scale>::value(str);
    }
    template<class Unit>
    std::string operator()(const Unit& unit) {
        return(to_string_impl(unit, *this));
    }
    template<class Unit>
    bool is_default_string(const std::string&, const Unit&) {
        return(true);
    }
};

struct format_symbol_impl : format_raw_symbol_impl {
    template<class Unit>
    std::string operator()(const Unit& unit) {
        return(symbol_string(unit));
    }
    template<class Unit>
    bool is_default_string(const std::string& str, const Unit& unit) {
        return(str == to_string_impl(unit, format_raw_symbol_impl()));
    }
};

struct format_raw_name_impl {
    template<class Units>
    void append_units_to(std::string& str) {
        detail::name_string_impl<(Units::size::value)>::template apply<Units>::value(str);
    }
    template<class Scale>
    void append_scale_to(std::string& str) {
        detail::scale_name_string_impl<Scale::size::value>::template apply<Scale>::value(str);
    }
    template<class Unit>
    std::string operator()(const Unit& unit) {
        return(to_string_impl(unit, *this));
    }
    template<class Unit>
    bool is_default_string(const std::string&, const Unit&) {
        return(true);
    }
};

struct format_name_impl : format_raw_name_impl {
    template<class Unit>
    std::string operator()(const Unit& unit) {
        return(name_string(unit));
    }
    template<class Unit>
    bool is_default_string(const std::string& str, const Unit& unit) {
        return(str == to_string_impl(unit, format_raw_name_impl()));
    }
};

} // namespace detail

template<class Dimension,class System>
inline std::string
typename_string(const unit<Dimension, System>&)
{
    return simplify_typename(typename reduce_unit< unit<Dimension,System> >::type());
}

template<class Dimension,class System>
inline std::string
symbol_string(const unit<Dimension, System>&)
{
    return detail::to_string_impl(unit<Dimension,System>(), detail::format_symbol_impl());
}

template<class Dimension,class System>
inline std::string
name_string(const unit<Dimension, System>&)
{
    return detail::to_string_impl(unit<Dimension,System>(), detail::format_name_impl());
}

/// Print an @c unit as a list of base units and exponents
///
///     for @c symbol_format this gives e.g. "m s^-1" or "J"
///     for @c name_format this gives e.g. "meter second^-1" or "joule"
///     for @c raw_format this gives e.g. "m s^-1" or "meter kilogram^2 second^-2"
///     for @c typename_format this gives the typename itself (currently demangled only on GCC)
template<class Char, class Traits, class Dimension, class System>
inline std::basic_ostream<Char, Traits>& operator<<(std::basic_ostream<Char, Traits>& os, const unit<Dimension, System>& u)
{
    if (units::get_format(os) == typename_fmt) 
    {
        os << typename_string(u);
    } 
    else if (units::get_format(os) == raw_fmt) 
    {
        os << detail::to_string_impl(u, detail::format_raw_symbol_impl());
    } 
    else if (units::get_format(os) == symbol_fmt) 
    {
        os << symbol_string(u);
    } 
    else if (units::get_format(os) == name_fmt) 
    {
        os << name_string(u);
    } 
    else 
    {
        assert(!"The format mode must be one of: typename_format, raw_format, name_format, symbol_format");
    }
    
    return(os);
}

/// INTERNAL ONLY
/// Print a @c quantity. Prints the value followed by the unit
template<class Char, class Traits, class Unit, class T>
inline std::basic_ostream<Char, Traits>& operator<<(std::basic_ostream<Char, Traits>& os, const quantity<Unit, T>& q)
{
    os << q.value() << ' ' << Unit();
    return(os);
}

} // namespace units

} // namespace boost

#endif