detail/utility/width.hpp

0001 ///////////////////////////////////////////////////////////////////////////////
0002 // width.hpp
0003 //
0004 //  Copyright 2008 Eric Niebler. Distributed under the Boost
0005 //  Software License, Version 1.0. (See accompanying file
0006 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0007
0008 #ifndef BOOST_XPRESSIVE_DETAIL_UTILITY_WIDTH_HPP_EAN_04_07_2006
0009 #define BOOST_XPRESSIVE_DETAIL_UTILITY_WIDTH_HPP_EAN_04_07_2006
0010
0011 // MS compatible compilers support #pragma once
0012 #if defined(_MSC_VER)
0013 # pragma once
0014 #endif
0015
0016 #include <climits> // for INT_MAX
0017 #include <boost/mpl/size_t.hpp>
0018
0019 namespace boost { namespace xpressive { namespace detail
0020 {
0021
0022 typedef mpl::size_t<INT_MAX / 2 - 1> unknown_width;
0023 struct width;
0024 bool is_unknown(width const &that);
0025
0026 ///////////////////////////////////////////////////////////////////////////////
0027 // width
0028 struct width
0029 {
0030     width(std::size_t val = 0)
0031       : value_(val)
0032     {
0033     }
0034
0035     bool operator !() const
0036     {
0037         return !this->value_;
0038     }
0039
0040     width &operator +=(width const &that)
0041     {
0042         this->value_ =
0043             !is_unknown(*this) && !is_unknown(that)
0044           ? this->value_ + that.value_
0045           : unknown_width();
0046         return *this;
0047     }
0048
0049     width &operator |=(width const &that)
0050     {
0051         this->value_ =
0052             this->value_ == that.value_
0053           ? this->value_
0054           : unknown_width();
0055         return *this;
0056     }
0057
0058     std::size_t value() const
0059     {
0060         return this->value_;
0061     }
0062
0063 private:
0064     std::size_t value_;
0065 };
0066
0067 inline bool is_unknown(width const &that)
0068 {
0069     return unknown_width::value == that.value();
0070 }
0071
0072 inline bool operator ==(width const &left, width const &right)
0073 {
0074     return left.value() == right.value();
0075 }
0076
0077 inline bool operator !=(width const &left, width const &right)
0078 {
0079     return left.value() != right.value();
0080 }
0081
0082 inline width operator +(width left, width const &right)
0083 {
0084     return left += right;
0085 }
0086
0087 inline width operator |(width left, width const &right)
0088 {
0089     return left |= right;
0090 }
0091
0092 }}} // namespace boost::xpressive::detail
0093
0094 #endif