THUAI6/CAPI/cpp/tclap/include/tclap/ArgTraits.h

// -*- Mode: c++; c-basic-offset: 4; tab-width: 4; -*-

/******************************************************************************
 *
 *  file:  ArgTraits.h
 *
 *  Copyright (c) 2007, Daniel Aarno, Michael E. Smoot .
 *  Copyright (c) 2017 Google LLC
 *  All rights reserved.
 *
 *  See the file COPYING in the top directory of this distribution for
 *  more information.
 *
 *  THE SOFTWARE IS PROVIDED _AS IS_, WITHOUT WARRANTY OF ANY KIND, EXPRESS
 *  OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 *  THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 *  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 *  DEALINGS IN THE SOFTWARE.
 *
 *****************************************************************************/

// This is an internal tclap file, you should probably not have to
// include this directly

#ifndef TCLAP_ARGTRAITS_H
#define TCLAP_ARGTRAITS_H

namespace TCLAP
{

    // We use two empty structs to get compile type specialization
    // function to work

    /**
     * A value like argument value type is a value that can be set using
     * operator>>. This is the default value type.
     */
    struct ValueLike
    {
        typedef ValueLike ValueCategory;
        virtual ~ValueLike()
        {
        }
    };

    /**
     * A string like argument value type is a value that can be set using
     * operator=(string). Useful if the value type contains spaces which
     * will be broken up into individual tokens by operator>>.
     */
    struct StringLike
    {
        virtual ~StringLike()
        {
        }
    };

    /**
     * A class can inherit from this object to make it have string like
     * traits. This is a compile time thing and does not add any overhead
     * to the inherenting class.
     */
    struct StringLikeTrait
    {
        typedef StringLike ValueCategory;
        virtual ~StringLikeTrait()
        {
        }
    };

    /**
     * A class can inherit from this object to make it have value like
     * traits. This is a compile time thing and does not add any overhead
     * to the inherenting class.
     */
    struct ValueLikeTrait
    {
        typedef ValueLike ValueCategory;
        virtual ~ValueLikeTrait()
        {
        }
    };

    /**
     * Arg traits are used to get compile type specialization when parsing
     * argument values. Using an ArgTraits you can specify the way that
     * values gets assigned to any particular type during parsing. The two
     * supported types are StringLike and ValueLike. ValueLike is the
     * default and means that operator>> will be used to assign values to
     * the type.
     */
    template<typename T>
    class ArgTraits
    {
        // This is a bit silly, but what we want to do is:
        // 1) If there exists a specialization of ArgTraits for type X,
        // use it.
        //
        // 2) If no specialization exists but X has the typename
        // X::ValueCategory, use the specialization for X::ValueCategory.
        //
        // 3) If neither (1) nor (2) defines the trait, use the default
        // which is ValueLike.

        // This is the "how":
        //
        // test<T>(0) (where 0 is the NULL ptr) will match
        // test(typename C::ValueCategory*) iff type T has the
        // corresponding typedef. If it does not test(...) will be
        // matched. This allows us to determine if T::ValueCategory
        // exists by checking the sizeof for the test function (return
        // value must have different sizeof).
        template<typename C>
        static short test(typename C::ValueCategory*);
        template<typename C>
        static long test(...);
        static const bool hasTrait = sizeof(test<T>(0)) == sizeof(short);

        template<typename C, bool>
        struct DefaultArgTrait
        {
            typedef ValueLike ValueCategory;
        };

        template<typename C>
        struct DefaultArgTrait<C, true>
        {
            typedef typename C::ValueCategory ValueCategory;
        };

    public:
        typedef typename DefaultArgTrait<T, hasTrait>::ValueCategory ValueCategory;
    };

}  // namespace TCLAP

#endif