src/common/optional.h

/***************************************************************************
 *                                                                         *
 *   LinuxSampler - modular, streaming capable sampler                     *
 *                                                                         *
 *   Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck   *
 *   Copyright (C) 2005 - 2010 Christian Schoenebeck                       *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the Free Software           *
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston,                 *
 *   MA  02111-1307  USA                                                   *
 ***************************************************************************/

#ifndef __LS_OPTIONAL_H__
#define __LS_OPTIONAL_H__

#include "Exception.h"

namespace LinuxSampler {

    /**
     * Base class of template class optional, not meant to be instantiated
     * directly. It just provides the optional<T>::nothing member.
     */
    class optional_base {
        public:
            class nothing_t { public: nothing_t() {} };

            static const nothing_t nothing;
    };

    /**
     * This class can be used for any variable that might not have a value
     * set. E.g. as a return value type of a function, since in the case of
     * return values of functions it's often difficult to return a pointer
     * variable which might do the trick of an optional return value. It
     * behaves pretty much like a pointer though. That is, it can be checked
     * against NULL and the actual value can be dereferenced with the
     * typical C pointer dereference operators.
     */
    template<class T>
    class optional : public optional_base {
        public:
            optional() {
                initialized = false;
            }

            optional(T data) {
                this->data  = data;
                initialized = true;
            }

            optional(nothing_t) {
                initialized = false;
            }

            template <class T_inner>
            optional(T_inner data) {
                this->data  = T(data);
                initialized = true;
            }

            const T& get() const throw (Exception) {
                if (!initialized) throw Exception("optional variable not initialized");
                return data;
            }

            T& get() throw (Exception) {
                if (!initialized) throw Exception("optional variable not initialized");
                return data;
            }

            optional& operator =(const optional& arg) {
                this->data  = arg.data;
                initialized = arg.initialized;
                return *this;
            }

            optional& operator =(const T& arg) {
                this->data  = arg;
                initialized = true;
                return *this;
            }

            const T& operator *() const throw (Exception) { return get(); }
            T&       operator *()       throw (Exception) { return get(); }

            const T* operator ->() const throw (Exception) {
                if (!initialized) throw Exception("optional variable not initialized");
                return &data;
            }

            T* operator ->() throw (Exception) {
                if (!initialized) throw Exception("optional variable not initialized");
                return &data;
            }

            operator bool()   const { return initialized; }
            bool operator !() const { return !initialized; }

        protected:
            T    data;
            bool initialized;
    };

} // namespace LinuxSampler

#endif // __LS_OPTIONAL_H__
1	/***************************************************************************
2	* *
3	* LinuxSampler - modular, streaming capable sampler *
4	* *
5	* Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck *
6	* Copyright (C) 2005 - 2010 Christian Schoenebeck *
7	* *
8	* This program is free software; you can redistribute it and/or modify *
9	* it under the terms of the GNU General Public License as published by *
10	* the Free Software Foundation; either version 2 of the License, or *
11	* (at your option) any later version. *
12	* *
13	* This program is distributed in the hope that it will be useful, *
14	* but WITHOUT ANY WARRANTY; without even the implied warranty of *
15	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
16	* GNU General Public License for more details. *
17	* *
18	* You should have received a copy of the GNU General Public License *
19	* along with this program; if not, write to the Free Software *
20	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, *
21	* MA 02111-1307 USA *
22	***************************************************************************/
23
24	#ifndef __LS_OPTIONAL_H__
25	#define __LS_OPTIONAL_H__
26
27	#include "Exception.h"
28
29	namespace LinuxSampler {
30
31	/**
32	* Base class of template class optional, not meant to be instantiated
33	* directly. It just provides the optional<T>::nothing member.
34	*/
35	class optional_base {
36	public:
37	class nothing_t { public: nothing_t() {} };
38
39	static const nothing_t nothing;
40	};
41
42	/**
43	* This class can be used for any variable that might not have a value
44	* set. E.g. as a return value type of a function, since in the case of
45	* return values of functions it's often difficult to return a pointer
46	* variable which might do the trick of an optional return value. It
47	* behaves pretty much like a pointer though. That is, it can be checked
48	* against NULL and the actual value can be dereferenced with the
49	* typical C pointer dereference operators.
50	*/
51	template<class T>
52	class optional : public optional_base {
53	public:
54	optional() {
55	initialized = false;
56	}
57
58	optional(T data) {
59	this->data = data;
60	initialized = true;
61	}
62
63	optional(nothing_t) {
64	initialized = false;
65	}
66
67	template <class T_inner>
68	optional(T_inner data) {
69	this->data = T(data);
70	initialized = true;
71	}
72
73	const T& get() const throw (Exception) {
74	if (!initialized) throw Exception("optional variable not initialized");
75	return data;
76	}
77
78	T& get() throw (Exception) {
79	if (!initialized) throw Exception("optional variable not initialized");
80	return data;
81	}
82
83	optional& operator =(const optional& arg) {
84	this->data = arg.data;
85	initialized = arg.initialized;
86	return *this;
87	}
88
89	optional& operator =(const T& arg) {
90	this->data = arg;
91	initialized = true;
92	return *this;
93	}
94
95	const T& operator *() const throw (Exception) { return get(); }
96	T& operator *() throw (Exception) { return get(); }
97
98	const T* operator ->() const throw (Exception) {
99	if (!initialized) throw Exception("optional variable not initialized");
100	return &data;
101	}
102
103	T* operator ->() throw (Exception) {
104	if (!initialized) throw Exception("optional variable not initialized");
105	return &data;
106	}
107
108	operator bool() const { return initialized; }
109	bool operator !() const { return !initialized; }
110
111	protected:
112	T data;
113	bool initialized;
114	};
115
116	} // namespace LinuxSampler
117
118	#endif // __LS_OPTIONAL_H__