Gamedev Framework (gf)  0.3.0
A C++11 framework for 2D games
Id.h
1 /*
2  * Gamedev Framework (gf)
3  * Copyright (C) 2016 Julien Bernard
4  *
5  * This software is provided 'as-is', without any express or implied
6  * warranty. In no event will the authors be held liable for any damages
7  * arising from the use of this software.
8  *
9  * Permission is granted to anyone to use this software for any purpose,
10  * including commercial applications, and to alter it and redistribute it
11  * freely, subject to the following restrictions:
12  *
13  * 1. The origin of this software must not be misrepresented; you must not
14  * claim that you wrote the original software. If you use this software
15  * in a product, an acknowledgment in the product documentation would be
16  * appreciated but is not required.
17  * 2. Altered source versions must be plainly marked as such, and must not be
18  * misrepresented as being the original software.
19  * 3. This notice may not be removed or altered from any source distribution.
20  */
21 #ifndef GF_ID_H
22 #define GF_ID_H
23 
24 #include <cstdint>
25 #include <string>
26 
27 #include "Portability.h"
28 
29 namespace gf {
30 #ifndef DOXYGEN_SHOULD_SKIP_THIS
31 inline namespace v1 {
32 #endif
33 
34  /**
35  * @ingroup core
36  * @brief An identifier
37  */
38  using Id = uint64_t;
39 
40  /**
41  * @ingroup core
42  * @brief The invalid id (which is 0)
43  */
44  constexpr Id InvalidId = 0;
45 
46  /**
47  * @ingroup core
48  * @brief Get an identifier from a string
49  *
50  * The hash is a Fowler–Noll–Vo 1a hash. This function is mainly for
51  * internal use. You should instead use the user-defined literal `_id`.
52  *
53  * Example:
54  *
55  * ~~~{.cc}
56  * gf::Id id = "A string"_id; // computed at compile time
57  * ~~~
58  *
59  * @param str The string
60  * @param sz The size of the string
61  */
62  constexpr Id hash(const char *str, std::size_t sz) {
63  return sz == 0 ? 0xcbf29ce484222325 : (str[sz - 1] ^ hash(str, sz - 1)) * 0x100000001b3;
64  }
65 
66  /**
67  * @ingroup core
68  * @brief Get an idenfitier from a string
69  *
70  * The hash is a Fowler–Noll–Vo 1a hash. This function can be used
71  * for computing an id at runtime. For computing an id from a string
72  * at compile time, you should use the the user-defined literal `_id`.
73  */
74  inline Id hash(const std::string& str) {
75  return hash(str.c_str(), str.size());
76  }
77 
78  namespace literals {
79 
80  /**
81  * @brief User defined operator for creating compile time ids from strings
82  *
83  * To use it, you have to use the `gf::literals` namespace:
84  *
85  * ~~~{.cc}
86  * using namespace gf::literals;
87  *
88  * Id id = "FooBar"_id;
89  * ~~~
90  *
91  */
92  constexpr gf::Id operator"" _id(const char *str, std::size_t sz) {
93  return gf::hash(str, sz);
94  }
95 
96  }
97 
98 #ifndef DOXYGEN_SHOULD_SKIP_THIS
99 }
100 #endif
101 }
102 
103 #endif // GF_ID_H
Id hash(const std::string &str)
Get an idenfitier from a string.
Definition: Id.h:74
Definition: Id.h:78
constexpr Id hash(const char *str, std::size_t sz)
Get an identifier from a string.
Definition: Id.h:62
constexpr gf::Id operator""_id(const char *str, std::size_t sz)
User defined operator for creating compile time ids from strings.
Definition: Id.h:92
Definition: Action.h:34
constexpr Id InvalidId
The invalid id (which is 0)
Definition: Id.h:44