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fixedsizearray.hpp
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1 /* $Id: fixedsizearray.hpp 27363 2015-08-08 13:19:38Z alberth $ */
2
3 /*
4 * This file is part of OpenTTD.
5 * OpenTTD 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, version 2.
6 * OpenTTD 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.
7 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
8 */
9
12 #ifndef FIXEDSIZEARRAY_HPP
13 #define FIXEDSIZEARRAY_HPP
14
15 #include "../core/alloc_func.hpp"
16
23 template <class T, uint C>
24 struct FixedSizeArray {
25 protected:
27 struct ArrayHeader
28 {
29 uint items;
30 uint reference_count;
31 };
32
33 /* make constants visible from outside */
34 static const uint Tsize = sizeof(T);
35 static const uint HeaderSize = sizeof(ArrayHeader);
36
41 T *data;
42
44 inline ArrayHeader& Hdr()
45 {
46 return *(ArrayHeader*)(((byte*)data) - HeaderSize);
47 }
48
50 inline const ArrayHeader& Hdr() const
51 {
52 return *(ArrayHeader*)(((byte*)data) - HeaderSize);
53 }
54
56 inline uint& RefCnt()
57 {
58 return Hdr().reference_count;
59 }
60
62 inline uint& SizeRef()
63 {
64 return Hdr().items;
65 }
66
67 public:
69 FixedSizeArray()
70 {
71 /* Ensure the size won't overflow. */
72 assert_compile(C < (SIZE_MAX - HeaderSize) / Tsize);
73
74 /* allocate block for header + items (don't construct items) */
75 data = (T*)((MallocT<byte>(HeaderSize + C * Tsize)) + HeaderSize);
76 SizeRef() = 0; // initial number of items
77 RefCnt() = 1; // initial reference counter
78 }
79
81 FixedSizeArray(const FixedSizeArray<T, C> &src)
82 {
83 /* share block (header + items) with the source array */
84 data = src.data;
85 RefCnt()++; // now we share block with the source
86 }
87
89 ~FixedSizeArray()
90 {
91 /* release one reference to the shared block */
92 if ((--RefCnt()) > 0) return; // and return if there is still some owner
93
94 Clear();
95 /* free the memory block occupied by items */
96 free(((byte*)data) - HeaderSize);
97 data = NULL;
98 }
99
101 inline void Clear()
102 {
103 /* Walk through all allocated items backward and destroy them
104 * Note: this->Length() can be zero. In that case data[this->Length() - 1] is evaluated unsigned
105 * on some compilers with some architectures. (e.g. gcc with x86) */
106 for (T *pItem = this->data + this->Length() - 1; pItem >= this->data; pItem--) {
107 pItem->~T();
108 }
109 /* number of items become zero */
110 SizeRef() = 0;
111 }
112
114 inline uint Length() const
115 {
116 return Hdr().items;
117 }
118
120 inline bool IsFull() const
121 {
122 return Length() >= C;
123 }
124
126 inline bool IsEmpty() const
127 {
128 return Length() <= 0;
129 }
130
132 inline T *Append()
133 {
134 assert(!IsFull());
135 return &data[SizeRef()++];
136 }
137
139 inline T *AppendC()
140 {
141 T *item = Append();
142 new(item)T;
143 return item;
144 }
146 inline T& operator[](uint index)
147 {
148 assert(index < Length());
149 return data[index];
150 }
151
153 inline const T& operator[](uint index) const
154 {
155 assert(index < Length());
156 return data[index];
157 }
158 };
159
160 #endif /* FIXEDSIZEARRAY_HPP */