blob: a36a810f2795817545245d3706fc039fa14bab8c (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
|
/*
* This file is part of OpenTTD.
* 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.
* 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.
* 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/>.
*/
/** @file fixedsizearray.hpp A fixed size array that doesn't create items until needed. */
#ifndef FIXEDSIZEARRAY_HPP
#define FIXEDSIZEARRAY_HPP
#include "../core/alloc_func.hpp"
/**
* fixed size array
* Upon construction it preallocates fixed size block of memory
* for all items, but doesn't construct them. Item's construction
* is delayed.
*/
template <class T, uint C>
struct FixedSizeArray {
protected:
/** header for fixed size array */
struct ArrayHeader
{
uint items; ///< number of items in the array
uint reference_count; ///< block reference counter (used by copy constructor and by destructor)
};
/* make constants visible from outside */
static const uint Tsize = sizeof(T); ///< size of item
static const uint HeaderSize = sizeof(ArrayHeader); ///< size of header
/**
* the only member of fixed size array is pointer to the block
* of C array of items. Header can be found on the offset -sizeof(ArrayHeader).
*/
T *data;
/** return reference to the array header (non-const) */
inline ArrayHeader& Hdr()
{
return *(ArrayHeader*)(((byte*)data) - HeaderSize);
}
/** return reference to the array header (const) */
inline const ArrayHeader& Hdr() const
{
return *(ArrayHeader*)(((byte*)data) - HeaderSize);
}
/** return reference to the block reference counter */
inline uint& RefCnt()
{
return Hdr().reference_count;
}
/** return reference to number of used items */
inline uint& SizeRef()
{
return Hdr().items;
}
public:
/** Default constructor. Preallocate space for items and header, then initialize header. */
FixedSizeArray()
{
/* Ensure the size won't overflow. */
static_assert(C < (SIZE_MAX - HeaderSize) / Tsize);
/* allocate block for header + items (don't construct items) */
data = (T*)((MallocT<byte>(HeaderSize + C * Tsize)) + HeaderSize);
SizeRef() = 0; // initial number of items
RefCnt() = 1; // initial reference counter
}
/** Copy constructor. Preallocate space for items and header, then initialize header. */
FixedSizeArray(const FixedSizeArray<T, C> &src)
{
/* share block (header + items) with the source array */
data = src.data;
RefCnt()++; // now we share block with the source
}
/** destroy remaining items and free the memory block */
~FixedSizeArray()
{
/* release one reference to the shared block */
if ((--RefCnt()) > 0) return; // and return if there is still some owner
Clear();
/* free the memory block occupied by items */
free(((byte*)data) - HeaderSize);
data = nullptr;
}
/** Clear (destroy) all items */
inline void Clear()
{
/* Walk through all allocated items backward and destroy them
* Note: this->Length() can be zero. In that case data[this->Length() - 1] is evaluated unsigned
* on some compilers with some architectures. (e.g. gcc with x86) */
for (T *pItem = this->data + this->Length() - 1; pItem >= this->data; pItem--) {
pItem->~T();
}
/* number of items become zero */
SizeRef() = 0;
}
/** return number of used items */
inline uint Length() const
{
return Hdr().items;
}
/** return true if array is full */
inline bool IsFull() const
{
return Length() >= C;
}
/** return true if array is empty */
inline bool IsEmpty() const
{
return Length() <= 0;
}
/** add (allocate), but don't construct item */
inline T *Append()
{
assert(!IsFull());
return &data[SizeRef()++];
}
/** add and construct item using default constructor */
inline T *AppendC()
{
T *item = Append();
new(item)T;
return item;
}
/** return item by index (non-const version) */
inline T& operator[](uint index)
{
assert(index < Length());
return data[index];
}
/** return item by index (const version) */
inline const T& operator[](uint index) const
{
assert(index < Length());
return data[index];
}
};
#endif /* FIXEDSIZEARRAY_HPP */
|
