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
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
|
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef MOZILLA_GFX_ITERABLEARENA_H_
#define MOZILLA_GFX_ITERABLEARENA_H_
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <utility>
#include <vector>
#include "mozilla/Assertions.h"
#include "mozilla/gfx/Logging.h"
namespace mozilla {
namespace gfx {
/// A simple pool allocator for plain data structures.
///
/// Beware that the pool will not attempt to run the destructors. It is the
/// responsibility of the user of this class to either use objects with no
/// destructor or to manually call the allocated objects destructors.
/// If the pool is growable, its allocated objects must be safely moveable in
/// in memory (through memcpy).
class IterableArena {
protected:
struct Header {
size_t mBlocSize;
};
public:
enum ArenaType { FIXED_SIZE, GROWABLE };
IterableArena(ArenaType aType, size_t aStorageSize)
: mSize(aStorageSize), mCursor(0), mIsGrowable(aType == GROWABLE) {
if (mSize == 0) {
mSize = 128;
}
mStorage = (uint8_t*)malloc(mSize);
if (mStorage == nullptr) {
gfxCriticalError() << "Not enough Memory allocate a memory pool of size "
<< aStorageSize;
MOZ_CRASH("GFX: Out of memory IterableArena");
}
}
~IterableArena() { free(mStorage); }
/// Constructs a new item in the pool and returns a positive offset in case of
/// success.
///
/// The offset never changes even if the storage is reallocated, so users
/// of this class should prefer storing offsets rather than direct pointers
/// to the allocated objects.
/// Alloc can cause the storage to be reallocated if the pool was initialized
/// with IterableArena::GROWABLE.
/// If for any reason the pool fails to allocate enough space for the new item
/// Alloc returns a negative offset and the object's constructor is not
/// called.
template <typename T, typename... Args>
ptrdiff_t Alloc(Args&&... aArgs) {
void* storage = nullptr;
auto offset = AllocRaw(sizeof(T), &storage);
if (offset < 0) {
return offset;
}
new (storage) T(std::forward<Args>(aArgs)...);
return offset;
}
ptrdiff_t AllocRaw(size_t aSize, void** aOutPtr = nullptr) {
const size_t blocSize = AlignedSize(sizeof(Header) + aSize);
if (AlignedSize(mCursor + blocSize) > mSize) {
if (!mIsGrowable) {
return -1;
}
size_t newSize = mSize * 2;
while (AlignedSize(mCursor + blocSize) > newSize) {
newSize *= 2;
}
uint8_t* newStorage = (uint8_t*)realloc(mStorage, newSize);
if (!newStorage) {
gfxCriticalError()
<< "Not enough Memory to grow the memory pool, size: " << newSize;
return -1;
}
mStorage = newStorage;
mSize = newSize;
}
ptrdiff_t offset = mCursor;
GetHeader(offset)->mBlocSize = blocSize;
mCursor += blocSize;
if (aOutPtr) {
*aOutPtr = GetStorage(offset);
}
return offset;
}
/// Get access to an allocated item at a given offset (only use offsets
/// returned by Alloc or AllocRaw).
///
/// If the pool is growable, the returned pointer is only valid temporarily.
/// The underlying storage can be reallocated in Alloc or AllocRaw, so do not
/// keep these pointers around and store the offset instead.
void* GetStorage(ptrdiff_t offset = 0) {
MOZ_ASSERT(offset >= 0);
MOZ_ASSERT(offset < mCursor);
return offset >= 0 ? mStorage + offset + sizeof(Header) : nullptr;
}
/// Clears the storage without running any destructor and without deallocating
/// it.
void Clear() { mCursor = 0; }
/// Iterate over the elements allocated in this pool.
///
/// Takes a lambda or function object accepting a void* as parameter.
template <typename Func>
void ForEach(Func cb) {
Iterator it;
while (void* ptr = it.Next(this)) {
cb(ptr);
}
}
/// A simple iterator over an arena.
class Iterator {
public:
Iterator() : mCursor(0) {}
void* Next(IterableArena* aArena) {
if (mCursor >= aArena->mCursor) {
return nullptr;
}
void* result = aArena->GetStorage(mCursor);
const size_t blocSize = aArena->GetHeader(mCursor)->mBlocSize;
MOZ_ASSERT(blocSize != 0);
mCursor += blocSize;
return result;
}
private:
ptrdiff_t mCursor;
};
protected:
Header* GetHeader(ptrdiff_t offset) { return (Header*)(mStorage + offset); }
size_t AlignedSize(size_t aSize) const {
const size_t alignment = sizeof(uintptr_t);
return aSize + (alignment - (aSize % alignment)) % alignment;
}
uint8_t* mStorage;
uint32_t mSize;
ptrdiff_t mCursor;
bool mIsGrowable;
friend class Iterator;
};
} // namespace gfx
} // namespace mozilla
#endif
|
