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
|
/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef AAPT_BIG_BUFFER_H
#define AAPT_BIG_BUFFER_H
#include <cassert>
#include <cstring>
#include <memory>
#include <type_traits>
#include <vector>
namespace aapt {
/**
* Inspired by protobuf's ZeroCopyOutputStream, offers blocks of memory
* in which to write without knowing the full size of the entire payload.
* This is essentially a list of memory blocks. As one fills up, another
* block is allocated and appended to the end of the list.
*/
class BigBuffer {
public:
/**
* A contiguous block of allocated memory.
*/
struct Block {
/**
* Pointer to the memory.
*/
std::unique_ptr<uint8_t[]> buffer;
/**
* Size of memory that is currently occupied. The actual
* allocation may be larger.
*/
size_t size;
private:
friend class BigBuffer;
/**
* The size of the memory block allocation.
*/
size_t mBlockSize;
};
typedef std::vector<Block>::const_iterator const_iterator;
/**
* Create a BigBuffer with block allocation sizes
* of blockSize.
*/
BigBuffer(size_t blockSize);
BigBuffer(const BigBuffer&) = delete; // No copying.
BigBuffer(BigBuffer&& rhs);
/**
* Number of occupied bytes in all the allocated blocks.
*/
size_t size() const;
/**
* Returns a pointer to an array of T, where T is
* a POD type. The elements are zero-initialized.
*/
template <typename T>
T* nextBlock(size_t count = 1);
/**
* Moves the specified BigBuffer into this one. When this method
* returns, buffer is empty.
*/
void appendBuffer(BigBuffer&& buffer);
/**
* Pads the block with 'bytes' bytes of zero values.
*/
void pad(size_t bytes);
/**
* Pads the block so that it aligns on a 4 byte boundary.
*/
void align4();
const_iterator begin() const;
const_iterator end() const;
private:
/**
* Returns a pointer to a buffer of the requested size.
* The buffer is zero-initialized.
*/
void* nextBlockImpl(size_t size);
size_t mBlockSize;
size_t mSize;
std::vector<Block> mBlocks;
};
inline BigBuffer::BigBuffer(size_t blockSize) : mBlockSize(blockSize), mSize(0) {
}
inline BigBuffer::BigBuffer(BigBuffer&& rhs) :
mBlockSize(rhs.mBlockSize), mSize(rhs.mSize), mBlocks(std::move(rhs.mBlocks)) {
}
inline size_t BigBuffer::size() const {
return mSize;
}
template <typename T>
inline T* BigBuffer::nextBlock(size_t count) {
static_assert(std::is_standard_layout<T>::value, "T must be standard_layout type");
assert(count != 0);
return reinterpret_cast<T*>(nextBlockImpl(sizeof(T) * count));
}
inline void BigBuffer::appendBuffer(BigBuffer&& buffer) {
std::move(buffer.mBlocks.begin(), buffer.mBlocks.end(), std::back_inserter(mBlocks));
mSize += buffer.mSize;
buffer.mBlocks.clear();
buffer.mSize = 0;
}
inline void BigBuffer::pad(size_t bytes) {
nextBlock<char>(bytes);
}
inline void BigBuffer::align4() {
const size_t unaligned = mSize % 4;
if (unaligned != 0) {
pad(4 - unaligned);
}
}
inline BigBuffer::const_iterator BigBuffer::begin() const {
return mBlocks.begin();
}
inline BigBuffer::const_iterator BigBuffer::end() const {
return mBlocks.end();
}
} // namespace aapt
#endif // AAPT_BIG_BUFFER_H
|
