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1 /*
2  * Copyright 2015, The Android Open Source Project
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *  * Redistributions of source code must retain the above copyright
8  *    notice, this list of conditions and the following disclaimer.
9  *  * Redistributions in binary form must reproduce the above copyright
10  *    notice, this list of conditions and the following disclaimer in the
11  *    documentation and/or other materials provided with the distribution.
12  *
13  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24  */
25 
26 #ifndef ANDROID_FAT_VECTOR_H
27 #define ANDROID_FAT_VECTOR_H
28 
29 #include "utils/Macros.h"
30 
31 #include <stddef.h>
32 #include <stdlib.h>
33 #include <type_traits>
34 #include <utils/Log.h>
35 
36 #include <vector>
37 
38 namespace android {
39 namespace uirenderer {
40 
41 template <typename T, size_t SIZE>
42 class InlineStdAllocator {
43 public:
44     struct Allocation {
45         PREVENT_COPY_AND_ASSIGN(Allocation);
46     public:
AllocationAllocation47         Allocation() {};
48         // char array instead of T array, so memory is uninitialized, with no destructors run
49         char array[sizeof(T) * SIZE];
50         bool inUse = false;
51     };
52 
53     typedef T value_type; // needed to implement std::allocator
54     typedef T* pointer; // needed to implement std::allocator
55 
InlineStdAllocator(Allocation & allocation)56     explicit InlineStdAllocator(Allocation& allocation)
57             : mAllocation(allocation) {}
InlineStdAllocator(const InlineStdAllocator & other)58     InlineStdAllocator(const InlineStdAllocator& other)
59             : mAllocation(other.mAllocation) {}
~InlineStdAllocator()60     ~InlineStdAllocator() {}
61 
62     T* allocate(size_t num, const void* = 0) {
63         if (!mAllocation.inUse && num <= SIZE) {
64             mAllocation.inUse = true;
65             return (T*) mAllocation.array;
66         } else {
67             return (T*) malloc(num * sizeof(T));
68         }
69     }
70 
deallocate(pointer p,size_t num)71     void deallocate(pointer p, size_t num) {
72         if (p == (T*)mAllocation.array) {
73             mAllocation.inUse = false;
74         } else {
75             // 'free' instead of delete here - destruction handled separately
76             free(p);
77         }
78     }
79     Allocation& mAllocation;
80 };
81 
82 /**
83  * std::vector with SIZE elements preallocated into an internal buffer.
84  *
85  * Useful for avoiding the cost of malloc in cases where only SIZE or
86  * fewer elements are needed in the common case.
87  */
88 template <typename T, size_t SIZE>
89 class FatVector : public std::vector<T, InlineStdAllocator<T, SIZE>> {
90 public:
FatVector()91     FatVector() : std::vector<T, InlineStdAllocator<T, SIZE>>(
92             InlineStdAllocator<T, SIZE>(mAllocation)) {
93         this->reserve(SIZE);
94     }
95 
FatVector(size_t capacity)96     explicit FatVector(size_t capacity) : FatVector() {
97         this->resize(capacity);
98     }
99 
100 private:
101     typename InlineStdAllocator<T, SIZE>::Allocation mAllocation;
102 };
103 
104 }; // namespace uirenderer
105 }; // namespace android
106 
107 #endif // ANDROID_FAT_VECTOR_H
108