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allocation.h
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1 // Copyright 2013 The Flutter Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #ifndef FLUTTER_IMPELLER_BASE_ALLOCATION_H_
6 #define FLUTTER_IMPELLER_BASE_ALLOCATION_H_
7
8 #include <cstdint>
9 #include <memory>
10
11 #include "flutter/fml/mapping.h"
12 #include "impeller/base/allocation_size.h"
13
14 namespace impeller {
15
16 //------------------------------------------------------------------------------
17 /// @brief Describes an allocation on the heap.
18 ///
19 /// Managing allocations through this utility makes it harder to
20 /// miss allocation failures.
21 ///
22 class Allocation {
23 public:
24 //----------------------------------------------------------------------------
25 /// @brief Constructs a new zero-sized allocation.
26 ///
27 Allocation();
28
29 //----------------------------------------------------------------------------
30 /// @brief Destroys the allocation.
31 ///
32 ~Allocation();
33
34 //----------------------------------------------------------------------------
35 /// @brief Gets the pointer to the start of the allocation.
36 ///
37 /// This pointer is only valid till the next call to `Truncate`.
38 ///
39 /// @return The pointer to the start of the allocation.
40 ///
41 uint8_t* GetBuffer() const;
42
43 //----------------------------------------------------------------------------
44 /// @brief Gets the length of the allocation.
45 ///
46 /// @return The length.
47 ///
48 Bytes GetLength() const;
49
50 //----------------------------------------------------------------------------
51 /// @brief Gets the reserved length of the allocation. Calls to truncate
52 /// may be ignored till the length exceeds the reserved length.
53 ///
54 /// @return The reserved length.
55 ///
56 Bytes GetReservedLength() const;
57
58 //----------------------------------------------------------------------------
59 /// @brief Resize the underlying allocation to at least given number of
60 /// bytes.
61 ///
62 /// In case of failure, false is returned and the underlying
63 /// allocation remains unchanged.
64 ///
65 /// @warning Pointers to buffers obtained via previous calls to `GetBuffer`
66 /// may become invalid at this point.
67 ///
68 /// @param[in] length The length.
69 /// @param[in] npot Whether to round up the length to the next power of
70 /// two.
71 ///
72 /// @return If the underlying allocation was resized to the new size.
73 ///
74 [[nodiscard]] bool Truncate(Bytes length, bool npot = true);
75
76 //----------------------------------------------------------------------------
77 /// @brief Gets the next power of two size.
78 ///
79 /// @param[in] x The size.
80 ///
81 /// @return The next power of two of x.
82 ///
83 static uint32_t NextPowerOfTwoSize(uint32_t x);
84
85 private:
86 uint8_t* buffer_ = nullptr;
87 Bytes length_;
88 Bytes reserved_;
89
90 [[nodiscard]] bool Reserve(Bytes reserved);
91
92 [[nodiscard]] bool ReserveNPOT(Bytes reserved);
93
94 Allocation(const Allocation&) = delete;
95
96 Allocation& operator=(const Allocation&) = delete;
97 };
98
99 //------------------------------------------------------------------------------
100 /// @brief Creates a mapping with copy of the bytes.
101 ///
102 /// @param[in] contents The contents
103 /// @param[in] length The length
104 ///
105 /// @return The new mapping or nullptr if the copy could not be performed.
106 ///
107 std::shared_ptr<fml::Mapping> CreateMappingWithCopy(const uint8_t* contents,
108 Bytes length);
109
110 //------------------------------------------------------------------------------
111 /// @brief Creates a mapping from allocation.
112 ///
113 /// No data copy occurs. Only a reference to the underlying
114 /// allocation is bumped up.
115 ///
116 /// Changes to the underlying allocation will not be reflected in
117 /// the mapping and must not change.
118 ///
119 /// @param[in] allocation The allocation.
120 ///
121 /// @return A new mapping or nullptr if the argument allocation was invalid.
122 ///
123 std::shared_ptr<fml::Mapping> CreateMappingFromAllocation(
124 const std::shared_ptr<Allocation>& allocation);
125
126 //------------------------------------------------------------------------------
127 /// @brief Creates a mapping with string data.
128 ///
129 /// Only a reference to the underlying string is bumped up and the
130 /// string is not copied.
131 ///
132 /// @param[in] string The string
133 ///
134 /// @return A new mapping or nullptr in case of allocation failures.
135 ///
136 std::shared_ptr<fml::Mapping> CreateMappingWithString(
137 std::shared_ptr<const std::string> string);
138
139 //------------------------------------------------------------------------------
140 /// @brief Creates a mapping with string data.
141 ///
142 /// The string is copied.
143 ///
144 /// @param[in] string The string
145 ///
146 /// @return A new mapping or nullptr in case of allocation failures.
147 ///
148 std::shared_ptr<fml::Mapping> CreateMappingWithString(std::string string);
149
150 } // namespace impeller
151
152 #endif // FLUTTER_IMPELLER_BASE_ALLOCATION_H_
impeller::Allocation::~Allocation
~Allocation()
Destroys the allocation.
Definition: allocation.cc:16
impeller::Allocation::NextPowerOfTwoSize
static uint32_t NextPowerOfTwoSize(uint32_t x)
Gets the next power of two size.
Definition: allocation.cc:41
impeller::CreateMappingFromAllocation
std::shared_ptr< fml::Mapping > CreateMappingFromAllocation(const std::shared_ptr< Allocation > &allocation)
Creates a mapping from allocation.
Definition: allocation.cc:99
impeller::Allocation::Truncate
bool Truncate(Bytes length, bool npot=true)
Resize the underlying allocation to at least given number of bytes.
Definition: allocation.cc:32
impeller::Allocation::Allocation
Allocation()
Constructs a new zero-sized allocation.
impeller::AllocationSize< 1u >
impeller::Allocation::GetBuffer
uint8_t * GetBuffer() const
Gets the pointer to the start of the allocation.
Definition: allocation.cc:20
impeller::Allocation
Describes an allocation on the heap.
Definition: allocation.h:22
impeller::CreateMappingWithCopy
std::shared_ptr< fml::Mapping > CreateMappingWithCopy(const uint8_t *contents, Bytes length)
Creates a mapping with copy of the bytes.
Definition: allocation.cc:83
impeller::CreateMappingWithString
std::shared_ptr< fml::Mapping > CreateMappingWithString(std::string string)
Creates a mapping with string data.
Definition: allocation.cc:111
allocation_size.h
impeller::Allocation::GetReservedLength
Bytes GetReservedLength() const
Gets the reserved length of the allocation. Calls to truncate may be ignored till the length exceeds ...
Definition: allocation.cc:28
impeller::Allocation::GetLength
Bytes GetLength() const
Gets the length of the allocation.
Definition: allocation.cc:24
impeller
Definition: allocation.cc:12