stack.h
1 // Tencent is pleased to support the open source community by making RapidJSON available.
2 //
3 // Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
4 //
5 // Licensed under the MIT License (the "License"); you may not use this file except
6 // in compliance with the License. You may obtain a copy of the License at
7 //
8 // http://opensource.org/licenses/MIT
9 //
10 // Unless required by applicable law or agreed to in writing, software distributed
11 // under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
12 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
13 // specific language governing permissions and limitations under the License.
14
15 #ifndef RAPIDJSON_INTERNAL_STACK_H_
16 #define RAPIDJSON_INTERNAL_STACK_H_
17
18 #include "../allocators.h"
19 #include "swap.h"
20
21 #if defined(__clang__)
22 RAPIDJSON_DIAG_PUSH
23 RAPIDJSON_DIAG_OFF(c++98-compat)
24 #endif
25
26 RAPIDJSON_NAMESPACE_BEGIN
27 namespace internal {
28
29 ///////////////////////////////////////////////////////////////////////////////
30 // Stack
31
32 //! A type-unsafe stack for storing different types of data.
33 /*! \tparam Allocator Allocator for allocating stack memory.
34 */
35 template <typename Allocator>
36 class Stack {
37 public:
38 // Optimization note: Do not allocate memory for stack_ in constructor.
39 // Do it lazily when first Push() -> Expand() -> Resize().
40 Stack(Allocator* allocator, size_t stackCapacity) : allocator_(allocator), ownAllocator_(0), stack_(0), stackTop_(0), stackEnd_(0), initialCapacity_(stackCapacity) {
41 }
42
43 #if RAPIDJSON_HAS_CXX11_RVALUE_REFS
44 Stack(Stack&& rhs)
45 : allocator_(rhs.allocator_),
46 ownAllocator_(rhs.ownAllocator_),
47 stack_(rhs.stack_),
48 stackTop_(rhs.stackTop_),
49 stackEnd_(rhs.stackEnd_),
50 initialCapacity_(rhs.initialCapacity_)
51 {
52 rhs.allocator_ = 0;
53 rhs.ownAllocator_ = 0;
54 rhs.stack_ = 0;
55 rhs.stackTop_ = 0;
56 rhs.stackEnd_ = 0;
57 rhs.initialCapacity_ = 0;
58 }
59 #endif
60
61 ~Stack() {
62 Destroy();
63 }
64
65 #if RAPIDJSON_HAS_CXX11_RVALUE_REFS
66 Stack& operator=(Stack&& rhs) {
67 if (&rhs != this)
68 {
69 Destroy();
70
71 allocator_ = rhs.allocator_;
72 ownAllocator_ = rhs.ownAllocator_;
73 stack_ = rhs.stack_;
74 stackTop_ = rhs.stackTop_;
75 stackEnd_ = rhs.stackEnd_;
76 initialCapacity_ = rhs.initialCapacity_;
77
78 rhs.allocator_ = 0;
79 rhs.ownAllocator_ = 0;
80 rhs.stack_ = 0;
81 rhs.stackTop_ = 0;
82 rhs.stackEnd_ = 0;
83 rhs.initialCapacity_ = 0;
84 }
85 return *this;
86 }
87 #endif
88
89 void Swap(Stack& rhs) RAPIDJSON_NOEXCEPT {
90 internal::Swap(allocator_, rhs.allocator_);
91 internal::Swap(ownAllocator_, rhs.ownAllocator_);
92 internal::Swap(stack_, rhs.stack_);
93 internal::Swap(stackTop_, rhs.stackTop_);
94 internal::Swap(stackEnd_, rhs.stackEnd_);
95 internal::Swap(initialCapacity_, rhs.initialCapacity_);
96 }
97
98 void Clear() { stackTop_ = stack_; }
99
100 void ShrinkToFit() {
101 if (Empty()) {
102 // If the stack is empty, completely deallocate the memory.
103 Allocator::Free(stack_);
104 stack_ = 0;
105 stackTop_ = 0;
106 stackEnd_ = 0;
107 }
108 else
109 Resize(GetSize());
110 }
111
112 // Optimization note: try to minimize the size of this function for force inline.
113 // Expansion is run very infrequently, so it is moved to another (probably non-inline) function.
114 template<typename T>
115 RAPIDJSON_FORCEINLINE void Reserve(size_t count = 1) {
116 // Expand the stack if needed
117 if (RAPIDJSON_UNLIKELY(stackTop_ + sizeof(T) * count > stackEnd_))
118 Expand<T>(count);
119 }
120
121 template<typename T>
122 RAPIDJSON_FORCEINLINE T* Push(size_t count = 1) {
123 Reserve<T>(count);
124 return PushUnsafe<T>(count);
125 }
126
127 template<typename T>
128 RAPIDJSON_FORCEINLINE T* PushUnsafe(size_t count = 1) {
129 RAPIDJSON_ASSERT(stackTop_ + sizeof(T) * count <= stackEnd_);
130 T* ret = reinterpret_cast<T*>(stackTop_);
131 stackTop_ += sizeof(T) * count;
132 return ret;
133 }
134
135 template<typename T>
136 T* Pop(size_t count) {
137 RAPIDJSON_ASSERT(GetSize() >= count * sizeof(T));
138 stackTop_ -= count * sizeof(T);
139 return reinterpret_cast<T*>(stackTop_);
140 }
141
142 template<typename T>
143 T* Top() {
144 RAPIDJSON_ASSERT(GetSize() >= sizeof(T));
145 return reinterpret_cast<T*>(stackTop_ - sizeof(T));
146 }
147
148 template<typename T>
149 const T* Top() const {
150 RAPIDJSON_ASSERT(GetSize() >= sizeof(T));
151 return reinterpret_cast<T*>(stackTop_ - sizeof(T));
152 }
153
154 template<typename T>
155 T* End() { return reinterpret_cast<T*>(stackTop_); }
156
157 template<typename T>
158 const T* End() const { return reinterpret_cast<T*>(stackTop_); }
159
160 template<typename T>
161 T* Bottom() { return reinterpret_cast<T*>(stack_); }
162
163 template<typename T>
164 const T* Bottom() const { return reinterpret_cast<T*>(stack_); }
165
166 bool HasAllocator() const {
167 return allocator_ != 0;
168 }
169
170 Allocator& GetAllocator() {
171 RAPIDJSON_ASSERT(allocator_);
172 return *allocator_;
173 }
174
175 bool Empty() const { return stackTop_ == stack_; }
176 size_t GetSize() const { return static_cast<size_t>(stackTop_ - stack_); }
177 size_t GetCapacity() const { return static_cast<size_t>(stackEnd_ - stack_); }
178
179 private:
180 template<typename T>
181 void Expand(size_t count) {
182 // Only expand the capacity if the current stack exists. Otherwise just create a stack with initial capacity.
183 size_t newCapacity;
184 if (stack_ == 0) {
185 if (!allocator_)
186 ownAllocator_ = allocator_ = RAPIDJSON_NEW(Allocator());
187 newCapacity = initialCapacity_;
188 } else {
189 newCapacity = GetCapacity();
190 newCapacity += (newCapacity + 1) / 2;
191 }
192 size_t newSize = GetSize() + sizeof(T) * count;
193 if (newCapacity < newSize)
194 newCapacity = newSize;
195
196 Resize(newCapacity);
197 }
198
199 void Resize(size_t newCapacity) {
200 const size_t size = GetSize(); // Backup the current size
201 stack_ = static_cast<char*>(allocator_->Realloc(stack_, GetCapacity(), newCapacity));
202 stackTop_ = stack_ + size;
203 stackEnd_ = stack_ + newCapacity;
204 }
205
206 void Destroy() {
207 Allocator::Free(stack_);
208 RAPIDJSON_DELETE(ownAllocator_); // Only delete if it is owned by the stack
209 }
210
211 // Prohibit copy constructor & assignment operator.
212 Stack(const Stack&);
213 Stack& operator=(const Stack&);
214
215 Allocator* allocator_;
216 Allocator* ownAllocator_;
217 char *stack_;
218 char *stackTop_;
219 char *stackEnd_;
220 size_t initialCapacity_;
221 };
222
223 } // namespace internal
224 RAPIDJSON_NAMESPACE_END
225
226 #if defined(__clang__)
227 RAPIDJSON_DIAG_POP
228 #endif
229
230 #endif // RAPIDJSON_STACK_H_
RAPIDJSON_NEW
#define RAPIDJSON_NEW(x)
! customization point for global new
Definition: rapidjson.h:586
RAPIDJSON_UNLIKELY
#define RAPIDJSON_UNLIKELY(x)
Compiler branching hint for expression with low probability to be true.
Definition: rapidjson.h:468
RAPIDJSON_DELETE
#define RAPIDJSON_DELETE(x)
! customization point for global delete
Definition: rapidjson.h:590
RAPIDJSON_ASSERT
#define RAPIDJSON_ASSERT(x)
Assertion.
Definition: rapidjson.h:402