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| 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_ALLOCATORS_H_ |
| 16 | +#define RAPIDJSON_ALLOCATORS_H_ |
| 17 | + |
| 18 | +#include "rapidjson.h" |
| 19 | + |
| 20 | +RAPIDJSON_NAMESPACE_BEGIN |
| 21 | + |
| 22 | +/////////////////////////////////////////////////////////////////////////////// |
| 23 | +// Allocator |
| 24 | + |
| 25 | +/*! \class rapidjson::Allocator |
| 26 | + \brief Concept for allocating, resizing and freeing memory block. |
| 27 | + |
| 28 | + Note that Malloc() and Realloc() are non-static but Free() is static. |
| 29 | + |
| 30 | + So if an allocator need to support Free(), it needs to put its pointer in |
| 31 | + the header of memory block. |
| 32 | +
|
| 33 | +\code |
| 34 | +concept Allocator { |
| 35 | + static const bool kNeedFree; //!< Whether this allocator needs to call Free(). |
| 36 | +
|
| 37 | + // Allocate a memory block. |
| 38 | + // \param size of the memory block in bytes. |
| 39 | + // \returns pointer to the memory block. |
| 40 | + void* Malloc(size_t size); |
| 41 | +
|
| 42 | + // Resize a memory block. |
| 43 | + // \param originalPtr The pointer to current memory block. Null pointer is permitted. |
| 44 | + // \param originalSize The current size in bytes. (Design issue: since some allocator may not book-keep this, explicitly pass to it can save memory.) |
| 45 | + // \param newSize the new size in bytes. |
| 46 | + void* Realloc(void* originalPtr, size_t originalSize, size_t newSize); |
| 47 | +
|
| 48 | + // Free a memory block. |
| 49 | + // \param pointer to the memory block. Null pointer is permitted. |
| 50 | + static void Free(void *ptr); |
| 51 | +}; |
| 52 | +\endcode |
| 53 | +*/ |
| 54 | + |
| 55 | +/////////////////////////////////////////////////////////////////////////////// |
| 56 | +// CrtAllocator |
| 57 | + |
| 58 | +//! C-runtime library allocator. |
| 59 | +/*! This class is just wrapper for standard C library memory routines. |
| 60 | + \note implements Allocator concept |
| 61 | +*/ |
| 62 | +class CrtAllocator { |
| 63 | +public: |
| 64 | + static const bool kNeedFree = true; |
| 65 | + void* Malloc(size_t size) { |
| 66 | + if (size) // behavior of malloc(0) is implementation defined. |
| 67 | + return std::malloc(size); |
| 68 | + else |
| 69 | + return NULL; // standardize to returning NULL. |
| 70 | + } |
| 71 | + void* Realloc(void* originalPtr, size_t originalSize, size_t newSize) { |
| 72 | + (void)originalSize; |
| 73 | + if (newSize == 0) { |
| 74 | + std::free(originalPtr); |
| 75 | + return NULL; |
| 76 | + } |
| 77 | + return std::realloc(originalPtr, newSize); |
| 78 | + } |
| 79 | + static void Free(void *ptr) { std::free(ptr); } |
| 80 | +}; |
| 81 | + |
| 82 | +/////////////////////////////////////////////////////////////////////////////// |
| 83 | +// MemoryPoolAllocator |
| 84 | + |
| 85 | +//! Default memory allocator used by the parser and DOM. |
| 86 | +/*! This allocator allocate memory blocks from pre-allocated memory chunks. |
| 87 | +
|
| 88 | + It does not free memory blocks. And Realloc() only allocate new memory. |
| 89 | +
|
| 90 | + The memory chunks are allocated by BaseAllocator, which is CrtAllocator by default. |
| 91 | +
|
| 92 | + User may also supply a buffer as the first chunk. |
| 93 | +
|
| 94 | + If the user-buffer is full then additional chunks are allocated by BaseAllocator. |
| 95 | +
|
| 96 | + The user-buffer is not deallocated by this allocator. |
| 97 | +
|
| 98 | + \tparam BaseAllocator the allocator type for allocating memory chunks. Default is CrtAllocator. |
| 99 | + \note implements Allocator concept |
| 100 | +*/ |
| 101 | +template <typename BaseAllocator = CrtAllocator> |
| 102 | +class MemoryPoolAllocator { |
| 103 | +public: |
| 104 | + static const bool kNeedFree = false; //!< Tell users that no need to call Free() with this allocator. (concept Allocator) |
| 105 | + |
| 106 | + //! Constructor with chunkSize. |
| 107 | + /*! \param chunkSize The size of memory chunk. The default is kDefaultChunkSize. |
| 108 | + \param baseAllocator The allocator for allocating memory chunks. |
| 109 | + */ |
| 110 | + MemoryPoolAllocator(size_t chunkSize = kDefaultChunkCapacity, BaseAllocator* baseAllocator = 0) : |
| 111 | + chunkHead_(0), chunk_capacity_(chunkSize), userBuffer_(0), baseAllocator_(baseAllocator), ownBaseAllocator_(0) |
| 112 | + { |
| 113 | + } |
| 114 | + |
| 115 | + //! Constructor with user-supplied buffer. |
| 116 | + /*! The user buffer will be used firstly. When it is full, memory pool allocates new chunk with chunk size. |
| 117 | +
|
| 118 | + The user buffer will not be deallocated when this allocator is destructed. |
| 119 | +
|
| 120 | + \param buffer User supplied buffer. |
| 121 | + \param size Size of the buffer in bytes. It must at least larger than sizeof(ChunkHeader). |
| 122 | + \param chunkSize The size of memory chunk. The default is kDefaultChunkSize. |
| 123 | + \param baseAllocator The allocator for allocating memory chunks. |
| 124 | + */ |
| 125 | + MemoryPoolAllocator(void *buffer, size_t size, size_t chunkSize = kDefaultChunkCapacity, BaseAllocator* baseAllocator = 0) : |
| 126 | + chunkHead_(0), chunk_capacity_(chunkSize), userBuffer_(buffer), baseAllocator_(baseAllocator), ownBaseAllocator_(0) |
| 127 | + { |
| 128 | + RAPIDJSON_ASSERT(buffer != 0); |
| 129 | + RAPIDJSON_ASSERT(size > sizeof(ChunkHeader)); |
| 130 | + chunkHead_ = reinterpret_cast<ChunkHeader*>(buffer); |
| 131 | + chunkHead_->capacity = size - sizeof(ChunkHeader); |
| 132 | + chunkHead_->size = 0; |
| 133 | + chunkHead_->next = 0; |
| 134 | + } |
| 135 | + |
| 136 | + //! Destructor. |
| 137 | + /*! This deallocates all memory chunks, excluding the user-supplied buffer. |
| 138 | + */ |
| 139 | + ~MemoryPoolAllocator() { |
| 140 | + Clear(); |
| 141 | + RAPIDJSON_DELETE(ownBaseAllocator_); |
| 142 | + } |
| 143 | + |
| 144 | + //! Deallocates all memory chunks, excluding the user-supplied buffer. |
| 145 | + void Clear() { |
| 146 | + while (chunkHead_ && chunkHead_ != userBuffer_) { |
| 147 | + ChunkHeader* next = chunkHead_->next; |
| 148 | + baseAllocator_->Free(chunkHead_); |
| 149 | + chunkHead_ = next; |
| 150 | + } |
| 151 | + if (chunkHead_ && chunkHead_ == userBuffer_) |
| 152 | + chunkHead_->size = 0; // Clear user buffer |
| 153 | + } |
| 154 | + |
| 155 | + //! Computes the total capacity of allocated memory chunks. |
| 156 | + /*! \return total capacity in bytes. |
| 157 | + */ |
| 158 | + size_t Capacity() const { |
| 159 | + size_t capacity = 0; |
| 160 | + for (ChunkHeader* c = chunkHead_; c != 0; c = c->next) |
| 161 | + capacity += c->capacity; |
| 162 | + return capacity; |
| 163 | + } |
| 164 | + |
| 165 | + //! Computes the memory blocks allocated. |
| 166 | + /*! \return total used bytes. |
| 167 | + */ |
| 168 | + size_t Size() const { |
| 169 | + size_t size = 0; |
| 170 | + for (ChunkHeader* c = chunkHead_; c != 0; c = c->next) |
| 171 | + size += c->size; |
| 172 | + return size; |
| 173 | + } |
| 174 | + |
| 175 | + //! Allocates a memory block. (concept Allocator) |
| 176 | + void* Malloc(size_t size) { |
| 177 | + if (!size) |
| 178 | + return NULL; |
| 179 | + |
| 180 | + size = RAPIDJSON_ALIGN(size); |
| 181 | + if (chunkHead_ == 0 || chunkHead_->size + size > chunkHead_->capacity) |
| 182 | + if (!AddChunk(chunk_capacity_ > size ? chunk_capacity_ : size)) |
| 183 | + return NULL; |
| 184 | + |
| 185 | + void *buffer = reinterpret_cast<char *>(chunkHead_) + RAPIDJSON_ALIGN(sizeof(ChunkHeader)) + chunkHead_->size; |
| 186 | + chunkHead_->size += size; |
| 187 | + return buffer; |
| 188 | + } |
| 189 | + |
| 190 | + //! Resizes a memory block (concept Allocator) |
| 191 | + void* Realloc(void* originalPtr, size_t originalSize, size_t newSize) { |
| 192 | + if (originalPtr == 0) |
| 193 | + return Malloc(newSize); |
| 194 | + |
| 195 | + if (newSize == 0) |
| 196 | + return NULL; |
| 197 | + |
| 198 | + originalSize = RAPIDJSON_ALIGN(originalSize); |
| 199 | + newSize = RAPIDJSON_ALIGN(newSize); |
| 200 | + |
| 201 | + // Do not shrink if new size is smaller than original |
| 202 | + if (originalSize >= newSize) |
| 203 | + return originalPtr; |
| 204 | + |
| 205 | + // Simply expand it if it is the last allocation and there is sufficient space |
| 206 | + if (originalPtr == reinterpret_cast<char *>(chunkHead_) + RAPIDJSON_ALIGN(sizeof(ChunkHeader)) + chunkHead_->size - originalSize) { |
| 207 | + size_t increment = static_cast<size_t>(newSize - originalSize); |
| 208 | + if (chunkHead_->size + increment <= chunkHead_->capacity) { |
| 209 | + chunkHead_->size += increment; |
| 210 | + return originalPtr; |
| 211 | + } |
| 212 | + } |
| 213 | + |
| 214 | + // Realloc process: allocate and copy memory, do not free original buffer. |
| 215 | + if (void* newBuffer = Malloc(newSize)) { |
| 216 | + if (originalSize) |
| 217 | + std::memcpy(newBuffer, originalPtr, originalSize); |
| 218 | + return newBuffer; |
| 219 | + } |
| 220 | + else |
| 221 | + return NULL; |
| 222 | + } |
| 223 | + |
| 224 | + //! Frees a memory block (concept Allocator) |
| 225 | + static void Free(void *ptr) { (void)ptr; } // Do nothing |
| 226 | + |
| 227 | +private: |
| 228 | + //! Copy constructor is not permitted. |
| 229 | + MemoryPoolAllocator(const MemoryPoolAllocator& rhs) /* = delete */; |
| 230 | + //! Copy assignment operator is not permitted. |
| 231 | + MemoryPoolAllocator& operator=(const MemoryPoolAllocator& rhs) /* = delete */; |
| 232 | + |
| 233 | + //! Creates a new chunk. |
| 234 | + /*! \param capacity Capacity of the chunk in bytes. |
| 235 | + \return true if success. |
| 236 | + */ |
| 237 | + bool AddChunk(size_t capacity) { |
| 238 | + if (!baseAllocator_) |
| 239 | + ownBaseAllocator_ = baseAllocator_ = RAPIDJSON_NEW(BaseAllocator)(); |
| 240 | + if (ChunkHeader* chunk = reinterpret_cast<ChunkHeader*>(baseAllocator_->Malloc(RAPIDJSON_ALIGN(sizeof(ChunkHeader)) + capacity))) { |
| 241 | + chunk->capacity = capacity; |
| 242 | + chunk->size = 0; |
| 243 | + chunk->next = chunkHead_; |
| 244 | + chunkHead_ = chunk; |
| 245 | + return true; |
| 246 | + } |
| 247 | + else |
| 248 | + return false; |
| 249 | + } |
| 250 | + |
| 251 | + static const int kDefaultChunkCapacity = 64 * 1024; //!< Default chunk capacity. |
| 252 | + |
| 253 | + //! Chunk header for perpending to each chunk. |
| 254 | + /*! Chunks are stored as a singly linked list. |
| 255 | + */ |
| 256 | + struct ChunkHeader { |
| 257 | + size_t capacity; //!< Capacity of the chunk in bytes (excluding the header itself). |
| 258 | + size_t size; //!< Current size of allocated memory in bytes. |
| 259 | + ChunkHeader *next; //!< Next chunk in the linked list. |
| 260 | + }; |
| 261 | + |
| 262 | + ChunkHeader *chunkHead_; //!< Head of the chunk linked-list. Only the head chunk serves allocation. |
| 263 | + size_t chunk_capacity_; //!< The minimum capacity of chunk when they are allocated. |
| 264 | + void *userBuffer_; //!< User supplied buffer. |
| 265 | + BaseAllocator* baseAllocator_; //!< base allocator for allocating memory chunks. |
| 266 | + BaseAllocator* ownBaseAllocator_; //!< base allocator created by this object. |
| 267 | +}; |
| 268 | + |
| 269 | +RAPIDJSON_NAMESPACE_END |
| 270 | + |
| 271 | +#endif // RAPIDJSON_ENCODINGS_H_ |
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