| // Tencent is pleased to support the open source community by making RapidJSON available. |
| // |
| // Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved. |
| // |
| // Licensed under the MIT License (the "License"); you may not use this file except |
| // in compliance with the License. You may obtain a copy of the License at |
| // |
| // http://opensource.org/licenses/MIT |
| // |
| // 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 RAPIDJSON_ALLOCATORS_H_ |
| #define RAPIDJSON_ALLOCATORS_H_ |
| |
| #include "rapidjson.h" |
| |
| RAPIDJSON_NAMESPACE_BEGIN |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // Allocator |
| |
| /*! \class rapidjson::Allocator |
| \brief Concept for allocating, resizing and freeing memory block. |
| |
| Note that Malloc() and Realloc() are non-static but Free() is static. |
| |
| So if an allocator need to support Free(), it needs to put its pointer in |
| the header of memory block. |
| |
| \code |
| concept Allocator { |
| static const bool kNeedFree; //!< Whether this allocator needs to call Free(). |
| |
| // Allocate a memory block. |
| // \param size of the memory block in bytes. |
| // \returns pointer to the memory block. |
| void* Malloc(size_t size); |
| |
| // Resize a memory block. |
| // \param originalPtr The pointer to current memory block. Null pointer is permitted. |
| // \param originalSize The current size in bytes. (Design issue: since some allocator may not book-keep this, explicitly pass to it can save memory.) |
| // \param newSize the new size in bytes. |
| void* Realloc(void* originalPtr, size_t originalSize, size_t newSize); |
| |
| // Free a memory block. |
| // \param pointer to the memory block. Null pointer is permitted. |
| static void Free(void *ptr); |
| }; |
| \endcode |
| */ |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // CrtAllocator |
| |
| //! C-runtime library allocator. |
| /*! This class is just wrapper for standard C library memory routines. |
| \note implements Allocator concept |
| */ |
| class CrtAllocator { |
| public: |
| static const bool kNeedFree = true; |
| void* Malloc(size_t size) { |
| if (size) // behavior of malloc(0) is implementation defined. |
| return std::malloc(size); |
| else |
| return NULL; // standardize to returning NULL. |
| } |
| void* Realloc(void* originalPtr, size_t originalSize, size_t newSize) { |
| (void)originalSize; |
| if (newSize == 0) { |
| std::free(originalPtr); |
| return NULL; |
| } |
| return std::realloc(originalPtr, newSize); |
| } |
| static void Free(void *ptr) { std::free(ptr); } |
| }; |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| // MemoryPoolAllocator |
| |
| //! Default memory allocator used by the parser and DOM. |
| /*! This allocator allocate memory blocks from pre-allocated memory chunks. |
| |
| It does not free memory blocks. And Realloc() only allocate new memory. |
| |
| The memory chunks are allocated by BaseAllocator, which is CrtAllocator by default. |
| |
| User may also supply a buffer as the first chunk. |
| |
| If the user-buffer is full then additional chunks are allocated by BaseAllocator. |
| |
| The user-buffer is not deallocated by this allocator. |
| |
| \tparam BaseAllocator the allocator type for allocating memory chunks. Default is CrtAllocator. |
| \note implements Allocator concept |
| */ |
| template <typename BaseAllocator = CrtAllocator> |
| class MemoryPoolAllocator { |
| public: |
| static const bool kNeedFree = false; //!< Tell users that no need to call Free() with this allocator. (concept Allocator) |
| |
| //! Constructor with chunkSize. |
| /*! \param chunkSize The size of memory chunk. The default is kDefaultChunkSize. |
| \param baseAllocator The allocator for allocating memory chunks. |
| */ |
| MemoryPoolAllocator(size_t chunkSize = kDefaultChunkCapacity, BaseAllocator* baseAllocator = 0) : |
| chunkHead_(0), chunk_capacity_(chunkSize), userBuffer_(0), baseAllocator_(baseAllocator), ownBaseAllocator_(0) |
| { |
| } |
| |
| //! Constructor with user-supplied buffer. |
| /*! The user buffer will be used firstly. When it is full, memory pool allocates new chunk with chunk size. |
| |
| The user buffer will not be deallocated when this allocator is destructed. |
| |
| \param buffer User supplied buffer. |
| \param size Size of the buffer in bytes. It must at least larger than sizeof(ChunkHeader). |
| \param chunkSize The size of memory chunk. The default is kDefaultChunkSize. |
| \param baseAllocator The allocator for allocating memory chunks. |
| */ |
| MemoryPoolAllocator(void *buffer, size_t size, size_t chunkSize = kDefaultChunkCapacity, BaseAllocator* baseAllocator = 0) : |
| chunkHead_(0), chunk_capacity_(chunkSize), userBuffer_(buffer), baseAllocator_(baseAllocator), ownBaseAllocator_(0) |
| { |
| RAPIDJSON_ASSERT(buffer != 0); |
| RAPIDJSON_ASSERT(size > sizeof(ChunkHeader)); |
| chunkHead_ = reinterpret_cast<ChunkHeader*>(buffer); |
| chunkHead_->capacity = size - sizeof(ChunkHeader); |
| chunkHead_->size = 0; |
| chunkHead_->next = 0; |
| } |
| |
| //! Destructor. |
| /*! This deallocates all memory chunks, excluding the user-supplied buffer. |
| */ |
| ~MemoryPoolAllocator() { |
| Clear(); |
| RAPIDJSON_DELETE(ownBaseAllocator_); |
| } |
| |
| //! Deallocates all memory chunks, excluding the user-supplied buffer. |
| void Clear() { |
| while (chunkHead_ && chunkHead_ != userBuffer_) { |
| ChunkHeader* next = chunkHead_->next; |
| baseAllocator_->Free(chunkHead_); |
| chunkHead_ = next; |
| } |
| if (chunkHead_ && chunkHead_ == userBuffer_) |
| chunkHead_->size = 0; // Clear user buffer |
| } |
| |
| //! Computes the total capacity of allocated memory chunks. |
| /*! \return total capacity in bytes. |
| */ |
| size_t Capacity() const { |
| size_t capacity = 0; |
| for (ChunkHeader* c = chunkHead_; c != 0; c = c->next) |
| capacity += c->capacity; |
| return capacity; |
| } |
| |
| //! Computes the memory blocks allocated. |
| /*! \return total used bytes. |
| */ |
| size_t Size() const { |
| size_t size = 0; |
| for (ChunkHeader* c = chunkHead_; c != 0; c = c->next) |
| size += c->size; |
| return size; |
| } |
| |
| //! Allocates a memory block. (concept Allocator) |
| void* Malloc(size_t size) { |
| if (!size) |
| return NULL; |
| |
| size = RAPIDJSON_ALIGN(size); |
| if (chunkHead_ == 0 || chunkHead_->size + size > chunkHead_->capacity) |
| if (!AddChunk(chunk_capacity_ > size ? chunk_capacity_ : size)) |
| return NULL; |
| |
| void *buffer = reinterpret_cast<char *>(chunkHead_) + RAPIDJSON_ALIGN(sizeof(ChunkHeader)) + chunkHead_->size; |
| chunkHead_->size += size; |
| return buffer; |
| } |
| |
| //! Resizes a memory block (concept Allocator) |
| void* Realloc(void* originalPtr, size_t originalSize, size_t newSize) { |
| if (originalPtr == 0) |
| return Malloc(newSize); |
| |
| if (newSize == 0) |
| return NULL; |
| |
| originalSize = RAPIDJSON_ALIGN(originalSize); |
| newSize = RAPIDJSON_ALIGN(newSize); |
| |
| // Do not shrink if new size is smaller than original |
| if (originalSize >= newSize) |
| return originalPtr; |
| |
| // Simply expand it if it is the last allocation and there is sufficient space |
| if (originalPtr == reinterpret_cast<char *>(chunkHead_) + RAPIDJSON_ALIGN(sizeof(ChunkHeader)) + chunkHead_->size - originalSize) { |
| size_t increment = static_cast<size_t>(newSize - originalSize); |
| if (chunkHead_->size + increment <= chunkHead_->capacity) { |
| chunkHead_->size += increment; |
| return originalPtr; |
| } |
| } |
| |
| // Realloc process: allocate and copy memory, do not free original buffer. |
| if (void* newBuffer = Malloc(newSize)) { |
| if (originalSize) |
| std::memcpy(newBuffer, originalPtr, originalSize); |
| return newBuffer; |
| } |
| else |
| return NULL; |
| } |
| |
| //! Frees a memory block (concept Allocator) |
| static void Free(void *ptr) { (void)ptr; } // Do nothing |
| |
| private: |
| //! Copy constructor is not permitted. |
| MemoryPoolAllocator(const MemoryPoolAllocator& rhs) /* = delete */; |
| //! Copy assignment operator is not permitted. |
| MemoryPoolAllocator& operator=(const MemoryPoolAllocator& rhs) /* = delete */; |
| |
| //! Creates a new chunk. |
| /*! \param capacity Capacity of the chunk in bytes. |
| \return true if success. |
| */ |
| bool AddChunk(size_t capacity) { |
| if (!baseAllocator_) |
| ownBaseAllocator_ = baseAllocator_ = RAPIDJSON_NEW(BaseAllocator()); |
| if (ChunkHeader* chunk = reinterpret_cast<ChunkHeader*>(baseAllocator_->Malloc(RAPIDJSON_ALIGN(sizeof(ChunkHeader)) + capacity))) { |
| chunk->capacity = capacity; |
| chunk->size = 0; |
| chunk->next = chunkHead_; |
| chunkHead_ = chunk; |
| return true; |
| } |
| else |
| return false; |
| } |
| |
| static const int kDefaultChunkCapacity = 64 * 1024; //!< Default chunk capacity. |
| |
| //! Chunk header for perpending to each chunk. |
| /*! Chunks are stored as a singly linked list. |
| */ |
| struct ChunkHeader { |
| size_t capacity; //!< Capacity of the chunk in bytes (excluding the header itself). |
| size_t size; //!< Current size of allocated memory in bytes. |
| ChunkHeader *next; //!< Next chunk in the linked list. |
| }; |
| |
| ChunkHeader *chunkHead_; //!< Head of the chunk linked-list. Only the head chunk serves allocation. |
| size_t chunk_capacity_; //!< The minimum capacity of chunk when they are allocated. |
| void *userBuffer_; //!< User supplied buffer. |
| BaseAllocator* baseAllocator_; //!< base allocator for allocating memory chunks. |
| BaseAllocator* ownBaseAllocator_; //!< base allocator created by this object. |
| }; |
| |
| RAPIDJSON_NAMESPACE_END |
| |
| #endif // RAPIDJSON_ENCODINGS_H_ |