assimp/code/Common/StackAllocator.h

/*
Open Asset Import Library (assimp)
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*/

/** @file  StackAllocator.h
 *  @brief A very bare-bone allocator class that is suitable when
 *      allocating many small objects, e.g. during parsing.
 *      Individual objects are not freed, instead only the whole memory
 *      can be deallocated.
 */
#ifndef AI_STACK_ALLOCATOR_H_INC
#define AI_STACK_ALLOCATOR_H_INC

#include <vector>
#include <stdint.h>
#include <stddef.h>

namespace Assimp {

/** @brief A very bare-bone allocator class that is suitable when
 *      allocating many small objects, e.g. during parsing.
 *      Individual objects are not freed, instead only the whole memory
 *      can be deallocated.
*/
class StackAllocator {
public:
    /// @brief Constructs the allocator
    StackAllocator();

    /// @brief Destructs the allocator and frees all memory
    ~StackAllocator();

    // non copyable
    StackAllocator(const StackAllocator &) = delete;
    StackAllocator &operator=(const StackAllocator &) = delete;

    /// @brief Returns a pointer to byteSize bytes of heap memory that persists
    ///        for the lifetime of the allocator (or until FreeAll is called).
    inline void *Allocate(size_t byteSize);

    /// @brief Releases all the memory owned by this allocator.
    //         Memory provided through function Allocate is not valid anymore after this function has been called.
    inline void FreeAll();

private:
    constexpr const static size_t g_maxBytesPerBlock = 64 * 1024 * 1024; // The maximum size (in bytes) of a block
    constexpr const static size_t g_startBytesPerBlock = 16 * 1024;  // Size of the first block. Next blocks will double in size until maximum size of g_maxBytesPerBlock
    size_t m_blockAllocationSize = g_startBytesPerBlock; // Block size of the current block
    size_t m_subIndex = g_maxBytesPerBlock; // The current byte offset in the current block
    std::vector<uint8_t *> m_storageBlocks;  // A list of blocks
};

} // namespace Assimp

/// @brief Fixes an undefined reference error when linking in certain build environments.
//         May throw warnings about needing stdc++17, but should compile without issues on modern compilers.
inline const size_t Assimp::StackAllocator::g_maxBytesPerBlock;
inline const size_t Assimp::StackAllocator::g_startBytesPerBlock;

#include "StackAllocator.inl"

#endif // include guard