godot/core/pool_allocator.h

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/*  pool_allocator.h                                                     */
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/* Copyright (c) 2007-2016 Juan Linietsky, Ariel Manzur.                 */
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#ifndef POOL_ALLOCATOR_H
#define POOL_ALLOCATOR_H

#include "typedefs.h"

/**
	@author Juan Linietsky <reduzio@gmail.com>
 * Generic Pool Allocator.
 * This is a generic memory pool allocator, with locking, compacting and alignment. (@TODO alignment)
 * It used as a standard way to manage alloction in a specific region of memory, such as texture memory,
 * audio sample memory, or just any kind of memory overall.
 * (@TODO) abstraction should be greater, because in many platforms, you need to manage a nonreachable memory.
*/

enum {

	POOL_ALLOCATOR_INVALID_ID=-1 ///< default invalid value. use INVALID_ID( id ) to test
};

class PoolAllocator {
public:
	typedef int ID;
private:
	enum {
		CHECK_BITS=8,
  		CHECK_LEN=(1<<CHECK_BITS),
		CHECK_MASK=CHECK_LEN-1

	};


	struct Entry {

		unsigned int pos;
		unsigned int len;
		unsigned int lock;
		unsigned int check;

		inline void clear() { pos=0; len=0; lock=0; check=0; }
		Entry() { clear(); }
	};


	typedef int EntryArrayPos;
	typedef int EntryIndicesPos;

	Entry *entry_array;
	int *entry_indices;
	int entry_max;
	int entry_count;

	uint8_t *pool;
	void *mem_ptr;
	int pool_size;

	int free_mem;
	int free_mem_peak;

	unsigned int check_count;
	int align;

	bool needs_locking;

	inline int entry_end(const Entry& p_entry) const {
		return p_entry.pos+aligned(p_entry.len);
	}
	inline int aligned(int p_size) const {

		int rem=p_size%align;
		if (rem)
			p_size+=align-rem;

		return p_size;
	}

	void compact(int p_up_to=-1);
	void compact_up(int p_from=0);
	bool get_free_entry(EntryArrayPos* p_pos);
	bool find_hole(EntryArrayPos *p_pos, int p_for_size);
	bool find_entry_index(EntryIndicesPos *p_map_pos,Entry *p_entry);
	Entry* get_entry(ID p_mem);
	const Entry* get_entry(ID p_mem) const;

	void create_pool(void * p_mem,int p_size,int p_max_entries);
protected:
	virtual void mt_lock() const; ///< Reimplement for custom mt locking
	virtual void mt_unlock() const; ///< Reimplement for custom mt locking

public:

	enum {
		DEFAULT_MAX_ALLOCS=4096,
	};

	ID alloc(int p_size); ///< Alloc memory, get an ID on success, POOL_ALOCATOR_INVALID_ID on failure
	void free(ID p_mem); ///< Free allocated memory
	Error resize(ID p_mem,int p_new_size); ///< resize a memory chunk
	int get_size(ID p_mem) const;

	int get_free_mem(); ///< get free memory
	int get_used_mem() const;
	int get_free_peak(); ///< get free memory

	Error lock(ID p_mem); //@todo move this out
	void *get(ID p_mem);
	const void *get(ID p_mem) const;
	void unlock(ID p_mem);
	bool is_locked(ID p_mem) const;

	PoolAllocator(int p_size,bool p_needs_locking=false,int p_max_entries=DEFAULT_MAX_ALLOCS);
	PoolAllocator(void * p_mem,int p_size, int p_align = 1, bool p_needs_locking=false,int p_max_entries=DEFAULT_MAX_ALLOCS);
	PoolAllocator(int p_align,int p_size,bool p_needs_locking=false,int p_max_entries=DEFAULT_MAX_ALLOCS);

	virtual ~PoolAllocator();

};

#endif