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/*****************************************************************************\
* Copyright (c) Athena Dev Teams - Licensed under GNU GPL *
* For more information, see LICENCE in the main folder *
* *
* <H1>Entry Reusage System</H1> *
* *
* There are several root entry managers, each with a different entry size. *
* Each manager will keep track of how many instances have been 'created'. *
* They will only automatically destroy themselves after the last instance *
* is destroyed. *
* *
* Entries can be allocated from the managers. *
* If it has reusable entries (freed entry), it uses one. *
* So no assumption should be made about the data of the entry. *
* Entries should be freed in the manager they where allocated from. *
* Failure to do so can lead to unexpected behaviours. *
* *
* <H2>Advantages:</H2> *
* - The same manager is used for entries of the same size. *
* So entries freed in one instance of the manager can be used by other *
* instances of the manager. *
* - Much less memory allocation/deallocation - program will be faster. *
* - Avoids memory fragmentaion - program will run better for longer. *
* *
* <H2>Disavantages:</H2> *
* - Unused entries are almost inevitable - memory being wasted. *
* - A manager will only auto-destroy when all of its instances are *
* destroyed so memory will usually only be recovered near the end. *
* - Always wastes space for entries smaller than a pointer. *
* *
* WARNING: The system is not thread-safe at the moment. *
* *
* HISTORY: *
* 0.1 - Initial version *
* *
* @version 0.1 - Initial version *
* @author Flavio @ Amazon Project *
* @encoding US-ASCII *
\*****************************************************************************/
#ifndef _ERS_H_
#define _ERS_H_
#include "../common/cbasetypes.h"
/*****************************************************************************\
* (1) All public parts of the Entry Reusage System. *
* DISABLE_ERS - Define to disable this system. *
* ERS_ALIGNED - Alignment of the entries in the blocks. *
* ERS - Entry manager. *
* ers_new - Allocate an instance of an entry manager. *
* ers_report - Print a report about the current state. *
* ers_force_destroy_all - Force the destruction of all the managers. *
\*****************************************************************************/
/**
* Define this to disable the Entry Reusage System.
* All code except the typedef of ERInterface will be disabled.
* To allow a smooth transition,
*/
//#define DISABLE_ERS
/**
* Entries are aligned to ERS_ALIGNED bytes in the blocks of entries.
* By default it aligns to one byte, using the "natural order" of the entries.
* This should NEVER be set to zero or less.
* If greater than one, some memory can be wasted. This should never be needed
* but is here just in case some aligment issues arise.
*/
#ifndef ERS_ALIGNED
# define ERS_ALIGNED 1
#endif /* not ERS_ALIGN_ENTRY */
/**
* Public interface of the entry manager.
* @param alloc Allocate an entry from this manager
* @param free Free an entry allocated from this manager
* @param entry_size Return the size of the entries of this manager
* @param destroy Destroy this instance of the manager
*/
typedef struct eri {
/**
* Allocate an entry from this entry manager.
* If there are reusable entries available, it reuses one instead.
* @param self Interface of the entry manager
* @return An entry
*/
void *(*alloc)(struct eri *self);
/**
* Free an entry allocated from this manager.
* WARNING: Does not check if the entry was allocated by this manager.
* Freeing such an entry can lead to unexpected behaviour.
* @param self Interface of the entry manager
* @param entry Entry to be freed
*/
void (*free)(struct eri *self, void *entry);
/**
* Return the size of the entries allocated from this manager.
* @param self Interface of the entry manager
* @return Size of the entries of this manager in bytes
*/
uint32 (*entry_size)(struct eri *self);
/**
* Destroy this instance of the manager.
* The manager is actually only destroyed when all the instances are destroyed.
* When destroying the manager a warning is shown if the manager has
* missing/extra entries.
* @param self Interface of the entry manager
*/
void (*destroy)(struct eri *self);
} *ERS;
#ifdef DISABLE_ERS
// Use memory manager to allocate/free and disable other interface functions
# define ers_alloc(obj,type) (type *)aMalloc(sizeof(type))
# define ers_free(obj,entry) aFree(entry)
# define ers_entry_size(obj) (uint32)0
# define ers_destroy(obj)
// Disable the public functions
# define ers_new(size) NULL
# define ers_report()
# define ers_force_destroy_all()
#else /* not DISABLE_ERS */
// These defines should be used to allow the code to keep working whenever
// the system is disabled
# define ers_alloc(obj,type) (type *)(obj)->alloc(obj)
# define ers_free(obj,entry) (obj)->free((obj),(entry))
# define ers_entry_size(obj) (obj)->entry_size(obj)
# define ers_destroy(obj) (obj)->destroy(obj)
/**
* Get a new instance of the manager that handles the specified entry size.
* Size has to greater than 0.
* If the specified size is smaller than a pointer, the size of a pointer is
* used instead.
* It's also aligned to ERS_ALIGNED bytes, so the smallest multiple of
* ERS_ALIGNED that is greater or equal to size is what's actually used.
* @param The requested size of the entry in bytes
* @return Interface of the object
*/
ERS ers_new(uint32 size);
/**
* Print a report about the current state of the Entry Reusage System.
* Shows information about the global system and each entry manager.
* The number of entries are checked and a warning is shown if extra reusable
* entries are found.
* The extra entries are included in the count of reusable entries.
*/
void ers_report(void);
/**
* Forcibly destroy all the entry managers, checking for nothing.
* The system is left as if no instances or entries had ever been allocated.
* All previous entries and instances of the managers become invalid.
* The use of this is NOT recommended.
* It should only be used in extreme situations to make shure all the memory
* allocated by this system is released.
*/
void ers_force_destroy_all(void);
#endif /* DISABLE_ERS / not DISABLE_ERS */
#endif /* _ERS_H_ */
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