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efl/src/lib/eo/eo_ptr_indirection.x

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#include <assert.h>
#ifdef HAVE_MMAP
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#endif
/* Start of pointer indirection:
*
* This feature is responsible of hiding from the developer the real pointer of
* the Eo object to supply a better memory management by preventing bad usage
* of the pointers.
*
* Eo * is no more a pointer but indexes to an entry into an ids table.
* For a better memory usage:
* - a tree structure is used, composed of a top level table pointing at
* mid tables pointing at tables composed of entries.
* - tables are allocated when needed (i.e no more empty entries in allocated tables.
* - empty tables are freed, except one kept as spare table.
*
* An Eo id is contructed by bits manipulation of table indexes and a generation.
*
* id = Mid Table | Table | Entry | Generation
*
* Generation helps finding abuse of ids. When an entry is assigned to an
* object, a generation is inserted into the id. If the developer uses this id
* although the object is freed and another one has replaced it into the same
* entry of the table, the generation will be different and an error will
* occur when accessing with the old id.
*
* Each Table is composed of:
* - an index 'start' indicating which free entry is the next one to use.
* - 2 indexes 'fifo_head' and 'fifo_tail' defining a fifo,
* that will help us to store the entries to be reused. It stores only the
* entries that have been used at least one time. The entries that have
* never been used are "pointed" by the start parameter.
* - entries composed of:
* - a pointer to the object
* - an index 'next_in_fifo' used to chain the free entries in the fifo
* - a flag indicating if the entry is active
* - a generation assigned to the object
*
* When an entry is searched into a table, we first use one of the entries that
* has never been used. If there is none, we try to pop from the fifo.
* If a such entry doesn't exist, we pass to the next table.
* When an entry is found, we reserve it to the object pointer
* then contruct and return the related Eo id.
*
* Assigning all the entries of a table before trying to reuse them from
* the fifo ensures that we are not going to soon recycle a released entry,
* thus minimize the risks of an aggressive del() then use() on a single entry.
*
* The indexes and a reference to the last table which served an entry is kept
* and is reused prior to the others untill it is full.
* When an object is freed, the entry into the table is released by appending
* it to the fifo.
*/
/* most significant bit is kept to tag Eo_Id with 1 */
#if SIZEOF_UINTPTR_T == 4
/* 32 bits */
# define BITS_MID_TABLE_ID 5
# define BITS_TABLE_ID 5
# define BITS_ENTRY_ID 12
# define BITS_GENERATION_COUNTER 9
# define REF_TAG_SHIFT 31
# define DROPPED_TABLES 0
# define DROPPED_ENTRIES 4
typedef int16_t Table_Index;
typedef uint16_t Generation_Counter;
#else
/* 64 bits */
# define BITS_MID_TABLE_ID 11
# define BITS_TABLE_ID 11
# define BITS_ENTRY_ID 12
# define BITS_GENERATION_COUNTER 29
# define REF_TAG_SHIFT 63
# define DROPPED_TABLES 2
# define DROPPED_ENTRIES 3
typedef int16_t Table_Index;
typedef uint32_t Generation_Counter;
#endif
/* Shifts macros to manipulate the Eo id */
#define SHIFT_MID_TABLE_ID (BITS_TABLE_ID + \
BITS_ENTRY_ID + BITS_GENERATION_COUNTER)
#define SHIFT_TABLE_ID (BITS_ENTRY_ID + BITS_GENERATION_COUNTER)
#define SHIFT_ENTRY_ID (BITS_GENERATION_COUNTER)
/* Maximum ranges - a few tables and entries are dropped to minimize the amount
* of wasted bytes, see _eo_id_mem_alloc */
#define MAX_MID_TABLE_ID (1 << BITS_MID_TABLE_ID)
#define MAX_TABLE_ID ((1 << BITS_TABLE_ID) - DROPPED_TABLES )
#define MAX_ENTRY_ID ((1 << BITS_ENTRY_ID) - DROPPED_ENTRIES)
#define MAX_GENERATIONS (1 << BITS_GENERATION_COUNTER)
/* Masks */
#define MASK_MID_TABLE_ID (MAX_MID_TABLE_ID - 1)
#define MASK_TABLE_ID ((1 << BITS_TABLE_ID) - 1)
#define MASK_ENTRY_ID ((1 << BITS_ENTRY_ID) - 1)
#define MASK_GENERATIONS (MAX_GENERATIONS - 1)
/* This only applies to classes. Used to artificially enlarge the class ids
* to reduce the likelihood of a clash with normal integers. */
#define CLASS_TAG_SHIFT (REF_TAG_SHIFT - 1)
#define MASK_CLASS_TAG (((Eo_Id) 1) << (CLASS_TAG_SHIFT))
#define MEM_HEADER_SIZE 16
#define MEM_PAGE_SIZE 4096
#define MEM_MAGIC 0x3f61ec8a
typedef struct _Mem_Header
{
size_t size;
size_t magic;
} Mem_Header;
static void *
_eo_id_mem_alloc(size_t size)
{
#ifdef HAVE_MMAP
void *ptr;
Mem_Header *hdr;
size_t newsize;
newsize = MEM_PAGE_SIZE * ((size + MEM_HEADER_SIZE + MEM_PAGE_SIZE - 1) /
MEM_PAGE_SIZE);
ptr = mmap(NULL, newsize, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (ptr == MAP_FAILED)
{
ERR("mmap of eo id table region failed!");
return NULL;
}
hdr = ptr;
hdr->size = newsize;
hdr->magic = MEM_MAGIC;
/* DBG("asked:%lu allocated:%lu wasted:%lu bytes", size, newsize, (newsize - size)); */
return (void *)(((unsigned char *)ptr) + MEM_HEADER_SIZE);
#else
return malloc(size);
#endif
}
static void *
_eo_id_mem_calloc(size_t num, size_t size)
{
void *ptr = _eo_id_mem_alloc(num * size);
if (!ptr) return NULL;
memset(ptr, 0, num * size);
return ptr;
}
static void
_eo_id_mem_free(void *ptr)
{
#ifdef HAVE_MMAP
Mem_Header *hdr;
if (!ptr) return;
hdr = (Mem_Header *)(((unsigned char *)ptr) - MEM_HEADER_SIZE);
if (hdr->magic != MEM_MAGIC)
{
ERR("unmap of eo table region has bad magic!");
return;
}
munmap(hdr, hdr->size);
#else
free(ptr);
#endif
}
#ifdef EINA_DEBUG_MALLOC
static void
_eo_id_mem_protect(void *ptr, Eina_Bool may_not_write)
{
# ifdef HAVE_MMAP
Mem_Header *hdr;
if (!ptr) return;
hdr = (Mem_Header *)(((unsigned char *)ptr) - MEM_HEADER_SIZE);
if (hdr->magic != MEM_MAGIC)
{
ERR("mprotect of eo table region has bad magic!");
return;
}
mprotect(hdr, hdr->size, PROT_READ | ( may_not_write ? 0 : PROT_WRITE) );
# endif
}
# define PROTECT(_ptr_) _eo_id_mem_protect((_ptr_), EINA_TRUE)
# define UNPROTECT(_ptr_) _eo_id_mem_protect((_ptr_), EINA_FALSE)
#else
# define PROTECT(_ptr_)
# define UNPROTECT(_ptr_)
#endif
#define EO_ALIGN_SIZE(size) eina_mempool_alignof(size)
/* Entry */
typedef struct
{
/* Pointer to the object */
_Eo_Object *ptr;
/* Indicates where to find the next entry to recycle */
Table_Index next_in_fifo;
/* Active flag */
unsigned int active : 1;
/* Generation */
unsigned int generation : BITS_GENERATION_COUNTER;
} _Eo_Id_Entry;
/* Table */
typedef struct
{
/* Indicates where start the "never used" entries */
Table_Index start;
/* Indicates where to find the next entry to recycle */
Table_Index fifo_head;
/* Indicates where to add an entry to recycle */
Table_Index fifo_tail;
/* Packed mid table and table indexes */
Eo_Id partial_id;
/* Counter of free entries */
unsigned int free_entries;
/* Entries of the table holding real pointers and generations */
_Eo_Id_Entry entries[MAX_ENTRY_ID];
} _Eo_Ids_Table;
/* Tables handling pointers indirection */
extern _Eo_Ids_Table **_eo_ids_tables[MAX_MID_TABLE_ID];
/* Current table used for following allocations */
extern _Eo_Ids_Table *_current_table;
/* Spare empty table */
extern _Eo_Ids_Table *_empty_table;
/* Next generation to use when assigning a new entry to a Eo pointer */
extern Generation_Counter _eo_generation_counter;
/* Macro used to compose an Eo id */
#define EO_COMPOSE_PARTIAL_ID(MID_TABLE, TABLE) \
(((Eo_Id) 0x1 << REF_TAG_SHIFT) | \
((Eo_Id)(MID_TABLE & MASK_MID_TABLE_ID) << SHIFT_MID_TABLE_ID) | \
((Eo_Id)(TABLE & MASK_TABLE_ID) << SHIFT_TABLE_ID))
#define EO_COMPOSE_FINAL_ID(PARTIAL_ID, ENTRY, GENERATION) \
(PARTIAL_ID | \
((ENTRY & MASK_ENTRY_ID) << SHIFT_ENTRY_ID) | \
(GENERATION & MASK_GENERATIONS ))
/* Macro to extract from an Eo id the indexes of the tables */
#define EO_DECOMPOSE_ID(ID, MID_TABLE, TABLE, ENTRY, GENERATION) \
MID_TABLE = (ID >> SHIFT_MID_TABLE_ID) & MASK_MID_TABLE_ID; \
TABLE = (ID >> SHIFT_TABLE_ID) & MASK_TABLE_ID; \
ENTRY = (ID >> SHIFT_ENTRY_ID) & MASK_ENTRY_ID; \
GENERATION = ID & MASK_GENERATIONS;
/* Macro used for readability */
#define TABLE_FROM_IDS _eo_ids_tables[mid_table_id][table_id]
static inline _Eo_Object *
_eo_obj_pointer_get(const Eo_Id obj_id)
{
#ifdef HAVE_EO_ID
_Eo_Id_Entry *entry;
Generation_Counter generation;
Table_Index mid_table_id, table_id, entry_id;
// NULL objects will just be sensibly ignored. not worth complaining
// every single time.
if (!obj_id)
{
DBG("obj_id is NULL. Possibly unintended access?");
return NULL;
}
EO_DECOMPOSE_ID(obj_id, mid_table_id, table_id, entry_id, generation);
/* Check the validity of the entry */
if (_eo_ids_tables[mid_table_id] && TABLE_FROM_IDS)
{
entry = &(TABLE_FROM_IDS->entries[entry_id]);
if (entry && entry->active && (entry->generation == generation))
return entry->ptr;
}
ERR("obj_id %p is not pointing to a valid object. Maybe it has already been freed.",
(void *)obj_id);
return NULL;
#else
return (_Eo_Object *) obj_id;
#endif
}
static inline _Eo_Id_Entry *
_get_available_entry(_Eo_Ids_Table *table)
{
_Eo_Id_Entry *entry = NULL;
if (table->start != MAX_ENTRY_ID)
{
/* Serve never used entries first */
entry = &(table->entries[table->start]);
UNPROTECT(table);
table->start++;
table->free_entries--;
}
else if (table->fifo_head != -1)
{
/* Pop a free entry from the fifo */
entry = &(table->entries[table->fifo_head]);
UNPROTECT(table);
if (entry->next_in_fifo == -1)
table->fifo_head = table->fifo_tail = -1;
else
table->fifo_head = entry->next_in_fifo;
table->free_entries--;
}
return entry;
}
static inline _Eo_Id_Entry *
_search_tables(void)
{
_Eo_Ids_Table *table;
_Eo_Id_Entry *entry;
for (Table_Index mid_table_id = 0; mid_table_id < MAX_MID_TABLE_ID; mid_table_id++)
{
if (!_eo_ids_tables[mid_table_id])
{
/* Allocate a new intermediate table */
_eo_ids_tables[mid_table_id] = _eo_id_mem_calloc(MAX_TABLE_ID, sizeof(_Eo_Ids_Table*));
}
for (Table_Index table_id = 0; table_id < MAX_TABLE_ID; table_id++)
{
table = TABLE_FROM_IDS;
if (!table)
{
if (_empty_table)
{
/* Recycle the available empty table */
table = _empty_table;
_empty_table = NULL;
UNPROTECT(table);
}
else
{
/* Allocate a new table */
table = _eo_id_mem_calloc(1, sizeof(_Eo_Ids_Table));
}
/* Initialize the table and reserve the first entry */
table->start = 1;
table->free_entries = MAX_ENTRY_ID - 1;
table->fifo_head = table->fifo_tail = -1;
table->partial_id = EO_COMPOSE_PARTIAL_ID(mid_table_id, table_id);
entry = &(table->entries[0]);
UNPROTECT(_eo_ids_tables[mid_table_id]);
TABLE_FROM_IDS = table;
PROTECT(_eo_ids_tables[mid_table_id]);
}
else
entry = _get_available_entry(table);
if (entry)
{
/* Store table info into current table */
_current_table = table;
return entry;
}
}
}
ERR("no more available entries to store eo objects");
_current_table = NULL;
return NULL;
}
/* Gives a fake id that serves as a marker if eo id is off. */
static inline Eo_Id
_eo_id_allocate(const _Eo_Object *obj)
{
#ifdef HAVE_EO_ID
_Eo_Id_Entry *entry = NULL;
if (_current_table)
entry = _get_available_entry(_current_table);
if (!entry)
{
entry = _search_tables();
}
if (!_current_table || !entry)
return 0;
/* [1;max-1] thus we never generate an Eo_Id equal to 0 */
_eo_generation_counter++;
if (_eo_generation_counter == MAX_GENERATIONS)
_eo_generation_counter = 1;
/* Fill the entry and return it's Eo Id */
entry->ptr = (_Eo_Object *)obj;
entry->active = 1;
entry->generation = _eo_generation_counter;
PROTECT(_current_table);
return EO_COMPOSE_FINAL_ID(_current_table->partial_id,
(entry - _current_table->entries),
entry->generation);
#else
Eo_Id ret = 0x1;
(void) obj;
return ret << REF_TAG_SHIFT;
#endif
}
static inline void
_eo_id_release(const Eo_Id obj_id)
{
#ifdef HAVE_EO_ID
_Eo_Ids_Table *table;
_Eo_Id_Entry *entry;
Generation_Counter generation;
Table_Index mid_table_id, table_id, entry_id;
EO_DECOMPOSE_ID(obj_id, mid_table_id, table_id, entry_id, generation);
/* Check the validity of the entry */
if (_eo_ids_tables[mid_table_id] && (table = TABLE_FROM_IDS))
{
entry = &(table->entries[entry_id]);
if (entry && entry->active && (entry->generation == generation))
{
UNPROTECT(table);
table->free_entries++;
/* Disable the entry */
entry->active = 0;
entry->next_in_fifo = -1;
/* Push the entry into the fifo */
if (table->fifo_tail == -1)
{
table->fifo_head = table->fifo_tail = entry_id;
}
else
{
table->entries[table->fifo_tail].next_in_fifo = entry_id;
table->fifo_tail = entry_id;
}
PROTECT(table);
if (table->free_entries == MAX_ENTRY_ID)
{
UNPROTECT(_eo_ids_tables[mid_table_id]);
TABLE_FROM_IDS = NULL;
PROTECT(_eo_ids_tables[mid_table_id]);
/* Recycle or free the empty table */
if (!_empty_table)
_empty_table = table;
else
_eo_id_mem_free(table);
if (_current_table == table)
_current_table = NULL;
}
return;
}
}
ERR("obj_id %p is not pointing to a valid object. Maybe it has already been freed.", (void *)obj_id);
#else
EINA_MAGIC_SET((Eo_Base *) obj_id, EO_FREED_EINA_MAGIC);
#endif
}
static inline void
_eo_free_ids_tables(void)
{
for (Table_Index mid_table_id = 0; mid_table_id < MAX_MID_TABLE_ID; mid_table_id++)
{
if (_eo_ids_tables[mid_table_id])
{
for (Table_Index table_id = 0; table_id < MAX_TABLE_ID; table_id++)
{
if (TABLE_FROM_IDS)
{
_eo_id_mem_free(TABLE_FROM_IDS);
}
}
_eo_id_mem_free(_eo_ids_tables[mid_table_id]);
}
_eo_ids_tables[mid_table_id] = NULL;
}
if (_empty_table) _eo_id_mem_free(_empty_table);
_empty_table = _current_table = NULL;
}
#ifdef EFL_DEBUG
static inline void
_eo_print(void)
{
_Eo_Id_Entry *entry;
unsigned long obj_number = 0;
for (Table_Index mid_table_id = 0; mid_table_id < MAX_MID_TABLE_ID; mid_table_id++)
{
if (_eo_ids_tables[mid_table_id])
{
for (Table_Index table_id = 0; table_id < MAX_TABLE_ID; table_id++)
{
if (TABLE_FROM_IDS)
{
for (Table_Index entry_id = 0; entry_id < MAX_ENTRY_ID; entry_id++)
{
entry = &(TABLE_FROM_IDS->entries[entry_id]);
if (entry->active)
{
printf("%ld: %p -> (%p, %p, %p, %p)\n", obj_number++,
entry->ptr,
(void *)mid_table_id, (void *)table_id, (void *)entry_id,
(void *)entry->generation);
}
}
}
}
}
}
}
#endif
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