Panda3D
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Manage a set of ID values from min to max inclusive. More...
#include "uniqueIdAllocator.h"
Public Member Functions | |
UniqueIdAllocator (PN_uint32 min=0, PN_uint32 max=20) | |
Create a free id pool in the range [min:max]. | |
PN_uint32 | allocate () |
Returns an id between _min and _max (that were passed to the constructor). | |
PN_stdfloat | fraction_used () const |
return the decimal fraction of the pool that is used. | |
void | free (PN_uint32 index) |
Free an allocated index (index must be between _min and _max that were passed to the constructor). | |
void | initial_reserve_id (PN_uint32 id) |
This may be called to mark a particular id as having already been allocated (for instance, by a prior pass). | |
void | output (ostream &out) const |
...intended for debugging only. | |
void | write (ostream &out) const |
...intended for debugging only. | |
Static Public Attributes | |
static const PN_uint32 | IndexAllocated = (PN_uint32)-2 |
static const PN_uint32 | IndexEnd = (PN_uint32)-1 |
Protected Attributes | |
PN_uint32 | _free |
PN_uint32 | _last_free |
PN_uint32 | _max |
PN_uint32 | _min |
PN_uint32 | _next_free |
PN_uint32 | _size |
PN_uint32 * | _table |
Manage a set of ID values from min to max inclusive.
The ID numbers that are freed will be allocated (reused) in the same order. I.e. the oldest ID numbers will be allocated.
This implementation will use 4 bytes per id number, plus a few bytes of management data. e.g. 10,000 ID numbers will use 40KB.
Also be advised that ID -1 and -2 are used internally by the allocator. If allocate returns IndexEnd (-1) then the allocator is out of free ID numbers.
There are other implementations that can better leverage runs of used or unused IDs or use bit arrays for the IDs. But, it takes extra work to track the age of freed IDs, which is required for what we wanted. If you would like to kick around other implementation ideas, please contact Schuyler.
Definition at line 44 of file uniqueIdAllocator.h.
UniqueIdAllocator::UniqueIdAllocator | ( | PN_uint32 | min = 0 , |
PN_uint32 | max = 20 |
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Create a free id pool in the range [min:max].
Definition at line 57 of file uniqueIdAllocator.cxx.
PN_uint32 UniqueIdAllocator::allocate | ( | ) |
Returns an id between _min and _max (that were passed to the constructor).
IndexEnd is returned if no ids are available.
Definition at line 97 of file uniqueIdAllocator.cxx.
PN_stdfloat UniqueIdAllocator::fraction_used | ( | ) | const |
return the decimal fraction of the pool that is used.
The range is 0 to 1.0 (e.g. 75% would be 0.75).
Definition at line 226 of file uniqueIdAllocator.cxx.
Referenced by write().
void UniqueIdAllocator::free | ( | PN_uint32 | index | ) |
Free an allocated index (index must be between _min and _max that were passed to the constructor).
Definition at line 197 of file uniqueIdAllocator.cxx.
void UniqueIdAllocator::initial_reserve_id | ( | PN_uint32 | id | ) |
This may be called to mark a particular id as having already been allocated (for instance, by a prior pass).
The specified id is removed from the available pool.
Because of the limitations of this algorithm, this is most efficient when it is called before the first call to allocate(), and when all the calls to initial_reserve_id() are made in descending order by id. However, this is a performance warning only; if performance is not an issue, any id may be reserved at any time.
Definition at line 133 of file uniqueIdAllocator.cxx.
void UniqueIdAllocator::output | ( | ostream & | out | ) | const |
...intended for debugging only.
Definition at line 236 of file uniqueIdAllocator.cxx.
void UniqueIdAllocator::write | ( | ostream & | out | ) | const |
...intended for debugging only.
Definition at line 247 of file uniqueIdAllocator.cxx.
References fraction_used().