Manage a set of ID values from min to max inclusive. More...
#include "uniqueIdAllocator.h"
Public Member Functions | |
| UniqueIdAllocator (uint32_t min=0, uint32_t max=20) | |
| Create a free id pool in the range [min:max]. More... | |
| uint32_t | allocate () |
| Returns an id between _min and _max (that were passed to the constructor). More... | |
| PN_stdfloat | fraction_used () const |
| return the decimal fraction of the pool that is used. More... | |
| void | free (uint32_t index) |
| Free an allocated index (index must be between _min and _max that were passed to the constructor). More... | |
| void | initial_reserve_id (uint32_t id) |
| This may be called to mark a particular id as having already been allocated (for instance, by a prior pass). More... | |
| void | output (std::ostream &out) const |
| ...intended for debugging only. More... | |
| void | write (std::ostream &out) const |
| ...intended for debugging only. More... | |
Static Public Attributes | |
| static const uint32_t | IndexAllocated = (uint32_t)-2 |
| static const uint32_t | IndexEnd = (uint32_t)-1 |
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 38 of file uniqueIdAllocator.h.
|
explicit |
Create a free id pool in the range [min:max].
Definition at line 55 of file uniqueIdAllocator.cxx.
| uint32_t 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 90 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 209 of file uniqueIdAllocator.cxx.
Referenced by write().
| void UniqueIdAllocator::free | ( | uint32_t | index | ) |
Free an allocated index (index must be between _min and _max that were passed to the constructor).
Definition at line 182 of file uniqueIdAllocator.cxx.
| void UniqueIdAllocator::initial_reserve_id | ( | uint32_t | 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 121 of file uniqueIdAllocator.cxx.
| void UniqueIdAllocator::output | ( | std::ostream & | out | ) | const |
...intended for debugging only.
Definition at line 217 of file uniqueIdAllocator.cxx.
| void UniqueIdAllocator::write | ( | std::ostream & | out | ) | const |
...intended for debugging only.
Definition at line 226 of file uniqueIdAllocator.cxx.
References fraction_used().
1.8.15