ObjectPool.ooc

/* 
 * Copyright (c) 2010 Nick Markwell
 *
 * This is released under the MIT/X11 license.
 * See COPYING
 */

import structs/ArrayList

/**
 *  ObjectPool new(min, max: Int, reset: Func)
 *  - min is a used_objects/total_objects ratio which must be less than
 *    used size/(used size + free size)
 *  - max is a used_objects/total_objects ratio which must be greater than
 *    used size/(used size + free size)
 *  - reset is a function/closure which specifies what to do to reset each object,
 *    it is passed a single variable, which is the object to be reset
 *  If the reset block is not defined, it is assumed the object does not need resetting.
*/

ObjectPool: class<T> {
    min, max: SizeT
    used := ArrayList<T> new()
    free := ArrayList<T> new()
    _reset: Func(T)

    init: func (=min, =max, fn: Func(T)) {
        _reset = fn
    }

    init: func ~noReset(=min, =max) {
        free add(T alloc())
    }

    ratio: func -> SizeT {
        used size/(used size + free size)
    }

    reset: func(obj: T) {
        if((_reset as Closure) thunk != null) {
          _reset(obj)
        }
    }

    use: func -> T {
        if(min >= ratio)
          free add(T alloc())

        used add(free[0])
        free removeAt(0)
        used[-1]
    }

    free: func(obj: T) -> T {
        reset(obj)
        free add(obj)
        used remove(obj)
        while (max <= ratio() && ratio() > 0) {
          free removeAt(-1)
        }
        obj
    }
}