// allocates a slot; p can be null; returns slot index
protected int alloc(Promise p, EvictHandler h)
{
// using promise to alloc?
if (p != null)
{
// yes: clear out contents if there are any
if (slots[p.slot].used)
{
// shouldn't already have promised this slot
if (slots[p.slot].promise)
throw new Exception("attempting to use promise on already-promised slot!");
// evict speculative contents...
slots[p.slot].handler();
slots[p.slot].used = false;
}
slots[p.slot].used = true;
slots[p.slot].promise = true;
slots[p.slot].handler = null;
return p.slot;
}
else
{
// no: attempt to grab a free slot if there is one
for (int i = 0; i < slots.Length; i++)
{
if (!slots[i].used)
{
slots[i].used = true;
slots[i].promise = false;
slots[i].handler = h;
return i;
}
}
// no free slots
return -1;
}
}
public void putPromise(Promise p)
{
#if DEBUG
Console.WriteLine("putting promise {0} back, count was {1}", p, promises.Count);
#endif
if (!p.active)
throw new Exception("returning inactive promise!");
p.active = false;
promises.Enqueue(p);
}