internal void Subscribe(Action <T> action)
{
Debug.Assert(action is not null);
_lock.Enter(); // ---- enter
try {
var count = _count;
if (count == 0)
{
Debug.Assert(_actions is null);
_actions = action;
}
else if (count == 1)
{
Debug.Assert(_actions is Action <T>);
if (ArrayPoolForEventRaiser.TryGetArray4Fast(out var actions) == false)
{
actions = new object[DefaultBufferCapacity];
}
Debug.Assert(actions.Length >= 2);
MemoryMarshal.GetArrayDataReference(actions) = _actions;
Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(actions), 1) = action;
_actions = actions;
}
else
{
var actions = SafeCast.NotNullAs <object?[]>(_actions);
if (actions.Length == count)
{
var newActions = new object[actions.Length * 2];
actions.AsSpan().CopyTo(newActions);
if (actions.Length == ArrayPoolForEventRaiser.LengthOfPoolTargetArray)
{
actions[0] = null;
actions[1] = null;
actions[2] = null;
actions[3] = null;
ArrayPoolForEventRaiser.ReturnArray4Fast(actions);
}
_actions = newActions;
actions = newActions;
}
actions[count] = action;
}
_count = count + 1;
}
finally {
_lock.Exit(); // ---- exit
}
}
internal void Unsubscribe(Action <T>?action)
{
if (action is null)
{
return;
}
_lock.Enter(); // ---- enter
try {
var actions = _actions;
var count = _count;
if (count == 0)
{
Debug.Assert(actions is null);
return;
}
else if (count == 1)
{
if (ReferenceEquals(_actions, action))
{
_count = 0;
_actions = null;
}
return;
}
else
{
var actionSpan = SafeCast.NotNullAs <object?[]>(actions).AsSpan(0, count);
for (int i = 0; i < actionSpan.Length; i++)
{
if (ReferenceEquals(actionSpan[i], action))
{
_count = count - 1;
if (i < _count)
{
var copyLen = _count - i;
actionSpan.Slice(i + 1, copyLen).CopyTo(actionSpan.Slice(i));
}
actionSpan[_count] = null;
if (_count == 1)
{
var a = actionSpan[0];
var actionsArray = SafeCast.NotNullAs <object?[]>(actions);
if (actionsArray.Length == ArrayPoolForEventRaiser.LengthOfPoolTargetArray)
{
actionsArray[0] = null;
actionsArray[1] = null;
actionsArray[2] = null;
actionsArray[3] = null;
ArrayPoolForEventRaiser.ReturnArray4Fast(actionsArray);
}
_actions = a;
}
return;
}
}
return;
}
}
finally {
_lock.Exit(); // ---- exit
}
}