AppleWin/source/SynchronousEventManager.cpp

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/*
AppleWin : An Apple //e emulator for Windows
Copyright (C) 1994-1996, Michael O'Brien
Copyright (C) 1999-2001, Oliver Schmidt
Copyright (C) 2002-2005, Tom Charlesworth
Copyright (C) 2006-2020, Tom Charlesworth, Michael Pohoreski, Nick Westgate
AppleWin is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
AppleWin is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with AppleWin; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/* Description: Synchronous Event Manager
*
* This manager class maintains a linked-list of ordered timer-based event,
* where only the head of the list needs updating after every opcode.
*
* The Nth event in the list will expire in: event[1] + ... + event[N] cycles time.
* (So each event has a cycle delta expiry time relative to the previous event.)
*
* A synchronous event is used for a deterministic event that will occur in N cycles' time,
* eg. 6522 timer & Mousecard VBlank. (As opposed to async events, like SSC Rx/Tx interrupts.)
*
* Events that are active in the list can be removed before they expire,
* eg. 6522 timer when the interval changes.
*
* Author: Various
*
*/
#include "StdAfx.h"
#include "SynchronousEventManager.h"
#include "CPU.h"
void SynchronousEventManager::Insert(SyncEvent* pNewEvent)
{
pNewEvent->m_active = true; // add always succeeds
if (!m_syncEventHead)
{
m_syncEventHead = pNewEvent;
return;
}
// walk list to find where to insert new event
SyncEvent* pPrevEvent = NULL;
SyncEvent* pCurrEvent = m_syncEventHead;
int newEventExtraCycles = pNewEvent->m_cyclesRemaining;
while (pCurrEvent)
{
if (newEventExtraCycles >= pCurrEvent->m_cyclesRemaining)
{
newEventExtraCycles -= pCurrEvent->m_cyclesRemaining;
pPrevEvent = pCurrEvent;
pCurrEvent = pCurrEvent->m_next;
if (!pCurrEvent) // end of list
{
pPrevEvent->m_next = pNewEvent;
pNewEvent->m_cyclesRemaining = newEventExtraCycles;
}
continue;
}
// insert new event
if (!pPrevEvent)
m_syncEventHead = pNewEvent;
else
pPrevEvent->m_next = pNewEvent;
pNewEvent->m_next = pCurrEvent;
pNewEvent->m_cyclesRemaining = newEventExtraCycles;
// update cycles for next event
if (pCurrEvent)
{
pCurrEvent->m_cyclesRemaining -= newEventExtraCycles;
_ASSERT(pCurrEvent->m_cyclesRemaining >= 0);
}
return;
}
}
bool SynchronousEventManager::Remove(int id)
{
SyncEvent* pPrevEvent = NULL;
SyncEvent* pCurrEvent = m_syncEventHead;
while (pCurrEvent)
{
if (pCurrEvent->m_id != id)
{
pPrevEvent = pCurrEvent;
pCurrEvent = pCurrEvent->m_next;
continue;
}
// remove event
if (!pPrevEvent)
m_syncEventHead = pCurrEvent->m_next;
else
pPrevEvent->m_next = pCurrEvent->m_next;
int oldEventExtraCycles = pCurrEvent->m_cyclesRemaining;
pPrevEvent = pCurrEvent;
pCurrEvent = pCurrEvent->m_next;
pPrevEvent->m_active = false;
pPrevEvent->m_next = NULL;
// update cycles for next event
if (pCurrEvent)
pCurrEvent->m_cyclesRemaining += oldEventExtraCycles;
return true;
}
_ASSERT(0);
return false;
}
void SynchronousEventManager::Update(int cycles, ULONG uExecutedCycles)
{
SyncEvent* pCurrEvent = m_syncEventHead;
if (!pCurrEvent)
return;
pCurrEvent->m_cyclesRemaining -= cycles;
if (pCurrEvent->m_cyclesRemaining <= 0)
{
if (pCurrEvent->m_cyclesRemaining == 0 && pCurrEvent->m_canAssertIRQ)
SetIrqOnLastOpcodeCycle(); // IRQ occurs on last cycle of opcode
int cyclesUnderflowed = -pCurrEvent->m_cyclesRemaining;
pCurrEvent->m_cyclesRemaining = pCurrEvent->m_callback(pCurrEvent->m_id, cycles, uExecutedCycles);
m_syncEventHead = pCurrEvent->m_next; // unlink this event
pCurrEvent->m_active = false;
pCurrEvent->m_next = NULL;
// Always Update even if cyclesUnderflowed=0, as next event may have cycleRemaining=0 (ie. the 2 events fire at the same time)
Update(cyclesUnderflowed, uExecutedCycles); // update (potential) next event with underflow cycles
if (pCurrEvent->m_cyclesRemaining)
Insert(pCurrEvent); // re-add event
}
}