IMemoryMapping IMemoryBus.RegisterMappedDevice(IMemoryMappedDevice device, int startAddress, int endAddress)
{
MemoryMapping mapping = new MemoryMapping(device, startAddress, endAddress);
this.mappings.Add(mapping);
this.mappingsArray = this.mappings.ToArray();
return(mapping);
}
void IMemoryBus.RemoveMapping(IMemoryMapping mapping)
{
MemoryMapping mappingToRemove = this.mappings.FirstOrDefault(m =>
m.Device == mapping.Device &&
m.StartAddress == mapping.StartAddress &&
m.EndAddress == mapping.EndAddress);
if (mappingToRemove != null)
{
this.mappings.Remove(mappingToRemove);
this.mappingsArray = this.mappings.ToArray();
}
}
private IMemoryMappedDevice GetDeviceAtAddress(ref int address)
{
// This method is on a very hot path - use arrays instead of List<T>, indexed loops instead
// of foreach or LINQ, and inline as much as possible. Improves perf by ~40%.
MemoryMapping activeMapping = null;
for (int i = 0; i < this.mappingsArray.Length; i++)
{
MemoryMapping mapping = this.mappingsArray[i];
if (mapping.StartAddress <= address && mapping.EndAddress >= address)
{
activeMapping = mapping;
break;
}
}
if (activeMapping == null)
{
// If we weren't able to find a mapping for the address, check to see if the address is in a mirrored range
MemoryMirroring activeMirroring = null;
for (int i = 0; i < this.mirroringsArray.Length; i++)
{
MemoryMirroring mirroring = this.mirroringsArray[i];
if (mirroring.MirrorStartAddress <= address && mirroring.MirrorEndAddress >= address)
{
activeMirroring = mirroring;
break;
}
}
if (activeMirroring != null)
{
// Calculate the base address and try to find a mapping again
address = activeMirroring.SourceStartAddress + ((address - activeMirroring.MirrorStartAddress) % activeMirroring.SourceSize);
for (int i = 0; i < this.mappingsArray.Length; i++)
{
MemoryMapping mapping = this.mappingsArray[i];
if (mapping.StartAddress <= address && mapping.EndAddress >= address)
{
activeMapping = mapping;
break;
}
}
}
}
return(activeMapping?.Device);
}