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have the Bus support devices with overlapping memory regions

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This commit is contained in:
Maik Merten 2014-07-17 21:43:46 +02:00
parent f5a25b7303
commit 44151f3a9c
1 changed files with 75 additions and 27 deletions
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102
src/main/java/com/loomcom/symon/Bus.java
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@ -47,6 +47,13 @@ public class Bus {
// Ordered list of IO devices.
private SortedSet<Device> devices;
// Ordered list of IO devices that have overlapping memory locations
private SortedSet<Device> overlapDevices;
// an array for quick lookup of adresses, brute-force style
private Device[] deviceAddressArray;
public Bus(int size) {
this(0, size - 1);
@ -54,6 +61,7 @@ public class Bus {
public Bus(int startAddress, int endAddress) {
this.devices = new TreeSet<Device>();
this.overlapDevices = new TreeSet<Device>();
this.startAddress = startAddress;
this.endAddress = endAddress;
}
@ -65,7 +73,56 @@ public class Bus {
public int endAddress() {
return endAddress;
}
private void buildDeviceAddressArray() {
// TODO: Find out why +2 and not +1 is needed here
int size = (this.endAddress - this.startAddress) + 2;
deviceAddressArray = new Device[size];
for(Device device : devices) {
MemoryRange range = device.getMemoryRange();
for(int address = range.startAddress; address <= range.endAddress; ++address) {
deviceAddressArray[address] = device;
}
}
for(Device device : overlapDevices) {
MemoryRange range = device.getMemoryRange();
for(int address = range.startAddress; address <= range.endAddress; ++address) {
deviceAddressArray[address] = device;
}
}
}
/**
* Add a device to the bus. Throws a MemoryRangeException if the device overlaps with any others, unless the overlap parameter is true.
*
* @param device
* @param overlap
* @throws MemoryRangeException
*/
public void addDevice(Device device, boolean overlap) throws MemoryRangeException {
// Make sure there's no memory overlap.
MemoryRange memRange = device.getMemoryRange();
if(!overlap) {
for (Device d : devices) {
if (d.getMemoryRange().overlaps(memRange)) {
throw new MemoryRangeException("The device being added at " +
String.format("$%04X", memRange.startAddress()) +
" overlaps with an existing " +
"device, '" + d + "'");
}
}
}
// Add the device
device.setBus(this);
if(overlap) {
overlapDevices.add(device);
} else {
devices.add(device);
}
buildDeviceAddressArray();
}
/**
* Add a device to the bus. Throws a MemoryRangeException if the device overlaps with any others.
*
@ -73,21 +130,9 @@ public class Bus {
* @throws MemoryRangeException
*/
public void addDevice(Device device) throws MemoryRangeException {
// Make sure there's no memory overlap.
MemoryRange memRange = device.getMemoryRange();
for (Device d : devices) {
if (d.getMemoryRange().overlaps(memRange)) {
throw new MemoryRangeException("The device being added at " +
String.format("$%04X", memRange.startAddress()) +
" overlaps with an existing " +
"device, '" + d + "'");
}
}
// Add the device
device.setBus(this);
devices.add(device);
addDevice(device, false);
}
/**
* Remove a device from the bus.
@ -97,6 +142,11 @@ public class Bus {
public void removeDevice(Device device) {
if (devices.contains(device)) {
devices.remove(device);
buildDeviceAddressArray();
}
if (overlapDevices.contains(device)) {
overlapDevices.remove(device);
buildDeviceAddressArray();
}
}
@ -127,27 +177,25 @@ public class Bus {
}
public int read(int address) throws MemoryAccessException {
for (Device d : devices) {
Device d = deviceAddressArray[address];
if(d != null) {
MemoryRange range = d.getMemoryRange();
if (range.includes(address)) {
// Compute offset into this device's address space.
int devAddr = address - range.startAddress();
return d.read(devAddr);
}
int devAddr = address - range.startAddress();
return d.read(devAddr);
}
throw new MemoryAccessException("Bus read failed. No device at address " + String.format("$%04X", address));
}
public void write(int address, int value) throws MemoryAccessException {
for (Device d : devices) {
Device d = deviceAddressArray[address];
if(d != null) {
MemoryRange range = d.getMemoryRange();
if (range.includes(address)) {
// Compute offset into this device's address space.
int devAddr = address - range.startAddress();
d.write(devAddr, value);
return;
}
int devAddr = address - range.startAddress();
d.write(devAddr, value);
return;
}
throw new MemoryAccessException("Bus write failed. No device at address " + String.format("$%04X", address));
}