/**
* Writes a byte to memory given a 32-bit integer whose low bits are interpreted as a virtual
* address - To be implemented for all version.
*
* @param fourByteInteger A 32-bit integer
* @param value The byte Value written to memory at the relevant address
* @throws MemoryException If there is an invalid access
*/
public void writeByte(Integer fourByteInteger, byte value) throws MemoryException {
// TO IMPLEMENT: V0, V1, V2, V3, V4
int pageNumber = fourByteInteger / this.pageSize;
byte[] values = disk.readPage(pageNumber);
byte readValue; // The value to be return
int address; // The address to be use
int getFrame;
if (this.pageTable[pageNumber] == -1) { // if the page is not in memory
if (frameTable.size() == this.numOfFrames) { // If frame table is full
System.out.println("Evicting page " + frameTable.peek());
this.nextFrame = this.pageTable[frameTable.peek()];
getFrame = this.pageTable[frameTable.peek()];
address = this.pageSize * getFrame;
byte[] values2 = new byte[this.pageSize];
for (int j = 0; j < this.pageSize; j++) { // Putting the evicted page contents back to disk
values2[j] = memory.readByte(address);
address++;
this.byteCount++;
}
disk.writePage(frameTable.peek(), values2);
this.pageTable[frameTable.peek()] = -1;
this.frameTable.remove();
}
System.out.println("Bringing page " + pageNumber + " into frame " + this.nextFrame);
this.pageTable[pageNumber] = this.nextFrame; // Adding the frame in the page table
frameTable.addLast(pageNumber);
address = this.nextFrame * this.pageSize; // getting the physical adress
for (int i = 0; i < this.pageSize; i++) {
memory.writeByte(address, values[i]);
address++;
this.byteCount++;
}
address =
(this.pageSize * this.nextFrame)
+ (fourByteInteger
- (pageNumber * this.pageSize)); // translating the address to physical
System.out.println(
"RAM: " + this.btb.getBitString(address, bitCounter - 1) + " <-- " + value);
memory.writeByte(address, value);
this.nextFrame++;
this.pageFault++;
} else { // else the page is in memory
System.out.println("Page " + pageNumber + " is in memory");
getFrame = this.pageTable[pageNumber];
address =
(this.pageSize * getFrame)
+ (fourByteInteger
- (pageNumber * this.pageSize)); // translating the address to physical
System.out.println(
"RAM: " + this.btb.getBitString(address, bitCounter - 1) + " <-- " + value);
memory.writeByte(address, value);
}
}
/**
* Prints the content of the disk as a sequence of lines with the format "PAGE pageNumber:
* byteValue, byteValue, ... byteValue" to System.out, where pageNumber is a virtual page number
* and the list of byte values corresponds to all bytes in a given page on disk - To be
* implemented in versions V1 and above.
*
* @throws MemoryException If there is an invalid access
*/
public void printDiskContent() throws MemoryException {
// TO IMPLEMENT: V1, V2, V3, V4
byte[] values;
for (int i = 0; i < numOfPages; i++) {
values = disk.readPage(i);
System.out.print("PAGE " + i + ": ");
for (int j = 0; j < values.length; j++) {
if (j + 1 == values.length) {
System.out.print(values[j]);
} else {
System.out.print(values[j] + ",");
}
}
System.out.println();
}
return;
}
