Operating System: General Description In this homework, you will implement a Jav
ID: 3575143 • Letter: O
Question
Operating System:
General Description
In this homework, you will implement a Java class called Paging that simulates certain aspects of a memory management system based on paging. The memory management system simulated by the class Paging has a physical memory with 16 physical frames, all of which are initially unoccupied. The size of each physical frame (and hence, the size of each logical page) is 4096 bytes.
The class Paging should implement the following three public methods, and any other helper methods you deem necessary to implement the three methods.
public void allocate(int processID, int numberOfPages)
This method should simulate allocation of free physical frames for a process (whose ID is processID) that needs numberOfPages logical pages. After updating proper data structures for the simulation, this method should display the new physical memory status showing which frame is allocated to which process.
public void free(int processID)
This method should simulate deallocation of all of the physical frames allocated for a process (processID). Deallocated physical frames become available for subsequent allocation requests. After updating proper data structures, this method should display the new physical memory status showing which frame is allocated to which process.
public int resolve(int processID, int logicalAddress)
This method should translate a logical address (logicalAddress) for a process (processID) into a corresponding physical address. (In order to perform this function, you will need to maintain page tables for all processes that are in the memory.) Before returning the physical address, this method should display the resolved physical address, and display the physical memory status showing which frame is allocated to which process.
In order for you to test the three methods you implement, I have created a class called Console (attached with an accompanying class MemoryRequest), which interacts with the user to get requests, and calls the three methods in the class Paging. The provided Paging.java is merely a skeleton code that just has the three methods unimplemented.
I suggest that you copy all of the Java files to your own directory, and just modify Paging.java.
Error Checking
Your three methods in the class Paging can assume that every request will be immediately fulfilled. For instance, there will be no request that asks for more frames than are available. Also, there will be no erroneous requests. For instance, there will be no request to allocate memory for a process that already exists in memory, nor will there be requests to free memory for a process that no longer exists in memory.
Example Implementation
The attached .class files implement the paging scheme. Execute “java Console” to see how it interacts with the user. The following shows an interaction example.
[FirstName LastName@LastName-x61t ...CAIS339/paging]$ java Console
Menu
----------------------------------------------
a) Allocate pages
f) Free pages
r) Resolve logical address to physical address
q) Quit
Enter your choice: a
Enter process ID: 3
Enter number of Pages: 4
Memory Map (frame #, process ID)
(0,3) (1,3) (2,3) (3,3) (4,*) (5,*) (6,*) (7,*) (8,*) (9,*) (10,*) (11,*) (12,*)
(13,*) (14,*) (15,*)
Enter your choice: a
Enter process ID: 0
Enter number of Pages: 5
Memory Map (frame #, process ID)
(0,3) (1,3) (2,3) (3,3) (4,0) (5,0) (6,0) (7,0) (8,0) (9,*) (10,*) (11,*) (12,*)
(13,*) (14,*) (15,*)
Enter your choice: f
Enter process ID: 3
Memory Map (frame #, process ID)
(0,*) (1,*) (2,*) (3,*) (4,0) (5,0) (6,0) (7,0) (8,0) (9,*) (10,*) (11,*) (12,*)
(13,*) (14,*) (15,*)
Enter your choice: r
Enter process ID: 0
Enter logical address to resolve: 4096
Resolved to 20480
Memory Map (frame #, process ID)
(0,*) (1,*) (2,*) (3,*) (4,0) (5,0) (6,0) (7,0) (8,0) (9,*) (10,*) (11,*) (12,*)
(13,*) (14,*) (15,*)
Enter your choice: q
Goodbye
[FirstName LastName@LastName-x61t ...CAIS339/paging]$
Program Submission
Submit the SOURCE CODE for the class Paging (the Paging.java files) only.
Please download java files from link below:
https://drive.google.com/open?id=0BzF317vP_-m-X3I5SDJvbGljMW8
Explanation / Answer
Solution: See the code below
------------------------------------------
/**
* Paging class
*
*/
public class Paging {
private int memorySize;
private int pageSize;
private int numberOfPagesInMemory;
private int maxNumberOfProcesses;
private int remainingPages;
private int[] pageAllocatedPerProcess;
private int[] pageTable;
/**
* Constructor
*/
public Paging() {
// TODO Auto-generated constructor stub
numberOfPagesInMemory = 16;
pageSize = 4096;
memorySize = numberOfPagesInMemory * pageSize;
remainingPages = numberOfPagesInMemory;
maxNumberOfProcesses = 10;
pageAllocatedPerProcess = new int[maxNumberOfProcesses];
pageTable = new int[numberOfPagesInMemory];
// initialize page table
for (int i = 0; i < numberOfPagesInMemory; i++) {
pageTable[i] = -1; // -1 means page is not allocated
}
}
/**
* Simulates allocation of free physical frames for a process needing
* numberOfPages logical pages.
*
* @param processID
* @param numberOfPages
*/
public void allocate(int processID, int numberOfPages) {
// check if memory can be allocated
if (numberOfPages > remainingPages) {
System.out.println("Invalid number of pages. Memory can not be allocated");
} else {
// allocate memory (required number of pages)
pageAllocatedPerProcess[processID] = numberOfPages;
remainingPages -= numberOfPages;
for (int i = 0; i < numberOfPagesInMemory; i++) {
for (int j = 1; j <= numberOfPages; j++) {
if (pageTable[i] == -1)
pageTable[i] = processID;
}
}
}
// show memory map
System.out.println("Memory Map (frame #, process ID");
for (int i = 0; i < numberOfPagesInMemory; i++) {
if (pageTable[i] != 0) {
System.out.print("(" + i + "," + pageTable[i] + ")");
} else {
System.out.print("(" + i + ",*)");
}
}
System.out.println();
}
/**
* Simulates deallocation of all of the physical frames allocated for
* process
*
* @param processID
*/
public void free(int processID) {
int pagesAllocated = pageAllocatedPerProcess[processID];
// return pages to memory
remainingPages += pagesAllocated;
// update page table
for (int i = 0; i < numberOfPagesInMemory; i++) {
if (pageTable[i] == processID)
pageTable[i] = -1;
}
}
/**
* Translates a logical address for a process into a corresponding physical
* address.
*
* @param processID
* @param logicalAddress
* @return
*/
public int resolve(int processID, int logicalAddress) {
int physicalAddress = 0;
int pageAllocated = pageAllocatedPerProcess[processID];
if (processID > maxNumberOfProcesses || logicalAddress != pageSize) {
System.out.println("Invalid process or logical address");
} else {
physicalAddress = pageAllocated * logicalAddress; // depends on how
// logiocal
// address is
// defined.
System.out.println("Resolved to:" + physicalAddress);
}
// show memory map
System.out.println("Memory Map (frame #, process ID");
for (int i = 0; i < numberOfPagesInMemory; i++) {
if (pageTable[i] != 0) {
System.out.print("(" + i + "," + pageTable[i] + ")");
} else {
System.out.print("(" + i + ",*)");
}
}
System.out.println();
return physicalAddress;
}
/**
* @return the memorySize
*/
int getMemorySize() {
return memorySize;
}
/**
* @return the pageSize
*/
int getPageSize() {
return pageSize;
}
/**
* @return the numberOfPagesInMemory
*/
int getNumberOfPagesInMemory() {
return numberOfPagesInMemory;
}
/**
* @return the maxNumberOfProcesses
*/
int getMaxNumberOfProcesses() {
return maxNumberOfProcesses;
}
/**
* @return the remainingPages
*/
int getRemainingPages() {
return remainingPages;
}
}
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