70 lines
3.1 KiB
Java
70 lines
3.1 KiB
Java
package Others;
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import java.util.ArrayList;
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/**
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* @author Dekas Dimitrios
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*/
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public class FirstFit {
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private static final int NO_ALLOCATION = -255; // if a process has been allocated in position -255,
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// it means that it has not been actually allocated.
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/**
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* Method to find the index of the memory block that is going to fit the given process based on the first fit algorithm.
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*
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* @param blocks: the array with the available memory blocks.
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* @param process: the size of the process.
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* @return the index of the block that fits, or -255 if no such block exists.
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*/
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private static int findFirstFit(int[] blockSizes, int processSize) {
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for(int i=0 ; i < blockSizes.length ; i++) {
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if(blockSizes[i] >= processSize) {
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return i;
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}
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}
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// If there is not a block that can fit the process, return -255 as the result
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return NO_ALLOCATION;
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}
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/**
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* Method to allocate memory to blocks according to the first fit
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* algorithm. It should return an ArrayList of Integers, where the
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* index is the process ID (zero-indexed) and the value is the block
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* number (also zero-indexed).
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*
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* @param sizeOfBlocks: an int array that contains the sizes of the memory blocks available.
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* @param sizeOfProcesses: an int array that contains the sizes of the processes we need memory blocks for.
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* @return the ArrayList filled with Integers repressenting the memory allocation that took place.
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*/
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static ArrayList<Integer> firstFit(int[] sizeOfBlocks, int[] sizeOfProcesses) {
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// The array list responsible for saving the memory allocations done by the first-fit algorithm
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ArrayList<Integer> memAlloc = new ArrayList<>();
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// Do this for every process
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for(int processSize : sizeOfProcesses) {
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int chosenBlockIdx = findFirstFit(sizeOfBlocks, processSize); // Find the index of the memory block going to be used
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memAlloc.add(chosenBlockIdx); // Store the chosen block index in the memAlloc array list
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if(chosenBlockIdx != NO_ALLOCATION) { // Only if a block was chosen to store the process in it,
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sizeOfBlocks[chosenBlockIdx] -= processSize; // resize the block based on the process size
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}
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}
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return memAlloc;
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}
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/**
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* Method to print the memory allocated.
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*
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* @param memAllocation: an ArrayList of Integer representing the memory allocation done by the firstFit method.
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*/
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public static void printMemoryAllocation(ArrayList<Integer> memAllocation) {
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System.out.println("Process No.\tBlock No.");
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System.out.println("===========\t=========");
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for (int i = 0; i < memAllocation.size(); i++) {
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System.out.print(" " + i + "\t\t");
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if (memAllocation.get(i) != NO_ALLOCATION)
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System.out.print(memAllocation.get(i));
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else
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System.out.print("Not Allocated");
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System.out.println();
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}
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}
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} |