Create LRU-paging-algorithm.c

Author: tr3sp4ss3rexe

LRU-paging-algorithm.c

@@ -0,0 +1,93 @@
+/*
+Simulating the physical memory and its paging process
+using the Least Recently Used (LRU) algorithm and
+counting the page faults
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+
+int findLRU(int* timestamps, int noPhysPages) {
+    int min = timestamps[0], lruIndex = 0;
+    for (int i = 1; i < noPhysPages; i++) {
+        if (timestamps[i] < min) {
+            min = timestamps[i];
+            lruIndex = i;
+        }
+    }
+    return lruIndex;
+}
+
+int main(int argc, char** argv) {
+    if (argc != 4) {
+        printf("Wrong inputs. Should be 3 arguments!\n");
+        return 0;
+    }
+
+    unsigned int noPhysPages = atoi(argv[1]);
+    unsigned int pageSize = atoi(argv[2]);
+    char* fileName = argv[3];
+
+    if (noPhysPages == 0 || pageSize == 0) {
+        printf("Page size or number of physical pages cannot be 0!\n");
+        return 0;
+    }
+
+    printf("No physical pages = %u, page size = %u\n", noPhysPages, pageSize);
+    printf("Reading memory trace from %s...\n", fileName);
+
+    FILE* fp = fopen(fileName, "r");
+    if (fp == NULL) {
+        printf("Failed to open file: %s\n", fileName);
+        return 0;
+    }
+
+    unsigned int* frames = malloc(noPhysPages * sizeof(unsigned int));
+    int* timestamps = malloc(noPhysPages * sizeof(int));
+    for (int i = 0; i < noPhysPages; i++) {
+        frames[i] = -1;
+        timestamps[i] = 0;
+    }
+
+    unsigned int address, page;
+    unsigned int pageFaults = 0, references = 0;
+    int time = 0;
+
+    while (fscanf(fp, "%u", &address) != EOF) {
+        page = address / pageSize;
+        int found = 0;
+
+        
+        for (unsigned int i = 0; i < noPhysPages; i++) {
+            if (frames[i] == page) {
+                found = 1; // Page found
+                timestamps[i] = time++; // Update the access time
+                break;
+            }
+        }
+
+        if (!found) {
+            pageFaults++;
+            int lruIndex = -1;
+
+            if (references < noPhysPages) {
+                lruIndex = references;
+            } else {
+                lruIndex = findLRU(timestamps, noPhysPages);
+            }
+
+            frames[lruIndex] = page;
+            timestamps[lruIndex] = time++;
+        }
+        references++;
+    }
+
+    fclose(fp);
+
+    printf("Read %u memory references\n", references);
+    printf("Result: %u page faults\n", pageFaults);
+
+    free(frames);
+    free(timestamps);
+    return 0;
+}