/** * This program simulates the most common algorithms * used for dynamic memory allocation. * To abstract the process i used an array with some * random generated values and a variable, which is * supposed to represent the process of N bytes, * that has to be placed inside one of the free chunks * of memory. * * For more informations: https://goo.gl/kr21Qk */ #include #include #include #include #define MEMORY_SIZE 10 #define MAX_CHUNK_SPACE 3200 int *fill(size_t N) { int *unallocatedSpace = (int *)malloc(MEMORY_SIZE * sizeof(int)); for (int i = 0; i < N; i++) unallocatedSpace[i] = (rand() % MAX_CHUNK_SPACE) + 1; return unallocatedSpace; } int assign_valid_value(const int *memory, size_t N, const int processBytes) { int smallest_value = -1; for (int i = 0; i < N; i++) { if (memory[i] >= processBytes) { smallest_value = memory[i]; break; } } return smallest_value; } void fit(const int *memory, size_t N, const int processBytes, const char *algorithm_name, int *currentIndex, int (*allocation_algorithm)(const int smallestValue, const int currentValue, const int processBytes)) { int value = assign_valid_value(memory, N, processBytes); int idx = !strcmp("Next Fit", algorithm_name) && *currentIndex + 1 < N ? *currentIndex + 1 : 0; if (value != -1) { for (int i = idx; i < N; i++) { if (allocation_algorithm(value, memory[i], processBytes)) { value = memory[i]; *currentIndex = i; if (strcmp("First Fit", algorithm_name) == 0 || strcmp("Next Fit", algorithm_name) == 0) break; } } printf("\n%s: %d bytes allocated into a memory chunk of %d bytes.", algorithm_name, processBytes, value); } else printf("\nThere is no available space for %d bytes", processBytes); } int best_fit(const int smallestValue, const int currentValue, const int processBytes) { if (smallestValue > currentValue && currentValue >= processBytes) return 1; return 0; } int worst_fit(const int greaterValue, const int currentValue, const int processBytes) { if (greaterValue < currentValue && currentValue >= processBytes) return 1; return 0; } int first_fit(const int greaterValue, const int currentValue, const int processBytes) { if (currentValue >= processBytes) return 1; return 0; } void print(const int *obj, size_t N) { printf("{\n"); for (int i = 0; i < N; i++) printf("\t%d bytes free\n", obj[i]); printf("}\n"); } int main(int argc, char const *argv[]) { srand(time(0)); unsigned int *unallocatedSpace = fill(MEMORY_SIZE); unsigned int process = (rand() % MAX_CHUNK_SPACE) + 1; int *currentIndex = (int *)calloc(1, sizeof(int)); print(unallocatedSpace, MEMORY_SIZE); fit(unallocatedSpace, MEMORY_SIZE, process, "Best Fit", currentIndex, best_fit); fit(unallocatedSpace, MEMORY_SIZE, process, "Worst Fit", currentIndex, worst_fit); fit(unallocatedSpace, MEMORY_SIZE, process, "First Fit", currentIndex, first_fit); fit(unallocatedSpace, MEMORY_SIZE, process, "Next Fit", currentIndex, first_fit); free(unallocatedSpace); unallocatedSpace = NULL; return 0; }

Simulation of dynamic memory allocation's algorithms