//Leif Messinger
const int BUZZER_PIN = 8;
const int BUTTON_PIN = 2;
const int BUTTON_PINMODE = INPUT_PULLUP;
#define DEBOUNCE_DELAY 50
class Button{
	private:
	short buttonPin;
	bool buttonState;
	bool lastButtonState;
	int lastDebounceTime;
	public:
	Button(short buttonPin): buttonState(HIGH), lastButtonState(LOW), lastDebounceTime(millis()){
	this->buttonPin = buttonPin;
	}
	bool checkForPress(const bool desiredState){ //Returns true if button pressed
	bool reading = (bool)digitalRead(buttonPin);
	
	// check to see if you just pressed the button
	// (i.e. the input went from LOW to HIGH), and you've waited long enough
	// since the last press to ignore any noise:
	
	// If the switch changed, due to noise or pressing:
	if (reading != lastButtonState) {
	// reset the debouncing timer
	lastDebounceTime = millis();
	}else if ((millis() - lastDebounceTime) > DEBOUNCE_DELAY) {
	// whatever the reading is at, it's been there for longer than the debounce
	// delay, so take it as the actual current state:
	
	// if the button state has changed:
	if (reading != buttonState) {
	buttonState = reading;
	
	// only toggle the LED if the new button state is HIGH
	if (buttonState == desiredState) {
	return true;
	}
	}
	}
	
	// save the reading. Next time through the loop, it'll be the lastButtonState:
	lastButtonState = reading;
	return false;
	}
	void waitForPress(const bool desiredState){
	while(!checkForPress(desiredState));
	}
};

class Note{
	public:
	short frequency; //Short max is ~ 30k, so way higher than you can hear
	short lag; //Also 30k ms is 30 seconds
	float sustainPercentage;
};
const short normalBeatLength = 500;
const short wholeNote = 4*normalBeatLength;
const short halfNote = 2*normalBeatLength;
const short dottedQuarterNote = normalBeatLength + (normalBeatLength / 2);
const short quarterNote = normalBeatLength;
const short dottedEighthNote = ((3 * normalBeatLength) / 4);
const short eighthNote = normalBeatLength/ 2;
const short sixteenthNote = normalBeatLength / 4;
const float normalSustainLength = .25;

void beep(const Note& note){ //It might go terribly wrong if you try to beep two tones at the same time.
	tone(BUZZER_PIN, note.frequency);
	delay(note.lag * note.sustainPercentage);
	noTone(BUZZER_PIN);
	delay(note.lag * (1.0 - note.sustainPercentage));
}

Note song[] = {
	{(int)523.25, halfNote, normalSustainLength},
	{(int)392, eighthNote, normalSustainLength},
	{(int)523.25, quarterNote, normalSustainLength},
	{(int)392, dottedEighthNote, normalSustainLength},
	{(int)440.00, sixteenthNote, normalSustainLength},
	{(int)493.88, quarterNote, normalSustainLength},
	{(int)329.63, eighthNote, normalSustainLength},
	{(int)329.63, eighthNote, normalSustainLength},
	{(int)440.00, quarterNote, normalSustainLength},
	{(int)392, dottedEighthNote, normalSustainLength},
	{(int)349.23, sixteenthNote, normalSustainLength},
	{(int)392, quarterNote, normalSustainLength},
	{(int)261.63, dottedEighthNote, normalSustainLength},
	{(int)261.63, sixteenthNote, normalSustainLength},
	{(int)293.66, quarterNote, normalSustainLength},
	{(int)293.66, dottedEighthNote, normalSustainLength},
	{(int)329.63, sixteenthNote, normalSustainLength},
	{(int)349.23, quarterNote, normalSustainLength},
	{(int)349.23, dottedEighthNote, normalSustainLength},
	{(int)392.00, sixteenthNote, normalSustainLength},
	{(int)440.00, quarterNote, normalSustainLength},
	{(int)493.88, eighthNote, normalSustainLength},
	{(int)523.25, eighthNote, normalSustainLength},
	{(int)587.33, dottedQuarterNote, normalSustainLength},
	{(int)392, eighthNote, normalSustainLength},
	{(int)659.25, quarterNote, normalSustainLength},
	{(int)587.33, dottedEighthNote, normalSustainLength},
	{(int)523.25, sixteenthNote, normalSustainLength},
	{(int)587.33, quarterNote, normalSustainLength},
	{(int)493.88, eighthNote, normalSustainLength},
	{(int)392, eighthNote, normalSustainLength},
	{(int)523.25, quarterNote, normalSustainLength},
	{(int)493.88, dottedEighthNote, normalSustainLength},
	{(int)440.00, sixteenthNote, normalSustainLength},
	{(int)493.88, quarterNote, normalSustainLength},
	{(int)329.63, eighthNote, normalSustainLength},
	{(int)329.63, eighthNote, normalSustainLength},
	{(int)440.00, quarterNote, normalSustainLength},
	{(int)392, dottedEighthNote, normalSustainLength},
	{(int)349.23, sixteenthNote, normalSustainLength},
	{(int)392, quarterNote, normalSustainLength},
	{(int)261.63, dottedEighthNote, normalSustainLength},
	{(int)261.63, sixteenthNote, normalSustainLength},
	{(int)523.25, quarterNote, normalSustainLength},
	{(int)493.88, dottedEighthNote, normalSustainLength},
	{(int)440.00, sixteenthNote, normalSustainLength},
	{(int)392.00, halfNote, normalSustainLength * .5},
};
size_t songLength = (sizeof(song) / sizeof(Note));

void playSong(){
	for(size_t pos = 0; pos < songLength; ++pos){
	const Note& bruh = song[pos];
	beep(bruh);
	}
}

void setup() {
	const int BUZZER_PIN = 8;
	pinMode(BUZZER_PIN, OUTPUT);
	pinMode(BUTTON_PIN, BUTTON_PINMODE);
	playSong();
}

Button button(BUTTON_PIN);
void loop() {
	button.waitForPress(LOW);
	// read the state of the switch into a local variable:
	playSong();
}

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

int main() {
  char * cmd[] = {
    "who",
    "ls",
    "date"
  };
  int i;
  while (1) {
    printf("0=who 1=ls 2=date : ");
    scanf("%d", & i);
    if (fork() == 0) {
      /* child */
      execlp(cmd[i], cmd[i], (char * ) 0);
      printf("execlp failed\n");
      exit(1);
    } else {
      /* parent */
      wait((int * ) 0);
      printf("child finished\n");
    }
  } /* while */
} /* main */

#include <stdio.h>
#include <stdlib.h>
int main(){

  int * int_ptr;
  int_ptr = (int *)malloc(2*sizeof(int));
  
  if(!int_ptr) {
    printf("Something went wrong while allocating memory. Exiting...");
    exit(1);
  }
  
  printf("Enter first integer: ");
  scanf("%i", &int_ptr[0]);
  
  printf("Enter second integer: ");
  scanf("%i", &int_ptr[1]);
  
  printf("Original values: 1st = %i 2nd = %i\n",int_ptr[0], int_ptr[1]);
  
  int_ptr[0] = int_ptr[0] ^ int_ptr[1];
  //printf("%i\n", int_ptr[0]);
  int_ptr[1] = int_ptr[0] ^ int_ptr[1];
  //printf("%i\n", int_ptr[1]);
  int_ptr[0] = int_ptr[0] ^ int_ptr[1];
  //printf("%i\n", int_ptr[0]);
  
  printf("Swapped values: 1st = %i 2nd = %i\n", int_ptr[0], int_ptr[1]);

  free(int_ptr);
  exit(0);
}

// Server side implementation of UDP client-server model
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#define PORT 8008
#define RECIEVE_BUFFER_SIZE 1024

// Driver code
int main() {

        //Create a UDP socket
        //int socket(int domain, int type, int protocol);
        //Domain is the place where the data goes. AF_BLUETOOTH, AF_INET6, AF_UNIX is local communication between different programs
        //Type is the type of connection, so connection based (TCP), connectionless (UDP) or somewhere in between or beyond
        //Protocol is an enum or flags that give some more options specific to that type. For SOCK_STREAM, you can force it to use SCTP instead of TCP. For SOCK_RAW, it can give you control over the ip frame, and even the ethernet frame.
        //So this function makes a file descriptor to an IPV4 UDP 'connection' with no options.
        int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
        // Creating socket file descriptor
        if ( sockfd < 0) {
                perror("socket creation failed");
                exit(EXIT_FAILURE);
        }


        struct sockaddr_in serverAddress;
        memset(&serverAddress, 0, sizeof(serverAddress));

        // Filling server information
        serverAddress.sin_family = AF_INET; // IPv4
        serverAddress.sin_addr.s_addr = INADDR_ANY;
        serverAddress.sin_port = htons(PORT);

        // Bind the socket with the server address
        if(bind(sockfd, (const struct sockaddr*)&serverAddress, sizeof(serverAddress))){        //Bind returns 0 if succeeded, or -1 if failed. -1 is still true.
                perror("bind failed");
                exit(EXIT_FAILURE);
        }

        struct sockaddr_in clientAddress; unsigned int clientAddressSize = sizeof(clientAddress);
        memset(&clientAddress, 0, clientAddressSize);

        char buffer[RECIEVE_BUFFER_SIZE];
        while(1){
                int bytesRecieved = recvfrom(sockfd, (char*)buffer, RECIEVE_BUFFER_SIZE, MSG_WAITALL, (struct sockaddr*) &clientAddress, &clientAddressSize); //sets clientAddress to the client's address and the new size
                buffer[bytesRecieved] = '\0';
                //printf("Client : %s\n", buffer);

                //The client might be like PINGUIN or something, but this is to ensure PING\n\r also gets accepted
                if(bytesRecieved >= 4 && (strncmp("PING", buffer, 4) == 0)){
                        const char* responseMessage = "PONG";
                        sendto(sockfd, (const char*)responseMessage, strlen(responseMessage), MSG_CONFIRM, (const struct sockaddr*) &clientAddress, clientAddressSize);
                        //printf("Hello message sent.\n");
                }else{
                        printf("Server bytes recieved: %d\nServer message recieved: %s", bytesRecieved, buffer);
                }
        }

        return 0;
}

#include <stdio.h>
#include <assert.h>
#include <signal.h>

void myHandler(int iSig) {
  printf("In myHandler with argument %d\n", iSig);
}
int main() {
  void( * pfRet)(int) = signal(SIGINT, myHandler);
  assert(pfRet != SIG_ERR);
  printf("Entering an infinite loop\n");
  while (1) {
    printf(".");
  }
  return 0; // use CTRL+\ to exit
}

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>

int main() {
  pid_t pid; /* could be int */
  int i;
  pid = fork();
  printf("PID=%d\n", pid);
  if (pid > 0) {
    /* parent */
    for (i = 0; i < 10; i++)
      printf("\t\t\tPARENT %d\n", i);
  } else {
    /* child */
    for (i = 0; i < 10; i++)
      printf("CHILD %d\n", i);
  }
  return 0;
}