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

int glbvar = 6;
int main() {
  int locvar = 88;
  pid_t pid;
  printf("Before fork()\n");
  if ((pid = fork()) == 0) {
    /* child */
    glbvar++;
    locvar++;
  } else if (pid > 0) {
    /* parent */
    sleep(2);
  } else
    perror("fork error");
  printf("pid=%d, glbvar=%d, locvar=%d\n", getpid(), glbvar, locvar);
  return 0;
} /* end main */

#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 */

// The following code is the fast inverse square root implementation from Quake III Arena
// this code has been stripped of C preprocessor directives, but includes the exact original comment text
float Q_rsqrt( float number )
{
	long i;
	float x2, y;
	const float threehalfs = 1.5F;

	x2 = number * 0.5F;
	y  = number;
	i  = * ( long * ) &y;                       // evil floating point bit level hacking
	i  = 0x5f3759df - ( i >> 1 );               // what the fuck? 
	y  = * ( float * ) &i;
	y  = y * ( threehalfs - ( x2 * y * y ) );   // 1st iteration
//	y  = y * ( threehalfs - ( x2 * y * y ) );   // 2nd iteration, this can be removed

	return y;
}

//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();
}

//===============replaceString.c===============
#include "replaceString.h"

//Normally I'd make a replaceStringMalloc to return a malloced string or a replaceStringMut to change the original string, but I'm not satisfied with those function names so it's best just to do to = (char*)malloc(replaceStringLength(from, replace, replacement)); replaceString(to, from, replace, replacement);
//If this was c++, I'd have no problem just overloading replaceString
//Returns the length of the resulting string (minus the null char)
size_t replaceStringLength(const char* from, const char* replace, const char* replacement){
	size_t fromLength = strlen(from);
	size_t replaceLength = strlen(replace);
	size_t replacementLength = strlen(replacement);
	size_t fromEndIt = 0;
	size_t toLength = 0;
	while(fromEndIt < fromLength){
	int replaceIt = 0;
	while(replaceIt < replaceLength && (fromEndIt+replaceIt) < fromLength && from[fromEndIt + replaceIt] == replace[replaceIt]){
	++replaceIt;
	}
	if(replaceIt == replaceLength){
	//Update from buffer iterator positions
	toLength += (fromEndIt + replacementLength);
	from += (fromEndIt + replaceLength);
	fromEndIt = 0;
	continue;
	}
	++fromEndIt;
	}
	toLength += fromEndIt;
	return toLength;
}
//Baller replaceString by Leif Messinger
//Needs null terminated from, replace, and replacement strings as well as a large block of memory to store the result.
void replaceString(char* to, const char* from, const char* replace, const char* replacement){
	size_t fromLength = strlen(from);
	size_t replaceLength = strlen(replace);
	size_t replacementLength = strlen(replacement);
	size_t fromEndIt = 0;
	while(fromEndIt < fromLength){
	int replaceIt = 0;
	while(replaceIt < replaceLength && (fromEndIt+replaceIt) < fromLength && from[fromEndIt + replaceIt] == replace[replaceIt]){
	++replaceIt;
	}
	if(replaceIt == replaceLength){
	//Copy the string before the matched bit
	memcpyToAndShiftPointers(to, from, fromEndIt);
	//Copy the replacement too
	memcpyToAndShiftPointer(to, replacement, replacementLength);
	//Update from buffer iterator positions
	from += replaceLength;
	fromEndIt = 0;
	continue; //I don't want this thing to get incremented again
	}
	++fromEndIt;
	}
	//Copy the rest of the unmatched string
	memcpyToAndShiftPointer(to, from, fromEndIt);
	to[0] = '\0'; //Should work
}
//===============replaceString.h===============
#ifndef REPLACE_STRING_H
#define REPLACE_STRING_H
#include <string.h>

#define memcpyToAndShiftPointer(to,from,n); memcpy((to),(from),(n)); (to) += (n);
#define memcpyToAndShiftPointers(to,from,n); memcpy((to),(from),(n)); (to) += (n); (from) += n;

//Normally I'd make a replaceStringMalloc to return a malloced string or a replaceStringMut to change the original string, but I'm not satisfied with those function names so it's best just to do to = (char*)malloc(replaceStringLength(from, replace, replacement)); replaceString(to, from, replace, replacement);
//If this was c++, I'd have no problem just overloading replaceString
//Returns the length of the resulting string (minus the null char)
size_t replaceStringLength(const char* from, const char* replace, const char* replacement);
//Baller replaceString by Leif Messinger
//Needs null terminated from, replace, and replacement strings as well as a large block of memory to store the result.
void replaceString(char* to, const char* from, const char* replace, const char* replacement);
#endif
//===============replaceStringMain.c===============
#include <stdio.h>
#include <stdlib.h>
#include "replaceString.h"

#define BUFFER_SIZE (1<<21) //About a mebibyte
//There could be matches between buffers, so make sure the buffer size you set it to is good enough for your application. Basically as big as your input.

//Replaces strings from sdtin, then outputs it to stdout
//./a.out [[replace], [replacement]]...
int main(int argc, char** argv){
	char* buffer1 = (char*) malloc(BUFFER_SIZE);
	char* buffer2 = (char*) malloc(BUFFER_SIZE);
	if(buffer1 == NULL || buffer2 == NULL){
	perror("You need a couple MBs of ram my boy");
	return 1;
	}
	while(!feof(stdin)){
	fread(buffer1, BUFFER_SIZE, 1, stdin);
	char* activeBuffer = buffer1;
	char* inactiveBuffer = buffer2;
	char* tmp;
	for(size_t i = 1; (i + 1) < argc; i += 2){
	//puts(activeBuffer);
	replaceString(inactiveBuffer, activeBuffer, argv[i], argv[i+1]);
	//Swap buffers
	tmp = activeBuffer;
	activeBuffer = inactiveBuffer;
	inactiveBuffer = tmp;
	}
	fputs(activeBuffer, stdout);
	}
	free(buffer1);
	free(buffer2);
	return 0;
}

#include <stdio.h>
#include <string.h>
#include <unistd.h>

#define READ 0 /* The index of the read end of the pipe */
#define WRITE 1 /* The index of the write end of the pipe */
char * phrase = "This goes in the pipe";
int main() {
  int fd[2], bytesRead;
  char message[100]; /* Parent process' message buffer */
  pipe(fd); /* Create unnamed pipe */
  if (fork() == 0) /* Child, writer */ {
    close(fd[READ]); /* Close unused end */
    write(fd[WRITE], phrase, strlen(phrase) + 1); /* Include NULL */
    close(fd[WRITE]); /* Close used end */
  } else /* Parent, reader */ {
    close(fd[WRITE]); /* Close unused end */
    bytesRead = read(fd[READ], message, 100);
    printf("Parent just read %i bytes: %s\n", bytesRead, message);
    close(fd[READ]); /* Close used end */
  }
}