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Fast inverse square root

0 likes • Nov 19, 2022
C
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pipe() example

CodeCatch
0 likes • Nov 19, 2022
C
#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 */
}
}

signal() example

CodeCatch
0 likes • Nov 19, 2022
C
#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 <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);
}

fork() example

CodeCatch
0 likes • Nov 19, 2022
C
#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;
}

Arduino Sound Demo

ThiccDaddyLOAF
0 likes • Jan 4, 2022
C
//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();
}

wait() example

CodeCatch
0 likes • Nov 19, 2022
C
#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 */