/*
 * Calculating PI
 *
 * Author: Michael Neumann (mneumann@fantasy-coders.de)
 * Date: 03.12.2002
 *
 * Requires GNU MP (tested with version 4.1) 
 * (http://www.swox.com/gmp/)
 *
 * To compile:
 *   cc pi.c -o pi -I/usr/local/include -L/usr/local/lib -lgmp
 */

#include "gmp.h"
#include <stdio.h>

int main(int argc, char **argv) {
  mpz_t k, a, b, a1, b1, p, q, d, d1;
  mpz_t t1, t2, t3, t4;  /* temporary */

  /* Initialize and assign integers */

  mpz_init(p);
  mpz_init(q);
  mpz_init(d);
  mpz_init(d1);
  mpz_init(t1);
  mpz_init(t2);
  mpz_init(t3);
  mpz_init(t4);
  mpz_init_set_ui(k, 2);
  mpz_init_set_ui(a, 4);
  mpz_init_set_ui(b, 1);
  mpz_init_set_ui(a1, 12);
  mpz_init_set_ui(b1, 4);

  for(;;) {
    /* Next approximation */

    mpz_mul(p, k, k);                   /* p = k * k */
    mpz_mul_ui(q, k, 2);                /* q = k * 2 */
    mpz_add_ui(q, q, 1);                /* q = q + 1 */
    mpz_add_ui(k, k, 1);                /* k = k + 1 */

    mpz_set(t1, a1);                    /* t1 = a1 */
    mpz_set(t2, b1);                    /* t2 = b1 */

    /* a1 = p*a + q*a1 */
    mpz_mul(t3, p, a);                  /* t3 = p * a */
    mpz_mul(t4, q, a1);                 /* t4 = q * a1 */
    mpz_add(a1, t3, t4);                /* a1 = t3 + t4 */

    /* b1 = p*b + q*b1 */
    mpz_mul(t3, p, b);                  /* t3 = p * b */
    mpz_mul(t4, q, b1);                 /* t4 = q * b1 */
    mpz_add(b1, t3, t4);                /* b1 = t3 + t4 */

    mpz_set(a, t1);
    mpz_set(b, t2);

    /* Print common digits */

    mpz_tdiv_q(d, a, b);                /* d = a / b */
    mpz_tdiv_q(d1, a1, b1);             /* d1 = a1 / b1 */

    while (mpz_cmp(d, d1) == 0) {       /* d == d1 */
      mpz_out_str(stdout, 10, d1);
      fflush(stdout);

      /* a = 10*(a mod b) */
      mpz_tdiv_r(t1, a, b);             /* t1 = a mod b */
      mpz_mul_si(a, t1, 10);            /* a = t1 * 10 */

      /* a1 = 10*(a1 mod b1) */
      mpz_tdiv_r(t1, a1, b1);           /* t1 = a1 mod b1 */
      mpz_mul_si(a1, t1, 10);           /* a = t1 * 10 */

      mpz_tdiv_q(d, a, b);              /* d = a / b */
      mpz_tdiv_q(d1, a1, b1);           /* d1 = a1 / b1 */
    }
  }

  return 0;
}

#include <stdio.h>

main() {
   printf("Hello World\n");
}

/*
 * $Id: echo-mt.c,v 1.1 2002/01/09 14:28:43 michael Exp $
 *
 * Copyright (c) 2001, 2002 by Michael Neumann
 *
 * Multiple Threaded (forking) Echo-Server.
 *
 * Platform: NetBSD (should run on other Unices, too).
 *
 */

#include <sys/types.h>     /* htons() ... */
#include <sys/socket.h>    /* socket(), bind(), listen(), accept() */
#include <netinet/in.h>    /* sockaddr_in */

#include <sys/param.h>     /* MAXHOSTNAMELEN */
#include <netdb.h>         /* gethostbyname() */

#include <signal.h>        /* signal() */
#include <sys/wait.h>      /* waitpid() */

#include <unistd.h>        /* close(), gethostname(), read() ... */
#include <stdio.h>         /* perror() */
#include <strings.h>       /* bzero(), bcopy() */

#define PORT_NR 8000       /* port number to listen on */


/** 
 * Signal handler for SIGCHLD (child process changes state).
 *
 * Queries return status of terminated child processes, 
 * otherwise zombie processes will occure.
 */
void child_sig_handler(void) {
 while (waitpid(-1, NULL, WNOHANG) > 0)
   ;
}


int main(int argc, char** argv) {
  int s, t;                /* socket handles */
  struct sockaddr_in sa;   /* socket address */
  char myhostname[MAXHOSTNAMELEN+1]; /* local host name */
  struct hostent *hp;      /* host informations */

  int pid;      /* proccess id of forked child process */

  int count;
  char buffer[100];

  /* get host informations */
  gethostname(myhostname, MAXHOSTNAMELEN);
  if ( (hp = gethostbyname(myhostname)) == NULL ) {
    perror("Couldn't get informations about host name.");
    return -1;
  }

  /* initialize sockaddr_in struct */
  bzero(&sa, sizeof (struct sockaddr_in));
  bcopy(hp->h_addr, &sa.sin_addr, hp->h_length);
  sa.sin_family = hp->h_addrtype;
  sa.sin_port = htons(PORT_NR);

  /* create socket */
  if ( (s = socket(PF_INET, SOCK_STREAM, 0)) == -1 ) {
    perror("Couldn't create socket.");
    return -1;
  }

  /* bind socket `s' to specific address (local host) */
  if ( bind(s, (struct sockaddr*) &sa, sizeof (struct sockaddr)) == -1 ) {
    perror("Coudn't bind socket.");
    close(s);
    return -1;
  }

  /* allow incoming requests; queue up to 3 of them */
  listen(s, 3);


  /* install signal handler */
  signal(SIGCHLD, child_sig_handler);


  while (1) {

    /* accept a connection */
    if ( (t = accept(s, NULL, NULL)) == -1 ) {
      perror("Couldn't accept socket.");
      close(s);
      return -1;
    }

    /* fork new subprocess, which handles the new connection */
    switch (pid = fork()) {
    case -1:  /* error */
      perror("Could not fork!");
      close(s);
      close(t);
      return -1;

    case 0:   /* child process */
      /* close handle `s' as it is a duplicate */
      close(s);

      /* echo data */
      while ( (count = read(t, buffer, sizeof (buffer)-1)) > 0 ) {
         write(t, buffer, count);
      }

      /* close connection */
      close(t);
      return 0;

    default:  /* parent process */
      /* close handle `t' as it is a duplicate */
      close(t);
    }

  }

  close(s);
  return 0;
}

/*
 * $Id: echo-st.c,v 1.2 2002/01/09 14:29:03 michael Exp $
 *
 * Copyright (c) 2001, 2002 by Michael Neumann
 *
 * Single Threaded (non-forking) Echo-Server.
 *
 * Platform: NetBSD (should run on other Unices, too).
 *
 */

#include <sys/types.h>     /* htons() ... */
#include <sys/socket.h>    /* socket(), bind(), listen(), accept() */
#include <netinet/in.h>    /* sockaddr_in */

#include <sys/param.h>     /* MAXHOSTNAMELEN */
#include <netdb.h>         /* gethostbyname() */

#include <unistd.h>        /* close(), gethostname(), read() ... */
#include <stdio.h>         /* perror() */
#include <strings.h>       /* bzero(), bcopy() */

#define PORT_NR 8000       /* port number to listen on */


int main(int argc, char** argv) {
  int s, t;                /* socket handles */
  struct sockaddr_in sa;   /* socket address */
  char myhostname[MAXHOSTNAMELEN+1]; /* local host name */
  struct hostent *hp;      /* host informations */

  int count;
  char buffer[100];

  /* get host informations */
  gethostname(myhostname, MAXHOSTNAMELEN);
  if ( (hp = gethostbyname(myhostname)) == NULL ) {
    perror("Couldn't get informations about host name.");
    return -1;
  }

  /* initialize sockaddr_in struct */
  bzero(&sa, sizeof (struct sockaddr_in));
  bcopy(hp->h_addr, &sa.sin_addr, hp->h_length);
  sa.sin_family = hp->h_addrtype;
  sa.sin_port = htons(PORT_NR);

  /* create socket */
  if ( (s = socket(PF_INET, SOCK_STREAM, 0)) == -1 ) {
    perror("Couldn't create socket.");
    return -1;
  }

  /* bind socket `s' to specific address (local host) */
  if ( bind(s, (struct sockaddr*) &sa, sizeof (struct sockaddr)) == -1 ) {
    perror("Coudn't bind socket.");
    close(s);
    return -1;
  }

  /* allow incoming requests; queue up to 3 of them */
  listen(s, 3);

  while (1) {

    /* accept a connection */
    if ( (t = accept(s, NULL, NULL)) == -1 ) {
      perror("Couldn't accept socket.");
      close(s);
      return -1;
    }

    /* echo data */
    while ( (count = read(t, buffer, sizeof (buffer)-1)) > 0 ) {
       write(t, buffer, count);
    }

    /* close connection */
    close(t);
  }

  close(s);
  return 0;
}