/* xinit.c
   diet -Os gcc -nostdinc -O2 -s -o xinit xinit.c -Wall -W
   diet -Os gcc -nostdinc -DUSE_XCLEAN -O2 -s -o xinit xinit.c -Wall -W
   diet -Os gcc -nostdinc -DXwrapper -O2 -s -o xinit xinit.c -Wall -W
   -DXwrapper --> try to exec first Xwrapper before X

   -DUSE_XCLEAN
   If the variable XCLEAN is present, then after
   finishing of the server xinit execs /bin/sh -c "$XCLEAN".  
   This is useful for cleaning of ~/.Xauthority
 */
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <string.h>
#ifndef __dietlibc__
#include <time.h>
extern char **environ;
#endif

/* A/UX setpgid incorrectly removes the controlling terminal.
   Per Posix, only setsid should do that. */
#define setpgrp setpgid
#define SIGVAL void
#define killpg(pgrp, sig) kill(-(pgrp), sig)

char *default_server = "X";
char *displayNum = ":0";
char *default_client[] ={"xterm", "-geometry", "+1+1", "-n", "login", NULL};
char *program;
int serverpid = -1;
int clientpid = -1;
volatile int gotSignal = 0;
volatile int gotAlarm = 0;

static char processTimeout ( int timeout, char *string );
static int startServer ( char *server[] );
static int startClient ( char *client[] );
static void shutDown ( void );
static void pathexec_run(char *file,char **argv,char **envp);
static void Fatal(char *msg);
static void Error(char *s);
static void Error_n(int n);

static SIGVAL sig_catch(int sig,void (*f)()) {
  struct sigaction sa;
  sa.sa_handler = f;
  sa.sa_flags = 0;
  sigemptyset(&sa.sa_mask);
  sigaction(sig,&sa,(struct sigaction *) 0);
}
static SIGVAL sigCatch(int sig) {gotSignal = sig;}
static SIGVAL sigAlarm(int sig) {gotAlarm = sig;}
static SIGVAL sigUsr1() {}

static void Execute(char **c) { 
  pathexec_run(*c,c,environ);
  if (errno != ENOEXEC) return;
  *--c = "/bin/sh";
  pathexec_run(*c,c,environ);
}

static unsigned int env_len;
static char *path_save;

int main(int argc, char *argv[]) {
  int pid;
  char **client, **cptr, **server, **ptr;
#ifdef USE_XCLEAN
  char *xclean[] = { "/bin/sh", "-c", 0, 0 };
#endif

  program = *argv++;
  /* sh 5 \0  sh X :0 \0  = 11 */
  client = (char **) alloca((13+argc) * sizeof (char *));
  if (!client) Fatal("no memory\n");
  cptr = ++client;

  /*  copy the client args. */
  if (*argv == 0 || (**argv != '/' && **argv != '.'))
    for (ptr = default_client; *ptr; )
      *cptr++ = *ptr++;
  while (*argv && strcmp(*argv, "--")) *cptr++ = *argv++;
  *cptr++ = NULL;
  if (*argv) argv++;

  /* Copy the server args. */
  server = ++cptr;
  if (*argv == 0 || (**argv != '/' && **argv != '.'))
    *cptr++ = default_server;
  else
    *cptr++ = *argv++;

  if (*argv && (argv[0][0] == ':' && (unsigned int)(argv[0][1] -'0')<10))
    displayNum = *argv;
  *cptr++ = displayNum;

  do { *cptr++ = *argv; } while (*argv++);

  /* Start the server and client. */
  sig_catch(SIGCHLD, SIG_DFL);	/* Insurance */

  /* Let those signal interrupt the wait() call in the main loop */
  sig_catch(SIGQUIT, sigCatch);
  sig_catch(SIGINT, sigCatch);
  sig_catch(SIGHUP, sigCatch);
  sig_catch(SIGPIPE, sigCatch);

  sig_catch(SIGUSR1, sigUsr1);

  /* count number of environment variables */
  for (ptr = environ; *ptr; ptr++) {
    char *x = *ptr;
    if (!memcmp("PATH=", x, 5)) path_save = x + 5;

#ifdef USE_XCLEAN
    if (!memcmp("XCLEAN=", x, 7)) {
      xclean[2] = x + 7;
      x = *environ++;
    }
#endif
  }
  env_len = ptr - environ;

  if (startServer(server) > 0 && startClient(client) > 0) {
    pid = -1;
    while (pid != clientpid && pid != serverpid
	   && gotSignal == 0 ) pid = wait(NULL);
  }
  sig_catch(SIGQUIT, SIG_IGN);
  sig_catch(SIGINT, SIG_IGN);
  sig_catch(SIGHUP, SIG_IGN);
  sig_catch(SIGPIPE, SIG_IGN);

  shutDown();
  if (gotSignal != 0) {
    Error(program); Error(": unexpected signal: "); 
    Error_n(gotSignal); Error("\n"); 
    _exit(1);
  }
  if (serverpid < 0 ) Fatal("Server error.\n");
  if (clientpid < 0 ) Fatal("Client error.\n");
#ifdef USE_XCLEAN
  if (xclean[2]) execve(xclean[0], xclean, environ);
#endif
  _exit(0);
}

/* return TRUE if we timeout waiting for pid to exit, FALSE otherwise. */
static char processTimeout(int timeout, char *string) {
  int	i = 0, pidfound = -1;
  time_t deadline = time(0) + timeout;
  for (;;) {
    if ((pidfound = waitpid(serverpid, 0, WNOHANG)) == serverpid)
      break;
    if (i == 0) {
      Error("\nwaiting for "); Error(string);
    } else
      Error(".");
    
    sleep (1);
    if (++i > 1024 || time(0) > deadline) break;
  }
  if (i>0) Error("\n");     /* tidy up after message */
  return( serverpid != pidfound );
}

static int startServer(char *server[]) {
  sigset_t mask, old;

  sigemptyset(&mask);
  sigaddset(&mask, SIGUSR1);
  sigprocmask(SIG_BLOCK, &mask, &old);

  switch((serverpid=fork())) {
  case 0:
    sigprocmask(SIG_UNBLOCK, &mask, 0);

    /* don't hang on read/write to control tty */
    sig_catch(SIGTTIN, SIG_IGN);
    sig_catch(SIGTTOU, SIG_IGN);

    /*
     * ignore SIGUSR1 in child.  The server
     * will notice this and send SIGUSR1 back
     * at xinit when ready to accept connections
     */
    (void) sig_catch(SIGUSR1, SIG_IGN);
    /*
     * prevent server from getting sighup from vhangup()
     * if client is xterm -L
     */
    setpgrp(0,getpid());

#ifdef Xwrapper
    if (!strcmp(server[0],default_server)) {
      server[0] = "Xwrapper";
      Execute(server);
      server[0] = default_server;
    }
#endif
    Execute (server);
    _exit(1);
    break;
  case -1:
    break;
  default:
    /* don't nice server */
    setpriority( PRIO_PROCESS, serverpid, -1 );
    /* kludge to avoid race with TCP, giving server time to
       set his socket options before we try to open it,
       either use the 15 second timeout, or await SIGUSR1.
       
       If your machine is substantially slower than 15 seconds,
       you can easily adjust this value. */
    sig_catch(SIGALRM, sigAlarm);
    alarm (15);
    sigsuspend(&old);
    alarm (0);
    sigprocmask(SIG_UNBLOCK, &mask, NULL);
    if (gotAlarm) {Error("unable to connect to X server\n"); 
      shutDown(); serverpid=-1; }
    break;
  }
  return(serverpid);
}

static int startClient(char *client[]) {
  if ((clientpid = fork()) == 0) {
    char **newenviron;
    char **newPtr, **oldPtr, *displaybuf;

    newenviron = (char **) alloca ((env_len + 2) * sizeof(char *));
    if (!newenviron) Fatal("no memory\n");
    displaybuf = (char *) alloca(9 + strlen(displayNum));
    if (!displaybuf) Fatal("no memory\n");
    
    /* put DISPLAY=displayname as first element */
    strcpy (displaybuf, "DISPLAY=");
    strcpy (displaybuf + 8, displayNum);
    newPtr = newenviron;
    *newPtr++ = displaybuf;
    
    /* copy pointers to other variables */
    for (oldPtr = environ; ; oldPtr++) {
      *newPtr = *oldPtr;
      if (*oldPtr == 0) break;
      if (memcmp (*newPtr, "DISPLAY=", 8))
	newPtr++;
    }
    environ = newenviron;
  
    setuid(getuid());
    setpgrp(0, getpid());

    Execute (client);
    _exit(1);
  }
  return (clientpid);
}

static void shutDown(void) {
  if (clientpid > 0) {
    /* HUP all local clients to allow them to clean up */
    if ((killpg(clientpid, SIGHUP) != 0) && (errno != ESRCH)) {
      Error("can't send HUP to process group ");
      Error_n(clientpid); Error("\n");
    }
  }

  if (serverpid < 0) return;
  if (killpg(serverpid, SIGTERM) < 0) {
    if (errno == EPERM) Fatal("Can't kill X server\n");
    if (errno == ESRCH) return;
  }
  if (! processTimeout(10, "X server to shut down")) {
    Error("\n");
    return;
  }

  Error("X server slow to shut down, sending KILL signal.\n");
  if (killpg(serverpid, SIGKILL) < 0) {
    if (errno == ESRCH)
      return;
  }
  if (processTimeout(3, "server to die")) Fatal("Can't kill X server\n");
  Error("\n");
  return;
}

static void Error(char *s) {write(2,s,strlen(s));}
static void Fatal(char *msg)
  {Error(program); Error(": "); Error(msg); _exit(1);}

static void Error_n(int k) {
  char buf[24], *last=buf+24, *p = last;
  unsigned int u;
  if (k<0) u=-k;
  else u=k;
  do { *--p = '0' + (u % 10); u /= 10; } while(u);
  if (k<0) *--p = '-';
  write(2,p,last-p);
}

static void pathexec_run(char *file,char **argv,char **envp) {
  char *tmp,*next, *path;
  int savederrno=0;

  if (strchr((char *)file,'/')) { execve(file,argv,envp); return; }
  
  path = (path_save) ? path_save : "/bin:/usr/bin";
  tmp = (char *)alloca(4+strlen(path) + strlen(file));
  if (!tmp) {errno=ENOMEM; return;}

  for (;;) {
    size_t len = 1;
    next = strchr(path,':');
    if (!next) next=path + strlen(path);

    if (path[0] == 0 || path[0] == ':') tmp[0] = '.';
    else { len = next-path; memcpy(tmp,path,len); }
    tmp[len++] = '/';
    strcpy(tmp+len,file);
 
    execve(tmp,argv,envp);
    if (errno != ENOENT) {
      savederrno = errno;
      if ((errno != EACCES) && (errno != ENOEXEC) && (errno != ENOTDIR)) return;
    }

    if (*next==0) {
      if (savederrno) errno = savederrno;
      return;
    }
    path=next+1;
  }
}


#if 0
--- startx.original	2009-08-18 21:27:17.000000000 +0300
+++ startx	2009-08-18 22:07:37.000000000 +0300
@@ -175,13 +175,18 @@
 fi
 
 
+XCLEAN=''
+if [ x"$enable_xauth" = x1 ] ; then
+    if [ x"$removelist" != x ]; then
+        XCLEAN="xauth remove $removelist;"
+    fi
+    if [ x"$xserverauthfile" != x ]; then
+        XCLEAN="$XCLEAN""rm -f $xserverauthfile"
+    fi
+fi
 
-
-
-
-
-
-xinit $client $clientargs -- $server $display $serverargs
+[ "$XCLEAN" != "" ] && export XCLEAN
+exec xinit $client $clientargs -- $server $display $serverargs
 
 
 if [ x"$enable_xauth" = x1 ] ; then
#endif