#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <strings.h>
#include <sys/file.h>

extern const char *__progname;

#include "lock.h"

char lock_nohandle;
char lock_errhandle;

LOCK_HANDLE set_lock(const char *fn, int pid, int errfatal)
{
 char *lfn;
 char *tfn;
 int l;
 int fd;
 int i;
 char pidbuf[7];

 sprintf(&pidbuf[0],"%d\n",pid);
 l = strlen(fn);
 lfn = malloc(l+5+1);
 tfn = malloc(l+6+5+1);
 sprintf(lfn,"%s.LOCK",fn);
 sprintf(tfn,"%s.%05d",lfn,pid);
 unlink(tfn);
 fd = open(tfn,O_WRONLY|O_CREAT|O_TRUNC,0644);
 if (fd < 0)
  { if (errfatal)
     { fprintf(stderr,"%s: can't create %s: %s\n",__progname,tfn,strerror(errno));
       exit(1);
     }
    free(lfn);
    free(tfn);
    return(LOCK_ERRHANDLE);
  }
 l = strlen(&pidbuf[0]);
 i = write(fd,&pidbuf[0],l);
 if (i != l)
  { if (errfatal)
     { if (i < 0)
	{ fprintf(stderr,"%s: can't write pid to %s: %s\n",__progname,tfn,strerror(errno));
	}
       else
	{ fprintf(stderr,"%s: can't write pid to %s: wrote %d not %d\n",__progname,tfn,i,l);
	}
       unlink(tfn);
       exit(1);
     }
    close(fd);
    unlink(tfn);
    free(lfn);
    free(tfn);
    return(LOCK_ERRHANDLE);
  }
 close(fd);
 while (link(tfn,lfn) < 0)
  { if (errno != EEXIST)
     { if (errfatal)
	{ fprintf(stderr,"%s: can't link %s to %s: %s\n",__progname,tfn,lfn,strerror(errno));
	  unlink(tfn);
	  exit(1);
	}
       unlink(tfn);
       free(lfn);
       free(tfn);
       return(LOCK_ERRHANDLE);
     }
    fd = open(lfn,O_RDONLY,0);
    if (fd < 0)
     { if (errno != ENOENT)
	{ if (errfatal)
	   { fprintf(stderr,"%s: can't open %s: %s\n",__progname,lfn,strerror(errno));
	     unlink(tfn);
	     exit(1);
	   }
	  unlink(tfn);
	  free(lfn);
	  free(tfn);
	  return(LOCK_ERRHANDLE);
	}
     }
    else
     { i = read(fd,&pidbuf[0],sizeof(pidbuf)-1);
       if (i < 0)
	{ if (errfatal)
	   { fprintf(stderr,"%s: can't read from %s: %s\n",__progname,lfn,strerror(errno));
	     unlink(tfn);
	     exit(1);
	   }
	  close(fd);
	  unlink(tfn);
	  free(lfn);
	  free(tfn);
	  return(LOCK_ERRHANDLE);
	}
       close(fd);
       pidbuf[i] = '\0';
       i = kill(atoi(&pidbuf[0]),0);
       if ((i >= 0) || (errno != ESRCH))
	{ if (errfatal)
	   { fprintf(stderr,"%s: %s is locked\n",__progname,fn);
	     unlink(tfn);
	     exit(1);
	   }
	  unlink(tfn);
	  free(lfn);
	  free(tfn);
	  return(LOCK_NOHANDLE);
	}
       unlink(lfn);
     }
  }
 unlink(tfn);
 free(tfn);
 return((LOCK_HANDLE)lfn);
}

void unset_lock(LOCK_HANDLE h)
{
 if (h == LOCK_NOHANDLE) return;
 if (h == LOCK_ERRHANDLE) abort();
 unlink((char *)h);
 free(h);
}