/*  $Id: crypt.c,v 1.1 2000/03/03 14:20:16 jan Exp $

    Part of SWI-Prolog
    Designed and implemented by Jan Wielemaker

    Copyright (C) 1999 SWI, University of Amsterdam. All rights reserved.
*/

#define _XOPEN_SOURCE
#include <unistd.h>
#include <stdlib.h>
#include <SWI-Prolog.h>
#include "clib.h"

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Simple interface to the Unix   password  encryption routine. Implemented
for providing authorization in  the   multi-threaded  Prolog  based HTTP
deamon and therefore providing a thread-safe interface.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

#ifdef _REENTRANT
#include <pthread.h>

static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
#define LOCK() pthread_mutex_lock(&mutex)
#define UNLOCK() pthread_mutex_unlock(&mutex)
#else
#define LOCK()
#define UNLOCK()
#endif


static foreign_t
pl_crypt(term_t passwd, term_t encrypted)
{ char *p, *e;
  char s[3];

  if ( !PL_get_chars(passwd, &p, CVT_ATOM|CVT_STRING|CVT_LIST|BUF_RING) )
    return pl_error("crypt", 2, NULL, ERR_ARGTYPE,
		    1, passwd, "text");

  if ( PL_get_chars(encrypted, &e, CVT_ATOM|CVT_STRING|CVT_LIST|BUF_RING) )
  { int rval;
    char *s2;
    
    s[0] = e[0];
    s[1] = e[1];
    s[2] = '\0';
    LOCK();
    s2 = crypt(p, s);
    rval = (strcmp(s2, e) == 0 ? TRUE : FALSE);
    UNLOCK();

    return rval;
  } else
  { term_t tail = PL_copy_term_ref(encrypted);
    term_t head = PL_new_term_ref();
    int n;
    int (*unify)(term_t t, const char *s) = PL_unify_list_codes;
    char *s2;
    int rval;

    for(n=0; n<2; n++)
    { if ( PL_get_list(tail, head, tail) )
      { int i;
	char *t;

	if ( PL_get_integer(head, &i) && i>=0 && i<=255 )
	{ s[n] = i;
	} else if ( PL_get_atom_chars(head, &t) && t[1] == '\0' )
	{ s[n] = t[0];
	  unify = PL_unify_list_chars;
	} else
	  return pl_error("crypt", 2, NULL, ERR_ARGTYPE,
			  2, head, "character");
      } else
	break;
    }
    for( ; n < 2; n++ )
    { int c = 'a'+(int)(26.0*rand()/(RAND_MAX+1.0));

      if ( rand() & 0x1 )
	c += 'A' - 'a';

      s[n] = c;
    }
    s[n] = 0;

    LOCK();
    s2 = crypt(p, s);
    rval = (*unify)(encrypted, s2);
    UNLOCK();
    
    return rval;
  }
}


install_t
install_crypt()
{ PL_register_foreign("crypt", 2, pl_crypt, 0);
}
