
/********************************************
rexp2.c
copyright 1991, Michael D. Brennan

This is a source file for mawk, an implementation of
the AWK programming language.

Mawk is distributed without warranty under the terms of
the GNU General Public License, version 2, 1991.
********************************************/

/*$Log: rexp2.c,v $
 * Revision 3.8  1992/12/24  00:36:44  mike
 * fixed major bozo for LMDOS when growing stack
 * fixed potential LMDOS bozo with M_STR+U_ON+END_ON
 * fixed minor bug in M_CLASS+U_ON+END_ON
 *
 * Revision 3.7  92/01/21  17:33:15  brennan
 * added some casts so that character classes work with signed chars
 * 
 * Revision 3.6  91/10/29  10:54:03  brennan
 * SIZE_T
 * 
 * Revision 3.5  91/08/13  09:10:15  brennan
 * VERSION .9994
 * 
 * Revision 3.4  91/08/08  07:53:34  brennan
 * work around for turboC realloc() bug
 * 
 * Revision 3.4  91/08/07  07:10:47  brennan
 * work around for TurboC realloc() bug
 * 
 * Revision 3.3  91/08/04  15:45:57  brennan
 * minor change for large model dos
 * 
 * Revision 3.2  91/06/10  16:18:14  brennan
 * changes for V7
 * 
 * Revision 3.1  91/06/07  10:33:25  brennan
 * VERSION 0.995
 * 
 * Revision 1.8  91/06/05  09:01:33  brennan
 * changes to RE_new_run_stack
 * 
 * Revision 1.7  91/05/31  10:56:02  brennan
 * stack_empty hack for DOS large model
 * 
*/



/*  test a string against a machine   */

#include "rexp.h"

#define  STACKGROWTH    16

#ifdef  DEBUG
static RT_STATE *PROTO(slow_push,(RT_STATE *,STATE*,char*,int)); 
#endif


RT_STATE *RE_run_stack_base; 
RT_STATE *RE_run_stack_limit ;

/* Large model DOS segment arithemetic breaks the current stack.
   This hack fixes it without rewriting the whole thing, 5/31/91 */
RT_STATE *RE_run_stack_empty ;

void RE_run_stack_init()
{ 
  if ( !RE_run_stack_base )
  {
    RE_run_stack_base = (RT_STATE *)
                 RE_malloc(sizeof(RT_STATE) * STACKGROWTH ) ;
    RE_run_stack_limit = RE_run_stack_base + STACKGROWTH ;
    RE_run_stack_empty = RE_run_stack_base-1 ;
  }
}

/* sometimes during REmatch(), this stack can grow pretty large.
   In real life cases, the back tracking usually fails. Some
   work is needed here to improve the algorithm.
   I.e., figure out how not to stack useless paths.
*/

RT_STATE  *RE_new_run_stack()
{ 
  int oldsize = RE_run_stack_limit - RE_run_stack_base ;
  int newsize = oldsize + STACKGROWTH ;

#ifdef  LMDOS   /* large model DOS */
  /* have to worry about overflow on multiplication (ugh) */
  if ( newsize >= 4096 ) RE_run_stack_base = (RT_STATE*) 0 ;
  else
#endif

  RE_run_stack_base = (RT_STATE *) realloc( RE_run_stack_base ,
          SIZE_T(newsize * sizeof(RT_STATE)) ) ;

  if ( ! RE_run_stack_base )
  { fprintf(stderr, "out of memory for RE run time stack\n") ;
    /* this is pretty unusual, I've only seen it happen on
       weird input to REmatch() under 16bit DOS , the same
       situation worked easily on 32bit machine.  */
    exit(100) ;
  }

  RE_run_stack_limit = RE_run_stack_base + newsize ;
  RE_run_stack_empty = RE_run_stack_base - 1 ;

  /* return the new stackp */
  return  RE_run_stack_base + oldsize ;
}

#ifdef  DEBUG
static RT_STATE *slow_push(sp, m, s, u)
  RT_STATE *sp ;
  STATE *m ;
  char *s ;
  int   u ;
{ 
  if ( sp == RE_run_stack_limit ) sp = RE_new_run_stack() ;
  sp->m = m ; sp->s = s ; sp->u = u ;
  return sp ;
}
#endif

#ifdef   DEBUG
#define  push(mx,sx,ux)   stackp = slow_push(++stackp, mx, sx, ux)
#else
#define  push(mx,sx,ux)   if (++stackp == RE_run_stack_limit)\
                                stackp = RE_new_run_stack() ;\
                          stackp->m=(mx);stackp->s=(sx);stackp->u=(ux)
#endif


#define   CASE_UANY(x)  case  x + U_OFF :  case  x + U_ON

/* test if str ~ /machine/
*/

int  REtest( str, machine)
  char *str ;
  VOID *machine ;
{ register STATE *m = (STATE *) machine ;
  register char *s = str ;
  register RT_STATE *stackp ;
  int u_flag ;
  char *str_end ;
  int t ; /*convenient temps */
  STATE *tm ;

  /* handle the easy case quickly */
  if ( (m+1)->type == M_ACCEPT && m->type == M_STR )
        return  str_str(s, m->data.str, m->len) != (char *) 0 ;
  else
  { u_flag = U_ON ; str_end = (char *) 0 ;
    stackp = RE_run_stack_empty ;
    goto  reswitch ;
  }

refill :
  if ( stackp == RE_run_stack_empty )  return  0 ;
  m = stackp->m ;
  s = stackp->s ;
  u_flag  = stackp-- -> u ;


reswitch  :

  switch( m->type + u_flag )
  {
    case M_STR + U_OFF + END_OFF :
            if ( strncmp(s, m->data.str, SIZE_T(m->len)) ) goto refill ;
            s += m->len ;  m++ ;
            goto reswitch ;

    case M_STR + U_OFF + END_ON :
            if ( strcmp(s, m->data.str) ) goto refill ;
            s += m->len ;  m++ ;
            goto reswitch ;

    case M_STR + U_ON + END_OFF :
            if ( !(s = str_str(s, m->data.str, m->len)) ) goto refill ;
            push(m, s+1, U_ON) ;
            s += m->len ; m++ ; u_flag = U_OFF ;
            goto reswitch ;

    case M_STR + U_ON + END_ON :
            if ( !str_end )  str_end = s + strlen(s) ;
	    t = (str_end - s) - m->len ;
            if (t < 0 || memcmp(s+t,m->data.str,SIZE_T(m->len)))
			goto refill ;
            s = str_end ; m++ ; u_flag = U_OFF ;
            goto reswitch ;

    case M_CLASS + U_OFF + END_OFF :
            if ( !ison(*m->data.bvp, s[0] ) )  goto refill ;
            s++ ; m++ ;
            goto reswitch ;

    case M_CLASS + U_OFF + END_ON :
            if ( s[1] || !ison(*m->data.bvp,s[0]) )  goto refill ;
            s++ ; m++ ;
            goto reswitch ;
    case M_CLASS + U_ON + END_OFF :
            while ( !ison(*m->data.bvp,s[0]) )
                if ( s[0] == 0 )  goto refill ;
                else  s++ ;
            s++ ;
            push(m, s, U_ON) ;
            m++ ; u_flag = U_OFF ;
            goto reswitch ;

    case M_CLASS + U_ON + END_ON :
            if ( ! str_end )  str_end = s + strlen(s) ;
            if ( s[0] == 0 || ! ison(*m->data.bvp, str_end[-1]) )
				goto refill ;
            s = str_end ; m++ ; u_flag = U_OFF ;
            goto reswitch ;

    case M_ANY + U_OFF + END_OFF :
            if ( s[0] == 0 )  goto refill ;
            s++ ; m++ ;
            goto  reswitch ;

    case M_ANY + U_OFF + END_ON :
            if ( s[0] == 0 || s[1] != 0 )  goto refill ;
            s++ ; m++ ;
            goto reswitch ;

    case M_ANY + U_ON + END_OFF :
            if ( s[0] == 0 )  goto refill ;
            s++ ; 
            push(m, s, U_ON) ;
            m++ ; u_flag = U_OFF ;
            goto  reswitch ;

    case M_ANY + U_ON + END_ON :
            if ( s[0] == 0 )  goto refill ;
            if ( ! str_end )  str_end = s + strlen(s) ;
            s = str_end ; m++ ; u_flag = U_OFF ;
            goto reswitch ;

    case  M_START + U_OFF + END_OFF :
    case  M_START + U_ON  + END_OFF :
            if ( s != str )  goto  refill ;
            m++ ;  u_flag = U_OFF ;
            goto  reswitch ;

    case  M_START + U_OFF + END_ON :
    case  M_START + U_ON  + END_ON :
            if ( s != str || s[0] != 0 )  goto  refill ;
            m++ ; u_flag = U_OFF ;
            goto  reswitch ;

    case  M_END + U_OFF  :
            if ( s[0]  != 0 )  goto  refill ;
            m++ ; goto reswitch ;

    case  M_END + U_ON :
            s += strlen(s) ;
            m++ ; u_flag = U_OFF ;
            goto reswitch ;

    CASE_UANY(M_U) :
            u_flag = U_ON ; m++ ;
            goto reswitch ;

    CASE_UANY(M_1J) :
            m += m->data.jump ;
            goto reswitch ;

    CASE_UANY(M_2JA) : /* take the non jump branch */
            /* don't stack an ACCEPT */
            if ( (tm = m + m->data.jump)->type == M_ACCEPT ) return 1 ;
            push(tm, s, u_flag) ;
            m++ ;
            goto reswitch ;

    CASE_UANY(M_2JB) : /* take the jump branch */
            /* don't stack an ACCEPT */
            if ( (tm = m + 1)->type == M_ACCEPT ) return 1 ;
            push(tm, s, u_flag) ;
            m += m->data.jump ;
            goto reswitch ;

    CASE_UANY(M_ACCEPT) :
            return 1 ;

    default :
            RE_panic("unexpected case in REtest") ;
  }
}

  

#ifdef  MAWK

char *is_string_split( p, lenp )
  register STATE *p ;
  unsigned *lenp ;
{
  if ( p[0].type == M_STR && p[1].type == M_ACCEPT )
  { *lenp = p->len ;
    return  p->data.str ;
  }
  else   return  (char *) 0 ;
}
#else /* mawk provides its own str_str */

char *str_str(target, key, klen)
  register char *target ;
  register char *key ;
  unsigned klen ;
{ int c = key[0] ;

  switch( klen )
  { case 0 :  return (char *) 0 ;
    case 1 :  return strchr(target, c) ;
    case 2 :  
              while ( target = strchr(target, c) )
                    if ( target[1] == key[1] ) return target ;
                    else target++ ;
              break ;

    default :
              klen-- ; key++ ;
              while ( target = strchr(target, c) )
                    if (memcmp(target+1,key,SIZE_T(klen)) == 0) return target ;
                    else target++ ;
              break ;
  }
  return (char *) 0 ;
}
              

#endif  /* MAWK */
