File: operator.c

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/*-
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Cimarron D. Taylor of the University of California, Berkeley.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "tweak.h"
#ifndef VMS
#include <sys/types.h>
#include <sys/stat.h>
#else
#include "types.h"
#include "stat.h"
#endif
#include <stdio.h>
#include "find.h"

/*
 * yanknode --
 *	destructively removes the top from the plan
 */
static PLAN *yanknode PROTO1(PLAN **, planp)    
{
  PLAN *node;		/* top node removed from the plan */
  
  if ((node = (*planp)) == NULL) return(NULL);
  (*planp) = (*planp)->next;
  node->next = NULL;
  return(node);
}

/*
 * yankexpr --
 *	Removes one expression from the plan.  This is used mainly by
 *	paren_squish.  In comments below, an expression is either a
 *	simple node or a N_EXPR node containing a list of simple nodes.
 */
static PLAN *yankexpr PROTO1(PLAN **, planp)    
{
  register PLAN *next;	/* temp node holding subexpression results */
  PLAN *node;           /* pointer to returned node or expression */
  PLAN *tail;		/* pointer to tail of subplan */
  PLAN *subplan;	/* pointer to head of ( ) expression */
  
  /* first pull the top node from the plan */
  if ((node = yanknode(planp)) == NULL) return(NULL);
  
  /*
   * If the node is an '(' then we recursively slurp up expressions
   * until we find its associated ')'.  If it's a closing paren we
   * just return it and unwind our recursion; all other nodes are
   * complete expressions, so just return them.
   */
  if (node->type == N_OPENPAREN)
    for (tail = subplan = NULL;;) {
      if ((next = yankexpr(planp)) == NULL)
	fprintf(stderr,"(: missing closing ')'");
      /*
       * If we find a closing ')' we store the collected
       * subplan in our '(' node and convert the node to
       * a N_EXPR.  The ')' we found is ignored.  Otherwise,
       * we just continue to add whatever we get to our
       * subplan.
       */
      if (next->type == N_CLOSEPAREN) {
	if (subplan == NULL) {
	  fprintf(stderr,"(): empty inner expression");
	  exit(1);
	}
	node->p_data[0] = subplan;
	node->type = N_EXPR;
	node->eval = find_expr;
	break;
      } else {
	if (subplan == NULL) tail = subplan = next;
	else {
	  tail->next = next;
	  tail = next;
	}
	tail->next = NULL;
      }
    }
  return(node);
}

/*
 * paren_squish --
 *	replaces "parentheisized" plans in our search plan with "expr" nodes.
 */
PLAN *paren_squish PROTO1(PLAN *, plan)
{
  register PLAN *expr;	/* pointer to next expression */
  register PLAN *tail;	/* pointer to tail of result plan */
  PLAN *result;		/* pointer to head of result plan */
  
  result = tail = NULL;
  
  /*
   * the basic idea is to have yankexpr do all our work and just
   * collect it's results together.
   */
  while ((expr = yankexpr(&plan)) != NULL) {
    /*
     * if we find an unclaimed ')' it means there is a missing
     * '(' someplace.
     */
    if (expr->type == N_CLOSEPAREN) {
      fprintf(stderr,"): no beginning '('");
      exit(1);
    }
    
    /* add the expression to our result plan */
    if (result == NULL) tail = result = expr;
    else {
      tail->next = expr;
      tail = expr;
    }
    tail->next = NULL;
  }
  return(result);
}

/*
 * not_squish --
 *	compresses "!" expressions in our search plan.
 */
PLAN *not_squish PROTO1(PLAN *, plan)
{
  register PLAN *next;	/* next node being processed */
  register PLAN *node;	/* temporary node used in N_NOT processing */
  register PLAN *tail;	/* pointer to tail of result plan */
  PLAN *result;		/* pointer to head of result plan */
  
  tail = result = next = NULL;
  
  while ((next = yanknode(&plan)) != NULL) {
    /*
     * if we encounter a ( expression ) then look for nots in
     * the expr subplan.
     */
    if (next->type == N_EXPR) next->p_data[0] = not_squish(next->p_data[0]);
    
    /*
     * if we encounter a not, then snag the next node and place
     * it in the not's subplan.  As an optimization we compress
     * several not's to zero or one not.
     */
    if (next->type == N_NOT) {
      int notlevel = 1;
      
      node = yanknode(&plan);
      while (node->type == N_NOT) {
	++notlevel;
	node = yanknode(&plan);
      }
      if (node == NULL) {
	fprintf(stderr,"!: no following expression");
	exit(1);
      }
      if (node->type == N_OR) {
	fprintf(stderr,"!: nothing between ! and -o");
	exit(1);
      }
      if (notlevel % 2 != 1) next = node;
      else next->p_data[0] = node;
    }
    
    /* add the node to our result plan */
    if (result == NULL) tail = result = next;
    else {
      tail->next = next;
      tail = next;
    }
    tail->next = NULL;
  }
  return(result);
}

/*
 * or_squish --
 *	compresses -o expressions in our search plan.
 */
PLAN *or_squish PROTO1(PLAN *, plan)
{
  register PLAN *next;	/* next node being processed */
  register PLAN *tail;	/* pointer to tail of result plan */
  PLAN *result;		/* pointer to head of result plan */
  
  tail = result = next = NULL;
  
  while ((next = yanknode(&plan)) != NULL) {
    /*
     * if we encounter a ( expression ) then look for or's in
     * the expr subplan.
     */
    if (next->type == N_EXPR) next->p_data[0] = or_squish(next->p_data[0]);
    
    /* if we encounter a not then look for not's in the subplan */
    if (next->type == N_NOT) next->p_data[0] = or_squish(next->p_data[0]);
    
    /*
     * if we encounter an or, then place our collected plan in the
     * or's first subplan and then recursively collect the
     * remaining stuff into the second subplan and return the or.
     */
    if (next->type == N_OR) {
      if (result == NULL) {
	fprintf(stderr,"-o: no expression before -o");
	exit(1);
      }
      next->p_data[0] = result;
      next->p_data[1] = or_squish(plan);
      if (next->p_data[1] == NULL) {
	fprintf(stderr,"-o: no expression after -o");
	exit(1);
      }
      return(next);
    }
    
    /* add the node to our result plan */
    if (result == NULL) tail = result = next;
    else {
      tail->next = next;
      tail = next;
    }
    tail->next = NULL;
  }
  return(result);
}