4.3BSD-Reno/src/usr.bin/find/operator.c
/*-
* 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 are permitted provided
* that: (1) source distributions retain this entire copyright notice and
* comment, and (2) distributions including binaries display the following
* acknowledgement: ``This product includes software developed by the
* University of California, Berkeley and its contributors'' in the
* documentation or other materials provided with the distribution and in
* all advertising materials mentioning features or use of this software.
* 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
#ifndef lint
static char sccsid[] = "@(#)operator.c 5.1 (Berkeley) 4/16/90";
#endif /* not lint */
#include <sys/types.h>
#include <stdio.h>
#include "find.h"
/*
* find_yanknode --
* destructively removes the top from the plan
*/
PLAN *
find_yanknode(planp)
PLAN **planp; /* pointer to top of plan (modified) */
{
PLAN *node; /* top node removed from the plan */
if ((node = (*planp)) == NULL)
return(NULL);
(*planp) = (*planp)->next;
node->next = NULL;
return(node);
}
/*
* find_yankexpr --
* Removes one expression from the plan. This is used mainly by
* find_squish_paren. In comments below, an expression is either
* a simple node or a T_EXPR node containing a list of simple nodes.
*/
PLAN *
find_yankexpr(planp)
PLAN **planp; /* pointer to top of plan (modified) */
{
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 */
int f_expr();
/* first pull the top node from the plan */
if ((node = find_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 == T_OPENPAREN)
for (tail = subplan = NULL;;) {
if ((next = find_yankexpr(planp)) == NULL)
bad_arg("(", "missing closing ')'");
/*
* If we find a closing ')' we store the collected
* subplan in our '(' node and convert the node to
* a T_EXPR. The ')' we found is ignored. Otherwise,
* we just continue to add whatever we get to our
* subplan.
*/
if (next->type == T_CLOSEPAREN) {
if (subplan == NULL)
bad_arg("()", "empty inner expression");
node->p_data[0] = subplan;
node->type = T_EXPR;
node->eval = f_expr;
break;
} else {
if (subplan == NULL)
tail = subplan = next;
else {
tail->next = next;
tail = next;
}
tail->next = NULL;
}
}
return(node);
}
/*
* find_squish_paren --
* replaces "parentheisized" plans in our search plan with "expr" nodes.
*/
PLAN *
find_squish_paren(plan)
PLAN *plan; /* plan with ( ) nodes */
{
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 find_yankexpr do all our work and just
* collect it's results together.
*/
while ((expr = find_yankexpr(&plan)) != NULL) {
/*
* if we find an unclaimed ')' it means there is a missing
* '(' someplace.
*/
if (expr->type == T_CLOSEPAREN)
bad_arg(")", "no beginning '('");
/* add the expression to our result plan */
if (result == NULL)
tail = result = expr;
else {
tail->next = expr;
tail = expr;
}
tail->next = NULL;
}
return(result);
}
/*
* find_squish_not --
* compresses "!" expressions in our search plan.
*/
PLAN *
find_squish_not(plan)
PLAN *plan; /* plan to process */
{
register PLAN *next; /* next node being processed */
register PLAN *node; /* temporary node used in T_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 = find_yanknode(&plan)) != NULL) {
/*
* if we encounter a ( expression ) then look for nots in
* the expr subplan.
*/
if (next->type == T_EXPR)
next->p_data[0] = find_squish_not(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 == T_NOT) {
int notlevel = 1;
node = find_yanknode(&plan);
while (node->type == T_NOT) {
++notlevel;
node = find_yanknode(&plan);
}
if (node == NULL)
bad_arg("!", "no following expression");
if (node->type == T_OR)
bad_arg("!", "nothing between ! and -o");
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);
}
/*
* find_squish_or --
* compresses -o expressions in our search plan.
*/
PLAN *
find_squish_or(plan)
PLAN *plan; /* plan with ors to be squished */
{
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 = find_yanknode(&plan)) != NULL) {
/*
* if we encounter a ( expression ) then look for or's in
* the expr subplan.
*/
if (next->type == T_EXPR)
next->p_data[0] = find_squish_or(next->p_data[0]);
/* if we encounter a not then look for not's in the subplan */
if (next->type == T_NOT)
next->p_data[0] = find_squish_or(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 == T_OR) {
if (result == NULL)
bad_arg("-o", "no expression before -o");
next->p_data[0] = result;
next->p_data[1] = find_squish_or(plan);
if (next->p_data[1] == NULL)
bad_arg("-o", "no expression after -o");
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);
}