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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* $XConsortium: ifparser.c,v 1.8 95/06/03 00:01:41 gildea Exp $
*
* Copyright 1992 Network Computing Devices, Inc.
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for any purpose and without fee is hereby granted, provided
* that the above copyright notice appear in all copies and that both that
* copyright notice and this permission notice appear in supporting
* documentation, and that the name of Network Computing Devices may not be
* used in advertising or publicity pertaining to distribution of the software
* without specific, written prior permission. Network Computing Devices makes
* no representations about the suitability of this software for any purpose.
* It is provided ``as is'' without express or implied warranty.
*
* NETWORK COMPUTING DEVICES DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
* SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS,
* IN NO EVENT SHALL NETWORK COMPUTING DEVICES BE LIABLE FOR ANY SPECIAL,
* INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
* OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*
* Author: Jim Fulton
* Network Computing Devices, Inc.
*
* Simple if statement processor
*
* This module can be used to evaluate string representations of C language
* if constructs. It accepts the following grammar:
*
* EXPRESSION := VALUE
* | VALUE BINOP EXPRESSION
*
* VALUE := '(' EXPRESSION ')'
* | '!' VALUE
* | '-' VALUE
* | 'defined' '(' variable ')'
* | 'defined' variable
* | # variable '(' variable-list ')'
* | variable
* | number
*
* BINOP := '*' | '/' | '%'
* | '+' | '-'
* | '<<' | '>>'
* | '<' | '>' | '<=' | '>='
* | '==' | '!='
* | '&' | '|'
* | '&&' | '||'
*
* The normal C order of precedence is supported.
*
*
* External Entry Points:
*
* ParseIfExpression parse a string for #if
*/
#include "ifparser.h"
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
/****************************************************************************
Internal Macros and Utilities for Parser
****************************************************************************/
#define DO(val) if (!(val)) return NULL
#define CALLFUNC(ggg,fff) (*((ggg)->funcs.fff))
#define SKIPSPACE(ccc) while (isspace((unsigned char)*ccc)) ccc++
#define isvarfirstletter(ccc) (isalpha((unsigned char)(ccc)) || (ccc) == '_')
static const char *
parse_variable (IfParser *g, const char *cp, const char **varp)
{
SKIPSPACE (cp);
if (!isvarfirstletter (*cp))
return CALLFUNC(g, handle_error) (g, cp, "variable name");
*varp = cp;
/* EMPTY */
for (cp++; isalnum((unsigned char)*cp) || *cp == '_'; cp++) ;
return cp;
}
static const char *
parse_number (IfParser *g, const char *cp, int *valp)
{
SKIPSPACE (cp);
if (!isdigit((unsigned char)*cp))
return CALLFUNC(g, handle_error) (g, cp, "number");
#ifdef _WIN32
{
char *cp2;
*valp = strtol(cp, &cp2, 0);
}
#else
*valp = atoi (cp);
/* EMPTY */
for (cp++; isdigit((unsigned char)*cp); cp++) ;
#endif
return cp;
}
static const char *
parse_value (IfParser *g, const char *cp, int *valp)
{
const char *var;
*valp = 0;
SKIPSPACE (cp);
if (!*cp)
return cp;
switch (*cp) {
case '(':
DO (cp = ParseIfExpression (g, cp + 1, valp));
SKIPSPACE (cp);
if (*cp != ')')
return CALLFUNC(g, handle_error) (g, cp, ")");
return cp + 1; /* skip the right paren */
case '!':
DO (cp = parse_value (g, cp + 1, valp));
*valp = !(*valp);
return cp;
case '-':
DO (cp = parse_value (g, cp + 1, valp));
*valp = -(*valp);
return cp;
case '#':
DO (cp = parse_variable (g, cp + 1, &var));
SKIPSPACE (cp);
if (*cp != '(')
return CALLFUNC(g, handle_error) (g, cp, "(");
do {
DO (cp = parse_variable (g, cp + 1, &var));
SKIPSPACE (cp);
} while (*cp && *cp != ')');
if (*cp != ')')
return CALLFUNC(g, handle_error) (g, cp, ")");
*valp = 1; /* XXX */
return cp + 1;
case 'd':
if (strncmp (cp, "defined", 7) == 0 && !isalnum((unsigned char)cp[7])) {
int paren = 0;
size_t len;
cp += 7;
SKIPSPACE (cp);
if (*cp == '(') {
paren = 1;
cp++;
}
DO (cp = parse_variable (g, cp, &var));
len = (size_t)(cp - var);
SKIPSPACE (cp);
if (paren && *cp != ')')
return CALLFUNC(g, handle_error) (g, cp, ")");
*valp = (*(g->funcs.eval_defined)) (g, var, len);
return cp + paren; /* skip the right paren */
}
/* fall out */
}
if (isdigit((unsigned char)*cp)) {
DO (cp = parse_number (g, cp, valp));
} else if (!isvarfirstletter(*cp))
return CALLFUNC(g, handle_error) (g, cp, "variable or number");
else {
DO (cp = parse_variable (g, cp, &var));
*valp = (*(g->funcs.eval_variable)) (g, var, (size_t)(cp - var));
}
return cp;
}
static const char *
parse_product (IfParser *g, const char *cp, int *valp)
{
int rightval;
DO (cp = parse_value (g, cp, valp));
SKIPSPACE (cp);
switch (*cp) {
case '*':
DO (cp = parse_product (g, cp + 1, &rightval));
*valp = (*valp * rightval);
break;
case '/':
DO (cp = parse_product (g, cp + 1, &rightval));
/* Do nothing in the divide-by-zero case. */
if (rightval) {
*valp = (*valp / rightval);
}
break;
case '%':
DO (cp = parse_product (g, cp + 1, &rightval));
*valp = (*valp % rightval);
break;
}
return cp;
}
static const char *
parse_sum (IfParser *g, const char *cp, int *valp)
{
int rightval;
DO (cp = parse_product (g, cp, valp));
SKIPSPACE (cp);
switch (*cp) {
case '+':
DO (cp = parse_sum (g, cp + 1, &rightval));
*valp = (*valp + rightval);
break;
case '-':
DO (cp = parse_sum (g, cp + 1, &rightval));
*valp = (*valp - rightval);
break;
}
return cp;
}
static const char *
parse_shift (IfParser *g, const char *cp, int *valp)
{
int rightval;
DO (cp = parse_sum (g, cp, valp));
SKIPSPACE (cp);
switch (*cp) {
case '<':
if (cp[1] == '<') {
DO (cp = parse_shift (g, cp + 2, &rightval));
*valp = (*valp << rightval);
}
break;
case '>':
if (cp[1] == '>') {
DO (cp = parse_shift (g, cp + 2, &rightval));
*valp = (*valp >> rightval);
}
break;
}
return cp;
}
static const char *
parse_inequality (IfParser *g, const char *cp, int *valp)
{
int rightval;
DO (cp = parse_shift (g, cp, valp));
SKIPSPACE (cp);
switch (*cp) {
case '<':
if (cp[1] == '=') {
DO (cp = parse_inequality (g, cp + 2, &rightval));
*valp = (*valp <= rightval);
} else {
DO (cp = parse_inequality (g, cp + 1, &rightval));
*valp = (*valp < rightval);
}
break;
case '>':
if (cp[1] == '=') {
DO (cp = parse_inequality (g, cp + 2, &rightval));
*valp = (*valp >= rightval);
} else {
DO (cp = parse_inequality (g, cp + 1, &rightval));
*valp = (*valp > rightval);
}
break;
}
return cp;
}
static const char *
parse_equality (IfParser *g, const char *cp, int *valp)
{
int rightval;
DO (cp = parse_inequality (g, cp, valp));
SKIPSPACE (cp);
switch (*cp) {
case '=':
if (cp[1] == '=')
cp++;
DO (cp = parse_equality (g, cp + 1, &rightval));
*valp = (*valp == rightval);
break;
case '!':
if (cp[1] != '=')
break;
DO (cp = parse_equality (g, cp + 2, &rightval));
*valp = (*valp != rightval);
break;
}
return cp;
}
static const char *
parse_band (IfParser *g, const char *cp, int *valp)
{
int rightval;
DO (cp = parse_equality (g, cp, valp));
SKIPSPACE (cp);
switch (*cp) {
case '&':
if (cp[1] != '&') {
DO (cp = parse_band (g, cp + 1, &rightval));
*valp = (*valp & rightval);
}
break;
}
return cp;
}
static const char *
parse_bor (IfParser *g, const char *cp, int *valp)
{
int rightval;
DO (cp = parse_band (g, cp, valp));
SKIPSPACE (cp);
switch (*cp) {
case '|':
if (cp[1] != '|') {
DO (cp = parse_bor (g, cp + 1, &rightval));
*valp = (*valp | rightval);
}
break;
}
return cp;
}
static const char *
parse_land (IfParser *g, const char *cp, int *valp)
{
int rightval;
DO (cp = parse_bor (g, cp, valp));
SKIPSPACE (cp);
switch (*cp) {
case '&':
if (cp[1] != '&')
return CALLFUNC(g, handle_error) (g, cp, "&&");
DO (cp = parse_land (g, cp + 2, &rightval));
*valp = (*valp && rightval);
break;
}
return cp;
}
static const char *
parse_lor (IfParser *g, const char *cp, int *valp)
{
int rightval;
DO (cp = parse_land (g, cp, valp));
SKIPSPACE (cp);
switch (*cp) {
case '|':
if (cp[1] != '|')
return CALLFUNC(g, handle_error) (g, cp, "||");
DO (cp = parse_lor (g, cp + 2, &rightval));
*valp = (*valp || rightval);
break;
}
return cp;
}
/****************************************************************************
External Entry Points
****************************************************************************/
const char *
ParseIfExpression (IfParser *g, const char *cp, int *valp)
{
return parse_lor (g, cp, valp);
}
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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