4.4BSD/usr/src/usr.bin/m4/expr.c
/*
* Copyright (c) 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Ozan Yigit at York University.
*
* 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.
*/
#ifndef lint
static char sccsid[] = "@(#)expr.c 8.1 (Berkeley) 6/6/93";
#endif /* not lint */
#include <sys/cdefs.h>
#include <stdio.h>
/*
* expression evaluator: performs a standard recursive
* descent parse to evaluate any expression permissible
* within the following grammar:
*
* expr : query EOS
* query : lor
* | lor "?" query ":" query
* lor : land { "||" land }
* land : bor { "&&" bor }
* bor : bxor { "|" bxor }
* bxor : band { "^" band }
* band : eql { "&" eql }
* eql : relat { eqrel relat }
* relat : shift { rel shift }
* shift : primary { shop primary }
* primary : term { addop term }
* term : unary { mulop unary }
* unary : factor
* | unop unary
* factor : constant
* | "(" query ")"
* constant: num
* | "'" CHAR "'"
* num : DIGIT
* | DIGIT num
* shop : "<<"
* | ">>"
* eqlrel : "="
* | "=="
* | "!="
* rel : "<"
* | ">"
* | "<="
* | ">="
*
*
* This expression evaluator is lifted from a public-domain
* C Pre-Processor included with the DECUS C Compiler distribution.
* It is hacked somewhat to be suitable for m4.
*
* Originally by: Mike Lutz
* Bob Harper
*/
#define TRUE 1
#define FALSE 0
#define EOS (char) 0
#define EQL 0
#define NEQ 1
#define LSS 2
#define LEQ 3
#define GTR 4
#define GEQ 5
#define OCTAL 8
#define DECIMAL 10
static char *nxtch; /* Parser scan pointer */
static int query __P((void));
static int lor __P((void));
static int land __P((void));
static int bor __P((void));
static int bxor __P((void));
static int band __P((void));
static int eql __P((void));
static int relat __P((void));
static int shift __P((void));
static int primary __P((void));
static int term __P((void));
static int unary __P((void));
static int factor __P((void));
static int constant __P((void));
static int num __P((void));
static int geteql __P((void));
static int getrel __P((void));
static int skipws __P((void));
static void experr __P((char *));
/*
* For longjmp
*/
#include <setjmp.h>
static jmp_buf expjump;
/*
* macros:
* ungetch - Put back the last character examined.
* getch - return the next character from expr string.
*/
#define ungetch() nxtch--
#define getch() *nxtch++
int
expr(expbuf)
char *expbuf;
{
register int rval;
nxtch = expbuf;
if (setjmp(expjump) != 0)
return FALSE;
rval = query();
if (skipws() == EOS)
return rval;
printf("m4: ill-formed expression.\n");
return FALSE;
}
/*
* query : lor | lor '?' query ':' query
*/
static int
query()
{
register int bool, true_val, false_val;
bool = lor();
if (skipws() != '?') {
ungetch();
return bool;
}
true_val = query();
if (skipws() != ':')
experr("bad query");
false_val = query();
return bool ? true_val : false_val;
}
/*
* lor : land { '||' land }
*/
static int
lor()
{
register int c, vl, vr;
vl = land();
while ((c = skipws()) == '|' && getch() == '|') {
vr = land();
vl = vl || vr;
}
if (c == '|')
ungetch();
ungetch();
return vl;
}
/*
* land : bor { '&&' bor }
*/
static int
land()
{
register int c, vl, vr;
vl = bor();
while ((c = skipws()) == '&' && getch() == '&') {
vr = bor();
vl = vl && vr;
}
if (c == '&')
ungetch();
ungetch();
return vl;
}
/*
* bor : bxor { '|' bxor }
*/
static int
bor()
{
register int vl, vr, c;
vl = bxor();
while ((c = skipws()) == '|' && getch() != '|') {
ungetch();
vr = bxor();
vl |= vr;
}
if (c == '|')
ungetch();
ungetch();
return vl;
}
/*
* bxor : band { '^' band }
*/
static int
bxor()
{
register int vl, vr;
vl = band();
while (skipws() == '^') {
vr = band();
vl ^= vr;
}
ungetch();
return vl;
}
/*
* band : eql { '&' eql }
*/
static int
band()
{
register int vl, vr, c;
vl = eql();
while ((c = skipws()) == '&' && getch() != '&') {
ungetch();
vr = eql();
vl &= vr;
}
if (c == '&')
ungetch();
ungetch();
return vl;
}
/*
* eql : relat { eqrel relat }
*/
static int
eql()
{
register int vl, vr, rel;
vl = relat();
while ((rel = geteql()) != -1) {
vr = relat();
switch (rel) {
case EQL:
vl = (vl == vr);
break;
case NEQ:
vl = (vl != vr);
break;
}
}
return vl;
}
/*
* relat : shift { rel shift }
*/
static int
relat()
{
register int vl, vr, rel;
vl = shift();
while ((rel = getrel()) != -1) {
vr = shift();
switch (rel) {
case LEQ:
vl = (vl <= vr);
break;
case LSS:
vl = (vl < vr);
break;
case GTR:
vl = (vl > vr);
break;
case GEQ:
vl = (vl >= vr);
break;
}
}
return vl;
}
/*
* shift : primary { shop primary }
*/
static int
shift()
{
register int vl, vr, c;
vl = primary();
while (((c = skipws()) == '<' || c == '>') && c == getch()) {
vr = primary();
if (c == '<')
vl <<= vr;
else
vl >>= vr;
}
if (c == '<' || c == '>')
ungetch();
ungetch();
return vl;
}
/*
* primary : term { addop term }
*/
static int
primary()
{
register int c, vl, vr;
vl = term();
while ((c = skipws()) == '+' || c == '-') {
vr = term();
if (c == '+')
vl += vr;
else
vl -= vr;
}
ungetch();
return vl;
}
/*
* <term> := <unary> { <mulop> <unary> }
*/
static int
term()
{
register int c, vl, vr;
vl = unary();
while ((c = skipws()) == '*' || c == '/' || c == '%') {
vr = unary();
switch (c) {
case '*':
vl *= vr;
break;
case '/':
vl /= vr;
break;
case '%':
vl %= vr;
break;
}
}
ungetch();
return vl;
}
/*
* unary : factor | unop unary
*/
static int
unary()
{
register int val, c;
if ((c = skipws()) == '!' || c == '~' || c == '-') {
val = unary();
switch (c) {
case '!':
return !val;
case '~':
return ~val;
case '-':
return -val;
}
}
ungetch();
return factor();
}
/*
* factor : constant | '(' query ')'
*/
static int
factor()
{
register int val;
if (skipws() == '(') {
val = query();
if (skipws() != ')')
experr("bad factor");
return val;
}
ungetch();
return constant();
}
/*
* constant: num | 'char'
* Note: constant() handles multi-byte constants
*/
static int
constant()
{
register int i;
register int value;
register char c;
int v[sizeof(int)];
if (skipws() != '\'') {
ungetch();
return num();
}
for (i = 0; i < sizeof(int); i++) {
if ((c = getch()) == '\'') {
ungetch();
break;
}
if (c == '\\') {
switch (c = getch()) {
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
ungetch();
c = num();
break;
case 'n':
c = 012;
break;
case 'r':
c = 015;
break;
case 't':
c = 011;
break;
case 'b':
c = 010;
break;
case 'f':
c = 014;
break;
}
}
v[i] = c;
}
if (i == 0 || getch() != '\'')
experr("illegal character constant");
for (value = 0; --i >= 0;) {
value <<= 8;
value += v[i];
}
return value;
}
/*
* num : digit | num digit
*/
static int
num()
{
register int rval, c, base;
int ndig;
base = ((c = skipws()) == '0') ? OCTAL : DECIMAL;
rval = 0;
ndig = 0;
while (c >= '0' && c <= (base == OCTAL ? '7' : '9')) {
rval *= base;
rval += (c - '0');
c = getch();
ndig++;
}
ungetch();
if (ndig == 0)
experr("bad constant");
return rval;
}
/*
* eqlrel : '=' | '==' | '!='
*/
static int
geteql()
{
register int c1, c2;
c1 = skipws();
c2 = getch();
switch (c1) {
case '=':
if (c2 != '=')
ungetch();
return EQL;
case '!':
if (c2 == '=')
return NEQ;
ungetch();
ungetch();
return -1;
default:
ungetch();
ungetch();
return -1;
}
}
/*
* rel : '<' | '>' | '<=' | '>='
*/
static int
getrel()
{
register int c1, c2;
c1 = skipws();
c2 = getch();
switch (c1) {
case '<':
if (c2 == '=')
return LEQ;
ungetch();
return LSS;
case '>':
if (c2 == '=')
return GEQ;
ungetch();
return GTR;
default:
ungetch();
ungetch();
return -1;
}
}
/*
* Skip over any white space and return terminating char.
*/
static int
skipws()
{
register char c;
while ((c = getch()) <= ' ' && c > EOS)
;
return c;
}
/*
* resets environment to eval(), prints an error
* and forces eval to return FALSE.
*/
static void
experr(msg)
char *msg;
{
printf("m4: %s in expr.\n", msg);
longjmp(expjump, -1);
}