587 lines
12 KiB
C
587 lines
12 KiB
C
/*
|
|
* 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 : decnum
|
|
* | "0" octnum
|
|
* | "0x" hexnum
|
|
* octnum : OCTDIGIT
|
|
* | OCTDIGIT octnum
|
|
* decnum : DECDIGIT
|
|
* | DECDIGIT decnum
|
|
* hexnum : HEXDIGIT
|
|
* | HEXDIGIT hexnum
|
|
* 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
|
|
*/
|
|
|
|
#include "mdef.h"
|
|
|
|
#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
|
|
|
|
static char *nxtch; /* Parser scan pointer */
|
|
|
|
/*
|
|
* 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);
|
|
experr("Ill-formed expression");
|
|
/* NOTREACHED */
|
|
return(0);
|
|
}
|
|
|
|
/*
|
|
* query : lor | lor '?' query ':' query
|
|
*
|
|
*/
|
|
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 }
|
|
*
|
|
*/
|
|
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 }
|
|
*
|
|
*/
|
|
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 }
|
|
*
|
|
*/
|
|
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 }
|
|
*
|
|
*/
|
|
int bxor()
|
|
{
|
|
register int vl, vr;
|
|
|
|
vl = band();
|
|
while (skipws() == '^') {
|
|
vr = band();
|
|
vl ^= vr;
|
|
}
|
|
|
|
ungetch();
|
|
return(vl);
|
|
}
|
|
|
|
/*
|
|
* band : eql { '&' eql }
|
|
*
|
|
*/
|
|
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 }
|
|
*
|
|
*/
|
|
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 }
|
|
*
|
|
*/
|
|
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 }
|
|
*
|
|
*/
|
|
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 }
|
|
*
|
|
*/
|
|
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> }
|
|
*
|
|
*/
|
|
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
|
|
*
|
|
*/
|
|
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 ')'
|
|
*
|
|
*/
|
|
int factor()
|
|
{
|
|
register int val;
|
|
|
|
if (skipws() == '(') {
|
|
val = query();
|
|
if (skipws() != ')')
|
|
experr("Bad factor");
|
|
return(val);
|
|
}
|
|
|
|
ungetch();
|
|
return(constant());
|
|
}
|
|
|
|
/*
|
|
* constant: num | 'char'
|
|
*
|
|
*/
|
|
int constant()
|
|
{
|
|
/*
|
|
* Note: constant() handles multi-byte constants
|
|
*/
|
|
|
|
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
|
|
*
|
|
*/
|
|
int num()
|
|
{
|
|
register int rval, c, base;
|
|
int ndig;
|
|
|
|
ndig = 0;
|
|
if ((c = skipws()) == '0') {
|
|
c = getch ();
|
|
if (c == 'x' || c == 'X') {
|
|
base = 16;
|
|
c = getch ();
|
|
} else {
|
|
base = 8;
|
|
ndig = 1;
|
|
}
|
|
} else {
|
|
base = 10;
|
|
}
|
|
rval = 0;
|
|
for (;;) {
|
|
if (isdigit(c)) c -= '0';
|
|
else if (isupper (c)) c -= ('A' - 10);
|
|
else if (islower (c)) c -= ('a' - 10);
|
|
else break;
|
|
if (c < 0 || c >= base)
|
|
break;
|
|
|
|
rval *= base;
|
|
rval += c;
|
|
c = getch();
|
|
ndig++;
|
|
}
|
|
ungetch();
|
|
if (ndig)
|
|
return(rval);
|
|
experr("Bad constant");
|
|
/* NOTREACHED */
|
|
return(0);
|
|
}
|
|
|
|
/*
|
|
* eqlrel : '=' | '==' | '!='
|
|
*
|
|
*/
|
|
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 : '<' | '>' | '<=' | '>='
|
|
*
|
|
*/
|
|
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.
|
|
*/
|
|
int skipws()
|
|
{
|
|
register char c;
|
|
|
|
while ((c = getch()) <= ' ' && c > EOS)
|
|
;
|
|
return(c);
|
|
}
|
|
|
|
/*
|
|
* Error handler - resets environment to eval(), prints an error,
|
|
* and returns FALSE.
|
|
*/
|
|
int experr(msg)
|
|
char *msg;
|
|
{
|
|
printf("mp: %s\n",msg);
|
|
longjmp(expjump, -1); /* Force eval() to return FALSE */
|
|
}
|