+/*
+ * Copyright (c) 1989 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Ozan Yigit.
+ *
+ * Redistribution and use in source and binary forms are permitted
+ * provided that the above copyright notice and this paragraph are
+ * duplicated in all such forms and that any documentation,
+ * advertising materials, and other materials related to such
+ * distribution and use acknowledge that the software was developed
+ * by the University of California, Berkeley. The name of the
+ * University may not 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[] = "@(#)expr.c 5.1 (Berkeley) %G%";
+#endif /* not lint */
+
+/*
+ * 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 */
+
+/*
+ * 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++
+
+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");
+}
+
+/*
+ * query : lor | lor '?' query ':' query
+ *
+ */
+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 }
+ *
+ */
+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 }
+ *
+ */
+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 }
+ *
+ */
+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 }
+ *
+ */
+bxor()
+{
+ register int vl, vr;
+
+ vl = band();
+ while (skipws() == '^') {
+ vr = band();
+ vl ^= vr;
+ }
+
+ ungetch();
+ return(vl);
+}
+
+/*
+ * band : eql { '&' eql }
+ *
+ */
+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 }
+ *
+ */
+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 }
+ *
+ */
+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 }
+ *
+ */
+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 }
+ *
+ */
+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> }
+ *
+ */
+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
+ *
+ */
+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 ')'
+ *
+ */
+factor()
+{
+ register int val;
+
+ if (skipws() == '(') {
+ val = query();
+ if (skipws() != ')')
+ experr("Bad factor");
+ return(val);
+ }
+
+ ungetch();
+ return(constant());
+}
+
+/*
+ * constant: num | 'char'
+ *
+ */
+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
+ *
+ */
+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)
+ return(rval);
+ experr("Bad constant");
+}
+
+/*
+ * eqlrel : '=' | '==' | '!='
+ *
+ */
+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 : '<' | '>' | '<=' | '>='
+ *
+ */
+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.
+ */
+skipws()
+{
+ register char c;
+
+ while ((c = getch()) <= ' ' && c > EOS)
+ ;
+ return(c);
+}
+
+/*
+ * Error handler - resets environment to eval(), prints an error,
+ * and returns FALSE.
+ */
+experr(msg)
+char *msg;
+{
+ printf("mp: %s\n",msg);
+ longjmp(expjump, -1); /* Force eval() to return FALSE */
+}
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