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+/*
+ * $Xorg: ifparser.c,v 1.3 2000/08/17 19:41:50 cpqbld 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 precidence is supported.
+ *
+ *
+ * External Entry Points:
+ *
+ * ParseIfExpression parse a string for #if
+ */
+
+#include "ifparser.h"
+#include <ctype.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(*ccc)) ccc++
+#define isvarfirstletter(ccc) (isalpha(ccc) || (ccc) == '_')
+
+
+static const char *
+parse_variable (g, cp, varp)
+ 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(*cp) || *cp == '_'; cp++) ;
+ return cp;
+}
+
+
+static const char *
+parse_number (g, cp, valp)
+ IfParser *g;
+ const char *cp;
+ long *valp;
+{
+ SKIPSPACE (cp);
+
+ if (!isdigit(*cp))
+ return CALLFUNC(g, handle_error) (g, cp, "number");
+
+ *valp = strtol(cp, &cp, 0);
+ /* skip trailing qualifiers */
+ while (*cp == 'U' || *cp == 'u' || *cp == 'L' || *cp == 'l') cp++;
+#if 0
+ *valp = atoi (cp);
+ /* EMPTY */
+ for (cp++; isdigit(*cp); cp++) ;
+#endif
+ return cp;
+}
+
+static const char *
+parse_character (g, cp, valp)
+ IfParser *g;
+ const char *cp;
+ long *valp;
+{
+ char val;
+
+ SKIPSPACE (cp);
+ if (*cp == '\\')
+ switch (cp[1]) {
+ case 'n': val = '\n'; break;
+ case 't': val = '\t'; break;
+ case 'v': val = '\v'; break;
+ case 'b': val = '\b'; break;
+ case 'r': val = '\r'; break;
+ case 'f': val = '\f'; break;
+ case 'a': val = '\a'; break;
+ case '\\': val = '\\'; break;
+ case '?': val = '\?'; break;
+ case '\'': val = '\''; break;
+ case '\"': val = '\"'; break;
+ case 'x': val = (char) strtol (cp + 2, NULL, 16); break;
+ default: val = (char) strtol (cp + 1, NULL, 8); break;
+ }
+ else
+ val = *cp;
+ while (*cp != '\'') cp++;
+ *valp = (long) val;
+ return cp;
+}
+
+static const char *
+parse_value (g, cp, valp)
+ IfParser *g;
+ const char *cp;
+ long *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 '\'':
+ DO (cp = parse_character (g, cp + 1, valp));
+ if (*cp != '\'')
+ return CALLFUNC(g, handle_error) (g, cp, "'");
+ return cp + 1;
+
+ case 'd':
+ if (strncmp (cp, "defined", 7) == 0 && !isalnum(cp[7])) {
+ int paren = 0;
+ int len;
+
+ cp += 7;
+ SKIPSPACE (cp);
+ if (*cp == '(') {
+ paren = 1;
+ cp++;
+ }
+ DO (cp = parse_variable (g, cp, &var));
+ len = 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(*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, cp - var);
+ }
+
+ return cp;
+}
+
+
+
+static const char *
+parse_product (g, cp, valp)
+ IfParser *g;
+ const char *cp;
+ long *valp;
+{
+ long 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));
+ *valp = (*valp / rightval);
+ break;
+
+ case '%':
+ DO (cp = parse_product (g, cp + 1, &rightval));
+ *valp = (*valp % rightval);
+ break;
+ }
+ return cp;
+}
+
+
+static const char *
+parse_sum (g, cp, valp)
+ IfParser *g;
+ const char *cp;
+ long *valp;
+{
+ long 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 (g, cp, valp)
+ IfParser *g;
+ const char *cp;
+ long *valp;
+{
+ long 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 (g, cp, valp)
+ IfParser *g;
+ const char *cp;
+ long *valp;
+{
+ long 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 (g, cp, valp)
+ IfParser *g;
+ const char *cp;
+ long *valp;
+{
+ long 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 (g, cp, valp)
+ IfParser *g;
+ const char *cp;
+ long *valp;
+{
+ long 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 (g, cp, valp)
+ IfParser *g;
+ const char *cp;
+ long *valp;
+{
+ long 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 (g, cp, valp)
+ IfParser *g;
+ const char *cp;
+ long *valp;
+{
+ long 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 (g, cp, valp)
+ IfParser *g;
+ const char *cp;
+ long *valp;
+{
+ long 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 (g, cp, valp)
+ IfParser *g;
+ const char *cp;
+ long *valp;
+{
+ return parse_lor (g, cp, valp);
+}
+
+
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