ifparser.cpp

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/*
 * $XConsortium: ifparser.c,v 1.7 94/01/18 21:30:50 rws 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
 */

#ifdef __WIN32__
  #pragma warning(disable : 4996)
#endif

#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(*ccc)) ccc++
#define isvarfirstletter(ccc) (isalpha(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(*cp) || *cp == '_'; cp++) ;
    return cp;
}


static const char *parse_number(IfParser *g, const char *cp, int *valp)
{
    SKIPSPACE (cp);

    if (!isdigit(*cp))
  return CALLFUNC(g, handle_error) (g, cp, "number");

#ifdef WIN32
    char *hold_result;
    *valp = strtol(cp, &hold_result, 0);
    cp = hold_result;
#else
    *valp = atoi (cp);
    /* EMPTY */
    for (cp++; isdigit(*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(cp[7])) {
      int paren = 0;
      cp += 7;
      SKIPSPACE (cp);
      if (*cp == '(') {
    paren = 1;
    cp++;
      }
      DO (cp = parse_variable (g, cp, &var));
      SKIPSPACE (cp);
      if (paren && *cp != ')')
    return CALLFUNC(g, handle_error) (g, cp, ")");
      *valp = (*(g->funcs.eval_defined)) (g, var, int(cp - var));
      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, int(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));
  *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);
}