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expr.c

/* -----------------------------------------------------------------------------
 * expr.c
 *
 *     Integer arithmetic expression evaluator used to handle expressions
 *     encountered during preprocessing.
 *
 * Author(s) : David Beazley (beazley@cs.uchicago.edu)
 *
 * Copyright (C) 1999-2000.  The University of Chicago
 * See the file LICENSE for information on usage and redistribution.
 * ----------------------------------------------------------------------------- */

char cvsroot_expr_c[] = "/cvsroot/SWIG/Source/Preprocessor/expr.c,v 1.10 2004/01/15 00:58:13 beazley Exp";

#include "swig.h"
#include "preprocessor.h"

static SwigScanner *scan = 0;

typedef struct {
  int       op;
  long      value;
  String   *svalue;
} exprval;

#define  EXPR_TOP      1
#define  EXPR_VALUE    2
#define  EXPR_OP       3
#define  EXPR_GROUP    4
#define  EXPR_UMINUS   100

static exprval stack[256];              /* Parsing stack       */
static int     sp = 0;                  /* Stack pointer       */
static int     prec[256];               /* Precedence rules    */
static int     expr_init = 0;           /* Initialization flag */
static char   *errmsg = 0;              /* Parsing error       */

/* Initialize the precedence table for various operators.  Low values have higher precedence */
static void init_precedence() {
  prec[SWIG_TOKEN_NOT] = 10;
  prec[EXPR_UMINUS] = 10;
  prec[SWIG_TOKEN_STAR] = 20;
  prec[SWIG_TOKEN_SLASH] = 20;
  prec[SWIG_TOKEN_PERCENT] = 20;
  prec[SWIG_TOKEN_PLUS] = 30;
  prec[SWIG_TOKEN_MINUS] = 30;
  prec[SWIG_TOKEN_LSHIFT] = 40;
  prec[SWIG_TOKEN_RSHIFT] = 40;
  prec[SWIG_TOKEN_AND] = 50;
  prec[SWIG_TOKEN_XOR] = 60;
  prec[SWIG_TOKEN_OR] = 70;
  prec[SWIG_TOKEN_EQUALTO] = 80;
  prec[SWIG_TOKEN_NOTEQUAL] = 80;
  prec[SWIG_TOKEN_LESSTHAN] = 80;
  prec[SWIG_TOKEN_GREATERTHAN] = 80;
  prec[SWIG_TOKEN_LTEQUAL] = 80;
  prec[SWIG_TOKEN_GTEQUAL] = 80;
  prec[SWIG_TOKEN_LNOT] = 90;
  prec[SWIG_TOKEN_LAND] = 100;
  prec[SWIG_TOKEN_LOR] = 110;
  expr_init = 1;
}

/* Reduce a single operator on the stack */
static void reduce_op() {
  if (stack[sp-1].op != EXPR_OP) {
    errmsg = "Missing operator";
    sp = 0;
    return;
  }
  if (stack[sp-2].svalue || stack[sp].svalue) {
    /* A string expression */
    if (!(stack[sp-2].svalue && stack[sp].svalue)) {
      errmsg = "Can't mix strings and integers in expression";
      sp = 0;
      return;
    }
    switch(stack[sp-1].value) {
    case SWIG_TOKEN_EQUALTO:
      stack[sp-2].value = (Strcmp(stack[sp-2].svalue,stack[sp].svalue) == 0);
      Delete(stack[sp-2].svalue);
      Delete(stack[sp].svalue);
      sp -= 2;
      break;
    case SWIG_TOKEN_NOTEQUAL:
      stack[sp-2].value = (Strcmp(stack[sp-2].svalue,stack[sp].svalue) != 0);
      Delete(stack[sp-2].svalue);
      Delete(stack[sp].svalue);
      sp -= 2;
      break;
    default:
      errmsg = "Syntax error";
      sp = 0;
      break;
    }
  } else {
    switch(stack[sp-1].value) {
    case SWIG_TOKEN_STAR:
      stack[sp-2].value = stack[sp-2].value * stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_EQUALTO:
      stack[sp-2].value = stack[sp-2].value == stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_NOTEQUAL:
      stack[sp-2].value = stack[sp-2].value != stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_PLUS:
      stack[sp-2].value = stack[sp-2].value + stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_MINUS:
      stack[sp-2].value = stack[sp-2].value - stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_AND:
      stack[sp-2].value = stack[sp-2].value & stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_LAND:
      stack[sp-2].value = stack[sp-2].value && stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_OR:
      stack[sp-2].value = stack[sp-2].value | stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_LOR:
      stack[sp-2].value = stack[sp-2].value || stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_XOR:
      stack[sp-2].value = stack[sp-2].value ^ stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_LESSTHAN:
      stack[sp-2].value = stack[sp-2].value < stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_GREATERTHAN:
      stack[sp-2].value = stack[sp-2].value > stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_LTEQUAL:
      stack[sp-2].value = stack[sp-2].value <= stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_GTEQUAL:
      stack[sp-2].value = stack[sp-2].value >= stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_NOT:
      stack[sp-1].value = ~stack[sp].value;
      sp--;
      break;
    case SWIG_TOKEN_LNOT:
      stack[sp-1].value = !stack[sp].value;
      sp--;
      break;
    case EXPR_UMINUS:
      stack[sp-1].value = -stack[sp].value;
      sp--;
      break;
    case SWIG_TOKEN_SLASH:
      stack[sp-2].value = stack[sp-2].value / stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_PERCENT:
      stack[sp-2].value = stack[sp-2].value % stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_LSHIFT:
      stack[sp-2].value = stack[sp-2].value << stack[sp].value;
      sp -= 2;
      break;
    case SWIG_TOKEN_RSHIFT:
      stack[sp-2].value = stack[sp-2].value >> stack[sp].value;
      sp -= 2;
      break;
    default:
      errmsg = "Syntax error";
      sp = 0;
      break;
    }
  }
  stack[sp].op = EXPR_VALUE;
}

/* -----------------------------------------------------------------------------
 * Preprocessor_expr_init()
 *
 * Initialize the expression evaluator
 * ----------------------------------------------------------------------------- */

void
Preprocessor_expr_init (void) {
  if (!expr_init) init_precedence();
  if (!scan) scan = NewSwigScanner();
}

/* -----------------------------------------------------------------------------
 * Tokenizer 
 * ----------------------------------------------------------------------------- */

static int expr_token(SwigScanner *s) {
  int t;
  while(1) {
    t = SwigScanner_token(s);
    if (!((t == SWIG_TOKEN_BACKSLASH) || (t == SWIG_TOKEN_ENDLINE))) break;
  }
  return t;
}

/* -----------------------------------------------------------------------------
 * Preprocessor_expr()
 *
 * Evaluates an arithmetic expression.  Returns the result and sets an error code.
 * ----------------------------------------------------------------------------- */

int
Preprocessor_expr(DOH *s, int *error) {
  int     token = 0;
  int     op = 0;

  sp = 0;
  assert(s);
  assert(scan);

  Seek(s,0,SEEK_SET);
  /* Printf(stdout,"evaluating : '%s'\n", s); */
  *error = 0;
  SwigScanner_clear(scan);
  SwigScanner_push(scan,s);

  /* Put initial state onto the stack */
  stack[sp].op = EXPR_TOP;
  stack[sp].value = 0;

  while (1) {
    /* Look at the top of the stack */
    switch(stack[sp].op) {
    case EXPR_TOP:
      /* An expression.   Can be a number or another expression enclosed in parens */
      token = expr_token(scan);
      if (!token) {
      errmsg = "Expected an expression";
      *error = 1;
      return 0;
      }
      if ((token == SWIG_TOKEN_INT) || (token == SWIG_TOKEN_UINT) || (token == SWIG_TOKEN_LONG) || (token == SWIG_TOKEN_ULONG)) {
      /* A number.  Reduce EXPR_TOP to an EXPR_VALUE */
      char *c = Char(SwigScanner_text(scan));
      stack[sp].value = (long) strtol(c,0,0);
      stack[sp].svalue = 0;
      /*      stack[sp].value = (long) atol(Char(SwigScanner_text(scan))); */
      stack[sp].op = EXPR_VALUE;
      } else if (token == SWIG_TOKEN_PLUS) { }
       else if ((token == SWIG_TOKEN_MINUS) || (token == SWIG_TOKEN_LNOT) || (token==SWIG_TOKEN_NOT)) {
      if (token == SWIG_TOKEN_MINUS) token = EXPR_UMINUS;
      stack[sp].value = token;
      stack[sp++].op = EXPR_OP;
      stack[sp].op = EXPR_TOP;
      stack[sp].svalue = 0;
      } else if ((token == SWIG_TOKEN_LPAREN)) {
      stack[sp++].op = EXPR_GROUP;
      stack[sp].op = EXPR_TOP;
      stack[sp].value = 0;
      stack[sp].svalue = 0;
      } else if (token == SWIG_TOKEN_ENDLINE) { 
      } else if ((token == SWIG_TOKEN_STRING)) {
      stack[sp].svalue = NewString(SwigScanner_text(scan));
      stack[sp].op = EXPR_VALUE;
      } else if ((token == SWIG_TOKEN_ID)) {
      stack[sp].value = 0;
      stack[sp].svalue = 0;
      stack[sp].op = EXPR_VALUE;
      } else goto syntax_error;
      break;
    case EXPR_VALUE:
      /* A value is on the stack.   We may reduce or evaluate depending on what the next token is */
      token = expr_token(scan);
      if (!token) {
      /* End of input. Might have to reduce if an operator is on stack */
      while (sp > 0) {
        if (stack[sp-1].op == EXPR_OP) {
          reduce_op();
        } else if (stack[sp-1].op == EXPR_GROUP) {
          errmsg = "Missing \')\'";
          *error = 1;
          return 0;
        } else goto syntax_error;
      }
      return stack[sp].value;
      }
      /* Token must be an operator */
      switch(token) {
      case SWIG_TOKEN_STAR:
      case SWIG_TOKEN_EQUALTO:
      case SWIG_TOKEN_NOTEQUAL:
      case SWIG_TOKEN_PLUS:
      case SWIG_TOKEN_MINUS:
      case SWIG_TOKEN_AND:
      case SWIG_TOKEN_LAND:
      case SWIG_TOKEN_OR:
      case SWIG_TOKEN_LOR:
      case SWIG_TOKEN_XOR:
      case SWIG_TOKEN_LESSTHAN:
      case SWIG_TOKEN_GREATERTHAN:
      case SWIG_TOKEN_LTEQUAL:
      case SWIG_TOKEN_GTEQUAL:
      case SWIG_TOKEN_SLASH:
      case SWIG_TOKEN_PERCENT:
      case SWIG_TOKEN_LSHIFT:
      case SWIG_TOKEN_RSHIFT:
      if ((sp == 0) || (stack[sp-1].op == EXPR_GROUP)) {
        /* No possibility of reduce. Push operator and expression */
        sp++;
        stack[sp].op = EXPR_OP;
        stack[sp].value = token;
        sp++;
        stack[sp].op = EXPR_TOP;
        stack[sp].value = 0;
      } else {
        if (stack[sp-1].op != EXPR_OP) goto syntax_error;
        op = stack[sp-1].value;         /* Previous operator */

        /* Now, depending on the precedence relationship between the last operator and the current
           we will reduce or push */

        if (prec[op] <= prec[token]) {
          /* Reduce the previous operator */
          reduce_op();
          if (stack[sp].op != EXPR_VALUE) goto syntax_error;
        }
        sp++;
        stack[sp].op = EXPR_OP;
        stack[sp].value = token;
        sp++;
        stack[sp].op = EXPR_TOP;
        stack[sp].value = 0;
      }
      break;
      case SWIG_TOKEN_RPAREN:
      if (sp ==  0) goto extra_rparen;

      /* Might have to reduce operators first */
      while ((sp > 0) && (stack[sp-1].op == EXPR_OP)) reduce_op();
      if ((sp == 0) || (stack[sp-1].op != EXPR_GROUP)) goto extra_rparen;
      stack[sp-1].op = EXPR_VALUE;
      stack[sp-1].value = stack[sp].value;
      sp--;
      break;
      default:
      goto syntax_error;
      break;
      }
      break;

    default:
      fprintf(stderr,"Internal error in expression evaluator.\n");
      abort();
    }
  }
 syntax_error:
  errmsg = "Syntax error";
  *error = 1;
  return 0;

 extra_rparen:
  errmsg = "Extra \')\'";
  *error = 1;
  return 0;
}

/* -----------------------------------------------------------------------------
 * Preprocessor_expr_error()
 *
 * Return error message set by the evaluator (if any)
 * ----------------------------------------------------------------------------- */

char *
Preprocessor_expr_error() {
  return errmsg;
}








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