/* -----------------------------------------------------------------------------
 * 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.
 * ----------------------------------------------------------------------------- */

static char cvsroot[] = "$Header: /cvs/projects/SWIG/Source/Preprocessor/expr.c,v 1.6.4.1 2001/12/21 02:56:26 beazley Exp $";

#include "preprocessor.h"

static SwigScanner *scan = 0;

typedef struct {
  int       op;
  long      value;
} 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;
  }
  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();
}

/* -----------------------------------------------------------------------------
 * 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);
  *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 = SwigScanner_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].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;
      } else if ((token == SWIG_TOKEN_LPAREN)) {
	stack[sp++].op = EXPR_GROUP;
	stack[sp].op = EXPR_TOP;
	stack[sp].value = 0;
      } else if (token == SWIG_TOKEN_ENDLINE) { }
      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 = SwigScanner_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;
}