%%	options

copyright owner	=	Dirk Krause
copyright year	=	2014
license		=	bsd



%%	header

/**	@file	dk3mai.h	Mathematical operations on int.
*/

#include <dk3conf.h>

#include <stdio.h>
#if DK3_HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#if DK3_HAVE_STDINT
#include <stdint.h>
#endif
#if DK3_HAVE_INTTYPES_H
#include <inttypes.h>
#endif
#if DK3_HAVE_LIMITS_H
#include <limits.h>
#endif
#if DK3_HAVE_MATH_H
#include <math.h>
#endif
#if DK3_HAVE_FLOAT_H
#include <float.h>
#endif


#ifdef __cplusplus
extern "C" {
#endif

/**	Absolute value.
	@param	a	Original value.
	@param	ec	Pointer to error code variable, may be NULL.
	@return	Non-negative value on success,
	DK3_I_MAX and ec = DK3_ERROR_MATH_OVERFLOW on error.
*/
int
dk3ma_i_abs_ok(int a, int *ec);

/**	Addition.
	@param	a	Left operand.
	@param	b	Right operand.
	@param	ec	Pointer to error code variable, may be NULL.
	The variable may be set to DK3_ERROR_MATH_OVERFLOW when returning.
	@return	Summary of a and b.
*/
int
dk3ma_i_add_ok(int a, int b, int *ec);

/**	Substraction.
	@param	a	Left operand.
	@param	b	Right operand.
	@param	ec	Pointer to error code variable, may be NULL.
	The variable may be set to DK3_ERROR_MATH_OVERFLOW when returning.
	@return	Difference of a and b.
*/
int
dk3ma_i_sub_ok(int a, int b, int *ec);

/**	Multiplication.
	@param	a	Left operand.
	@param	b	Right operand.
	@param	ec	Pointer to error code variable, may be NULL.
	The variable may be set to DK3_ERROR_MATH_OVERFLOW when returning.
	@return	Product of a and b.
*/
int
dk3ma_i_mul_ok(int a, int b, int *ec);

/**	Division.
	@param	a	Left operand (nominator).
	@param	b	Right operand (denominator).
	@param	ec	Pointer to error code variable, may be NULL.
	The variable may be set to DK3_ERROR_MATH_OVERFLOW or
	DK3_ERROR_MATH_DIVZERO when returning.
	@return	Fraction of a and b.
*/
int
dk3ma_i_div_ok(int a, int b, int *ec);

/**	Greatest common divisor.
	@param	a	Left operand.
	@param	b	Right operand.
	@param	ec	Pointer to error code variable, may be NULL.
	The variable may be set to DK3_ERROR_MATH_OVERFLOW when returning.
	@return	Greatest common divisor of a and b.
*/
int
dk3ma_i_gcd_ok(int a, int b, int *ec);

#ifdef __cplusplus
}
#endif



%%	module



#include "dk3ma.h"



$!trace-include



int
dk3ma_i_abs_ok(int a, int *ec)
{
  if (NULL != ec) { if (DK3_I_MIN == a) { *ec = DK3_ERROR_MATH_OVERFLOW; } }
  return ((0 <= a) ? a : (0 - a));
}



int
dk3ma_i_add_ok(int a, int b, int *ec)
{
  if (NULL != ec) {
    if ((0 < a) && (0 < b)) {
      if((DK3_I_MAX - a) < b) { *ec = DK3_ERROR_MATH_OVERFLOW; }
    } else {
      if ((0 > a) && (0 > b)) {
        if (DK3_I_MIN == a) {
	  *ec = DK3_ERROR_MATH_OVERFLOW;
	} else {
	  if ((DK3_I_MIN - a) > b) {
	    *ec = DK3_ERROR_MATH_OVERFLOW;
	  }
	}
      }
    }
  }
  return (a + b);
}



int
dk3ma_i_sub_ok(int a, int b, int *ec)
{
  if (NULL != ec) {
    if ((0 < a) && (0 > b)) {
      if((DK3_I_MAX + b) < a) { *ec = DK3_ERROR_MATH_OVERFLOW; }
    } else {
      if ((0 > a) && (0 < b)) {
        if((DK3_I_MIN + b) > a) { *ec = DK3_ERROR_MATH_OVERFLOW; }
      }
    }
  }
  return (a - b);
}




int
dk3ma_i_mul_ok(int a, int b, int *ec)
{
  if (NULL != ec) {
    if ((0 != a) && (0 != b)) {
      if ((DK3_I_MIN == a) && (1 != b)) {
        *ec = DK3_ERROR_MATH_OVERFLOW;
	goto checksfinished;
      }
      if ((DK3_I_MIN == b) && (1 != a)) {
        *ec = DK3_ERROR_MATH_OVERFLOW;
	goto checksfinished;
      }
      if ((DK3_I_MAX / dk3ma_i_abs_ok(a, ec)) < dk3ma_i_abs_ok(b, ec)) {
        *ec = DK3_ERROR_MATH_OVERFLOW;
	/* goto checksfinished; -- when adding further tests -- */
      }
    }
  }
  checksfinished:
  return (a * b);
}



int
dk3ma_i_div_ok(int a, int b, int *ec)
{
  int		back	= 0;
  if (0 != b) {
    if ((DK3_I_MIN == a) && (-1 == b)) {
      back = DK3_I_MAX;
      *ec = DK3_ERROR_MATH_OVERFLOW;
    } else {
      back = a / b;
    }
  } else {
    if (NULL != ec) { *ec = DK3_ERROR_MATH_DIVZERO; }
    if (0 <= a) { back = DK3_I_MAX; }
    else        { back = DK3_I_MIN; }
  }
  return back;
}



int
dk3ma_i_gcd_ok(int a, int b, int *ec)
{
  int	h;
  if (0 > a) {
    if (DK3_I_MIN == a) {
      a = 0;
      if (NULL != ec) { *ec = DK3_ERROR_MATH_OVERFLOW; }
      goto finished;
    } else {
      a = 0 - a;
    }
  }
  if (0 > b) {
    if (DK3_I_MIN == b) {
      a = 0;
      if (NULL != ec) { *ec = DK3_ERROR_MATH_OVERFLOW; }
      goto finished;
    } else {
      b = 0 - b;
    }
  }
  while (0 < b) {
    h = a % b;
    a = b;
    b = h;
  }
  if (0 == a) { a = 1; }
  finished:
  return a;
}