
/*
 *  M_APM  -  mapmpwr2.c
 *
 *  Copyright (C) 2002 - 2007   Michael C. Ring
 *
 *  Permission to use, copy, and distribute this software and its
 *  documentation for any purpose with or 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.
 *
 *  Permission to modify the software is granted. Permission to distribute
 *  the modified code is granted. Modifications are to be distributed by
 *  using the file 'license.txt' as a template to modify the file header.
 *  'license.txt' is available in the official MAPM distribution.
 *
 *  This software is provided "as is" without express or implied warranty.
 */

/*
 *      This file contains the Integer Power function and the result
 *	is NOT ROUNDED. The exponent must be an integer >= zero.
 *
 *      This will typically be used in an application where full integer
 *	precision is required to be maintained.
 *
 */

#include "pgAdmin3.h"
#include "pgscript/utilities/mapm-lib/m_apm_lc.h"

/****************************************************************************/
void	m_apm_integer_pow_nr(M_APM rr, M_APM aa, int mexp)
{
	M_APM   tmp0, tmpy, tmpz;
	int	nexp, ii;

	if (mexp == 0)
	{
		m_apm_copy(rr, MM_One);
		return;
	}
	else
	{
		if (mexp < 0)
		{
			M_apm_log_error_msg(M_APM_RETURN,
			                    "\'m_apm_integer_pow_nr\', Negative exponent");

			M_set_to_zero(rr);
			return;
		}
	}

	if (mexp == 1)
	{
		m_apm_copy(rr, aa);
		return;
	}

	if (mexp == 2)
	{
		m_apm_multiply(rr, aa, aa);
		return;
	}

	nexp = mexp;

	if (aa->m_apm_sign == 0)
	{
		M_set_to_zero(rr);
		return;
	}

	tmp0 = M_get_stack_var();
	tmpy = M_get_stack_var();
	tmpz = M_get_stack_var();

	m_apm_copy(tmpy, MM_One);
	m_apm_copy(tmpz, aa);

	while (TRUE)
	{
		ii   = nexp & 1;
		nexp = nexp >> 1;

		if (ii != 0)                       /* exponent -was- odd */
		{
			m_apm_multiply(tmp0, tmpy, tmpz);

			if (nexp == 0)
				break;

			m_apm_copy(tmpy, tmp0);
		}

		m_apm_multiply(tmp0, tmpz, tmpz);
		m_apm_copy(tmpz, tmp0);
	}

	m_apm_copy(rr, tmp0);

	M_restore_stack(3);
}
/****************************************************************************/

