/*
 *  M_APM  -  mapmipwr.c
 *
 *  Copyright (C) 1999 - 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.
 */

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

/****************************************************************************/
void	m_apm_integer_pow(M_APM rr, int places, M_APM aa, int mexp)
{
	M_APM   tmp0, tmpy, tmpz;
	int	nexp, ii, signflag, local_precision;

	if (mexp == 0)
	{
		m_apm_copy(rr, MM_One);
		return;
	}
	else
	{
		if (mexp > 0)
		{
			signflag = 0;
			nexp     = mexp;
		}
		else
		{
			signflag = 1;
			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();

	local_precision = places + 8;

	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);
			m_apm_round(tmpy, local_precision, tmp0);

			if (nexp == 0)
				break;
		}

		m_apm_multiply(tmp0, tmpz, tmpz);
		m_apm_round(tmpz, local_precision, tmp0);
	}

	if (signflag)
	{
		m_apm_reciprocal(rr, places, tmpy);
	}
	else
	{
		m_apm_round(rr, places, tmpy);
	}

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