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https://github.com/php/php-src.git
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Saki Takamachi
125 lines
3.6 KiB
C
125 lines
3.6 KiB
C
/* raise.c: bcmath library file. */
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/*
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Copyright (C) 1991, 1992, 1993, 1994, 1997 Free Software Foundation, Inc.
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Copyright (C) 2000 Philip A. Nelson
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details. (LICENSE)
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to:
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The Free Software Foundation, Inc.
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59 Temple Place, Suite 330
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Boston, MA 02111-1307 USA.
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You may contact the author by:
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e-mail: philnelson@acm.org
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us-mail: Philip A. Nelson
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Computer Science Department, 9062
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Western Washington University
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Bellingham, WA 98226-9062
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*************************************************************************/
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#include "bcmath.h"
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#include <assert.h>
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#include <stdbool.h>
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#include <stddef.h>
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void bc_square_ex(bc_num n1, bc_num *result, size_t scale_min) {
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bc_num square_ex = bc_square(n1, scale_min);
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bc_free_num(result);
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*(result) = square_ex;
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}
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/* Raise "base" to the "exponent" power. The result is placed in RESULT.
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Maximum exponent is LONG_MAX. If a "exponent" is not an integer,
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only the integer part is used. */
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bool bc_raise(bc_num base, long exponent, bc_num *result, size_t scale) {
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bc_num temp, power;
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size_t rscale;
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size_t pwrscale;
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size_t calcscale;
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bool is_neg;
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/* Special case if exponent is a zero. */
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if (exponent == 0) {
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bc_free_num (result);
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*result = bc_copy_num(BCG(_one_));
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return true;
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}
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/* Other initializations. */
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if (exponent < 0) {
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is_neg = true;
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exponent = -exponent;
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rscale = scale;
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} else {
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is_neg = false;
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rscale = MIN (base->n_scale * exponent, MAX(scale, base->n_scale));
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}
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/* Set initial value of temp. */
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power = bc_copy_num(base);
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pwrscale = base->n_scale;
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while ((exponent & 1) == 0) {
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pwrscale = 2 * pwrscale;
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bc_square_ex(power, &power, pwrscale);
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exponent = exponent >> 1;
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}
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temp = bc_copy_num(power);
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calcscale = pwrscale;
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exponent = exponent >> 1;
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/* Do the calculation. */
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while (exponent > 0) {
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pwrscale = 2 * pwrscale;
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bc_square_ex(power, &power, pwrscale);
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if ((exponent & 1) == 1) {
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calcscale = pwrscale + calcscale;
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bc_multiply_ex(temp, power, &temp, calcscale);
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}
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exponent = exponent >> 1;
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}
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/* Assign the value. */
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if (is_neg) {
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if (bc_divide(BCG(_one_), temp, result, rscale) == false) {
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bc_free_num (&temp);
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bc_free_num (&power);
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return false;
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}
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bc_free_num (&temp);
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} else {
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bc_free_num (result);
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*result = temp;
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(*result)->n_scale = MIN(scale, (*result)->n_scale);
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}
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bc_free_num (&power);
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return true;
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}
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/* This is used internally by BCMath */
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void bc_raise_bc_exponent(bc_num base, bc_num expo, bc_num *result, size_t scale) {
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/* Exponent must not have fractional part */
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assert(expo->n_scale == 0);
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long exponent = bc_num2long(expo);
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/* Exponent must be properly convertable to long */
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if (exponent == 0 && (expo->n_len > 1 || expo->n_value[0] != 0)) {
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assert(false && "Exponent is not well formed in internal call");
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//assert(exponent != 0 || (expo->n_len == 0 && expo->n_value[0] == 0));
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}
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//assert(exponent != 0 || (expo->n_len == 0 && expo->n_value[0] == 0));
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bc_raise(base, exponent, result, scale);
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}
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