forked from xuos/xiuos
100 lines
2.5 KiB
C
100 lines
2.5 KiB
C
/* Copyright JS Foundation and other contributors, http://js.foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is based on work under the following copyright and permission
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* notice:
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*
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunSoft, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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*
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* @(#)s_scalbn.c 1.3 95/01/18
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*/
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#include "jerry-math-internal.h"
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/* scalbn(x,n) returns x* 2**n computed by exponent
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* manipulation rather than by actually performing an
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* exponentiation or a multiplication.
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*/
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#define two54 1.80143985094819840000e+16 /* 0x43500000, 0x00000000 */
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#define twom54 5.55111512312578270212e-17 /* 0x3C900000, 0x00000000 */
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#define huge 1.0e+300
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#define tiny 1.0e-300
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double
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scalbn (double x, int n)
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{
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int k, hx, lx;
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hx = __HI (x);
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lx = __LO (x);
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k = (hx & 0x7ff00000) >> 20; /* extract exponent */
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if (k == 0) /* 0 or subnormal x */
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{
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if ((lx | (hx & 0x7fffffff)) == 0) /* +-0 */
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{
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return x;
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}
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x *= two54;
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hx = __HI (x);
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k = ((hx & 0x7ff00000) >> 20) - 54;
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if (n < -50000) /*underflow */
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{
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return tiny * x;
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}
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}
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if (k == 0x7ff) /* NaN or Inf */
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{
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return x + x;
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}
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k = k + n;
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if (k > 0x7fe) /* overflow */
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{
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return huge * copysign (huge, x);
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}
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if (k > 0) /* normal result */
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{
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double_accessor ret;
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ret.dbl = x;
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ret.as_int.hi = (hx & 0x800fffff) | (k << 20);
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return ret.dbl;
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}
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if (k <= -54)
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{
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if (n > 50000) /* in case integer overflow in n + k */
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{
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return huge * copysign (huge, x); /*overflow */
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}
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else
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{
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return tiny * copysign (tiny, x); /*underflow */
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}
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}
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k += 54; /* subnormal result */
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double_accessor ret;
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ret.dbl = x;
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ret.as_int.hi = (hx & 0x800fffff) | (k << 20);
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return ret.dbl * twom54;
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} /* scalbn */
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#undef two54
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#undef twom54
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#undef huge
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#undef tiny
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