| 0,0 → 1,139 |
|---|
| /* |
| * Copyright (C) 2005 Josef Cejka |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * - The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| #include "sftypes.h" |
| #include "sub.h" |
| |
| /** Subtract two float32 numbers with same signs |
| */ |
| float32 subFloat32(float32 a, float32 b) |
| { |
| int expdiff; |
| __u32 exp1,exp2,mant1,mant2; |
| float32 result; |
| |
| result.f = 0; |
| |
| expdiff=a.parts.exp - b.parts.exp; |
| if ((expdiff<0)||((expdiff==0)&&(a.parts.mantisa<b.parts.mantisa))) { |
| if (isFloat32NaN(b)) { |
| //TODO: fix SigNaN |
| if (isFloat32SigNaN(b)) { |
| }; |
| return b; |
| }; |
| |
| if (b.parts.exp==0xFF) { |
| b.parts.sign=!b.parts.sign; /* num -(+-inf) = -+inf */ |
| return b; |
| } |
| |
| result.parts.sign = !a.parts.sign; |
| |
| mant1=b.parts.mantisa; |
| exp1=b.parts.exp; |
| mant2=a.parts.mantisa; |
| exp2=a.parts.exp; |
| expdiff*=-1; |
| } else { |
| if (isFloat32NaN(a)) { |
| //TODO: fix SigNaN |
| if ((isFloat32SigNaN(a))||(isFloat32SigNaN(b))) { |
| }; |
| return a; |
| }; |
| |
| if (a.parts.exp==0xFF) { |
| if (b.parts.exp==0xFF) { |
| /* inf - inf => nan */ |
| //TODO: fix exception |
| result.binary = FLOAT32_NAN; |
| return result; |
| }; |
| return a; |
| } |
| |
| result.parts.sign = a.parts.sign; |
| |
| mant1=a.parts.mantisa; |
| exp1=a.parts.exp; |
| mant2=b.parts.mantisa; |
| exp2=b.parts.exp; |
| }; |
| |
| if (exp1==0) { |
| //both are denormalized |
| result.parts.mantisa=mant1-mant2; |
| if (result.parts.mantisa>mant1) { |
| //TODO: underflow exception |
| return result; |
| }; |
| result.parts.exp=0; |
| return result; |
| }; |
| |
| // create some space for rounding |
| mant1<<=6; |
| mant2<<=6; |
| |
| mant1|=0x20000000; //add hidden bit |
| |
| |
| if (exp2==0) { |
| --expdiff; |
| } else { |
| mant2|=0x20000000; //hidden bit |
| }; |
| |
| if (expdiff>24) { |
| goto done; |
| }; |
| |
| mant1 = mant1-(mant2>>expdiff); |
| done: |
| //TODO: find first nonzero digit and shift result and detect possibly underflow |
| while ((exp1>0)&&(!(mant1&0x20000000))) { |
| exp1--; |
| mant1 <<= 1; |
| /* TODO: fix underflow - mant1 == 0 does not necessary means underflow... */ |
| }; |
| |
| //rounding - if first bit after mantisa is set then round up |
| mant1 += 0x20; |
| |
| if (mant1&0x40000000) { |
| ++exp1; |
| mant1>>=1; |
| }; |
| |
| result.parts.mantisa = ((mant1&(~0x20000000))>>6); /*Clear hidden bit and shift */ |
| result.parts.exp = exp1; |
| |
| return result; |
| }; |
| |