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829 cejka 1
/*
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 * Copyright (C) 2005 Josef Cejka
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * - Redistributions of source code must retain the above copyright
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 *   notice, this list of conditions and the following disclaimer.
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 * - Redistributions in binary form must reproduce the above copyright
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 *   notice, this list of conditions and the following disclaimer in the
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 *   documentation and/or other materials provided with the distribution.
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 * - The name of the author may not be used to endorse or promote products
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 *   derived from this software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
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#include<sftypes.h>
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#include<common.h>
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/** Take fraction shifted by 10 bits to left, round it, normalize it and detect exceptions
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 * @param exp exponent with bias
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 * @param cfrac fraction shifted 10 places left with added hidden bit
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 * @return valied float64
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 */
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float64 finishFloat64(__s32 cexp, __u64 cfrac, char sign)
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{
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    float64 result;
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    result.parts.sign = sign;
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    /* find first nonzero digit and shift result and detect possibly underflow */
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    while ((cexp > 0) && (cfrac) && (!(cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1 ) )))) {
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        cexp--;
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        cfrac <<= 1;
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            /* TODO: fix underflow */
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    };
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    if ((cexp < 0) || ( cexp == 0 && (!(cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1)))))) {
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        /* FIXME: underflow */
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        result.parts.exp = 0;
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        if ((cexp + FLOAT64_FRACTION_SIZE + 1) < 0) { /* +1 is place for rounding */
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            result.parts.fraction = 0;
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            return result;
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        }
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        while (cexp < 0) {
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            cexp++;
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            cfrac >>= 1;
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        }
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        cfrac += (0x1 << (64 - FLOAT64_FRACTION_SIZE - 3));
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        if (!(cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_HIDDEN_BIT_MASK - 1)))) {
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            result.parts.fraction = ((cfrac >>(64 - FLOAT64_FRACTION_SIZE - 2) ) & (~FLOAT64_HIDDEN_BIT_MASK));
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            return result;
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        }  
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    } else {
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        cfrac += (0x1 << (64 - FLOAT64_FRACTION_SIZE - 3));
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    }
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    ++cexp;
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    if (cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1 ))) {
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        ++cexp;
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        cfrac >>= 1;
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    }  
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    /* check overflow */
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    if (cexp >= FLOAT64_MAX_EXPONENT ) {
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        /* FIXME: overflow, return infinity */
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        result.parts.exp = FLOAT64_MAX_EXPONENT;
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        result.parts.fraction = 0;
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        return result;
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    }
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    result.parts.exp = (__u32)cexp;
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    result.parts.fraction = ((cfrac >>(64 - FLOAT64_FRACTION_SIZE - 2 ) ) & (~FLOAT64_HIDDEN_BIT_MASK));
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    return result; 
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}
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