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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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874 cejka 32
/* Table for fast leading zeroes counting */
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char zeroTable[256] = {
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    8, 7, 7, 6, 6, 6, 6, 4, 4, 4, 4, 4, 4, 4, 4, \
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    3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, \
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    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, \
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    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, \
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    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
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    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
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    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
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    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \
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    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
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    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
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    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
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    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
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    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
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    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
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    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, \
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    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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};
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829 cejka 54
/** 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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 */
1031 cejka 59
float64 finishFloat64(int32_t cexp, uint64_t cfrac, char sign)
829 cejka 60
{
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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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834 cejka 72
    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;
835 cejka 75
        if ((cexp + FLOAT64_FRACTION_SIZE + 1) < 0) { /* +1 is place for rounding */
834 cejka 76
            result.parts.fraction = 0;
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            return result;
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        }
835 cejka 79
 
834 cejka 80
        while (cexp < 0) {
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            cexp++;
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            cfrac >>= 1;
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        }
835 cejka 84
 
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        cfrac += (0x1 << (64 - FLOAT64_FRACTION_SIZE - 3));
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874 cejka 87
        if (!(cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1)))) {
834 cejka 88
 
835 cejka 89
            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));
834 cejka 94
    }
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    ++cexp;
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829 cejka 98
    if (cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1 ))) {
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        ++cexp;
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        cfrac >>= 1;
834 cejka 101
    }  
829 cejka 102
 
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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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1031 cejka 111
    result.parts.exp = (uint32_t)cexp;
829 cejka 112
 
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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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}
834 cejka 117
 
874 cejka 118
/** Counts leading zeroes in 64bit unsigned integer
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 * @param i
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 */
1031 cejka 121
int countZeroes64(uint64_t i)
874 cejka 122
{
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    int j;
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    for (j =0; j < 64; j += 8) {
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        if ( i & (0xFFll << (56 - j))) {
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            return (j + countZeroes8(i >> (56 - j)));
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        }
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    }
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    return 64;
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}
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/** Counts leading zeroes in 32bit unsigned integer
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 * @param i
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 */
1031 cejka 136
int countZeroes32(uint32_t i)
874 cejka 137
{
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    int j;
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    for (j =0; j < 32; j += 8) {
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        if ( i & (0xFF << (24 - j))) {
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            return (j + countZeroes8(i >> (24 - j)));
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        }
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    }
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145
    return 32;
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}
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/** Counts leading zeroes in byte
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 * @param i
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 */
1031 cejka 151
int countZeroes8(uint8_t i)
874 cejka 152
{
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    return zeroTable[i];
154
}
155
 
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/** Round and normalize number expressed by exponent and fraction with first bit (equal to hidden bit) at 30. bit
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 * @param exp exponent
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 * @param fraction part with hidden bit shifted to 30. bit
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 */
1031 cejka 160
void roundFloat32(int32_t *exp, uint32_t *fraction)
874 cejka 161
{
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    /* rounding - if first bit after fraction is set then round up */
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    (*fraction) += (0x1 << 6);
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165
    if ((*fraction) & (FLOAT32_HIDDEN_BIT_MASK << 8)) {
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        /* rounding overflow */
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        ++(*exp);
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        (*fraction) >>= 1;
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    };
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    if (((*exp) >= FLOAT32_MAX_EXPONENT ) || ((*exp) < 0)) {
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        /* overflow - set infinity as result */
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        (*exp) = FLOAT32_MAX_EXPONENT;
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        (*fraction) = 0;
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        return;
176
    }
177
 
178
    return;
179
}
180
 
181
/** Round and normalize number expressed by exponent and fraction with first bit (equal to hidden bit) at 62. bit
182
 * @param exp exponent
183
 * @param fraction part with hidden bit shifted to 62. bit
184
 */
1031 cejka 185
void roundFloat64(int32_t *exp, uint64_t *fraction)
874 cejka 186
{
187
    /* rounding - if first bit after fraction is set then round up */
188
    (*fraction) += (0x1 << 9);
189
 
190
    if ((*fraction) & (FLOAT64_HIDDEN_BIT_MASK << 11)) {
191
        /* rounding overflow */
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        ++(*exp);
193
        (*fraction) >>= 1;
194
    };
195
 
196
    if (((*exp) >= FLOAT64_MAX_EXPONENT ) || ((*exp) < 0)) {
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        /* overflow - set infinity as result */
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        (*exp) = FLOAT64_MAX_EXPONENT;
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        (*fraction) = 0;
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        return;
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    }
202
 
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    return;
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}
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