source: mainline/softfloat/generic/conversion.c@ afffa1e

/*
 * 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 "conversion.h"
#include "comparison.h"

float64 convertFloat32ToFloat64(float32 a) 
{
        float64 result;
        __u64 frac;
        
        result.parts.sign = a.parts.sign;
        result.parts.fraction = a.parts.fraction;
        result.parts.fraction <<= (FLOAT64_FRACTION_SIZE - FLOAT32_FRACTION_SIZE );
        
        if ((isFloat32Infinity(a))||(isFloat32NaN(a))) {
                result.parts.exp = 0x7FF;
                /* TODO; check if its correct for SigNaNs*/
                return result;
        };
        
        result.parts.exp = a.parts.exp + ( (int)FLOAT64_BIAS - FLOAT32_BIAS );
        if (a.parts.exp == 0) {
                /* normalize denormalized numbers */

                if (result.parts.fraction == 0ll) { /* fix zero */
                        result.parts.exp = 0ll;
                        return result;
                }
                        
                frac = result.parts.fraction;
                
                while (!(frac & (0x10000000000000ll))) {
                        frac <<= 1;
                        --result.parts.exp;
                };
                
                ++result.parts.exp;
                result.parts.fraction = frac;
        };
        
        return result;
        
}

float32 convertFloat64ToFloat32(float64 a) 
{
        float32 result;
        __s32 exp;
        __u64 frac;
        
        result.parts.sign = a.parts.sign;
        
        if (isFloat64NaN(a)) {
                
                result.parts.exp = 0xFF;
                
                if (isFloat64SigNaN(a)) {
                        result.parts.fraction = 0x800000; /* set first bit of fraction nonzero */
                        return result;
                }
        
                result.parts.fraction = 0x1; /* fraction nonzero but its first bit is zero */
                return result;
        };

        if (isFloat64Infinity(a)) {
                result.parts.fraction = 0;
                result.parts.exp = 0xFF;
                return result;
        };

        exp = (int)a.parts.exp - FLOAT64_BIAS + FLOAT32_BIAS;
        
        if (exp >= 0xFF) {
                /*FIXME: overflow*/
                result.parts.fraction = 0;
                result.parts.exp = 0xFF;
                return result;
                
        } else if (exp <= 0 ) {
                
                /* underflow or denormalized */
                
                result.parts.exp = 0;
                
                exp *= -1;      
                if (exp > FLOAT32_FRACTION_SIZE ) {
                        /* FIXME: underflow */
                        result.parts.fraction = 0;
                        return result;
                };
                
                /* denormalized */
                
                frac = a.parts.fraction; 
                frac |= 0x10000000000000ll; /* denormalize and set hidden bit */
                
                frac >>= (FLOAT64_FRACTION_SIZE - FLOAT32_FRACTION_SIZE + 1);
                
                while (exp > 0) {
                        --exp;
                        frac >>= 1;
                };
                result.parts.fraction = frac;
                
                return result;
        };

        result.parts.exp = exp;
        result.parts.fraction = a.parts.fraction >> (FLOAT64_FRACTION_SIZE - FLOAT32_FRACTION_SIZE);
        return result;
}


/** Helping procedure for converting float32 to uint32
 * @param a floating point number in normalized form (no NaNs or Inf are checked )
 * @return unsigned integer
 */
static __u32 _float32_to_uint32_helper(float32 a)
{
        __u32 frac;
        
        if (a.parts.exp < FLOAT32_BIAS) {
                /*TODO: rounding*/
                return 0;
        }
        
        frac = a.parts.fraction;
        
        frac |= FLOAT32_HIDDEN_BIT_MASK;
        /* shift fraction to left so hidden bit will be the most significant bit */
        frac <<= 32 - FLOAT32_FRACTION_SIZE - 1; 

        frac >>= 32 - (a.parts.exp - FLOAT32_BIAS) - 1;
        if ((a.parts.sign == 1) && (frac != 0)) {
                frac = ~frac;
                ++frac;
        }
        
        return frac;
}

/* Convert float to unsigned int32
 * FIXME: Im not sure what to return if overflow/underflow happens 
 *      - now its the biggest or the smallest int
 */ 
__u32 float32_to_uint32(float32 a)
{
        if (isFloat32NaN(a)) {
                return MAX_UINT32;
        }
        
        if (isFloat32Infinity(a) || (a.parts.exp >= (32 + FLOAT32_BIAS)))  {
                if (a.parts.sign) {
                        return MIN_UINT32;
                }
                return MAX_UINT32;
        }
        
        return _float32_to_uint32_helper(a);    
}

/* Convert float to signed int32
 * FIXME: Im not sure what to return if overflow/underflow happens 
 *      - now its the biggest or the smallest int
 */ 
__s32 float32_to_int32(float32 a)
{
        if (isFloat32NaN(a)) {
                return MAX_INT32;
        }
        
        if (isFloat32Infinity(a) || (a.parts.exp >= (32 + FLOAT32_BIAS)))  {
                if (a.parts.sign) {
                        return MIN_INT32;
                }
                return MAX_INT32;
        }
        return _float32_to_uint32_helper(a);
}