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/*
* Copyright (c) 1994 MEDICAL RESEARCH COUNCIL
* All rights reserved
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1 Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2 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.
*
* 3 Neither the name of the MEDICAL RESEARCH COUNCIL, THE LABORATORY OF
* MOLECULAR BIOLOGY nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT OWNER OR CONTRIBUTORS 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.
*/
/*
* Copyright (c) Medical Research Council 1994. All rights reserved.
*
* Permission to use, copy, modify and distribute this software and its
* documentation for any purpose is hereby granted without fee, provided that
* this copyright and notice appears in all copies.
*
* This file was written by James Bonfield, Simon Dear, Rodger Staden,
* as part of the Staden Package at the MRC Laboratory of Molecular
* Biology, Hills Road, Cambridge, CB2 2QH, United Kingdom.
*
* MRC disclaims all warranties with regard to this software.
*/
#ifdef HAVE_CONFIG_H
#include "io_lib_config.h"
#endif
#include <math.h>
#include "io_lib/fpoint.h"
/*
extern double log ( double x ) ;
extern double exp ( double x ) ;
*/
#define IEEE
float int_to_float(int in)
/*
** interpret the integer in as a
** floating point number in IEEE format
*/
{
/*
Assume `in' is stored as a float according to the
ANSI IEEE 754-1985 standard. See the tables below:
s = sign ( 1 bit)
e = biased exponent (8 bits)
f = fraction (23 bits)
floating point number = (-1)^s 2^(e-127) 1.f
Bits Name Content
31 Sign 1 iff number is negative
23-30 Exponent Eight-Bit exponent, biased by 127
0-22 Fraction 23-bit fraction component of normalised significant.
The "one" bit is "hidden"
If IEEE floating point format is supported on your machine...
ensure there is a #define IEEE somewhere.
*/
#ifdef IEEE
union {
int i;
float f;
} cvt;
cvt.i = in;
return cvt.f;
#else
int fraction;
int exponent;
int sign;
fraction = in & ( (1<<23)-1 );
exponent = (in >> 23) & ( (1<<8)-1 );
sign = (in >> 31);
return
(float) (
(sign?-1.0:1.0) *
exp ( log ( (double) 2.0) * (double) (exponent - 127 - 23) ) *
(double) ((1<<23)+fraction)) ;
#endif
}
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