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/******************************************************************************
* $Id: dgnfloat.cpp 10645 2007-01-18 02:22:39Z warmerdam $
*
* Project: Microstation DGN Access Library
* Purpose: Functions for translating DGN floats into IEEE floats.
* Author: Frank Warmerdam, warmerdam@pobox.com
*
******************************************************************************
* Copyright (c) 2000, Avenza Systems Inc, http://www.avenza.com/
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
****************************************************************************/
#include "dgnlibp.h"
CPL_CVSID("$Id: dgnfloat.cpp 10645 2007-01-18 02:22:39Z warmerdam $");
typedef struct dbl {
GUInt32 hi;
GUInt32 lo;
} double64_t;
/************************************************************************/
/* DGN2IEEEDouble() */
/************************************************************************/
void DGN2IEEEDouble(void * dbl)
{
double64_t dt;
GUInt32 sign;
GUInt32 exponent;
GUInt32 rndbits;
unsigned char *src;
unsigned char *dest;
/* -------------------------------------------------------------------- */
/* Arrange the VAX double so that it may be accessed by a */
/* double64_t structure, (two GUInt32s). */
/* -------------------------------------------------------------------- */
src = (unsigned char *) dbl;
dest = (unsigned char *) &dt;
#ifdef CPL_LSB
dest[2] = src[0];
dest[3] = src[1];
dest[0] = src[2];
dest[1] = src[3];
dest[6] = src[4];
dest[7] = src[5];
dest[4] = src[6];
dest[5] = src[7];
#else
dest[1] = src[0];
dest[0] = src[1];
dest[3] = src[2];
dest[2] = src[3];
dest[5] = src[4];
dest[4] = src[5];
dest[7] = src[6];
dest[6] = src[7];
#endif
/* -------------------------------------------------------------------- */
/* Save the sign of the double */
/* -------------------------------------------------------------------- */
sign = dt.hi & 0x80000000;
/* -------------------------------------------------------------------- */
/* Adjust the exponent so that we may work with it */
/* -------------------------------------------------------------------- */
exponent = dt.hi >> 23;
exponent = exponent & 0x000000ff;
if (exponent)
exponent = exponent -129 + 1023;
/* -------------------------------------------------------------------- */
/* Save the bits that we are discarding so we can round properly */
/* -------------------------------------------------------------------- */
rndbits = dt.lo & 0x00000007;
dt.lo = dt.lo >> 3;
dt.lo = (dt.lo & 0x1fffffff) | (dt.hi << 29);
if (rndbits)
dt.lo = dt.lo | 0x00000001;
/* -------------------------------------------------------------------- */
/* Shift the hi-order int over 3 and insert the exponent and sign */
/* -------------------------------------------------------------------- */
dt.hi = dt.hi >> 3;
dt.hi = dt.hi & 0x000fffff;
dt.hi = dt.hi | (exponent << 20) | sign;
#ifdef CPL_LSB
/* -------------------------------------------------------------------- */
/* Change the number to a byte swapped format */
/* -------------------------------------------------------------------- */
src = (unsigned char *) &dt;
dest = (unsigned char *) dbl;
dest[0] = src[4];
dest[1] = src[5];
dest[2] = src[6];
dest[3] = src[7];
dest[4] = src[0];
dest[5] = src[1];
dest[6] = src[2];
dest[7] = src[3];
#else
memcpy( dbl, &dt, 8 );
#endif
}
/************************************************************************/
/* IEEE2DGNDouble() */
/************************************************************************/
void IEEE2DGNDouble(void * dbl)
{
double64_t dt;
GInt32 exponent;
GInt32 sign;
GByte *src,*dest;
#ifdef CPL_LSB
src = (GByte *) dbl;
dest = (GByte *) &dt;
dest[0] = src[4];
dest[1] = src[5];
dest[2] = src[6];
dest[3] = src[7];
dest[4] = src[0];
dest[5] = src[1];
dest[6] = src[2];
dest[7] = src[3];
#else
memcpy( &dt, dbl, 8 );
#endif
sign = dt.hi & 0x80000000;
exponent = dt.hi >> 20;
exponent = exponent & 0x000007ff;
/* -------------------------------------------------------------------- */
/* An exponent of zero means a zero value. */
/* -------------------------------------------------------------------- */
if (exponent)
exponent = exponent -1023+129;
/* -------------------------------------------------------------------- */
/* In the case of overflow, return the largest number we can */
/* -------------------------------------------------------------------- */
if (exponent > 255)
{
dest = (GByte *) dbl;
if (sign)
dest[1] = 0xff;
else
dest[1] = 0x7f;
dest[0] = 0xff;
dest[2] = 0xff;
dest[3] = 0xff;
dest[4] = 0xff;
dest[5] = 0xff;
dest[6] = 0xff;
dest[7] = 0xff;
return;
}
/* -------------------------------------------------------------------- */
/* In the case of of underflow return zero */
/* -------------------------------------------------------------------- */
else if ((exponent < 0 ) ||
(exponent == 0 && sign == 0))
{
dest = (GByte *) dbl;
dest[0] = 0x00;
dest[1] = 0x00;
dest[2] = 0x00;
dest[3] = 0x00;
dest[4] = 0x00;
dest[5] = 0x00;
dest[6] = 0x00;
dest[7] = 0x00;
return;
}
else
{
/* -------------------------------------------------------------------- */
/* Shift the fraction 3 bits left and set the exponent and sign*/
/* -------------------------------------------------------------------- */
dt.hi = dt.hi << 3;
dt.hi = dt.hi | (dt.lo >> 29);
dt.hi = dt.hi & 0x007fffff;
dt.hi = dt.hi | (exponent << 23) | sign;
dt.lo = dt.lo << 3;
}
/* -------------------------------------------------------------------- */
/* Convert the double back to VAX format */
/* -------------------------------------------------------------------- */
src = (GByte *) &dt;
dest = (GByte *) dbl;
#ifdef CPL_LSB
dest[2] = src[0];
dest[3] = src[1];
dest[0] = src[2];
dest[1] = src[3];
dest[6] = src[4];
dest[7] = src[5];
dest[4] = src[6];
dest[5] = src[7];
#else
dest[1] = src[0];
dest[0] = src[1];
dest[3] = src[2];
dest[2] = src[3];
dest[5] = src[4];
dest[4] = src[5];
dest[7] = src[6];
dest[6] = src[7];
#endif
}
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