/*-
* Copyright (c) 1992, 1993
* The Regents of the University of California. All rights reserved.
*
* This software was developed by the Computer Systems Engineering group
* at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
* contributed to Berkeley.
*
* 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 University 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 REGENTS 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 REGENTS 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.
*/
/*
* Convert double to (unsigned) int. All operations are done module 2^32.
*/
UINTXX_T
FIXUNSNAME(__fixunsgen)(int exp, bool sign, size_t mant_dig, size_t fracbits,
const uint32_t *frac)
{
UINTXX_T tmp;
/*
* If it's less than 1 (negative exponent), it's going to round
* to zero. If the exponent is so large that it is a multiple of
* 2^N, then x module 2^N will be 0. (we use the fact treating a
* negative value as unsigned will be greater than nonnegative value)
*/
if (__predict_false((size_t)exp >= mant_dig + sizeof(UINTXX_T)*8))
return 0;
/*
* This is simpler than it seems. Basically we are constructing
* fixed binary representation of the floating point number tossing
* away bits that wont be in the modulis we return.
*/
tmp = 1;
for (size_t ebits = exp;;) {
if (ebits <= fracbits) {
/*
* The current fraction has more bits than we need.
* Shift the current value over and insert the bits
* we want. We're done.
*/
tmp <<= (unsigned int)ebits;
tmp |= *frac >> (fracbits - ebits);
break;
}
if (fracbits == sizeof(tmp)*4) {
/*
* Shifts must be < sizeof(type). If it's going to be
* sizeof(type), just replace the value.
*/
tmp = *frac--;
} else {
tmp <<= (unsigned int)fracbits;
tmp |= *frac--;
}
ebits -= fracbits;
fracbits = sizeof(frac[0]) * 4;
}
/*
* If the input was negative, make tmp negative module 2^32.
*/
if (sign)
tmp = -tmp;
