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Cream of the Crop 1
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DJLSR106.ARJ
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FIX16.CC
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1992-03-30
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// This may look like C code, but it is really -*- C++ -*-
/*
Copyright (C) 1988 Free Software Foundation
written by Kurt Baudendistel (gt-eedsp!baud@gatech.edu)
adapted for libg++ by Doug Lea (dl@rocky.oswego.edu)
This file is part of the GNU C++ Library. This library is free
software; you can redistribute it and/or modify it under the terms of
the GNU Library General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your
option) any later version. This library is distributed in the hope
that it will be useful, but WITHOUT ANY WARRANTY; without even the
implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See the GNU Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the Free Software
Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
*/
//
// Fix.cc : fixed precision class support functions
//
#ifdef __GNUG__
#pragma implementation "Fix16.h"
#endif
#include <Fix16.h>
// basic operators too large to be inline
short Fix16::assign(double d)
{
if (d == 1.0)
return Fix16_m_max;
else if (d > Fix16_max)
{
short i = Fix16_m_max;
range_error(i);
return i;
}
else if (d < Fix16_min)
{
short i = Fix16_m_min;
range_error(i);
return i;
}
else
return round(Fix16_mult * d);
}
long Fix32::assign(double d)
{
if (d == 1.0)
return Fix32_m_max;
else if (d > Fix32_max)
{
long i = Fix32_m_max;
range_error(i);
return i;
}
else if (d < Fix32_min)
{
long i = Fix32_m_min;
range_error(i);
return i;
}
else
return round(Fix32_mult * d);
}
Fix32 operator * (Fix32& a, Fix32& b)
{
// break a and b into lo and hi parts, and do a multiple-precision
// multiply, with rounding
int apos = (a.m >= 0);
unsigned long ua = (apos)? a.m : - a.m;
ua <<= 1; // ua is biased so result will be 31 bit mantissa, not 30:
unsigned long hi_a = (ua >> 16) & ((1 << 16) - 1);
unsigned long lo_a = ua & ((1 << 16) - 1);
int bpos = (b.m >= 0);
unsigned long ub = (bpos)? b.m : -b.m;
unsigned long hi_b = (ub >> 16) & ((1 << 16) - 1);
unsigned long lo_b = ub & ((1 << 16) - 1);
unsigned long r = lo_a * lo_b + (1 << 15);
r = (r >> 16) + hi_a * lo_b + lo_a * hi_b + (1 << 15);
r = (r >> 16) + hi_a * hi_b;
long p = (apos != bpos)? -r : r;
return Fix32(p);
}
Fix16 operator / (Fix16& a, Fix16& b)
{
short q;
int apos = (a.m >= 0);
long la = (apos)? a.m : -a.m;
long scaled_a = la << 15;
int bpos = (b.m >= 0);
short sb = (bpos)? b.m: -b.m;
if (la >= sb)
{
q = (apos == bpos)? Fix16_m_max: Fix16_m_min;
a.range_error(q);
}
else
{
q = scaled_a / sb;
if ((scaled_a % sb) >= (sb / 2)) ++q;
if (apos != bpos) q = -q;
}
return Fix16(q);
}
Fix32 operator / (Fix32& a, Fix32& b)
{
long q;
int apos = (a.m >= 0);
unsigned long la = (apos)? a.m : -a.m;
int bpos = (b.m >= 0);
unsigned long lb = (bpos)? b.m: -b.m;
if (la >= lb)
{
q = (apos == bpos)? Fix32_m_max: Fix32_m_min;
a.range_error(q);
}
else // standard shift-based division alg
{
q = 0;
long r = la;
for (int i = 32; i > 0; i--)
{
if ((unsigned)(r) > lb) {
q = (q << 1) | 1;
r -= lb;
}
else
q = (q << 1);
r <<= 1;
}
if (apos != bpos) q = -q; // Fix sign
}
return Fix32(q);
}
// error handling
void Fix16::overflow(short& i)
{
(*Fix16_overflow_handler)(i);
}
void Fix32::overflow(long& i)
{
(*Fix32_overflow_handler)(i);
}
void Fix16::range_error(short& i)
{
(*Fix16_range_error_handler)(i);
}
void Fix32::range_error(long& i)
{
(*Fix32_range_error_handler)(i);
}
// data definitions
Fix16_peh Fix16_overflow_handler = Fix16_overflow_saturate;
Fix32_peh Fix32_overflow_handler = Fix32_overflow_saturate;
Fix16_peh Fix16_range_error_handler = Fix16_warning;
Fix32_peh Fix32_range_error_handler = Fix32_warning;
//function definitions
Fix16_peh set_Fix16_overflow_handler(Fix16_peh new_handler) {
Fix16_peh old_handler = Fix16_overflow_handler;
Fix16_overflow_handler = new_handler;
return old_handler;
}
Fix32_peh set_Fix32_overflow_handler(Fix32_peh new_handler) {
Fix32_peh old_handler = Fix32_overflow_handler;
Fix32_overflow_handler = new_handler;
return old_handler;
}
void set_overflow_handler(Fix16_peh handler16, Fix32_peh handler32) {
set_Fix16_overflow_handler(handler16);
set_Fix32_overflow_handler(handler32);
}
Fix16_peh set_Fix16_range_error_handler(Fix16_peh new_handler) {
Fix16_peh old_handler = Fix16_range_error_handler;
Fix16_range_error_handler = new_handler;
return old_handler;
}
Fix32_peh set_Fix32_range_error_handler(Fix32_peh new_handler) {
Fix32_peh old_handler = Fix32_range_error_handler;
Fix32_range_error_handler = new_handler;
return old_handler;
}
void set_range_error_handler(Fix16_peh handler16, Fix32_peh handler32) {
set_Fix16_range_error_handler(handler16);
set_Fix32_range_error_handler(handler32);
}
void Fix16_overflow_saturate(short& i)
{ i = (i > 0 ? Fix16_m_min : Fix16_m_max); }
void Fix16_ignore(short&) {}
void Fix16_warning(short&)
{ cerr << "warning: Fix16 result out of range\n"; }
void Fix16_overflow_warning_saturate(short& i)
{ cerr << "warning: Fix16 result out of range\n";
Fix16_overflow_saturate(i); }
void Fix16_abort(short&)
{ cerr << "error: Fix16 result out of range\n"; abort(); }
void Fix32_ignore(long&) {}
void Fix32_overflow_saturate(long& i)
{ i = (i > 0 ? Fix32_m_min : Fix32_m_max); }
void Fix32_warning(long&)
{ cerr << "warning: Fix32 result out of range\n"; }
void Fix32_overflow_warning_saturate(long& i)
{ cerr << "warning: Fix32 result out of range\n";
Fix32_overflow_saturate(i); }
void Fix32_abort(long&)
{ cerr << "error: Fix32 result out of range\n"; abort(); }