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Support unsigned divide of huge numbers.

This commit is contained in:
steve 2004-02-17 06:52:55 +00:00
parent 6f9ebb1e60
commit 38ec4b7851
2 changed files with 91 additions and 13 deletions
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96
verinum.cc
View File

@ -17,7 +17,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#ifdef HAVE_CVS_IDENT
#ident "$Id: verinum.cc,v 1.41 2003/10/26 04:54:56 steve Exp $"
#ident "$Id: verinum.cc,v 1.42 2004/02/17 06:52:55 steve Exp $"
#endif
# include "config.h"
@ -467,12 +467,16 @@ verinum::V operator <= (const verinum&left, const verinum&right)
if (right[idx-1] != verinum::V0) return verinum::V1;
}
idx = right.len();
if (left.len() < idx) idx = left.len();
while (idx > 0) {
if (left[idx-1] == verinum::Vx) return verinum::Vx;
if (left[idx-1] == verinum::Vz) return verinum::Vx;
if (right[idx-1] == verinum::Vx) return verinum::Vx;
if (right[idx-1] == verinum::Vz) return verinum::Vx;
if (left[idx-1] > right[idx-1]) return verinum::V0;
if (left[idx-1] < right[idx-1]) return verinum::V1;
idx -= 1;
}
@ -694,6 +698,68 @@ verinum operator * (const verinum&left, const verinum&right)
return trim_vnum(result);
}
verinum operator << (const verinum&that, unsigned shift)
{
verinum result(verinum::V0, that.len() + shift, that.has_len());
for (unsigned idx = 0 ; idx < that.len() ; idx += 1)
result.set(idx+shift, that.get(idx));
return result;
}
verinum operator >> (const verinum&that, unsigned shift)
{
if (shift >= that.len()) {
if (that.has_sign()) {
verinum result (that.get(that.len()-1), 1);
result.has_sign(true);
return result;
} else {
verinum result(verinum::V0, 1);
return result;
}
}
verinum result(that.has_sign()? that.get(that.len()-1) : verinum::V0,
that.len() - shift, that.has_len());
for (unsigned idx = shift ; idx < that.len() ; idx += 1)
result.set(idx-shift, that.get(idx));
return result;
}
static verinum unsigned_divide(verinum num, verinum den)
{
unsigned nwid = num.len();
while (nwid > 0 && (num.get(nwid-1) == verinum::V0))
nwid -= 1;
unsigned dwid = den.len();
while (dwid > 0 && (den.get(dwid-1) == verinum::V0))
dwid -= 1;
if (dwid > nwid)
return verinum(verinum::V0, 1);
den = den << (nwid-dwid);
unsigned idx = nwid - dwid + 1;
verinum result (verinum::V0, idx);
while (idx > 0) {
if (den <= num) {
verinum dif = num - den;
num = dif;
result.set(idx-1, verinum::V1);
}
den = den >> 1;
idx -= 1;
}
return result;
}
/*
* This operator divides the left number by the right number. If
* either value is signed, the result is signed. If both values have a
@ -716,7 +782,7 @@ verinum operator / (const verinum&left, const verinum&right)
/* If the right expression is a zero value, then the result is
filled with 'bx bits. */
if (right.as_ulong() == 0) {
if (right.is_zero()) {
verinum result (verinum::Vx, use_len, has_len_flag);
result.has_sign(left.has_sign() || right.has_sign());
return result;
@ -743,16 +809,19 @@ verinum operator / (const verinum&left, const verinum&right)
} else {
/* XXXX FIXME XXXX Use native unsigned division to do
the work. This does not work if the result is too
large for the native integer. */
assert(use_len <= 8*sizeof(unsigned long));
unsigned long l = left.as_ulong();
unsigned long r = right.as_ulong();
unsigned long v = l / r;
for (unsigned idx = 0 ; idx < use_len ; idx += 1) {
result.set(idx, (v & 1)? verinum::V1 : verinum::V0);
v >>= 1;
if (use_len <= 8 * sizeof(unsigned long)) {
/* Use native unsigned division to do the work. */
unsigned long l = left.as_ulong();
unsigned long r = right.as_ulong();
unsigned long v = l / r;
for (unsigned idx = 0 ; idx < use_len ; idx += 1) {
result.set(idx, (v & 1)? verinum::V1 : verinum::V0);
v >>= 1;
}
} else {
result = unsigned_divide(left, right);
}
}
@ -857,6 +926,9 @@ verinum::V operator ^ (verinum::V l, verinum::V r)
/*
* $Log: verinum.cc,v $
* Revision 1.42 2004/02/17 06:52:55 steve
* Support unsigned divide of huge numbers.
*
* Revision 1.41 2003/10/26 04:54:56 steve
* Support constant evaluation of binary ^ operator.
*

8
verinum.h
View File

@ -19,7 +19,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#ifdef HAVE_CVS_IDENT
#ident "$Id: verinum.h,v 1.25 2003/10/26 04:54:56 steve Exp $"
#ident "$Id: verinum.h,v 1.26 2004/02/17 06:52:55 steve Exp $"
#endif
# include <string>
@ -139,11 +139,17 @@ extern verinum operator * (const verinum&left, const verinum&right);
extern verinum operator / (const verinum&left, const verinum&right);
extern verinum operator % (const verinum&left, const verinum&right);
extern verinum operator<< (const verinum&left, unsigned shift);
extern verinum operator>> (const verinum&left, unsigned shift);
/* Bitwise not returns the ones complement. */
extern verinum v_not(const verinum&left);
/*
* $Log: verinum.h,v $
* Revision 1.26 2004/02/17 06:52:55 steve
* Support unsigned divide of huge numbers.
*
* Revision 1.25 2003/10/26 04:54:56 steve
* Support constant evaluation of binary ^ operator.
*