//------------------------------------------------------------------------------
double Area(OutRec outRec, bool UseFull64BitRange)
{
OutPt op = outRec.pts;
if (op == null) return 0;
if (UseFull64BitRange)
{
Int128 a = new Int128(0);
do
{
a += Int128.Int128Mul(op.pt.X + op.prev.pt.X, op.prev.pt.Y - op.pt.Y);
op = op.next;
} while (op != outRec.pts);
return a.ToDouble() / 2;
}
else
{
double a = 0;
do
{
a = a + (op.pt.X + op.prev.pt.X) * (op.prev.pt.Y - op.pt.Y);
op = op.next;
} while (op != outRec.pts);
return a / 2;
}
}
//------------------------------------------------------------------------------
public static double Area(PolygonClp poly)
{
int highI = poly.Count - 1;
if (highI < 2) return 0;
if (FullRangeNeeded(poly))
{
Int128 a = new Int128(0);
a = Int128.Int128Mul(poly[highI].X + poly[0].X, poly[0].Y - poly[highI].Y);
for (int i = 1; i <= highI; ++i)
a += Int128.Int128Mul(poly[i - 1].X + poly[i].X, poly[i].Y - poly[i - 1].Y);
return a.ToDouble() / 2;
}
else
{
double area = ((double)poly[highI].X + poly[0].X) * ((double)poly[0].Y - poly[highI].Y);
for (int i = 1; i <= highI; ++i)
area += ((double)poly[i - 1].X + poly[i].X) * ((double)poly[i].Y - poly[i - 1].Y);
return area / 2;
}
}
//nb: Constructing two new Int128 objects every time we want to multiply longs
//is slow. So, although calling the Int128Mul method doesn't look as clean, the
//code runs significantly faster than if we'd used the * operator.
public static Int128 Int128Mul(Int64 lhs, Int64 rhs)
{
bool negate = (lhs < 0) != (rhs < 0);
if (lhs < 0) lhs = -lhs;
if (rhs < 0) rhs = -rhs;
UInt64 int1Hi = (UInt64)lhs >> 32;
UInt64 int1Lo = (UInt64)lhs & 0xFFFFFFFF;
UInt64 int2Hi = (UInt64)rhs >> 32;
UInt64 int2Lo = (UInt64)rhs & 0xFFFFFFFF;
//nb: see comments in clipper.pas
UInt64 a = int1Hi * int2Hi;
UInt64 b = int1Lo * int2Lo;
UInt64 c = int1Hi * int2Lo + int1Lo * int2Hi;
UInt64 lo;
Int64 hi;
hi = (Int64)(a + (c >> 32));
unchecked { lo = (c << 32) + b; }
if (lo < b) hi++;
Int128 result = new Int128(hi, lo);
return negate ? -result : result;
}
public static Int128 operator /(Int128 lhs, Int128 rhs)
{
if (rhs.lo == 0 && rhs.hi == 0)
throw new ClipperException("Int128: divide by zero");
bool negate = (rhs.hi < 0) != (lhs.hi < 0);
if (lhs.hi < 0) lhs = -lhs;
if (rhs.hi < 0) rhs = -rhs;
if (rhs < lhs)
{
Int128 result = new Int128(0);
Int128 cntr = new Int128(1);
while (rhs.hi >= 0 && !(rhs > lhs))
{
rhs.hi <<= 1;
if ((Int64)rhs.lo < 0) rhs.hi++;
rhs.lo <<= 1;
cntr.hi <<= 1;
if ((Int64)cntr.lo < 0) cntr.hi++;
cntr.lo <<= 1;
}
rhs.lo >>= 1;
if ((rhs.hi & 1) == 1)
rhs.lo |= 0x8000000000000000;
rhs.hi = (Int64)((UInt64)rhs.hi >> 1);
cntr.lo >>= 1;
if ((cntr.hi & 1) == 1)
cntr.lo |= 0x8000000000000000;
cntr.hi >>= 1;
while (cntr.hi != 0 || cntr.lo != 0)
{
if (!(lhs < rhs))
{
lhs -= rhs;
result.hi |= cntr.hi;
result.lo |= cntr.lo;
}
rhs.lo >>= 1;
if ((rhs.hi & 1) == 1)
rhs.lo |= 0x8000000000000000;
rhs.hi >>= 1;
cntr.lo >>= 1;
if ((cntr.hi & 1) == 1)
cntr.lo |= 0x8000000000000000;
cntr.hi >>= 1;
}
return negate ? -result : result;
}
else if (rhs == lhs)
return new Int128(1);
else
return new Int128(0);
}
public Int128(Int128 val)
{
hi = val.hi;
lo = val.lo;
}
